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  • 1.
    Aghaali, H.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Ångström, H. -E
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Improving turbocharged engine simulation by including heat transfer in the turbocharger2012In: SAE technical paper series, ISSN 0148-7191Article in journal (Refereed)
    Abstract [en]

    Engine simulation based on one-dimensional gas dynamics is well suited for integration of all aspects arising in engine and powertrain developments. Commonly used turbocharger performance maps in engine simulation are measured in non-pulsating flow and without taking into account the heat transfer. Since on-engine turbochargers are exposed to pulsating flow and varying heat transfer situations, the maps in the engine simulation, i.e. GT-POWER, have to be shifted and corrected which are usually done by mass and efficiency multipliers for both turbine and compressor. The multipliers change the maps and are often different for every load point. Particularly, the efficiency multiplier is different for every heat transfer situation on the turbocharger. The aim of this paper is to include the heat transfer of the turbocharger in the engine simulation and consequently to reduce the use of efficiency multiplier for both the turbine and compressor. A set of experiment has been designed and performed on a water-oil-cooled turbocharger, which was installed on a 2 liter GDI engine with variable valve timing, for different load points of the engine and different conditions of heat transfer in the turbocharger. The experiments were the base to simulate heat transfer on the turbocharger, by adding a heat sink before the turbine and a heat source after the compressor. The efficiency multiplier of the turbine cannot compensate for all heat transfer in the turbine, so it is needed to put out heat from the turbine in addition to the using of efficiency multiplier. Results of this study show that including heat transfer of turbocharger in engine simulation enables to decrease the use of turbine efficiency multiplier and eliminate the use of compressor efficiency multiplier to correctly calculate the measured gas temperatures after turbine and compressor. 

  • 2. Armengaud, E.
    et al.
    Zoier, M.
    Baumgart, A.
    Biel, Martin
    KTH, School of Electrical Engineering and Computer Science (EECS), Automatic Control.
    Chen, D.
    KTH.
    Griessnig, G.
    Hein, C.
    Ritter, T.
    Tavakoli Kolagari, R.
    Model-based toolchain for the efficient development of safety-relevant automotive embedded systems2011In: SAE technical paper series, ISSN 0148-7191Article in journal (Refereed)
    Abstract [en]

    Advanced functionalities unthinkable a few decades ago are now being introduced into automotive vehicles through embedded systems for reasons like emission control, vehicle connectivity, safety and cooperative behaviors. As the development often involves stakeholders from different engineering disciplines and organizations, the complexity due to shared requirements, interdependencies of data, functions, and resources, as well as tight constraints in regards to timing, safety, and resource efficiency makes the system integration, quality control and assurance, reuse and change management increasingly more difficult. This calls for a more rigorous approach to the development of automotive embedded systems and components. This paper describes the CESAR reference technology platform (RTP) that supports the formalization of various engineering concerns in the development of safety-relevant embedded systems and thereby a model-based integration of various tools and methods to form seamless environments or toolchains for the development of such systems. 

  • 3.
    Boden, H.
    KTH.
    Recent Advances in IC-Engine Exhaust and Intake System Acoustic Source Characterization2012In: SAE technical paper series, ISSN 0148-7191, Vol. 2012-November, no NovemberArticle in journal (Refereed)
    Abstract [en]

    The paper gives an overview of techniques used for characterization of IC-engines as acoustic sources of exhaust and intake system noise. Some recent advances are introduced and discussed. Linear frequency domain prediction codes are frequently used for calculation of low frequency sound transmission in and sound radiation from IC-engine exhaust and intake systems, even though nonlinear time domain models are also developing fast. To calculate insertion loss of mufflers or the level of radiated sound information about the engine as an acoustic source is needed. The source model used in the low frequency plane wave range is often the linear time invariant one-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. It is therefore of interest to have models taking weak non-linearity into account while still maintaining a simple method for interfacing the source model with a linear frequency domain model for the attached exhaust or intake system. Some years ago a model which can consider weakly non-linear sources was presented, which gave an improvement over the traditional two-load technique for determining source data from experiments. It is however fairly complicated to implement and has not been used a lot. In this paper an alternative technique based on so called polyharmonic distortion modeling, used for nonlinear characterization of microwave systems is introduced and tested. Comparisons are made with the results from linear source models and the previously published weakly nonlinear source model. 

  • 4. Cracknell, R. F.
    et al.
    Head, R. A.
    McAllister, L. J.
    Andrae, Johan
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Octane sensitivity in gasoline fuels containing nitro-alkanes: A possible means of controlling combustion phasing for HCCI2009In: SAE technical paper series, ISSN 0148-7191Article in journal (Refereed)
    Abstract [en]

    Addition of nitroalkanes to gasoline is shown to reduce the octane quality. The reduction in the Motor Octane Number (MON) is greater than the reduction in the Research Octane Number (RON). In other words addition of nitroalkanes causes an increase in octane sensitivity. The temperature of the compressed air/fuel mixture in the MON test is higher then in the RON test. Through chemical kinetic modelling, we are able to show how the temperature dependence of the reactions responsible for break-up of the nitroalkane molecule can lead to an increase in octane sensitivity. Results are presented from an Homogenous Charge Compression Ignition (HCCI) engine with a homogeneous charge in which the air intake temperature was varied. When the engine was operated on gasoline-like fuels containing nitroalkanes, it was observed that the combustion phasing was much more sensitive to the air intake temperature. This suggests a possible means of controlling combustion phasing for HCCI.

  • 5.
    Crescenzo, Domenico
    et al.
    KTH.
    Olsson, Viktor
    KTH.
    Arco Sola, Javier
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Wu, Hongwen
    KTH.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Lycke, Eric
    Leufven, O.
    Stenlåås, Ola
    Turbocharger Speed Estimation via Vibration Analysis2016In: SAE technical paper series, ISSN 0148-7191, Vol. 2016-April, no AprilArticle in journal (Refereed)
    Abstract [en]

    Due to demanding legislation on exhaust emissions for internal combustion engines and increasing fuel prices, automotive manufacturers have focused their efforts on optimizing turbocharging systems. Turbocharger system control optimization is difficult: Unsteady flow conditions combined with not very accurate compressor maps make the real time turbocharger rotational speed one of the most important quantities in the optimization process. This work presents a methodology designed to obtain the turbocharger rotational speed via vibration analysis. Standard knock sensors have been employed in order to achieve a robust and accurate, yet still a low-cost solution capable of being mounted on-board. Results show that the developed method gives an estimation of the turbocharger rotational speed, with errors and accuracy acceptable for the proposed application. The method has been evaluated on a heavy duty diesel engine.

  • 6. Fairbrother, R.
    et al.
    Bodén, Hans
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Flow acoustics.
    Glav, Ragnar
    Linear acoustic exhaust system simulation using source data from non linear simulation2005In: SAE technical paper series, ISSN 0148-7191Article in journal (Refereed)
    Abstract [en]

    Both linear (frequency domain) and non-linear (time domain) prediction codes are used for the simulation of duct acoustics in exhaust systems. Each approach has its own set of advantages and disadvantages. One disadvantage of the linear method is that information about the engine as an acoustic source is needed in order to calculate the insertion loss of mufflers or the level of radiated sound. The source model used in the low frequency plane wave range is the linear time invariant 1-port model. This source characterization data is usually obtained from experimental tests where multi-load methods and especially the two-load method are most commonly used. These measurements are time consuming and expensive. However, this data can also be extracted from an existing 1-D non-linear CFD code describing the engine gas exchange process. The pressure and velocity predictions from two acoustic load cases can be used to determine the source strength and impedance at a particular location in the exhaust line. This has been done at a location downstream of the turbocharger in the exhaust system of a heavy diesel truck over a number of speeds and engine loads. This source data is then used in a linear simulation of the exhaust line to predict sound pressure levels at a free field microphone position. The predicted source data and sound output at the microphone position is validated against measured data. The results show that you can obtain reasonably accurate source data and approximate free field sound pressure level predictions using non linear simulation in a linear acoustic model of the exhaust system. This technique can be used to extend the use of linear acoustic simulations to models of the complete exhaust line with the characterized engine as a source and exhaust sound output as a result.

