Change search
Refine search result
1 - 11 of 11
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    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.

  • 2.
    Hellström, Fredrik
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics.
    Fuchs, Laszlo
    KTH, School of Engineering Sciences (SCI), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO. KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics.
    Effects of inlet conditions on the turbine performance of a radial turbine2008In: PROCEEDINGS OF THE ASME TURBO EXPO 2008: Power for Land, Sea and Air, 2008, Berlin, New York: AMER SOC MECHANICAL ENGINEERS , 2008, p. 1985-2001Conference paper (Refereed)
    Abstract [en]

    For a turbocharger working under internal combustion engine operating conditions, the flow will be highly pulsatile and the efficiency of the radial turbine will vary during the engine cycle. In addition to effects of the inflow unsteadiness, there is also always a substantial unsteady secondary flow component at the inlet to the turbine depending on the geometry upstream. These secondary motions may consist of swirl, Dean vortices and other cross-sectional velocity components formed in the exhaust manifold. The strength and the direction of the vortices vary in time depending on the unsteady flow in the engine exhaust manifold, the engine speed and the geometry of the manifold itself. The turbulence intensity may also vary during the engine cycle leading to a partially developed turbulent flow field. The effect of the different perturbations on the performance of a radial nozzle-less turbine is assessed and quantified by using Large Eddy Simulations. The turbine wheel is handled using a sliding mesh technique, whereby the turbine wheel, with its grid is rotating, while the turbine house and its grid are kept stationary. The turbine performance has been compared for several inflow conditions. The results show that an inflow-condition without any perturbations gives the highest shaft power output, while a turbulent flow with a strongly swirling motion at the inlet results in the lowest power output. An unexpected result is that a turbulent inflow yields a lower shaft power than a turbulent inflow with a secondary flow formed by a pair of Dean vortices. The flow field for the different cases is investigated to give a better insight into the unsteady flow field and the effects from the different inlet conditions.

  • 3.
    Hellström, Fredrik
    et al.
    KTH, School of Engineering Sciences (SCI), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO (closed 20101231). KTH, School of Engineering Sciences (SCI), Mechanics.
    Fuchs, Laszlo
    KTH, School of Engineering Sciences (SCI), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO (closed 20101231). KTH, School of Engineering Sciences (SCI), Mechanics.
    Numerical computations of pulsatile flow in a turbo-charger2008In: 46th AIAA Aerospace Sciences Meeting and Exhibit, 2008Conference paper (Refereed)
    Abstract [en]

    The non-pulsatile and pulsatile three-dimensional flow in the turbine part of a radial turbo-charger have been computed with different modeling approaches for the turbulence; using the Reynolds Averaged Navier-Stokes (RANS) and Large Eddy Simulations (LES). The performance of the turbine for the non-pulsatile computations have been compared with measured performance for the same geometry and the computations slightly over predict the pressure ratio and the shaft power for a given mass flow. The discrepancy between the measured and computed turbine performance can be attributed, among others, to uncertainties in the walls boundary conditions (i.e. using smooth and adiabatic), and in the inflow conditions in addition to the uncertainty in the bearing losses which are included in the shaft power in the measured data. To asses the effect of inlet condition three different cases with different frequencies and mass flow pulses have been considered. A comparison of the computed shaft power with results from a one-dimensional engine simulation code shows fairly good agreement. The computations also shows that the mass flow and pressure is out of phase, and the phase shift is not constant during the engine cycle, which also affects the calculated isentropic efficiency. The flow field in turbine has been further studied and the vortex cores are visualized to give a better insight into the unsteady flow field and the effects of the inflow pulsations.

