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  • 1.
    Aghaali, Habib
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Ångström, Hans-Erik
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    A review of turbocompounding as a waste heat recovery system for internal combustion engines2015In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 49, p. 813-824Article in journal (Refereed)
    Abstract [en]

    Internal combustion engines waste a large amount of fuel energy through their exhausts. Various technologies have been developed for waste heat recovery such as turbocompounds, Rankine bottoming cycles, and thermoelectric generators that reduce fuel consumption and CO2 emissions. Turbocompounding is still not widely applied to vehicular use despite the improved fuel economy, lower cost, volume, and complexity higher exhaust gas recirculation driving capability and improved transient response. This paper comprehensively reviews the latest developments and research on turbocompounding to discover important variables and provide insights into the implementation of a high-efficiency turbocompound engine. Attention should be paid to the optimization of turbocompound engines and their configurations because the major drawback of this technology is additional exhaust back-pressure, which leads to higher pumping loss in the engines. Applying different technologies and concepts on turbocompound engines makes the exhaust energy recovery more efficient and provides more freedom in the design and optimization of the engines. Turbine efficiency plays an important role in the recovery of the wasted heat so turbine design is a crucial issue in turbocompounding. In addition, variability in geometry and rotational speed of power turbines allows for more efficient turbocompound engines in different operating conditions. The conclusion drawn from this review is that turbocompounding is a promising technology for reducing fuel consumption in the coming decades in both light- and heavy-duty engines.

  • 2.
    Aghaali, Habib
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Ångström, Hans-Erik
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    The Exhaust Energy Utilization of a Turbocompound Engine Combined with Divided Exhaust Period2014Conference paper (Refereed)
    Abstract [en]

    To decrease the influence of the increased exhaust pressure of a turbocompound engine, a new architecture is developed by combining the turbocompound engine with divided exhaust period (DEP). The aim of this study is to utilize the earlier stage (blowdown) of the exhaust stroke in the turbine(s) and let the later stage (scavenging) of the exhaust stroke bypass the turbine(s). To decouple the blowdown phase from the scavenging phase, the exhaust flow is divided between two different exhaust manifolds with different valve timing. A variable valve train system is assumed to enable optimization at different load points. The fuel-saving potential of this architecture have been theoretically investigated by examining different parameters such as turbine flow capacity, blowdown valve timing and scavenging valve timing. Many combinations of these parameters are considered in the optimization of the engine for different engine loads and speeds.

    This architecture produces less negative pumping work for the same engine load point due to lower exhaust back pressure; however, the exhaust mass flow into the turbine(s) is decreased. Therefore, there is a compromise between the turbine energy recovery and the pumping work. According to this study, this combination shows fuel-saving potential in low engine speeds and limitations at high engine speeds. This is mainly due to the choked flow in the exhaust valves because this approach is using only one of the two exhaust valves at a time. To reveal the full potential of this approach, increasing the effective flow area of the valves should be studied.

  • 3.
    Aghaali, Habib
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Ångström, Hans-Erik
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Serrano, Jose R
    Universitat Politècnica de València.
    Evaluation of different heat transfer conditions on an automotive turbocharger2014In: International Journal of Engine Research, ISSN 1468-0874, E-ISSN 2041-3149, Vol. 16, no 2, p. 137-151Article in journal (Refereed)
    Abstract [en]

    This paper presents a combination of theoretical and experimental investigations for determining the main heat fluxes within a turbocharger. These investigations consider several engine speeds and loads as well as different methods of conduction, convection, and radiation heat transfer on the turbocharger. A one-dimensional heat transfer model of the turbocharger has been developed in combination with simulation of a turbocharged engine that includes the heat transfer of the turbocharger. Both the heat transfer model and the simulation were validated against experimental measurements. Various methods were compared for calculating heat transfer from the external surfaces of the turbocharger, and one new method was suggested.

    The effects of different heat transfer conditions were studied on the heat fluxes of the turbocharger using experimental techniques. The different heat transfer conditions on the turbocharger created dissimilar temperature gradients across the turbocharger. The results show that changing the convection heat transfer condition around the turbocharger affects the heat fluxes more noticeably than changing the radiation and conduction heat transfer conditions. Moreover, the internal heat transfers from the turbine to the bearing housing and from the bearing housing to the compressor are significant, but there is an order of magnitude difference between these heat transfer rates.

  • 4.
    Alenius, Emma
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Flow acoustics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Sound Generating Flow Structures in a Thick Orifice Plate Jet2014In: Progress in Turbulence V: Proceedings of the iTi Conference in Turbulence 2012, Cham, Switzerland: Springer, 2014, p. 201-204Conference paper (Refereed)
    Abstract [en]

    The aim of thiswork is to study sound generating flowstructures in a thickcircular orifice plate jet, placed in a circular duct. Large eddy simulations (LES)are performed for two jet Mach numbers, 0.4 and 0.9. Characteristic frequenciesin the flow, and their corresponding flow structures, are identified with dynamicmode decomposition (DMD). The results show that a tonal noise is generated atfrequencies where the jet displays strong ring vortices, in the plane wave range.The main sound generating mechanisms seems to be a fluctuating mass flow at theorifice opening and a fluctuating surface force at the plate sides, caused by the ringvortices. The frequencies are believed to be chosen, and strengthened, by a feedbackmechanism between the orifice in- and outlet.

  • 5.
    Alenius, Emma
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Flow acoustics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Flow acoustics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Fuchs, Laszlo
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Large eddy simulations of acoustic-flow interaction at an orifice plate2015In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 345, p. 162-177Article in journal (Refereed)
    Abstract [en]

    The scattering of plane waves by an orifice plate with a strong bias flow, placed in a circular or square duct, is studied through large eddy simulations and dynamic mode decomposition. The acoustic-flow interaction is illustrated, showing that incoming sound waves at a Strouhal number of 0.43 trigger a strong axisymmetric flow structure in the orifice in the square duct, and interact with a self-sustained axisymmetric oscillation in the circular duct orifice. These structures then generate a strong sound, increasing the acoustic energy at the frequency of the incoming wave. The structure triggered in the square duct is weaker than that present in the circular duct, but stronger than structures triggered by waves at other frequencies. Comparing the scattering matrix with measurements, there is a good agreement. However, the results are found to be sensitive to the inflow, where the self-sustained oscillation in the circular duct simulation is an artefact of an axisymmetric, undisturbed inflow. This illustrates a problem with using an undisturbed inflow for studying vortex-sound effects, and can be of interest when considering musical instruments, where the aim is to get maximum amplification of specific tones. Further, it illustrates that at the frequency where an amplification of acoustic energy is found for the orifice plate, the flow has a natural instability, which is suppressed by non-axisymmetry and incoming disturbances.

  • 6.
    Alenius, Emma
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Flow acoustics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Flow acoustics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Fuchs, Laszlo
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Scattering of Plane Waves by a Constriction2011In: Proceedings of ASME Turbo Expo 2011, Vol 7, Parts A-C, American Society Of Mechanical Engineers , 2011, p. 1043-1052Conference paper (Refereed)
    Abstract [en]

    Liner scattering of low frequency waves by an orifice plate has been studied using Large Eddy Simulation and an acoustic two-port model. The results have been compared to measurements with good agreement for waves coming from the downstream side. For waves coming from the upstream side the reflection is over-predicted, indicating that not enough of the acoustic energy is converted to vorticity at the upstream edge of the plate. Furthermore, the sensitivity to the amplitude of the acoustic waves has been studied, showing difficulties to simultaneously keep the amplitude low enough for linearity and high enough to suppress flow noise with the relatively short times series available in LES.