  • 7. Fairbrother, R.
    et al.
    Varhos, Eric
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Acoustic simulation of an automotive muffler with perforated baffles and pipes2007In: SAE technical paper series, ISSN 0148-7191Article in journal (Refereed)
    Abstract [en]

    A complex automotive muffler consisting of multiple chambers, perforated baffles and pipes with perforated sections is simulated with both a linear and non linear solver in regard to duct acoustics. The goal is to be able to predict the acoustic performance of the muffler and correctly assess the effect of any changes to the muffler configuration. The linear solver is a frequency domain code using the transfer matrix method to predict the acoustic performance. The non linear solver is a time domain code using a finite volume method to predict the flow distribution and pressure drop across the muffler. A recently developed linear acoustic model for perforates has been applied to the perforated sections of the automotive muffler. This includes different configurations of the muffler both with and without flow. The perforate model with flow requires the correct flow distribution throughout the muffler in terms of through flow and grazing flow for each perforated section. This flow distribution is determined from the non linear simulation of the different muffler configurations. This same code can also be used to determine the pressure drop across the muffler and thereby assess the effect of the muffler on engine performance. The predicted transmission loss for different muffler configurations, both with and without flow, has been validated against measured data. The predicted pressure drop of the muffler configurations has also been validated against measured data.

  • 8.
    Glav, R
    et al.
    Scania CV, Sweden .
    Karlsson, Mikael
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    The flow reversal resonator: basic concept and influence of mean flow2007In: SAE technical paper series, ISSN 0148-7191Article in journal (Refereed)
    Abstract [en]

    The flow reversal chamber is a commonly used element in practical silencer design. To lower its fundamental eigenfrequency, it is suggested to acoustically short circuit the inlet and outlet duct. In the low frequency limit such a configuration will correspond to a Helmholtz resonator, but with a choked flow through the short circuit, the main flow will be forced through the expansion volume. For the proposed concept, the flow reversal resonator, a theoretical model is derived and presented together with transfer matrix simulations. The possible extension to a semi active device as well as the influence of mean flow on the system is investigated experimentally. Finally the concept is implemented on a truck silencer. The results indicate that the flow reversal resonator would prove an interesting complement to traditional side branch resonators. The attenuation bandwidth is broader and it can be packaged very efficiently. Mean flow effects are still an issue and should be studied further.

  • 9.
    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.

  • 10.
    Hellström, Fredirk
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Renberg, Ulrica
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Westin, Fredrik
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO (closed 20101231).
    Fuchs, Laszlo
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO (closed 20101231).
    Predictions of the Performance of a Radial Turbine with Different Modeling Approaches: Comparison of the Results from 1-D and 3-D CFD2010In: SAE technical paper series, ISSN 0148-7191, no 01-1223Article in journal (Refereed)
    Abstract [en]

    In this paper, the performance of a radial turbine working under pulsatile flow conditions is computed with two different modeling approaches, time resolved 1-dimensional (1-D) and 3-dimensional (3-D) CFD. The 1-D modeling approach is based on measured turbine maps which are used to compute the mass flow rate and work output from the turbine for a given expansion ratio and temperature at the inlet. The map is measured under non-pulsatile flow conditions, and in the 1-D method the turbine is treated as being a quasi-stationary flow device. In the 3-D CFD approach, a Large Eddy Simulation (LES) turbulence approach is used. The objective of LES is to explicitly compute the large scales of the turbulence while modeling the effects of the unresolved scales.

    Three different cases are considered, where the simplest case only consist of the turbine and the most complex case consist of an exhaust manifold and the turbine. Both time resolved data, such as pressure ratio, temperature and shaft torque and time mean data from the two different modeling approaches are compared. The results show that the computed time mean shaft power differs between the two different modeling approaches with as much as 100%. Since the considered operation point for the engine in this study is 1500 rpm with wide open throttle, the turbine operates in an area where the turbine map is extrapolated. Only by using a few operation points from CFD to extend the map, an improvement is achieved for the 1-D results, but still the deviation is large. Also, the pressure ratio and temperature drop over the turbine differs for the used modeling approaches. The causes for the deviations are assessed and discussed to get a better understanding of eventually limitations of the 1-D modeling approach.

  • 11.
    Holen, Peter
    et al.
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Thorvald, Boris
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Load case characterization and modal coordinate estimates from damper displacements2004In: SAE technical paper series, ISSN 0148-7191, no 2004-01-2713Article in journal (Refereed)
  • 12.
    Holmberg, Ted
    et al.
    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.
    Stenlaas, O.
    Pressure Amplitude Influence on Pulsating Exhaust Flow Energy Utilization2018In: SAE technical paper series, ISSN 0148-7191, Vol. 2018-AprilArticle in journal (Refereed)
    Abstract [en]

    A turbocharged Diesel engine for heavy-duty on-road vehicle applications employs a compact exhaust manifold to satisfy transient torque and packaging requirements. The small exhaust manifold volume increases the unsteadiness of the flow to the turbine. The turbine therefore operates over a wider flow range, which is not optimal as radial turbines have narrow peak efficiency zone. This lower efficiency is compensated to some extent by the higher energy content of the unsteady exhaust flow compared to steady flow conditions. This paper experimentally investigates the relationship between exhaust energy utilization and available energy at the turbine inlet at different degrees of unsteady flow. A special exhaust manifold has been constructed which enables the internal volume of the manifold to be increased. The larger volume reduces the exhaust pulse amplitude and brings the operating condition for the turbine closer to steady-flow. The operating points are defined by engine speed and boost pressure. From these values the isentropic turbine work is calculated and with the measured compressor work the mean turbine efficiency is estimated. The results show that more energy has to be provided to the turbine at larger exhaust manifold volumes to maintain a constant boost pressure, indicating that the efficiency of the turbine decreases. 

  • 13.
    Holmberg, Ted
    et al.
    KTH.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Stenlaas, O.
    Pressure Ratio Influence on Exhaust Valve Flow Coefficients2017In: SAE technical paper series, ISSN 0148-7191, Vol. 2017-March, no MarchArticle in journal (Refereed)
    Abstract [en]

    In one dimensional engine simulation software, flow losses over complex geometries such as valves and ports are described using flow coefficients. It is generally assumed that the pressure ratio over the valve has a negligible influence on the flow coefficient. However during the exhaust valve opening the pressure difference between cylinder and port is large which questions the accuracy of this assumption. In this work the influence of pressure ratio on the exhaust valve flow coefficient has been investigated experimentally in a steady-flow test bench. Two cylinder heads, designated A and B, from a Heavy-Duty engine with different valve shapes and valve seat angles have been investigated. The tests were performed with both exhaust valves open and with only one of the two exhaust valves open. The pressure ratio over the exhaust port was varied from 1.1:1 to 5:1. For case A1 with a single exhaust valve open, the flow coefficient decreased significantly with pressure ratio. This trend was not replicated for the other single valve case B1, as pressure ratio only had a small influence on the flow coefficient. For the twin valve case A2, the pressure ratio influence was confined to the lower range of valve lifts as the limiting factor was the exhaust port outlet at higher valve lifts. The flow coefficient for the twin valve case B2 increased with pressure ratio in the mid-range of valve lifts.

  • 14.
    Juhlin, Magnus
    et al.
    KTH, Superseded Departments, Vehicle Engineering.
    Eriksson, Peter
    A Vehicle Parameter Study on Crosswind Sensitivity of Buses2004In: SAE technical paper series, ISSN 0148-7191, no 2004-01-2612Article in journal (Refereed)
    Abstract [en]

    Incidents with heavy vehicles have brought the issue of directional stability of buses under the influence of crosswind gusts into focus. In this work the directional stability of buses when exposed to crosswind gusts has been investigated by performing a parameter study on a MBS vehicle-model combined with a generalised cross­wind gust model. The study shows that the most important parameters are the magnitude of the yaw moment overshoot at gust entry and the weight distribution in combination with the location of the aerodynamic pressure centre.

  • 15.
    Kabral, Raimo
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Du, Lin
    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).
    Knutsson, M.
    Optimization of Compact Non-Fibrous Silencer for the Control of Compressor Noise2016In: SAE technical paper series, ISSN 0148-7191, Vol. 2016-June, no JuneArticle in journal (Refereed)
    Abstract [en]

    The concept of IC engine downsizing is a well-adapted industry standard, enabling better fuel conversion efficiency and the reduction of tailpipe emissions. This is achieved by utilizing different type of superchargers. As a consequence, the additional charger noise emission, at the IC engine inlet, can become a problem. In order to address such problem, the authors of this work have recently proposed a novel dissipative silencer for effective and robust noise control of the compressor. Essentially, it realizes an optimal flow channel impedance, referred to as the Cremer impedance. This is achieved by means of a straight flow channel with a locally reacting wall consisting of air cavities covered by an acoustic resistance, e.g., a micro-perforated panel (MPP). In this paper, an improved optimization method of this silencer is presented. The classical Cremer impedance model is modified to account for mean flow dependence of the optimal wave number. This modified model leads to significantly different impedance values compared to the classical model and consequently, the high damping of the classical model (hundreds of dB/m) is further increased. Moreover, the modeling herein, is performed by solving the convective wave equation, vital for accounting mean flow effects. The presented model is finally validated by experimental results included in the paper.

  • 16.
    Kabral, Raimo
    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).
    Rammal, H.
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Acoustical methods for investigating turbocharger flow instabilities2013In: SAE technical paper series, ISSN 0148-7191, Vol. 4, p. 2013-01-1879-Article in journal (Refereed)
    Abstract [en]

    In order to increase the internal combustion engine efficiency turbocharging is today widely used. The trend, in modern engine technology, is towards higher boost pressures while keeping the combustion pressure raise relatively small. The turbocharger surge occurs if the pressure at the outlet of the compressor is greater than it can maintain, i.e., a reverse flow will be induced. In presence of such flow conditions instabilities will occur which can couple to incident acoustic (pressure) waves and amplify them. The main objective of the present work is to propose a novel method for investigation of turbocharger flow instabilities or surge precursors. The method is based on the determination of the acoustic two-port data. The active part of this data describes the sound generation and the passive part the scattering of sound. The scattering data will contain information about flow-acoustic interaction and amplification of sound that could occur close to surge. Here the existence of such amplification will be investigated for a compressor operating at different operating points including points near the surge line. In addition the generated sound for reflection-free conditions is also investigated on both the up- and downstream side. All the measurements have been carried out in the unique CCGEx test rig for two-port testing of turbo-compressors.

  • 17.
    Kabral, Raimo
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Rämmal, Hans
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Auriemma, Fabio
    Luppin, Janek
    Koiv, Risto
    Tiikoja, Heiki
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Lavrentjev, Jüri
    A novel design for cruiser type motorcycle silencer based on micro-perforated elements2012In: SAE technical paper series, ISSN 0148-7191, Vol. 4Article in journal (Refereed)
    Abstract [en]

    Regulations stipulating the design of motorcycle silencers are strict, especially when the unit incorporates fibrous absorbing materials. Therefore, innovative designs substituting such materials while still preserving acceptable level of characteristic sound are currently of interest. Micro perforated elements are innovative acoustic solutions, which silencing effect is based on the dissipation of the acoustic wave energy in a pattern of sub-millimeter apertures. Similarly to fibrous materials the micro-perforated materials have been proved to provide effective sound absorption in a wide frequency range. Additionally, the silencer is designed as a two-stage system that provides an optimal solution for a variety of exploitation conditions. In this paper a novel design for a cruiser type motorcycle silencer, based on micro-perforated elements, is presented. It has been demonstrated that the micro-perforated elements can successfully be used to achieve high attenuation of IC-engine noise in strictly limited circumstances. A technical description of the design and manufacturing of the prototype silencer is given and technological issues are discussed. The acoustical and aerodynamical performance of the silencer is characterized by transmission loss and pressure drop data. The influence of the two-stage system valve operation has been analyzed by studying the acoustics data and engine output characteristics. In addition to the experimental investigations, numerical 1-D models were developed for the optimization of the silencer geometry and the results are compared in a number of operating conditions. The studies have resulted in development of a silencer system for a small series cruiser type motorcycle. The first silencer prototypes have been tested on the motorcycle. While maintaining acceptable pressure drop characteristics, it has proven to comply with standard noise criteria without incorporating fibrous materials. The radiated motorcycle sound, as one of the key features of successful design, has been evaluated. The sound design has been recognized as well suitable for the product.

  • 18.
    Kalghatgi, Gautam T.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Risberg, Per
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Ångström, Hans-Erik
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Partially pre-mixed auto-ignition of gasoline to attain low smoke and low NOx at high load in a compression ignition engine and comparison with a diesel fuel2007In: SAE technical paper series, ISSN 0148-7191Article in journal (Refereed)
    Abstract [en]

    A Swedish MK1 diesel fuel and a European gasoline of ∼95 RON have been compared in a single cylinder CI engine operating at 1200 RPM with an intake pressure of 2 bar abs., intake temperature of 40°C and 25% stoichiometric EGR at different fuelling rates and using different injection strategies. For the same operating conditions, gasoline always gives much lower smoke compared to the diesel fuel because of its higher ignition delay; this usually allows the heat release to be separate in time from the injection event. NOx can be controlled by EGR. With dual injection, for diesel fuel, there can be significant heat release during the compression stroke because of the pilot injection earlier in the compression stroke. For a fixed total fuelling rate, compared to single injection, this reduces fuel efficiency and increases the lowest achievable level of smoke. With gasoline, pilot injection helps reduce the maximum heat release rate for a given IMEP and enables heat release to occur later with low cyclic variation compared to single injection. This enables higher mean IMEP to be reached with lower smoke, NOx and maximum heat release rate compared to single injection. One of the operating points reached with gasoline with double injection had mean IMEP of 15.95 bar (stdev. 0.112 bar), AVL smoke opacity of 0.33% (FSN < 0.07), ISNOx of 0.58 g/kWh, ISFC of 179 g/kWh, ISHC of 2.9 g/kWh, ISCO of 6.8 g/kWh and peak pressure of ∼ 120 bar. At the same operating conditions, to get such low level of smoke with Swedish MK1 diesel fuel, IMEP has to be below 6.5 bar. There is scope for further improvements by increasing intake pressure and the EGR level and through optimisation of the injection and mixture preparation strategy e.g. more injection pulses and injector design e.g. more holes.

  • 19.
    Karlsson, M.
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Flow acoustics.
    Glav, Ragnar
    Aeroacoustics of duct branches: with application to silencers2011In: SAE technical paper series, ISSN 0148-7191Article in journal (Refereed)
    Abstract [en]

    The inclusion of flow-acoustic interaction effects in linear acoustic multiport models has been studied. It is shown, using a T-junction as illustration example, that as long the acoustic system is linear the required information is included in a scattering matrix obtained by experimental or numerical studies. Assuming small Mach numbers and low frequencies-as in most automotive silencer applications-the scattering matrix for the T-junction can be approximated using quasi-steady models. Models are derived that holds for all possible configurations of grazing and bias flow in the T-junctions. The derived models are then used to predict the performance of a novel silencer concept, where a resonator is formed by acoustically short-circuiting the inlet and outlet ducts of a flow reversal chamber. The agreement between experiments and simulations is excellent, justifying the use of the quasi-steady modeling approach.