  • 7.
    Allam, S.
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Cooling fan noise control using micro-perforates2012In: Int. Congr. Expos. Noise Control Eng., INTER-NOISE, 2012, p. 10434-10445Conference paper (Refereed)
    Abstract [en]

    Baffle or split silencers are commonly used, e.g., in HVAC systems and as inlet/outlet silencers on gas turbines. Another application is to reduce noise from the cooling fan inlet for large IC-engines. A baffle silencer can be seen as a periodic arrangement of parallel rectangular absorbers which can be placed in a rectangular duct. The noise reduction afforded by parallel baffles depends not only on the physical properties of the lining, but also upon the angle of incidence of the sound waves impinging and the baffle length. In this paper the potential of using baffles made of Micro-Perforated Panels is investigated in particular with the cooling fan inlet application in mind. Theoretical models for the damping is derived and used to design optimum configurations. The models are based on the wave propagation in a periodic array of baffles so that only one period can be investigated in order to find the different modes. In particular the least attenuated mode is important to find in order to optimize the behavior. An important aspect is the inner structure of the MPP baffle, i.e., can it just be an empty air volume or to what extent must internal waves be prevented by putting in walls. From a stiffness point of view some inner walls might also be needed to avoid vibration problems. Due to these complexities the theoretical models are only presented for the simplest cases. In order to validate the models and to get a more complete test of different designs experiments were also carried out. During these experiments the effect of flow was also tested.

  • 8. Allam, S.
    et al.
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Investigation of aerodynamic installation effects for an axial fan2013In: 19th AIAA/CEAS Aeroacoustics Conference, 2013Conference paper (Refereed)
    Abstract [en]

    The aim of the work reported in this paper is to investigate the aerodynamic installation effects for a generic cooling fan system. This is done by treating the ducted fan as a multi-port source and performing a source characterization, i.e., determining the source strength and source reflection matrix. From the source strength, which represents the sound radiated by the fan in a reflexion free (infinite) duct, the effect of various inflow distortions can be studied. The work is part of the EU-project ECOQUEST where the data will be used to validate the acoustic prediction tools.

  • 9.
    Allam, Sabry
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Knutsson, M.
    Bodén, Hans
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Development of acoustic models for high frequency resonators for turbocharged IC-engines2012In: SAE Technical Paper 2012-01-1559, 2012, 2012Conference paper (Refereed)
    Abstract [en]

    Automotive turbo compressors generate high frequency noise in the air intake system. This sound generation is of importance for the perceived sound quality of luxury cars and may need to be controlled by the use of silencers. The silencers usually contain resonators with slits, perforates and cavities. The purpose of the present work is to develop acoustic models for these resonators where relevant effects such as the effect of a realistic mean flow on losses and 3D effects are considered. An experimental campaign has been performed where the two-port matrices and transmission loss of sample resonators have been measured without flow and for two different mean flow speeds. Models for two resonators have been developed using 1D linear acoustic theory and a FEM code (COMSOL Multi-physics). For some resonators a separate linear 1D Matlab code has also been developed. Different models, from the literature, for including the effect of mean flow on the acoustic losses at slits and perforates have been implemented in the codes and compared to the experimental data. Correct modeling of acoustic losses for resonators with complicated geometry is important for the simulation and development of new and improved silencers, and the present work contributes to this understanding. The developed models give acceptable agreement with the measured results even with flow but can be improved for 3D FEM if correct CAD data is available. The 1D linear theory can be used for simple geometries and to get a general overview related to the resonance frequencies and damping level.

  • 10.
    Allam, Sabry
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Acoustic modelling and characterization of plate heat exchangers2012In: SAE Technical Paper 2012-01-1562, Society of Automotive Engineers, 2012Conference paper (Refereed)
    Abstract [en]

    There is increased concern about the noise emission from cooling systems. This is mainly due to an increased need for cooling needs due to turbo-charging and EGR systems, which tend to increase the fan power and thereby the noise. An important issue in this context is the behavior of the heat-exchanger and its acoustic transmission and absorption properties. In this paper an acoustic model to evaluate such data for a common type of heat exchanger, the parallel plate type, is presented. The basic configuration is assumed to be a matrix of parallel, narrow channels. The developed model is based on a so called equivalent fluid for an anisotropic medium. It is mainly dependent on the heat exchanger geometry combined with the Kirchhoff model for thermo-viscous wave propagation in narrow tubes. The proposed model can be used to predict the sound transmission and absorption for an entire heat exchanger for incident plane waves. This model is validated by comparison with measurement results for seven different heat exchangers used in vehicle and train cooling units at different flow speeds

  • 11.
    Allam, Sabry
    et al.
    Helwan University, Cairo, Egypt.
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Fan Noise Control Using Microperforated Splitter Silencers2014In: Journal of Vibration and Acoustics-Transactions of the ASME, ISSN 1048-9002, E-ISSN 1528-8927, Vol. 136, no 3, p. 031017-Article in journal (Refereed)
    Abstract [en]

    Splitter or baffle silencers are commonly used, for example, in heating ventilation and air conditioning (HVAC) systems and as inlet/outlet silencers on gas turbines. Another application is to reduce noise from the cooling fan inlet for large IC-engines. A splitter silencer can be seen as a periodic arrangement of parallel rectangular absorbers, which can be placed in a rectangular duct. The noise reduction afforded by parallel splitters depends not only on the physical properties of the lining but also upon the angle of incidence of the impinging sound waves, and the splitter and duct dimensions. In this paper, the potential of using splitters made of microperforated plates (MPPs) is investigated, with a particular focus on cooling fan inlet/outlet applications.

  • 12.
    Allam, Sabry
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Noise control for cooling fans on heavy vehicles2012In: Noise Control Engineering Journal, ISSN 0736-2501, E-ISSN 2168-8710, Vol. 60, no 6, p. 707-715Article in journal (Refereed)
    Abstract [en]

    In this paper two different objects for fan passive noise control have been examined: heat exchangers and inlet/outlet parallel splitter silencers based on micro-perforated panels. The first object is theoretically and experimentally examined while the second is only examined experimentally. Throughout this paper two measurement methods were used. The ISO 15186-1:2000 to test the acoustic transmission for a diffuse field and plane wave testing in a duct of a sample cut from each heat exchanger type. Based on an anisotropic equivalent fluid model a theoretical model for the heat exchanger acoustic transmission is presented. A new type of splitter silencers based on micro-perforated plates, which can add damping up 10-20 dB in the frequency range of interest (<5 kHz), are also presented.

  • 13.
    Appelquist, Ellinor
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Schlatter, Philipp
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics.
    Alfredsson, P. Henrik
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Lingwood, Rebecca
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Transition to turbulence in the rotating-disk boundary layer2020In: ETC 2013 - 14th European Turbulence Conference, Zakon Group LLC , 2020Conference paper (Refereed)
    Abstract [en]

    The development of the flow over a rotating disk is investigated by direct numerical simulations using both the linearised and fully nonlinear Navier-Stokes equations. The nonlinear simulations allow investigation of the transition to turbulence of the realistic spatially-developing boundary layer, and these simulations can be directly validated by physical experiments of the same case. The current research aims to elucidate further the global stability properties of the flow. So far, there are no conclusive simulations available in the literature for the fully nonlinear case for this flow, and since the nonlinearity is particularly relevant for transition to turbulence an increased understanding of this process is expected. 

  • 14.
    Bodin, Olle
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Wang, Yue
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Mihaescu, Mihai
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Fuchs, Laszlo
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    LES of the Exhaust Flow in a Heavy-Duty Engine2014In: Oil & gas science and technology, ISSN 1294-4475, E-ISSN 1953-8189, Vol. 69, no 1, p. 177-188Article in journal (Refereed)
    Abstract [en]

    The flow in the exhaust port and the exhaust manifold of a heavy-duty Diesel engine has been studied using the Large Eddy Simulation approach. Some of the flow characteristics in these components are: flow unsteadiness and separation combined with significant geometry-induced secondary flow motion. Detailed analysis of these features may add understanding which can be used to decrease the flow losses and increase the eciency of downstream components such as turbochargers and EGR coolers. Few LES studies of the flow in these components have been conducted in the past and this, together with the complexity of the flow are the motivations for this work. This paper shows that in the exhaust port, even global parameters like total pressure losses are handled better by LES than RANS. Flow structures of the type that afect both turbine performance and EGR cooler efficiency are generated in the manifold and these are found to vary significantly during the exhaust pulse. This paper also clearly illustrates the need to make coupled simulations in order to handle the complicated boundary conditions of these gas exchange components.

  • 15.
    Bodén, Hans
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    APPLICATION OF NONLINEAR SYSTEM IDENTIFICATION TECHNIQUES FOR DETERMINATION OF ACOUSTIC PROPERTIES OF IN-DUCT COMPONENTS2015In: PROCEEDINGS OF THE 22ND INTERNATIONAL CONGRESS ON SOUND AND VIBRATION: MAJOR CHALLENGES IN ACOUSTICS, NOISE AND VIBRATION RESEARCH, 2015 / [ed] Crocker, MJ Pawelczyk, M Pedrielli, F Carletti, E Luzzi, S, INT INST ACOUSTICS & VIBRATION , 2015Conference paper (Refereed)
    Abstract [en]

    This paper discusses the use of nonlinear system identification techniques for determination of linear and non-linear acoustic properties of in-duct components. Examples include perforates, orifices and acoustic liners. These types of components can for instance be found in aircraft engines, IC-engine exhaust and intake systems and ventilation ducts. Multiple input single output nonlinear system identification techniques are revisited and applied to the problem of nonlinear acoustic characterization of these components. Bi-linear signal analysis techniques are also discussed as well as empirical mode decomposition and Hilbert transform techniques applicable for non-stationary and nonlinear problems. Methods for studying nonlinear harmonic interaction effects, for perforates, using single tone excitation has been studied in previous work by the author. These techniques typically require measurements with a number of different acoustic loads. It would be more attractive to directly be able to extract the nonlinear acoustic properties from a more limited set of experiments using either random or periodic excitation. The idea of treating a nonlinear path as a separate non-linear input after which system identification is performed as for a linear two input one output system are revisited here in an attempt to analyze why unsatisfactory results were obtained in a previous study.

  • 16.
    Bodén, Hans
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Nonlinear source characterisation techniques for IC-engines2012In: 19th International Congress on Sound and Vibration 2012, ICSV 2012, 2012, p. 2442-2449Conference paper (Refereed)
    Abstract [en]

    A source characterization model for IC-engines, which can take weakly nonlinear source properties into account, is developed in the paper. It is based on so called polyharmonic distortion modeling, used for nonlinear characterization of microwave systems. Comparisons are made with the results from linear source models and another previously published weakly nonlinear source model. The results show that the new nonlinear impedance matrix model gives improvements in the prediction of sound pressure levels in the exhaust system.

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  • 17.
    Bodén, Hans
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    The effect of speed variation on in-duct source data determination2014In: 21st International Congress on Sound and Vibration 2014, ICSV 2014, 2014, p. 2395-2401Conference paper (Refereed)
    Abstract [en]

    Experimental acoustic source characterization is used for IC-engines and fluid machines connected to duct or pipe systems. Information about the engine as an acoustic source is needed to calculate insertion loss of mufflers or the level of radiated sound. The source model used in the low frequency plane wave range is often the linear time invariant 1 -port model. The acoustic source data is obtained from experimental tests or from 1 -D CFD codes describing the engine gas exchange process. Multi-load methods and especially the two-load method are most commonly used to extract the source data. The IC-engine is a high level acoustic source and in most cases not completely linear. The real part of the measured source impedance sometimes has negative values which is un-physical. This effect has been attributed to non-linearity and source time variation. Another possible explanation could be speed variation giving measurement errors especially for higher harmonics. In the present paper this effect is studied by re-visiting source data experiments for IC-engine exhausts and comparing the outcome of different methods for extracting the amplitude and phase of the pressure in terms of frequency components or engine orders.

  • 18.
    Bodén, Hans
    et al.
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics, Marcus Wallenberg Laboratory MWL.
    Kabral, Raimo
    KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics, Marcus Wallenberg Laboratory MWL.
    The effect of high temperatures and grazing flow on the acoustic properties of liners2020In: Euronoise 2015, DC/ConfOrg , 2020, p. 2261-2266Conference paper (Refereed)
    Abstract [en]

    Acoustic liners are used to reduce fan noise in aircraft engine intakes but also in hot stream parts of the engine. To gain confidence in liner impedance models which are used for design it is important to make experimental tests under realistic conditions as possible. This paper present results of hot stream impedance eduction tests for single degree of freedom Helmholtz resonator liners with different configurations. These types of liners consist of a perforate top sheet backed by a honeycomb cavity to give a locally reacting wall treatment which can be characterized by an acoustic impedance. In the present case a number of different perforate sheet geometries were tested under varying grazing flow and temperature conditions. In some cases the liner test samples also included a thin layer of metallic foam. These types of liners are used for aircraft engine applications but are also of interest for IC-engine applications. It could be argued that the main effect of high temperatures is a change of medium properties such as: density, viscosity and speed of sound. If this is true the high temperature impedance could be predicted by scaling from the result at cold conditions. This is investigated in the paper by comparing measured results from liner impedance models available in the literature.

  • 19.
    Bodén, Hans
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics, Marcus Wallenberg Laboratory MWL.
    Sack, Stefan
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics, Marcus Wallenberg Laboratory MWL. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Jacob, Stefan
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics, Marcus Wallenberg Laboratory MWL.
    Impedance measurements for 3-d printed liners2019In: 25th AIAA/CEAS Aeroacoustics Conference, 2019, [publishername] American Institute of Aeronautics and Astronautics Inc, AIAA , 2019Conference paper (Refereed)
    Abstract [en]

    The last twenty years have seen a great development in inverse techniques for the determination of liner impedance under grazing flow conditions, so called impedance eduction techniques. This paper contributes to a continuing effort to gain confidence in the results obtained, specifically in the dependence of the results on fabrication, data acquisition and analysis. It is part of the IFAR Acoustic Liner Challenge were data from multiple test rigs with similar liner configurations fabricated using 3D printing are gathered and compared. Experimental results are reported for two liner configurations obtained in KTH’s advanced impedance eduction flow rig.

  • 20.
    Bodén, Hans
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Zhou, Lin
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Acoustic Properties of an In-Duct Orifice Subjected to Bias Flow and High Level Acoustic Excitation2012In: Proceedings of the 10th International conference on Flow-Induced Vibration (& Flow-Induced Noise): FIV2012, Dublin, Ireland, 3-6 July 2012 FLOW-INDUCED VIBRATION, 2012, p. 187-193Conference paper (Refereed)
    Abstract [en]

    This paper experimentally investigates the acousticproperties of an orifice with bias flow under medium andhigh sound level excitation. The test included no bias flowand two bias speeds for three different frequencies. Experimentalresults are compared and discussed with theory.It is shown that bias flow makes the acoustic propertiesmuch more complex compared theory and with theno bias flow case, especially when velocity ratio betweenacoustic particle velocity and mean flow velocity is nearunity.

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  • 21.
    Bodén, Hans
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Zhou, Lin
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    An experimental study of the effect of flow and high level acoustic excitation on the acoustic properties of perforates and orifices2013In: 20th International Congress on Sound and Vibration 2013, ICSV 2013: Volume 3, 2013, International Institute of Acoustics and Vibrations , 2013, p. 2545-2552Conference paper (Refereed)
    Abstract [en]

    Perforates are for instance used in mufflers for automotive applications and in acoustic liners for aircraft engines. In these applications they are often exposed to high level acoustic excitation in combination with grazing or bias flow. The paper is based on an experimental study of the nonlinear properties of these types of samples without mean grazing or bias flow as well as on a study of an orifice with bias flow under medium and high sound level excitation. The effect of grazing flow is discussed based on data from the literature. It is known from previous studies that high level acoustic excitation at one frequency will change the acoustic impedance of perforates at other frequencies, thereby changing the boundary condition seen by the acoustic waves. This effect could be used to change the impedance boundary conditions and for instance increase the absorption. It could obviously also pose a problem for the correct modeling of sound transmission through ducts lined with such impedance surfaces. Experimental results are compared to a quasi-stationary model. The effect of the combination of frequency components and phase in the excitation signal is studied. The bias flow tests included different flow speeds for different frequencies. The level of acoustic excitation is varied from much smaller to larger than the mean flow velocity. It is shown that bias flow makes the acoustic properties more complex compared to the no bias flow case, especially when the velocity ratio between acoustic particle velocity and mean flow velocity is near unity.