  • 20. Knutsson, M.
    et al.
    Kjellson, E.
    Glover, R.
    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).
    In-Duct Acoustic Source Data for Roots Blowers2017In: SAE technical paper series, ISSN 0148-7191, no JuneArticle in journal (Refereed)
    Abstract [en]

    Increased demands for reduction of fuel consumption and CO2 emissions are driven by the global warming. To meet these challenges with respect to the passenger car segment the strategy of utilizing IC-engine downsizing has shown to be effective. In order to additionally meet requirements for high power and torque output supercharging is required. This can be realized using e.g. turbo-chargers, roots blowers or a combination of several such devices for the highest specific power segment. Both turbo-chargers and roots blowers can be strong sources of sound depending on the operating conditions and extensive NVH abatements such as resonators and encapsulation might be required to achieve superior vehicle NVH. For an efficient resonator tuning process in-duct acoustic source data is required. No published studies exists that describe how the gas exchange process for roots blowers can be described by acoustic sources in the frequency domain. This paper presents an experimental study that aims to investigate if a linear time invariant acoustic 1-port model can represent the in-duct sound source of a roots blower in- and outlet. Different operating conditions are investigated for a wide rotation speed range. The results show that it is possible to use a linear acoustic source model to represent a roots blower and that sound predictions can be performed with good accuracy.

  • 21. Knutsson, M.
    et al.
    Lennblad, J.
    Bodén, Hans
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    A study on acoustical time-domain two-ports based on digital filters with application to automotive air intake systems2011In: SAE technical paper series, ISSN 0148-7191Article in journal (Refereed)
    Abstract [en]

    Analysis of pressure pulsations in ducts is an active research field within the automotive industry. The fluid dynamics and the wave-transmission properties of internal combustion (IC) engine intake and exhaust systems contribute to the energy efficiency of the engines and are hence important for the final amount of CO2 that is emitted from the vehicles. Sound waves, originating from the pressure pulses caused by the in- and outflow at the engine valves, are transmitted through the intake and exhaust system and are an important cause of noise pollution from road traffic at low speeds. Reliable prediction methods are of major importance to enable effective optimization of gas exchange systems. The use of nonlinear one-dimensional (1D) gas dynamics simulation software packages is widespread within the automotive industry. These time-domain codes are mainly used to predict engine performance parameters such as output torque and power but can also give estimates of radiated orifice noise. However, components with large cross-dimensions, fluid-structural interaction, frequency-dependent damping and boundary conditions are difficult to describe analytically in 1D in the time domain. Since a frequency-domain description in the form of a two-port is normally straightforward to obtain analytically, numerically or experimentally it is of interest to introduce these in time-domain calculations as black box models. This paper suggests the use of Finite Impulse Response (FIR) filters as a method to achieve this improvement. An initial study is presented where tabulated frequency-domain two-port data representing an air cleaner unit on the impedance form is inversely transformed to the time domain and used as FIR filters in nonlinear time-domain 1D calculations with good accuracy. Favourable attenuation, achieved from the filter paper itself, is demonstrated experimentally as well as by the calculations. 

  • 22. Knutsson, M.
    et al.
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Acoustic analysis of charge air coolers2007In: SAE technical paper series, ISSN 0148-7191Article in journal (Refereed)
    Abstract [en]

    This paper presents the results from a study of the acoustic properties of charge air coolers for passenger cars. Charge air coolers are used on turbo charged engines to increase the overall performance. The cooling of the charged air results in higher density and thus volumetric efficiency. Important for petrol engines is also that the knock margin increases with reduced charge air temperature. A property that is still not very well investigated is the sound transmission through charge air coolers. The pressure drop in the narrow cooling tubes results in frequency dependent resistive effects on the transmitted sound that is non negligible. Since the cross dimensions of the connecting tanks, located on each side of the cooling tubes, are big compared to the wave length for engine breathing noise, three dimensional effects can also be of importance. In this study an acoustic two-port for sound propagation in narrow tubes, including the effect of viscous and thermal boundary layers, is combined with three dimensional acoustic finite element modeling to represent a complete air-to-air charge air cooler. From this a linear frequency domain model for the entire charge air cooler is extracted in the form of a two-port. The frequency dependent transmission loss is calculated and compared with corresponding experimental data. Finally, there is a discussion of the results and on how the acoustic response of charge air coolers could be modified.

  • 23.
    Knutsson, Magnus
    et al.
    Volvo Car Corporation, Sweden .
    Bodén, Hans
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    IC-engine intake acoustic source data from non-linear simulations2007In: SAE technical paper series, ISSN 0148-7191Article in journal (Refereed)
    Abstract [en]

    Non-linear 1-D CFD time domain prediction codes are used to calculate the performance of the gas exchange process for IC-engines. These softwares give time-varying pressures and velocities in the exhaust and intake systems. They could therefore in principle be used to predict radiated orifice noise. However, the accuracy is not sufficient for them to be used as a virtual design tool. More accurate results might be provided by dividing the problem into a source domain and a transmission domain and use linear 3-D frequency domain codes to describe the transmission part. Radiated shell noise and frequency dependent damping could also be included in the frequency domain models. The simplest source model used in the low frequency plane wave range for simulation of dominating engine harmonics is the linear time invariant 1-port model. This acoustic source data is usually obtained from experimental tests where the multi-load methods and especially the two-load method are most commonly used. The main limitations of these tests are that they are time consuming, expensive and require physical hardware which prevents them from being used for early predictions. It would therefore be of interest to extract the acoustic source data from the existing 1-D CFD gas exchange models. This paper presents a comparison between acoustic source data, obtained applying the two-load technique to measurements on a six-cylinder personal car petrol engine, and to 1-D simulations of identical intake systems on the same engine. The degree of non-linearity in the results is discussed as well as the choice of source type and its relation to engine properties. The results show that it is possible to obtain reasonably accurate source strength as well as source impedance estimates, for the intake side, from 1-D gas exchange simulations.

  • 24. Königsson, F.
    et al.
    Risberg, Per
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Ångström, Hans-Erik
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Nozzle Coking in CNG-Diesel Dual Fuel Engines2014In: SAE technical paper series, ISSN 0148-7191, Vol. October, article id 2014-01-2700Article in journal (Refereed)
    Abstract [en]

    Nozzle coking in diesel engines has received a lot of attention in recent years. High temperature in the nozzle tip is one of the key factors known to accelerate this process. In premixed CNG-diesel dual fuel, DDF, engines a large portion of the diesel fuel through the injector is removed compared to regular diesel operation. This can result in very high nozzle temperatures. Nozzle hole coking can therefore be expected to pose a significant challenge for DDF operation. In this paper an experimental study of nozzle coking has been performed on a DDF single cylinder engine. The objective was to investigate how the rate of injector nozzle hole coking during DDF operation compares to diesel operation. In addition to the nozzle tip temperature, the impact of other parameters on coking rate was also of interest. Start of injection, , diesel substitution ratio and common rail pressure were varied in two levels starting from a common baseline case, resulting in a total of 10 operating cases. These cases were run for three and a half hours in steady-state, using standard injectors and zinc contaminated diesel to accelerate the coking process. The zinc was added in form of zinc neodecanoate, similar to the practice in the standardized tests used to study nozzle coking in diesel engines. After the tests the injectors were disassembled and the steady state flow through the injector nozzles was measured to isolate the effect of nozzle hole coking. The results show significant coking from only a few hours of testing. The most challenging case was the combination of high nozzle tip temperature from DDF operation with low injection pressure. The flow loss from operation in DDF mode was far more severe compared to diesel operation. Elemental analysis of the deposits shows similar composition resulting from diesel and DDF operation. In the DDF deposits higher concentrations of elements from the engine oil were found in addition to higher carbon content. It is concluded that injector nozzle coking is a challenge which requires appropriate attention when developing DDF engines.

  • 25.
    Mahendar, Senthil Krishnan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Erlandsson, Anders
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Adlercreutz, L.
    Challenges for Spark Ignition Engines in Heavy Duty Application: A Review2018In: SAE technical paper series, ISSN 0148-7191, Vol. 2018-AprilArticle in journal (Refereed)
    Abstract [en]

    Spark Ignition (SI) engines operating on stoichiometric mixtures can employ a simple three-way catalyst as after-treatment to achieve low tailpipe emissions unlike diesel engines. This makes heavy duty (HD) SI engines an attractive proposition for low capital cost and potentially low noise engines, if the power density and efficiency requirement could be met. Specific torque at low speeds is limited in SI engines due to knock. In HD engines, the higher flame travel distances associated with higher bore diameters exacerbates knock due to increased residence time of the end gas. This report reviews the challenges in developing HD SI engines to meet current diesel power density. It also focuses on methods to mitigate them in order to achieve high thermal efficiency while running on stoichiometric condition. High octane renewable fuels are seen as a key enabler to achieve the performance level required in such applications. Apart from higher octane rating, the effect of higher latent heat of vaporization in liquid alcohol fuels was found to be beneficial in all operating conditions as it tended to reduce in-cylinder temperature and associated heat loss of the engine. Exhaust gas recirculation (EGR) was seen to be beneficial both at full load in limiting knock and part load conditions to decrease pumping losses. Increased in-cylinder turbulence was also seen to be beneficial in limiting knock as it reduces residence time of the end gas. Results and trends of combinations of these factors are discussed with respect to increasing engine specific torque and efficiency. The effect on emissions and part load conditions is included where results are available and gaps in knowledge are presented. 

  • 26.
    Mohan, Naveen
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Törngren, Martin
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    AD-eye: A co-simulation platform for early verification of functional safety concepts2019In: SAE technical paper series, ISSN 0148-7191, Vol. 2019-April, no AprilArticle in journal (Refereed)
    Abstract [en]

    Automated Driving is revolutionizing many of the traditional ways of operation in the automotive industry. The impact on safety engineering of automotive functions is arguably one of the most important changes. There has been a need to re-think the impact of the partial or complete absence of the human driver (in terms of a supervisory entity) in not only newly developed functions but also in the qualification of the use of legacy functions in new contexts. The scope of the variety of scenarios that a vehicle may encounter even within a constrained Operational Design Domain, and the highly dynamic nature of Automated Driving, mean that new methods such as simulation can greatly aid the process of safety engineering. This paper discusses the need for early verification of the Functional Safety Concepts (FSCs), details the information typically available at this stage in the product lifecycle, and proposes a co-simulation platform named AD-EYE designed for exploiting the possibilities in an industrial context by evaluating design decisions and refining Functional Safety Requirements based on a reusable scenario database. Leveraging our prior experiences in developing FSCs for Automated Driving functions, and the preliminary implementation of co-simulation platform, we demonstrate the advantages and identify the limitations of using simulations for refinement and early FSC verification using examples of types of requirements that could benefit from our methodology.

  • 27.
    Mohan, Naveen
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Törngren, Martin
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Behere, Sagar
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    A Method towards the Systematic Architecting of Functionally Safe Automated Driving- Leveraging Diagnostic Specifications for FSC design2017In: SAE technical paper series, ISSN 0148-7191, Vol. 2017-March, no MarchArticle in journal (Refereed)
    Abstract [en]

    With the advent of ISO 26262 there is an increased emphasis on top-down design in the automotive industry. While the standard delivers a best practice framework and a reference safety lifecycle, it lacks detailed requirements for its various constituent phases. The lack of guidance becomes especially evident for the reuse of legacy components and subsystems, the most common scenario in the cost-sensitive automotive domain, leaving vehicle architects and safety engineers to rely on experience without methodological support for their decisions. This poses particular challenges in the industry which is currently undergoing many significant changes due to new features like connectivity, servitization, electrification and automation. In this paper we focus on automated driving where multiple subsystems, both new and legacy, need to coordinate to realize a safety-critical function. This paper introduces a method to support consistent design of a work product required by ISO 26262, the Functional Safety Concept (FSC). The method arises from and addresses a need within the industry for architectural analysis, rationale management and reuse of legacy subsystems. The method makes use of an existing work product, the diagnostic specifications of a subsystem, to assist in performing a systematic assessment of the influence a human driver, in the design of the subsystem. The output of the method is a report with an abstraction level suitable for a vehicle architect, used as a basis for decisions related to the FSC such as generating a Preliminary Architecture (PA) and building up argumentation for verification of the FSC. The proposed method is tested in a safety-critical braking subsystem at one of the largest heavy vehicle manufacturers in Sweden, Scania C.V. AB. The results demonstrate the benefits of the method including (i) reuse of pre-existing work products, (ii) gathering requirements for automated driving functions while designing the PA and FSC, (iii) the parallelization of work across the organization on the basis of expertise, and (iv) the applicability of the method across all types of subsystems.

  • 28.
    Puttige, Anjan Rao
    et al.
    KTH.
    Hamberg, Robin
    KTH.
    Linschoten, Paul
    KTH.
    Reddy, G.
    KTH.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Stenlåås, Ola
    Surge Detection Using Knock Sensors in a Heavy Duty Diesel Engine2017In: SAE technical paper series, ISSN 0148-7191, Vol. 2017Article in journal (Refereed)
    Abstract [en]

    Improving turbocharger performance to increase engine efficiency has the potential to help meet current and upcoming exhaust legislation. One limiting factor is compressor surge, an air flow instability phenomenon capable of causing severe vibration and noise. To avoid surge, the turbocharger is operated with a safety margin (surge margin) which, as well as avoiding surge in steady state operation, unfortunately also lowers engine performance. This paper investigates the possibility of detecting compressor surge with a conventional engine knock sensor. It further recommends a surge detection algorithm based on their signals during transient engine operation. Three knock sensors were mounted on the turbocharger and placed along the axes of three dimensions of movement. The engine was operated in load steps starting from steady state. The steady state points of operation covered the vital parts of the engine speed and load range. The collected data was analysed with the objective of extracting information of a surging or non-surging compressor. In the charging system studied, the knock sensors detected a profound frequency peak between 5.0 Hz to 7.0 Hz. Another surge related frequency component of about 25 kHz was also observed, dependent on the turbocharger speed. Two surge detection algorithms were evaluated, one based on short time Fourier transform (STFT) and one based on the correlation integral (CI). These algorithms where then validated against temperature measurements at the compressor inlet and visual observation of oscillations of the air inlet piping. The surge detection algorithms were compared for accuracy and repeatability. The accuracy of the methods was found to be 73 % and 71 % respectively when compared to the temperature rise in the compressor inlet.

  • 29.
    Rehnberg, Adam
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Drugge, Lars
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Vehicle Dynamics.
    Pitch comfort optimisation of a front end loader using a hydropneumatic suspension2007In: SAE technical paper series, ISSN 0148-7191, no 2146, p. 67-76Article in journal (Refereed)
    Abstract [en]

    Front end loader vehicles are prone to excessive pitching when travelling at high speed, partly due to the absence of axle suspension. This paper studies the fundamental design of a hydropneumatic suspension for a medium wheel loader. The vehicle is analysed using an analytical frequency response model as well as multibody simulations. Results show that favourable pitching response can be achieved by increasing the rear axle stiffness, but also that a similar effect is achieved with higher front axle stiffness. For the loaded vehicle, it is also found that the benefits of an optimal stiffness distribution are offset to some extent by the reduction in relative damping as the vehicle mass and inertia increases. Thus, it is desirable to increase suspension damping under load to maintain a suitable level of relative damping.