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  • 22.
    Borodulin, V. I.
    et al.
    Khristianovich Inst Theoret & Appl Mech, Novosibirsk 630090, Russia..
    Ivanov, A. V.
    Khristianovich Inst Theoret & Appl Mech, Novosibirsk 630090, Russia..
    Kachanov, Y. S.
    Khristianovich Inst Theoret & Appl Mech, Novosibirsk 630090, Russia..
    Mischenko, D. A.
    Khristianovich Inst Theoret & Appl Mech, Novosibirsk 630090, Russia..
    Örlü, Ramis
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Hanifi, Ardeshir
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Hein, S.
    DLR, Inst Aerodynam & Flow Technol, D-37073 Gottingen, Germany..
    Experimental and theoretical study of swept-wing boundary-layer instabilities. Three-dimensional Tollmien-Schlichting instability2019In: Physics of fluids, ISSN 1070-6631, E-ISSN 1089-7666, Vol. 31, no 11, article id 114104Article in journal (Refereed)
    Abstract [en]

    Extensive combined experimental and theoretical investigations of the linear evolution of three-dimensional (3D) Tollmien-Schlichting (TS) instability modes of 3D boundary layers developing on a swept airfoil section have been carried out. The flow under consideration is the boundary layer over an airfoil at 350 sweep and an angle of attack of +1.5 degrees. At these conditions, TS instability is found to be the predominant one. Perturbations with different frequencies and spanwise wavenumbers are generated in a controlled way using a row of elastic membranes. All experimental results are deeply processed and compared with results of calculations based on theoretical approaches. Very good quantitative agreement of all measured and calculated stability characteristics of swept-wing boundary layers is achieved.

  • 23.
    Canton, Jacopo
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Schlatter, Philipp
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, School of Engineering Sciences (SCI), Mechanics.
    Örlü, Ramis
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Linear stability of the flow in a toroidal pipe2015In: 9th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2015, TSFP-9 , 2015Conference paper (Refereed)
    Abstract [en]

    While hydrodynamic stability and transition to turbulence in straight pipes - being one of the most fundamental problems in fluid mechanics - has been studied extensively, the stability of curved pipes has received less attention. In the present work, the first (linear) instability of the canonical flow inside a toroidal pipe is investigated as a first step in the study of the related laminar-turbulent transition process. The impact of the curvature of the pipe, in the range 8 e [0.002,1], on the stability properties of the flow is studied in the framework of linear stability analysis. Results show that the flow is indeed modally unstable for all curvatures investigated and that the wave number corresponding to the critical mode depends on the curvature, as do several other features of this problem. The critical modes are mainly located in the region of the Dean vortices, and are characterised by oscillations which are symmetric or antisymmetric as a function of the curvature. The neutral curve associated with the first bifurcation is the result of a complex interaction between isolated modes and branches composed by several modes characterised by a common structure. This behaviour is in obvious contrast to that of straight pipes, which are linearly stable for all Reynolds numbers.

  • 24.
    Ceci, Alessandro
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics.
    Gojon, Romain
    ISAE-SUPAERO, Université de Toulouse, France.
    Mihaescu, Mihai
    KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Computational analysis of the indirect combustion noise generation mechanism in a nozzle guided vane in transonic operating conditions2021In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 496Article in journal (Refereed)
    Abstract [en]

    The combustion noise in modern engines is mainly originating from two types of mechanisms. First, chemical reactions in the combustion chamber leads to an unsteady heat release which is responsible of the direct combustion noise. Second, hot and cold blobs of air coming from the combustion chamber are advected and accelerated through turbine stages, giving rise to entropy noise (or indirect combustion noise). In the present work, numerical characterization of indirect combustion noise of a Nozzle Guide Vane passage was assessed using three-dimensional Large Eddy Simulations. The present work offers an overview to the analytical, computational and experimental studies of the topic. Numerical simulations are conducted to reproduce the effects of incoming planar entropy waves from the combustion chamber and to characterize the generated acoustic power. The dynamic features of the flow are addressed by the means of frequency domain and modal analyses techniques such as Fourier Decomposition and Proper Orthogonal Decomposition. Finally, the predicted entropy noise from numerical calculations is compared with the analytical results of an actuator disk model for a stator stage. The present paper proves that the generated indirect combustion noise can be significant for transonic operating conditions. The blade acoustic response is characterized by the excitation of a latent dynamics at the forcing frequency of the planar entropy waves, and it increases as the amplitude of the incoming disturbances increases.

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  • 25.
    Chen, Song
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics.
    Gojon, Romain
    ISAE-SUPAERO.
    Mihaescu, Mihai
    KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Flow and aeroacoustic attributes of highly-heated transitional rectangular supersonic jets2021In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 114, no 106747Article in journal (Refereed)
    Abstract [en]

    Heated transitional supersonic jets exhausting from a rectangular nozzle at over-expanded conditions are investigated by Large Eddy Simulations and Ffowcs-Williams and Hawkings acoustic analogy. Four cases with a fixed nozzle pressure ratio but different temperature ratios (TR) of 1.0, 2.0, 4.0, and 7.0 are analyzed. Numerical results show that with the increasing temperature the jet velocity significantly increases, whereas its Reynolds number decreases by about one order of magnitude, which leads to a 30% decrease in the jet potential core length and reduction in the number of shock cells. The increasing temperatures also result in supersonic shear layer convection Mach numbers and consequently Mach wave radiations in the acoustic fields. Pressure skewness and kurtosis factors indicate crackle noise and non-linear propagation effects in high temperatures. For the most heated jet TR 7.0, the Mach wave radiation is identified radiating noise at about 120 degrees, while the large turbulence structure noise at about 150 degrees. Furthermore, the vortex sheet model analysis and the LES data detect the existence of upstream-propagating neutral waves inside jet TR 7.0. The observed screech frequency falls within the range of antisymmetric mode indicating that the highly-heated jet is characterized by an antisymmetric oscillation mode at the screech frequency.

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  • 26.
    Du, Lin
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). Beijing University of Aeronautics and Astronautics, China.
    Holmberg, Andreas
    Karlsson, Mikael
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Sound amplification at a rectangular T-junction with merging mean flows2016In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 367, p. 69-83Article in journal (Refereed)
    Abstract [en]

    This paper reports a numerical study on the aeroacoustic response of a rectangular T-junction with merging mean flows. The primary motivation of the work is to explain the high sound amplification, recently seen experimentally, when introducing a small merging bias flow. The acoustic results are found solving the compressible Linearized Navier-Stokes Equations (LNSEs) in the frequency domain, where the base flow is first obtained using RANS with a k-epsilon turbulence model. The model predicts the measured scattering data well, including the amplitude and Strouhal number for the peak amplification, if the effect of eddy viscosity damping is included. It is found that the base flow changes significantly with the presence of a small bias flow. Compared to pure grazing flow a strong unstable shear layer is created in the downstream main duct starting from the T-junction trailing edge. This means that the main region of vortex-sound interaction is moved away from the junction to a downstream region much larger than the junction width. To analyze the sound amplification in this region Howe's energy corollary and the growth of acoustic density are used.

  • 27.
    Du, Lin
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Sun, X.
    Effect of flapping frequency on aerodynamics of wing in freely hovering flight2015In: Computers & Fluids, ISSN 0045-7930, E-ISSN 1879-0747, Vol. 117, p. 79-87Article in journal (Refereed)
    Abstract [en]

    The two-dimensional incompressible Navier-Stokes equations are solved using the immersed boundary method. The wing is driven to translate in the horizontal direction and rotate periodically to emulate the wing motion of a fruit fly in normal hovering flight, while the motion in the vertical direction responds passively to the action of the wing aerodynamic lift and weight of the insect body. The insect body is modeled by a point mass. It is shown that flapping wing cannot produce required lift to maintain stable hovering flight in specified range with low flapping frequencies, if the insect weight is equivalent to the averaged wing lift in one cycle on the assumption of zero vertical velocity. The vertical velocity influences the instantaneous angle of attack of the hovering wing, which results in the variation in aerodynamics of the wing. The insect may experience fluctuating hovering flight with a reduced weight when the flapping frequency is low. The fluctuating amplitude decreases with increasing flapping frequency. The efficiency of hovering flight is also a problem of concern.