  • 30.
    Reifarth, Simon
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Kristensson, E.
    Borggren, J.
    Sakowitz, Alexander
    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), Centres, Competence Center for Gas Exchange (CCGEx).
    Analysis of EGR/Air Mixing by 1-D Simulation, 3-D Simulation and Experiments2014In: SAE technical paper series, ISSN 0148-7191, Vol. 2014-OctoberArticle in journal (Refereed)
    Abstract [en]

    The use of EGR for NO<inf>X</inf> reduction is today a standard technology for diesel engines. The mixing of air and EGR is an important issue, especially for high-pressure EGR-systems. An uneven distribution of EGR between the cylinders can lead to higher overall engine emissions when some cylinders produce more soot, others more NO<inf>X</inf> than they would with a perfectly even distribution. It is therefore important to understand the processes that control the mixing between air and EGR. The mixing is influenced by both the geometry of the mixing area and the pulsating nature of the flow. The aim of this work is to point out the high importance of the pulses present in the EGR-flow. By simulation in 1-D and 3-D as well as by a fast measurement method, it is shown that the EGR is transported in the air flow in packets. This implies that the timing between intake valve opening and the positioning of the EGR packets has a high influence of the distribution of EGR between the cylinders. The ability of 1-D and 3-D simulation to predict the behavior is evaluated. It is shown how standard 1-D simulations fail to predict the pulsation effects. Furthermore, it is shown how 1-D models can be modified to give results reasonably close to the 3-D simulation results.

  • 31.
    Reifarth, Simon
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Rajagopal, Vijayaraghunathan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Gritzun, Krister
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Ångström, Hans-Erik
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Measuring and Simulating EGR-Distribution on a HD-Diesel Engine2014In: SAE technical paper series, ISSN 0148-7191, Vol. 2014-OctoberArticle in journal (Refereed)
    Abstract [en]

    The distribution of EGR between the cylinders of an internal combustion engine has been shown to have large impact on the engine emissions. Especially at high EGR, the combustion reacts sensibly to variations in the EGR-rate. A cylinder that receives excessive EGR produces soot emissions while a cylinder with too little EGR has increased NO<inf>X</inf>-formation. It is therefore important to have knowledge about the mixing of air and EGR in an engine. This study compares two different EGR-mixing measurement methods. The first is based on CO<inf>2</inf> measurement with standard probes, placed at 36 different locations in the intake manifold of the engine. The second method uses a laser beam and a detector to gain information about the mixing with a high time-resolution. Additionally, 1-D simulations are used to gain information about the mixing process. To vary the mixing process on the engine, two different air/EGR mixers are used and their mixing performance is evaluated.

  • 32.
    Reifarth, Simon
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Rajagopal, Vijayaraghunathan
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Gritzun, Krister
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Ångström, Hans-Erik
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Measuring and simulating EGR-distribution on a HD-diesel engineIn: SAE technical paper series, ISSN 0148-7191Article in journal (Other academic)
    Abstract [en]

    The distribution of EGR between the cylinders of an internalcombustion engine has been shown to have large impact onthe engine emissions. Especially at high EGR, the combustionreacts sensibly to variations in the EGR-rate. A cylinder thatreceives excessive EGR produces soot particles while acylinder with too little EGR has increased NOX-emission. It istherefore important to have knowledge about the mixing in anengine.This study compares two different EGR-mixing measurementmethods. The first is based on CO2 measurement withstandard probes, placed at 36 different locations in the engine.The second method uses a laser beam and a detector to gaininformation about the mixing with a high time-resolution.Additionally, 1-D simulations are used to gain informationabout the mixing process.To vary the mixing process on the engine, two differentair/EGR mixers are used and their mixing performance isevaluated.

  • 33.
    Renberg, Ulrica
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Westin, Fredrik
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.). KTH, School of Industrial Engineering and Management (ITM), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO (closed 20101231).
    Ångström, Hans-Erik
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Fuchs, Laszlo
    KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Mechanics of Industrial Processes.
    Study of Junctions in 1-D & 3-D Simulation for Steady and Unsteady Flow2010In: SAE technical paper series, ISSN 0148-7191, no 01-1050Article in journal (Refereed)
    Abstract [en]

    In this work a comparative study between 1-D and 3-D calculations has been performed on different junctions. The geometries are a 90° T-junction with an area ratio of unity and a 45° junction with an area ratio of 1.78 between the main pipe and the side branch. The latter case had an offset between the centerlines of the main and the branched pipe. The 3-D modeling framework uses the Reynolds Averaged Navier-Stokes (RANS) equations with the k-ε model both for the steady and the unsteady flow cases. The comparison is made both under steady and pulsating flow conditions. The aim has been to assess the 1-D/3-D differences in terms of measures for flow losses.

    There are large discrepancies between the 1-D and 3-D computed losses in junctions. The relative differences between 1-D and 3-D computed losses in isentropic power are 63 % and 175 % for the 90° and the 45 ° junctions without including the losses in downstream pipe legs. These figures are reduced to 12 % and 114 % respectively when including a straight pipe segment of one diameter downstream of the junction outlets.

    For the 90° junction at pulsating flow, the discrepancy in 1-D and 3-D computed loss is lower compared to the steady flow case if comparing only the losses in the junction, but similar to the steady discrepancy if including the downstream pipe losses. For the 45° junction, the discrepancies are much larger. The 1-D loss is near six times that of the corresponding 3-D value if comparing the losses in the junction alone, and 3 times the 3-D value if including the losses in 10 diameter of the outlet pipe.

  • 34. Rodgers, L.
    et al.
    Jeunnette, M.
    Biffard, R.
    Möller, Björn
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Wu, E.
    Matthys, K.
    Analyzing the limitations of the rider and electric motorcycle at the pikes peak international hill climb race2019In: SAE technical paper series, ISSN 0148-7191, Vol. 2019-April, no AprilArticle in journal (Refereed)
    Abstract [en]

    This paper describes a post-race analysis of team KOMMIT EVT's electric motorcycle data collected during the 2016 Pikes Peak International Hill Climb (PPIHC). The motorcycle consumed approximately 4 kWh of battery energy with an average and maximum speed of 107 km/h and 149 km/h, respectively. It was the second fastest electric motorcycle with a finishing time of 11:10.480. Data was logged of the motorcycle's speed, acceleration, motor speed, power, currents, voltages, temperatures, throttle position, GPS position, rider's heart rate and the ambient environment (air temperature, pressure and humidity). The data was used to understand the following factors that may have prevented a faster time: physical fitness of the rider, thermal limits of the motor and controller, available battery energy and the sprocket ratio between the motor and rear wheel. Even though the rider's heart rate implied a vigorous exercise intensity level, throttle values indicated that the rider wanted to go faster ∼33% of the time. The motor reached a steady-state temperature that was approximately 30°C below the maximum allowable temperature and thus could have handled more current. By analyzing additional thermal and current data, it was concluded that the motor controller was likely a limiting factor but not the battery capacity since only ∼2/3 of the total available battery energy was consumed. A model that estimates the optimal sprocket ratio was derived and validated; It was determined that using the optimal sprocket ratio of 62/12 would have decreased the finishing time by approximately 2 seconds.

  • 35. Rugland, C.
    et al.
    Stenlaas, O.
    Knock Sensor Based Virtual Cylinder Pressure Sensor2019In: SAE technical paper series, ISSN 0148-7191, Vol. 2019-January, no JanuaryArticle in journal (Refereed)
    Abstract [en]

    Typically the combustion in a direct injected compression ignited internal combustion engine is open-loop controlled. The introduction of a cylinder pressure sensor opens up the possibility of a virtual combustion sensor which could enable closed-loop combustion control and thus the potential to counteract effects such as engine part to part variation, component ageing and fuel quality diversity. Closed-loop combustion control requires precise, robust and preferably cheap sensors. This paper presents a virtual cylinder pressure sensor based on the signal from the inexpensive but well proven knock sensor. The method used to convert the knock sensor signal into a pressure estimate included the stages: Phase correcting the raw signal, Filtering the raw signal, Scaling the signal to known thermodynamic laws and provided engine sensors signals and Reconstructing parts of the signal with other known models and assumptions. The modelled cylinder pressure shows high correlation with the measured pressure trace and it was concluded that it is possible to estimate many important combustion parameters - such as maximum pressure, mass fraction burned and total heat release.

  • 36.
    Rugland, Christian
    et al.
    KTH.
    Stenlaas, O.
    Knock Sensor Based Virtual Combustion Sensor Signal Bias Sensitivity2018In: SAE technical paper series, ISSN 0148-7191, Vol. 2018-AprilArticle in journal (Refereed)
    Abstract [en]

    The combustion in a direct injected internal combustion engine is normally open-loop controlled. The introduction of cylinder pressure sensors enables a virtual combustion sensor which in turn enables closed-loop combustion control, and the possibility to counteract effects such as engine part-to-part variation, component ageing and fuel quality diversity. Closed-loop combustion control requires precise, robust and preferably cheap sensors. This paper presents an investigation of the robustness and the limitation of a knock sensor based virtual combustion sensor. This virtual combustion sensor utilize the common heat release analysis using a knock sensor based virtual cylinder pressure signal. Major virtual sensor error sources in a heavy-duty engine were identified as: the specific heat ratio model, the boost pressure and the crank angle phasing. The virtual sensor errors were quantified in relation to both the measured cylinder pressure and the total virtual sensor error. The tolerance analysis of the virtual sensor showed the signals of the crank angles 10% and 50% heat release as robust with low sensitivity to errors. An additional dependency found for the crank angle of 10% heat release was the compression ratio error. The study concluded that it is possible to estimate the mass fraction of 10% and 50% heat release accurately enough to make the virtual sensor an option for closed loop combustion control. The study was not able to prove the virtual sensor cylinder pressure signal, crank angle of burned fractions signals or total heat release signal capable of confident determination of the amount of biodiesel in fossil diesel. 

  • 37.
    Rämmal, Hans
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Acoustics of turbochargers2007In: SAE technical paper series, ISSN 0148-7191Article in journal (Refereed)
    Abstract [en]

    Noise from turbo-chargers is increasingly becoming an issue. Partly due to improved noise control of other components and partly due to increased specific mass flows. Despite that the turbocharging technique was developed in the first part of the last century the acoustical behavior is still a field where there is a lack of research. In this paper an overview of the existing research is presented including the work done in the EC-project ARTEMIS. Some first results from recently started investigations at the new gas management research centre, KTH CICERO, will also be described. A turbo-unit always consists of a compressor which normally is driven by an exhaust turbine. Both the turbine and the compressor will have an influence on how the low frequency engine pulsations propagate in the intake/exhaust system. This is referred to as the passive acoustic property of the turbo-unit. If linear acoustic models are applied the passive properties can be described using reflection and transmission coefficients. A turbo-unit will also produce high frequency aerodynamic sound, which is referred to as its active ("sound generating") acoustic property. The sound generation is associated with the rotating blade pressures and for modern turbo-units, with supersonic tip speeds, also with rotating shock waves ("buzz-saw noise").

  • 38.
    Rämmal, Hans
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Experimental determination of sound transmission in turbo-compressors2009In: SAE technical paper series, ISSN 0148-7191Article in journal (Refereed)
    Abstract [en]

    In this paper experimental procedures to determine the sound transmission through automotive turbo-charger compressors are described. An overview of a unique turbocharger testing facility established at KTH CICERO in Stockholm is given. The facility can be used to measure acoustic two-port data for turbo-compressors. Results from measurements on a passenger car turbo-compressor are presented and the influence of operating conditions on the sound transmission is discussed.

  • 39.
    Scarpati, Jose
    et al.
    SCANIA CV, Södertälje, Sweden.
    Wikström, Adam
    Scania CV, Södertälje, Sweden.
    Jönsson, Ola
    Scania CV, Södertälje, Sweden.
    Glav, Ragnar
    Scania CV, Sweden.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Hjalmarsson, Håkan
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Prediction of Engine Noise using Parameterized Combustion Pressure Curves2007In: SAE technical paper series, ISSN 0148-7191Article in journal (Refereed)
    Abstract [en]

    A parameterization for combustion chamber cylinderpressures is tuned to measurements on an inline 6cylinder Diesel engine at different operating conditions.Both measured and modeled signals are filtered in thefrequency domain and according to the so called Lucasattenuation. Two different estimates of engine radiatednoise are obtained and compared in this fashion. Theinfluence of physically meaningful parameters on thefrequency contents of the final noise level is analyzed,as well as the contribution of the pressure trace of themotored engine. The scattering of data in the pressuresignal is calculated as a function of the crank angleallowing for statistical considerations.

  • 40. Söder, M.
    et al.
    Prahl Wittberg, Lisa
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Lindgren, B.
    Fuchs, Laszlo
    KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Mechanics of Industrial Processes. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Effect of Swirl/Tumble (Tilt) Angle on Flow Homogeneity, Turbulence and Mixing Properties2014In: SAE technical paper series, ISSN 0148-7191, Vol. 2014-OctoberArticle in journal (Refereed)
    Abstract [en]

    In this work, the effect of swirl to tumble ratio on homogeneity, turbulence and mixing in a generic heavy duty Diesel engine during compression, is investigated using Large-Eddy Simulations. The main conclusion is that the relative importance of dilatation (relative volume change) increases whereas the effect of tumble breakdown decreases with the swirl to tumble ratio. In detail, we show that an increase in tumble raises the peak turbulence level and shifts the peak to earlier crank angles, which in turn leads to higher dissipation. Moreover, maximum turbulence level at top dead center is obtained for a combination of swirl and tumble rather than for pure tumble. Furthermore, it is observed that the peak turbulent kinetic energy displays levels three times greater than the initial kinetic energy of the tumble motion. Thus, energy is added to the flow (turbulence) by the piston through generation of vorticity by vorticity-dilatation interaction. Also, the intermediate swirl/tumble ratios are found to introduce large non-uniformity in the flow field, leading to a non-solid body like rotation. Swirl/tumble (tilt) angles larger than 19°are necessary for complete mixing of the gas within the engine cylinder. Taken together, the combined effect of a combination of swirl and tumble turbulence during compression is investigated. This knowledge is important both for engine development as well as more theoretical aspects regarding the breakdown of large scale structures in an engine.

  • 41. Thibblin, A.
    et al.
    Olofsson, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    A test rig for evaluating thermal cyclic life and effectiveness of thermal barrier coatings inside exhaust manifolds2019In: SAE technical paper series, ISSN 0148-7191, Vol. 2019-April, no AprilArticle in journal (Refereed)
    Abstract [en]

    Thermal Barrier Coatings (TBCs) may be used on the inner surfaces of exhaust manifolds in heavy-duty diesel engines to improve the fuel efficiency and prolong the life of the component. The coatings need to have a long thermal cyclic life and also be able to reduce the temperature in the substrate material. A lower temperature of the substrate material reduces the oxidation rate and has a positive influence on the thermo-mechanical fatigue life. A test rig for evaluating these properties for several different coatings simultaneously in the correct environment was developed and tested for two different TBCs and one oxidation-resistant coating. Exhausts were redirected from a diesel engine and led through a series of coated pipes. These pipes were thermally cycled by alternating the temperature of the exhausts. Initial damage in the form of cracks within the top coats of the TBCs was found after cycling 150 times between 50°C and 530°C. Temperature calculations showed that, besides evaluating the thermal cyclic life, the test method has the potential to provide a quick ranking of coating materials with respect to thermal insulation by measuring the temperature on the outer surface of the coated pipes. One of the major advantages of the presented test method compared to other methods described in the literature is that it ranks the thermal cyclic life and thermal properties of different coatings under realistic conditions in the correct environment. More cycles and higher temperatures are recommended for future tests, to accelerate the test, as well as evaluate whether the initial cracks in the TBCs will lead to spallation.