  • 28.
    Du, Lin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Using micro-perforated plates to realize a silencer based on the Cremer impedance2014In: Proceedings of Forum Acusticum, European Acoustics Association (EAA), 2014Conference paper (Refereed)
    Abstract [en]

    Current trends for IC-engines are driving the development of more efficient engines with higher specific power. This is true for both light and heavy duty vehicles and has led to an increased use of charging. The charging can be both in the form of a single or multi-stage turbo-charger driven by exhaust gases or via a directly driven compressor. In both cases a possible noise problem can be a strong Blade Passing Frequency (BPF) typically in the kHz range and above the plane wave range. In this paper a novel type of compact dissipative silencer developed especially to handle this type of problem is described. The silencer is based on a combination of a micro-perforated tube backed by a locally reacting cavity. The combined impedance of micro-perforate and cavity is chosen to match the theoretical optimum known as the Cremer impedance at the mid-frequency in the frequency range of interest. Due to the high damping achieved at the Cremer optimum (hundreds of dB/m) it is easy to create a compact silencer with a significant damping (say >40 dB) in a range larger than an octave. Several principles are presented to determine the parameters of micro-perforate and cavity. The numerical results indicate that, following the principles, a silencer with broad-band damping can be achieved.

  • 29.
    Du, Lin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Åbom, Mats
    KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Karlsson, Mikael
    KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Knutsson, M.
    Modelling of Acoustic Resonators Using the Linearized Navier Stokes Equations2016Conference paper (Refereed)
    Abstract [en]

    To tune the acoustics of intake systems resonators are often used. A problem with this solution is that the performance of these resonators can be affected a lot by flow. First, for low frequencies (Strouhal-numbers) the acoustic induced vorticity across a resonator inlet opening will create damping, which can reduce the efficiency. Secondly, the vorticity across the opening can also change the end-correction (added mass) for the resonator, which can modify the resonance frequency. However, the largest problem that can occur is whistling. This happens since the vortex-sound interaction across a resonator opening for certain Strouhal-numbers will amplify incoming sound waves. A whistling can then be created if this amplified sound forms a feedback loop, e.g., via reflections from system boundaries or the resonator. To analyse this kind of problem it is necessary to have a model that allows for both sound and vorticity and their interaction. This means using a convected wave equation type of model is not sufficient. A better approach is to apply the linearized Navier Stokes equations, which will give a full model of the vortex-sound effects. In this paper an effort to apply this approach on a set of generic resonators is described. Besides the numerical results comparisons with experiments are also presented.

  • 30.
    Eitel-Amor, Georg
    et al.
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Örlü, Ramis
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics.
    Schlatter, Philipp
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics.
    The significance of hairpin vortices in turbulent boundary layers2020In: ETC 2013 - 14th European Turbulence Conference, Zakon Group LLC , 2020Conference paper (Refereed)
    Abstract [en]

    The elementary question whether hairpin vortices constitute an inherent, universal structure of wall turbulence at moderate and high Reynolds numbers (Re) is addressed in this study. The downstream evolution of a single, artificial hairpin vortex is first studied in a mean shear flow to investigate possible decay and package-creation processes under high Re conditions. In a second step, hairpin-dominated flow in a transitional turbulent boundary layer is considered, whereas the lifetime of individual vortices and possible connection mechanisms are evaluated. The statistics obtained from this flow regime will be compared with reference data from turbulent-boundary-layer studies employing different transition mechanisms. Vortex eduction will be applied to comprehend the evolution from a well organized to a more chaotic state. The results could explain discrepancies in boundary-layer data close to transition and will contribute to the discussion about the relevance of hairpin-like structures in fully developed wall turbulence.

  • 31. El Nemr, Y.
    et al.
    Veloso, R.
    Girstmair, J.
    Kabral, Raimo
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Schutting, E.
    Dumböck, O.
    Ludwig, C.
    Mirlach, R.
    Masrane, A.
    Koutsovasilis, P.
    Experimental investigation of transmission loss in an automotive turbocharger compressor under ideal and real engine operating conditions2017In: 12th European Conference on Turbomachinery Fluid Dynamics and Thermodynamics, ETC 2017, KTH Royal Institute of Technology, 2017Conference paper (Refereed)
    Abstract [en]

    Acoustic transmission losses are expected to occur over the turbocharger compressor, especially along its rotating wheel section. Experiments on the acoustic characteristics of automotive turbocharger compressors were performed to investigate this acoustic transmission loss behavior. Two different rotor sizes were acoustically investigated considering approximately the same performance characteristics of the compressors. The investigated variants passed through two phases of measurements: The first phase was performed under ideal operating conditions involving a steady non-pulsating flow on an acoustic component test rig for turbochargers. Whereas the second phase was conducted under real engine operating conditions including pulsating flow of a modern 6-cylinder gasoline engine on an engine test rig. Comparisons between the two measurement phases show a considerable agreement between the two test rig setups for different operating conditions.

  • 32.
    Fjällman, Johan
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Mihaescu, Mihai
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Fuchs, Laszlo
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Exhaust flow pulsation effect on radial turbine performance2015In: 11th European Conference on Turbomachinery Fluid Dynamics and Thermodynamics, ETC 2015, European Conference on Turbomachinery (ETC) , 2015Conference paper (Refereed)
    Abstract [en]

    In the current vehicle manufacturing world the chase for a better fuel economy and better driveability is in high gear. One way of doing so is to investigate and optimize the turbocharger. In this paper the flow in a radial turbine of a passenger car turbocharger has been analysed by Large Eddy Simulations. The current simulations have investigated the effects of changing the inlet pulse frequency and inlet pulse shape on turbine's performance parameters (e.g. efficiency, shaft power, pressure distributions). Three different engine speeds and two different pulse shapes were chosen to be compared and analysed. With the total mass flow per pulse being constant for all cases there is a clear dependence of both pulse shape and frequency when it comes to e.g. wheel momentum. Higher frequency increases the peak momentum more than the minimum level. A reduction in pulse duration also increases peak momentum more than the minimum.

  • 33.
    Ford, C. L.
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Winroth, Marcus
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Alfredsson, P. Henrik
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Development of a pressure based vortex-shedding meter: measuring unsteady mass-flow in variable density gases2016In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 27, no 8, article id 085901Article in journal (Refereed)
    Abstract [en]

    An entirely pressure-based vortex-shedding meter has been designed for use in practical time-dependent flows. The meter is capable of measuring mass-flow rate in variable density gases in spite of the fact that fluid temperature is not directly measured. Unlike other vortex meters, a pressure based meter is incredibly robust and may be used in industrial type flows; an environment wholly unsuitable for hot-wires for example. The meter has been tested in a number of static and dynamic flow cases, across a range of mass-flow rates and pressures. The accuracy of the meter is typically better than about 3% in a static flow and resolves the fluctuating mass-flow with an accuracy that is better than or equivalent to a hot-wire method.

  • 34.
    Ford, Christopher L.
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Winroth, Per Marcus
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    On the scaling and topology of confined bluff-body flows2019In: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 876, p. 1018-1040Article in journal (Refereed)
    Abstract [en]

    An experimental study of bluff bodies in confinement is presented. Two Reynolds matched rigs (pipe diameters: D D 40 mm and D D 194 mm) are used to derive a picture of the flow topology of the primary-shedding mode (Karman vortex, mode-I). Confined bluff bodies create an additional spectral mode (mode-II). This is caused by the close coupling of the shedder blockage and the wall and is unique to the confined bluff-body problem. Under certain conditions, modes-I and II can interact, resulting in a lock-on, wherein the modes cease to exist at independent frequencies. The topological effects of mode interaction are demonstrated using flow visualisation. Furthermore, the scaling of mode-II is explored. The two experimental facilities span Reynolds numbers (based on the shedder diameter, d) 104 < Red < 105 and bulk Mach numbers 0 : 02 < Mb < 0 : 4. Bluff bodies with a constant blockage ratio (d = D), forebody shape and various splitter-plate lengths (l) and thicknesses (t) are used. Results indicate that the flow topology changes substantially between short (l < d) and long (l > d) tailed geometries. Surface flow visualisation indicates that the primary vortex becomes anchored on the tail when l & 3h (2h D d t). This criterion prohibits the development of such a topology for short-tailed geometries. When mode interaction occurs, which it does exclusively in long-tailed cases, the tail-anchored vortex pattern is disrupted. The onset of mode-II occurs at approximately the same Reynolds number in both rigs, although the associated dimensionless frequency is principally a function of Mach number. Accordingly, mode interaction is avoided in the larger-scale rig, due to the increased separation of the modal frequencies.

  • 35.
    Giramondi, Nicola
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Mihaescu, Mihai
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Christiansen Erlandsson, Anders
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Jäger, Anders
    SCANIA CV AB.
    CFD-Driven Preliminary Investigation of Ethanol-Diesel Diffusive Combustion in Heavy-Duty Engines2019In: / [ed] SAE, 2019, p. 15-, article id 019-01-2192Conference paper (Refereed)
    Abstract [en]

    The introduction of renewable alcohols as fuels for heavy-duty engines may play a relevant role for the reduction of the carbon footprint of the transport sector. The direct injection of ethanol as main fuel and diesel as pilot fuel in the engine combustion chamber through two separate injectors may allow good combustion controllability over the entire engine operating range by targeting diffusive combustion. Closed-cycle combustion simulations have been carried out using AVL FIRE coupled to AVL TABKIN for the implementation of the Flamelet Generated Manifold (FGM) chemistry reduction technique in order to investigate the influence of the injection system geometry and the injection strategy of pure ethanol and diesel fuel on ignition characteristics and combustion at different operating conditions.

  • 36.
    Gundmalm, Stefan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Ångström, Hans-Erik
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Divided Exhaust Period: Effects of Changing the Relation between Intake, Blow-Down and Scavenging Valve Area2013In: SAE International Journal of Engines, ISSN 1946-3936, Vol. 6, no 2, p. 739-750Article in journal (Refereed)
    Abstract [en]

    In a previous paper we showed the effects of applying the Divided Exhaust Period (DEP) concept on two heavy-duty diesel engines, with and without Exhaust Gas Recirculation (EGR). Main findings were improved fuel consumption due to increased pumping work, improved boost control and reduced residual gas content. However, some limitations to the concept were discovered. In the case of high rates of short route EGR, it was apparent that deducting the EGR flow from the turbine manifold impaired optimal valve timing strategies. Furthermore, for both of the studied engines it was clear that the size and ratio of blow-down to scavenging valve area is of paramount importance for engine fuel efficiency. In this paper, the DEP concept has been studied together with a long route EGR system. As expected it gave more freedom to valve timing strategies when driving pressure for EGR is no longer controlled with the valve timing, as in the short route case. However, when evaluating different combinations of intake, blow-down and scavenging valve area, the optimal relation proves to be strongly dependent on the current EGR system and EGR rates. Hence, for different engine setups the trade-off between total intake and total exhaust area needs to be re-evaluated for optimal engine fuel efficiency. This paper also presents general trends in how different valve timing strategies and EGR rates affect both pumping work and boost pressure.

  • 37.
    Heide, Jakob
    et al.
    KTH.
    Karlsson, Mikael
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Altimira, Mireia
    KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Numerical Analysis of Urea-SCR Sprays under Cross-Flow Conditions2017In: SAE technical paper series, ISSN 0148-7191, Vol. 2017-March, no MarchArticle in journal (Refereed)
    Abstract [en]

    Selective Catalytic Reduction (SCR) of NOx through injection of Urea-Water-Solution (UWS) into the hot exhaust gas stream is an effective and extensively used strategy in internal combustion engines. Even though actual SCR systems have 95-96% de-NOx efficiency over test cycles, real driving emissions of NOx are a challenge, proving that there is room for improvement. The efficiency of the NOx conversion is highly dependent on the size of UWS droplets and their spatial distribution. These factors are, in turn, mainly determined by the spray characteristics and its interaction with the exhaust gas flow. The main purpose of this study is to numerically investigate the sensitivity to the modelling framework of the evaporation and mixing of the spray upstream of the catalyst. The dynamics of discrete droplets is handled through the Lagrangian Particle Tracking framework, with models that account for droplet breakup and coalescence, turbulence effects, and water evaporation. All simulations have been run in the commercial code Ansys Fluent 16.0. Experimental validation of droplet size distribution is carried out through PDPA measurements. Through the present study we have identified suitable modelling setup that provides accurate results with a competitive computational cost. Results also show the importance of accounting for the effects of evaporation and turbulent fluctuations in the droplet phase.

  • 38. Heo, Y. -H
    et al.
    Ih, J. -G
    Bodén, Hans
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics, Marcus Wallenberg Laboratory MWL.
    Identification of a rotating sound source in a duct with high spatial resolution2020In: Euronoise 2015, DC/ConfOrg , 2020, p. 2273-2278Conference paper (Refereed)
    Abstract [en]

    To identify the major sources of noise radiated from in-duct fluid machines, one needs to observe the source parameters such as pressure and velocity fields at the source plane. For this purpose, inverse estimation methods are generally used starting from measured pressures and a sound propagation model in the duct. In this paper, a technique is suggested for identifying the rotating noise source in a wide duct. For the detailed observation of sources with high spatial resolution, the evanescent wave is considered in the modeling based on the modal summation method. Also, the Doppler effect caused by rotation of the noise source is considered in the modeling. The validation experiment is conducted on the duct system excited by a rotating loudspeaker radiating a tonal sound in the absence of flow. The measured near-field pressure precisely shows spectral peaks at shifted frequencies due to the Doppler effect. The modal amplitude set related with the rotation of the loudspeaker is estimated to investigate the source parameters. The pressure in the near-fields very close to the source is regenerated by using the estimated modal amplitudes, and the maximum error is found to be less than -10 dB. The pressure and velocity fields at the source plane are restored by the estimated modal amplitudes, and the result clearly indicate the rotating loudspeaker as the main noise radiator within the rotating reference frame.

  • 39.
    Holmberg, Andreas
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Karlsson, Mikael
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Aeroacoustics of rectangular T-junctions subject to combined grazing and bias flows - An experimental investigation2015In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 340, p. 152-166Article in journal (Refereed)
    Abstract [en]

    Scattering matrices are determined experimentally and used to study the low amplitude interaction, between the acoustic and the hydrodynamic fields in a T-junction of rectangular ducts. In particular, combinations of grazing and bias flows are investigated in the study. It is observed that for all flow combinations, waves incident on the junction at the downstream side only are attenuated, while waves incident at the other branches may be amplified or attenuated, depending on the Strouhal number. When bias in flow is introduced to a grazing flow, there is first an increase and then a decrease in both amplification and attenuation, as the bias in-flow Mach number is increased. Comparing with T-junctions of circular ducts, the interaction is stronger for rectangular duct junctions.

  • 40.
    Holmberg, Andreas
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Kierkegaard, Axel
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Weng, Chenyang
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    A frequency domain linearized Navier-Stokes method including acoustic damping by eddy viscosity using RANS2015In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 346, p. 229-247Article in journal (Refereed)
    Abstract [en]

    In this paper, a method for including damping of acoustic energy in regions of strong turbulence is derived for a linearized Navier-Stokes method in the frequency domain. The proposed method is validated and analyzed in 2D only, although the formulation is fully presented in 3D. The result is applied in a study of the linear interaction between the acoustic and the hydrodynamic held in a 2D T-junction, subject to grazing flow at Mach 0.1. Part of the acoustic energy at the upstream edge of the junction is shed as harmonically oscillating disturbances, which are conveyed across the shear layer over the junction, where they interact with the acoustic field. As the acoustic waves travel in regions of strong shear, there is a need to include the interaction between the background turbulence and the acoustic field. For this purpose, the oscillation of the background turbulence Reynolds stress, due to the acoustic Field, is modeled using an eddy Newtonian model assumption. The time averaged flow is first solved for using RANS along with a k-epsilon turbulence model. The spatially varying turbulent eddy viscosity is then added to the spatially invariant kinematic viscosity in the acoustic set of equations. The response of the 2D T-junction to an incident acoustic field is analyzed via a plane wave scattering matrix model, and the result is compared to experimental data for a T-junction of rectangular ducts. A strong improvement in the agreement between calculation and experimental data is found when the modification proposed in this paper is implemented. Discrepancies remaining are likely due to inaccuracies in the selected turbulence model, which is known to produce large errors e.g. for flows with significant rotation, which the grazing flow across the T-junction certainly is A natural next step is therefore to test the proposed methodology together with more sophisticated turbulence models.