  • 42.
    Tiikoja, H.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Rämmal, H.
    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).
    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).
    Investigations of automotive turbocharger acoustics2011In: SAE technical paper series, ISSN 0148-7191Article in journal (Refereed)
    Abstract [en]

    In this paper an overview of recent experimental studies performed at KTH on the sound transmission and sound generation in turbochargers is presented. The compressor and turbine of the turbochargers are treated as acoustic active 2-ports and characterized using the unique experimental test facility established at KTH. The 2-port model is limited to the plane wave range so for higher frequencies the propagating acoustic power is estimated using an average based on pressure cross-spectra. A number of automotive turbochargers have been studied for a variety of operating conditions systematically selected from the compressor and turbine charts. The paper discusses the experimental procedures including special techniques implemented to improve the quality of the data. Results from a number of experiments on various modern automotive turbochargers including a unit with variable turbine geometry (VTG) are presented. Copyright 

  • 43. Vizzini, S.
    et al.
    Knutsson, M.
    Dybeck, M.
    Åbom, Mats
    KTH.
    Flow Noise Generation in a Pipe Bend2018In: SAE technical paper series, ISSN 0148-7191, Vol. 2018-June, no JuneArticle in journal (Refereed)
    Abstract [en]

    Noise generated by low Mach number flow in duct networks is important in many industrial applications. In the automotive industry the two most important are the ventilation duct network and the engine exhaust system. Traditionally, design is made based on rule-of thumb or slightly better by simple semi-empirical scaling laws for flow noise. In many cases, strong curvatures and local deviations from circular cross-sections are created due to outer geometry restrictions. This can result in local relatively high flow velocities and complex flow separation patterns and as a result, rule-of thumb and scaling law methods can become highly inaccurate and uncertain. More advanced techniques based on time domain modelling of the fluid dynamics equations together with acoustic analogies can offer a better understanding of the local noise generation, the propagation and interaction with the rest of the system. This investigation focuses on validating an SNGR numerical model to predict flow noise generation due to separation in a circular duct with a 90-degree bend carrying a flow lower than 0.3 Mach number. Experimental results are presented and compared to numerical simulations, based on a combination of steady computational fluid dynamics and the stochastic acoustic analogy by Lighthill, as well as semi-empirical models based two-ports.

  • 44.
    Zhang, Zhe
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Tiikoja, Heiki
    KTH.
    Peerlings, Luck
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Experimental Analysis on the 'Exact' Cremer Impedance in Rectangular Ducts2018In: SAE technical paper series, ISSN 0148-7191, Vol. 2018-June, no JuneArticle in journal (Refereed)
    Abstract [en]

    Cremer impedance, first proposed by Cremer (Acustica 3, 1953) and then improved by Tester (JSV 28, 1973), refers to the locally reacting boundary condition that can maximize the attenuation of a certain acoustic mode in a uniform waveguide. One limitation in Tester's work is that it simplified the analysis on the effect of flow by only considering high frequencies or the 'well cut-on' modes. This approximation is reasonable for large duct applications, e.g., aero-engines, but not for many other cases of interest, with the vehicle intake and exhaust system included. A recent modification done by Kabral et al. (Acta Acustica united with Acustica 102, 2016) has removed this limitation and investigated the 'exact' solution of Cremer impedance for circular waveguides, which reveals an appreciable difference between the exact and classic solution in the low frequency range. Consequently, the exact solution can lead to a much higher low-frequency attenuation level. In addition, the exact solution is found to exhibit some special properties at very low frequencies, e.g., a negative resistance. In this paper, liners designed on the basis of the exact solution are tested and the difference between the exact and classic solution in the low frequency range (not low enough to go into the negative resistance region) is experimentally investigated.

  • 45. Zhou, J.
    et al.
    Karlsson, Mikael
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Study of thermoacoustic engine for automotive exhaust waste heat recovery2019In: SAE technical paper series, ISSN 0148-7191, Vol. 2019-April, no AprilArticle in journal (Refereed)
    Abstract [en]

    In this paper, the travelling-wave thermoacoustic engine (TAE) and its application for recovery of waste heat from automotive exhaust systems is investigated. The aim is to give some insight into the potential, but also limitations of the technique for practical applications. This includes packaging, physical boundary conditions as heating and cooling available, but also system perspectives as influence of legislative drive cycles and degree of hybridization. First, the travelling-wave TAE is described as a low-order acoustic network in the frequency domain. Models, including non-linear effects, are set up for every component in the network to describe the propagation and dissipation of acoustic waves. For a TAE with looped structure, the continuity of pressure and volumetric velocity is employed to determine the saturation pressure, as well as the stable operating point. These models are validated against experimental data available in the literature [1]. This is an engine designed for high-temperature application, but is well documented and yields a good reference for the models and to further the understanding of the TAE. Next, an optimized design for a system to be adapted to the operating conditions typical for heavy-duty systems is studied and proposed. No actual physical prototype has been built and verified, but the design is based on, and is of the same efficiency, as machines that have been reported in the literature. The proposed design and the original TAE are then used to discuss the practical implementation for heavy- and light-duty vehicles on a system level. To improve the utilization of the available exhaust waste heat, a configuration of system heat exchangers combining a self-circulating loop with multiple TAE modules is preliminarily studied. Further research for this configuration is needed for practical implementation although current simulation results are encouraging.

  • 46.
    Åbom, Mats
    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).
    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).
    Turbocharger noise - Generation and control2014In: SAE technical paper series, ISSN 0148-7191, Vol. 2014Article in journal (Refereed)
    Abstract [en]

    An important part of modern engine design is the concept of downsizing where a key role is carried by the charging devices. These devices are effective aero-acoustic sources forming a coupled acoustic system with the connected flow-channel components. At KTH a unique test facility for determination of the complete acoustic Two-port for turbochargers has been built. Using this facility both the passive (transmission & reflection) as well as the active (sound generation) data for turbochargers can be measured at a given operating point. One important issue which has been studied in detail using this data is the coupling between the aerodynamic and acoustic fields close to "surge". In addition, the control of compressor noise is an increasing concern. For instance heavy duty diesels and light duty engines with screw (roots) compressors can create strong charging harmonics well below 10 kHz. The standard noise control solution for these cases is to build a series of resonators. As an alternative KTH has developed a novel compact and very efficient silencer in the form of an expansion chamber with locally reacting cavities. The cavities consists of a micro-perforated plate in front of a closed air volume. The micro-perforate and volume are then chosen so that the cavity impedance equals the so called Cremer impedance at a target frequency. This ensures a very high damping at one frequency (hundreds of dB/m) and using this concept compact silencers with a damping higher than 30 dB in octave around the target frequency can be designed.

  • 47. Åsbogård, M.
    et al.
    Johannesson, L.
    Angervall, D.
    Johansson, Peter
    KTH.
    Improving system design of a hybrid powertrain using stochastic drive cycles and dynamic programming2007In: SAE technical paper series, ISSN 0148-7191Article in journal (Refereed)
    Abstract [en]

    A new approach for system design of hybrid powertrains was demonstrated in a case study. The method is based on the following presumptions: The performance of a Hybrid Powertrain Concept (HPC) is evaluated using computer simulation; a HPC cannot be correctly evaluated without an Energy Management Strategy (EMS) for the energy buffer; the optimal EMS is different for each HPC. Dynamic programming was used to generate EMSs that were optimal for the vehicles intended traffic environment and for each given HPC, enabling evaluation of a large number of HPCs. Over-adaptation of the EMSs was avoided by using a stochastic drive cycle model. The final delivery is a competitive powertrain component sizing and the corresponding optimal EMS.

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