  • 41.
    Holmberg, Andreas
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Kierkegaard, Axel
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Weng, Chenyang
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    A linearized Navier-Stokes method including turbulence damping2013In: 19th AIAA/CEAS Aeroacoustics Conference, 2013Conference paper (Refereed)
    Abstract [en]

    In this paper, a method for including damping of acoustic energy in regions of strong turbulence is derived for a linearized Navier-Stokes method in the frequency domain. The result is applied in a study of the linear interaction of the acoustic and the hydrodynamic field in a 2D T-junction, subject to grazing flow at Mach 0.1. As the acoustic waves travel in regions of strong shear, there is a need to include the interaction between the background turbulence and the acoustic field. For this purpose, the oscillation of the background turbulence Reynold's stress, due to the acoustic field, is modeled using an eddy Newtonian model assumption. The time averaged flow is first solved for using RANS along with a k-ε turbulence model. The spatially varying turbulent viscosity is then added to the spatially invariant kinematic viscosity in the acoustic set of equations. The response of the 2D T-junction to an incident acoustic field is analyzed via a plane wave scattering matrix model, and the result is compared to experimental data for a T-junction of rectangular ducts. A strong improvement in the agreement between calculation and experimental data is found when the modification proposed in this paper is implemented.

  • 42.
    Holmberg, Andreas
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Karlsson, M.
    Aeroacoustics of rectangular T-junctions subject to combined grazing and bias flows - An experimental investigation2013In: 19th AIAA/CEAS Aeroacoustics Conference, 2013Conference paper (Refereed)
    Abstract [en]

    Experimentally determined scattering matrices are used to study the low-amplitude interaction between the acoustic and the hydrodynamic fields in a T-junction of rectangular ducts. In particular, combinations of grazing and bias flows are investigated in the study. Common for all flow combinations is that waves incident on the junction at the downstream side are only attenuated, while waves incident at the other branches may be amplified or attenuated, depending on the Strouhal number. When bias in-flow is introduced to a grazing flow, there is first an increase and then a decrease in both amplification and attenuation, as the bias in-flow Mach number is increased. Comparing with T junctions of circular ducts, the interaction is stronger for rectangular duct junctions.

  • 43.
    Hong, Beichuan
    KTH, School of Industrial Engineering and Management (ITM), Engineering Design, Mechatronics and Embedded Control Systems. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Exergy Evaluation of Engine Operations: Combustion Process to Exhaust Flow2023Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Transitioning the transport sector to clean energy sources is crucial for mitigating greenhouse gas emissions and achieving carbon neutrality. A collaborative solution, combining both electric vehicles and combustion engines using renewable fuels, may prove more effective than competitive ones. This necessitates a focus on developing sustainable combustion engines by improving their efficiency through renewable energy sources and innovative technologies.

    This thesis uses exergy analysis to evaluate engine efficiency, losses, and irreversibilities, as well as the work potential of exhaust flows. Particular emphasis is placed on the implications of these exergy analyses in relation to engine operations, especially concerning combustion processes and exhaust pulsations. Exergy analysis quantifies the maximum work extractable from an energy source, enabling the identification and quantification of losses and inefficiencies in thermal processes. A dual-fuel marine engine with two-stage turbocharging and an ethanol-fueled heavy-duty spark-ignition (SI) engine using lean burn are examined with validated one-dimensional engine models to analyze engine performance and losses from an exergy perspective. In the tested marine engine, irreversibilities are quantified and categorized into three types, with combustion irreversibility being the most significant, followed by losses through gas exchange and heat dissipation. In the ethanol-fueled SI engine, the effect of lean-burn combustion at high load is investigated through the excess air ratio up to 1.8, assessing its impact on thermal efficiency, combustion phasing, as well as energy and exergy distributions. Results indicate that employing lean burn improves engine efficiency with advanced combustion phasing but also leads to more exergy destruction. The importance of maintaining high exergy recovery through turbocharging for diluted operation is also highlighted.

    Additionally, high-frequency exhaust pulsations resulting from valve motion pose challenges in accurately resolving exhaust energy and exergy. To address this, this thesis investigates methods for exhaust pulse characterization and measurement under unsteady flow conditions. Sensitivity analyses, based on a heavy-duty engine simulation, highlight the importance of time-resolved mass flow measurements in quantifying the energy and exergy of exhaust pulsations. Subsequently, this research implements a Pitot tube-based approach to measure crank angle-resolved engine exhaust mass flow rates and to further analyze the effect of attenuated temperature measurements on resolving instantaneous mass flows. The findings indicate that temperature variations pertaining to exhaust flow conditions have only a relatively small impact on mass flow measurements. Based on the exhaust flow measurements, the mass flow characteristics of exhaust pulsations are also discussed with regard to the blow-down and scavenge phases.

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  • 44.
    Hong, Beichuan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Mahendar, Senthil
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Christiansen Erlandsson, Anders
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Quantification of Losses and Irreversibilities in a Marine Engine for Gas and Diesel Fuelled Operation Using an Exergy Analysis Approach2020Conference paper (Refereed)
    Abstract [en]

    Large bore marine engines are a major source of fossil fuel consumption in the transport sector. The development of more efficient and cleaner marine engine systems are always required. Exergy analysis is a second-law based approach to indicate the maximum amount of work obtainable from a given system.

    In this study, an exergy analysis is used to identify losses and improvement potential of a large bore Wärtsilä 31DF four-stroke marine engine system with two-stage turbocharging. An exergy-based framework is implemented on a calibrated 1D engine model to view the evolution of exergy flow over each engine sub-system while operating on different load points fuelled with natural gas and diesel separately.

    The overall distributions of engine energy and exergy are initially compared at a systematic level regarding the impact of fuel mode and operating load. Furthermore, the engine irreversibilities are characterized as three types: combustion, heat dissipation, and gas exchange losses. The first type, combustion irreversibility, is the largest source of engine exergy losses amounting to at least 25% of fuel exergy. A crank resolved analysis showed that premixed gas combustion produces lower exergy losses compared to diesel diffusion combustion. The second type, thermal exergy transferred and destroyed by heat losses, are summarized for the entire engine system. From the exergy view, the charge coolers present an opportunity to recover about 9% of the brake power at full load. The last type, gas exchange losses, are categorized by accounting the flow losses caused by the valve throttling, fluid friction in pipes and the irreversibility of the two-stage turbocharging system. Most of exergy destruction in gas paths occurs at turbocharging system, where the high pressure turbocharger contributes to around 40% of the total flow exergy destruction.

  • 45.
    Hong, Beichuan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Venkataraman, Varun
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Numerical Analysis of Engine Exhaust Flow Parameters for Resolving Pre-Turbine Pulsating Flow Enthalpy and Exergy2021In: Energies, E-ISSN 1996-1073, Vol. 14, no 19Article in journal (Refereed)
    Abstract [en]

    Energy carried by engine exhaust pulses is critical to the performance of a turbine or any other exhaust energy recovery system. Enthalpy and exergy are commonly used concepts to describe the energy transport by the flow based on the first and second laws of thermodynamics. However, in order to investigate the crank-angle-resolved exhaust flow enthalpy and exergy, the significance of the flow parameters (pressure, velocity, and temperature) and their demand for high resolution need to be ascertained. In this study, local and global sensitivity analyses were performed on a one-dimensional (1D) heavy-duty diesel engine model to quantify the significance of each flow parameter in the determination of exhaust enthalpy and exergy. The effects of parameter sweeps were analyzed by local sensitivity, and Sobol indices from the global sensitivity showed the correlations between each flow parameter and the computed enthalpy and exergy. The analysis indicated that when considering the specific enthalpy and exergy, flow temperature is the dominant parameter and requires high resolution of the temperature pulse. It was found that a 5% sweep over the temperature pulse leads to maximum deviations of 31% and 27% when resolving the crank angle-based specific enthalpy and specific exergy, respectively. However, when considering the total enthalpy and exergy rates, flow velocity is the most significant parameter, requiring high resolution with a maximum deviation of 23% for the enthalpy rate and 12% for the exergy rate over a 5% sweep of the flow velocity pulse. This study will help to quantify and prioritize fast measurements of pulsating flow parameters in the context of turbocharger turbine inlet flow enthalpy and exergy analysis.

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  • 46.
    Hong, Beichuan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Engineering Design, Mechatronics and Embedded Control Systems. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Venkataraman, Varun
    KTH, School of Industrial Engineering and Management (ITM), Engineering Design, Mechatronics and Embedded Control Systems. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Mihaescu, Mihai
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Engineering Design, Mechatronics and Embedded Control Systems. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Crank angle-resolved mass flow characterization of engine exhaust pulsations using a Pitot tube and thin-wire thermocouples2023In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, p. 121725-121725, article id 121725Article in journal (Refereed)
    Abstract [en]

    Characterizing pulsating flow in high-temperature, high-pressure engine exhaust gas is crucial for the development and optimization of exhaust energy recovery systems. However, the experimental investigation of engine exhaust pulses is challenging due to the difficulties in conducting crank angle-resolved measurements under these unsteady flow conditions. This study contributes to characterizing mass flow pulses from an isolated cylinder exhaust of a heavy-duty diesel engine using a single-pipe measurement system, developed for pulsating flow measurement. A Pitot tube-based approach is adopted to measure exhaust mass flow pulsations, complemented by fast temperature measurements obtained using customized unsheathed thin-wire thermocouples. The on-engine experiment is performed by isolating the in-cylinder trapped mass and the valve opening speed to produce different exhaust pulse waveforms. The adopted approach’s sensitivity in resolving instantaneous mass flows is evaluated analytically and experimentally, considering attenuated temperature measurement effects. Based on exhaust flow measurements, mass flow pulses are analyzed with regard to blow-down and scavenge phases. Under the load sweep, the main waveform change occurs during the blow-down phase, with pulse magnitude increasing with the load. In contrast, as the engine speeds up with a comparable trapped mass, the exhaust mass distribution in the blow-down phase decreases from 75.5% at 700 rpm to 41.9% at 1900 rpm. Additionally, it is observed that cycle-to-cycle variations in mass flow pulses align with combustion stability during the blow-down phase and are predominantly influenced by gas-exchange processes during the scavenge phase.

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  • 47. Hynninen, A.
    et al.
    Turunen, R.
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Bodén, Hans
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Acoustic source data for medium speed IC-engines2011In: 18th International Congress on Sound and Vibration 2011 (ICSV 18), 2011, p. 811-818Conference paper (Refereed)
    Abstract [en]

    Knowledge of the acoustic source characteristics of internal combustion engines (IC-engines) is of great importance when designing the exhaust duct system and its components to withstand the resulting dynamic loads and to reduce the exhaust noise emission. Number of studies has been published earlier on the low frequency in-duct exhaust noise of high speed engines. The goal of the present study is to investigate the medium speed IC-engine acoustic source characteristics numerically and experimentally not only in the low frequency - plane wave range but also in the high frequency range. The low frequency acoustic source characteristics were predicted by simulating the acoustic multi-load measurements using a one-dimensional process simulation code. The engine model used in the one-dimensional process simulations was validated with measurements. In this study, it is shown that the low frequency in-duct exhaust noise of a medium speed IC-engine can be predicted quite accurately by using a onedimensional process simulation code. The high frequency source data is estimated by averaging the measured acoustic pressures with different methods. According to this study, using the simple cross spectra averaging method instead of two microphone method to estimate the induct downstream acoustic power of medium speed IC-engine exhaust noise seems promising. The simulation of the high frequency exhaust noise is beyond this study.

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  • 48. Hynninen, A.
    et al.
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Acoustic two-port simulation model for the particle oxidation catalyst (POC®)2014In: INTERNOISE 2014 - 43rd International Congress on Noise Control Engineering: Improving the World Through Noise Control, 2014Conference paper (Refereed)
    Abstract [en]

    The reduction of the exhaust noise from internal combustion engine (IC-engine) is mainly managed by proper silencer design, while less attention is paid to the acoustic performance of the after treatment devices (ATD). It is known from the earlier studies, that the transmission loss of a typical ATD unit can be quite significant. An ATD unit for diesel engines is classically assembled from several specific parts such as selective catalytic reducers (SCR), diesel oxidation catalysts (DOC) and diesel particulate filters (DPF). One new alternative to the conventional DPF is the particle oxidation catalyst (POC®). The substrate used in the POC-X type filter consists of fine, corrugated metallic wire mesh screens piled askew and rolled into a cylindrical shape. In this paper an acoustic two-port simulation model for POC-X is sought starting from the classical Kirchhoff solution for prediction of the acoustic wave attenuation in narrow channels. According to experimental studies, correction factors to the narrow channel two-port model are proposed.

  • 49. Hynninen, A.
    et al.
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Estimating the high frequency in-duct sound power using sound pressures at the duct wall2013In: 20th International Congress on Sound and Vibration 2013, ICSV 2013: Volume 3, 2013, International Institute of Acoustics and Vibrations , 2013, p. 2553-2559Conference paper (Refereed)
    Abstract [en]

    When studying the acoustic wave propagation in a Channel, the frequency range can be divided to the low frequency plane wave range and to the high frequency range with non-plane waves. In the low frequency range the wave propagation is one-dimensional and the governing equations are rather simple. The larger the duct the lower the frequency limit of the non-plane waves. Therefore taking into account also the three-dimensional acoustic wave propagation is important especially when considering the duct systems used in large structures, e.g., medium speed internal combustion engines (IC-engines), fans, or compressors. Harsh environment and unmovable structures restrict the use of standardized noise measuring methods. To characterize the medium speed IC-engine exhaust noise in situ, the in-duct sound pressures are measured using wall mounted transducers. Then the source sound power is estimated from the propagating sound pressures, which is the power based approach. The power based approach is only valid in frequency averaged sense and therefore the source power must be defined in one-third octave frequency bands, for example. One way to estimate the source sound power in the high frequency range, is to extend the classical plane wave formulation by defining the one-third octave frequency band weighting factors for different excitation types. The aim of this study is to define these weighting factors using finite element method (FEM) simulations of a test duct with non-reflecting terminations. The sound pressures at the duct wall were compared to the sound pressures at the duct end for randomized multi-modal excitations. From statistics, the one-third octave band weighting factors and their reliability were estimated.

  • 50. Hynninen, A.
    et al.
    Åbom, Mats.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Procedure to estimate the in-duct sound power in the high frequency range with non-plane waves2012In: ASME 2012 Noise Control and Acoustics Division Conference at InterNoise 2012, ASME Press, 2012, p. 181-191Conference paper (Refereed)
    Abstract [en]

    The acoustic characterization of fluid machines, e.g., internal combustion engines, compressors, or fans is of great importance when designing the connected duct systems and its silencers. For machines connected to large ducts where also the non-plane wave range is important, for instance large diesels and gas turbines, a suitable way to characterize the source is to determine the sound power under reflection free conditions. For the low frequency plane wave range in-duct sound power can be measured with the widely used two microphone method. The goal of this study is to investigate how, starting from the two-microphone approach, a suitable wall mounted microphone configuration can be defined and used to estimate the propagating in-duct sound power also beyond the plane wave range. For this purpose an acoustic source test-rig was built and numerical simulations were also conducted. The in-duct sound power from monopole, dipole, and quadrupole source types was determined using twelve wall mounted microphones and cross-spectra averaging methods. The in-duct results were compared against sound power measured using the reverberation room method (ISO 3741). Based on the simulations and the experimental results the best microphone positions and weighting factors were determined.

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