  • 4.
    Kalpakli, Athanasia
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO (closed 20101231).
    Örlü, Ramis
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO (closed 20101231).
    Tillmark, Nils
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO (closed 20101231).
    Alfredsson, P. Henrik
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO (closed 20101231).
    Experimental investigation on the effect of pulsations on turbulent flow through a 90degrees pipe bend2010In: Proc. of 3rd Int. Conf. on Jets, Wakes & Separated Flows 2010, 2010Conference paper (Other academic)
    Abstract [en]

    Pulsatile turbulent flows in curved pipes at high Dean numbers are prevalent in various components of internal combustion engines, particularly the intake of exhaust manifolds. Despite their technological importance, there is a clear lack of experimental data. The present paper provides preliminary, albeit unique, data from an experimental investigation, thereby addressing this gap and depicts impressions of the phase evolution of the complex flow including a back flow region. It is also shown, that due to the scale separation of the pulsations and the turbulence, the pulsatile flow can statistically be decomposed into its large-scale pulsations and the steady case.

  • 5.
    Karlsson, Mikael
    et al.
    KTH, School of Engineering Sciences (SCI), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO. KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Flow acoustics.
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Flow acoustics.
    Aeroacoustics of T-junctions: An experimental investigation2010In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 329, no 10, p. 1793-1808Article in journal (Refereed)
    Abstract [en]

    An experimental method for determining the aeroacoustic properties of side branch orifices allowing for any combination of grazing and bias flow is presented. The geometry studied, a T-junction, is treated as an active acoustic three-port. The passive properties, describing the reflection and transmission of an incident acoustic wave, are described by a system matrix while the active properties are described by a source vector. Expressions for the acoustic impedance under various mean flow and acoustic incidence configurations are developed. In addition, methods for identifying regions where the system can generate sound, by studying only the passive properties, are discussed. A self-sustained oscillation is triggered at one of the identified regions by coupling a resonant system to the three-port.

  • 6.
    Knutsson, Magnus
    et al.
    KTH, School of Engineering Sciences (SCI), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO.
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO.
    Sound propagation in narrow tubes including effects of viscothermal and turbulent damping with application to charge air coolers2009In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 320, p. 289-321Article in journal (Refereed)
    Abstract [en]

    Charge air coolers (CACs) are used on turbocharged internal combustion engines to enhance the overall gas-exchange performance. The cooling of the charged air results in higher density and thus volumetric efficiency. It is also important for petrol engines that the knock margin increases with reduced charge air temperature. A property that is still not very well investigated is the sound transmission through a CAC. The losses, due to viscous and thermal boundary layers as well as turbulence, in the narrow cooling tubes result in frequency dependent attenuation of the transmitted sound that is significant and dependent on the flow conditions. Normally, the cross-sections of the cooling tubes are neither circular nor rectangular, which is why no analytical solution accounting for a superimposed mean flow exists. The cross-dimensions of the connecting tanks, located on each side of the cooling tubes, are large compared to the diameters of the inlet and outlet ducts. Three-dimensional effects will therefore be important at frequencies significantly lower than the cut-on frequencies of the inlet/outlet ducts. In this study the two-dimensional finite element solution scheme for sound propagation in narrow tubes, including the effect of viscous and thermal boundary layers, originally derived by Astley and Cummings [Wave propagation in catalytic converters: Formulation of the problem and finite element scheme, Journal of Sound and Vibration 188 (5) (1995) 635-657] is used to extract two-ports to represent the cooling tubes. The approximate solutions for sound propagation, accounting for viscothermal and turbulent boundary layers derived by Dokumaci [Sound transmission in narrow pipes with superimposed uniform mean flow and acoustic modelling of automobile catalytic converters, Journal of Sound and Vibration 182 (5) (1995) 799-808] and Howe [The damping of sound by wall turbulent shear layers, Journal of the Acoustical Society of America 98 (3) (1995) 1723-1730], are additionally calculated for corresponding circular cross-sections for comparison and discussion. The two-ports are thereafter combined with numerically obtained multi-ports, representing the connecting tanks, in order to obtain the transmission properties for the charged air when passing the complete CAC. An attractive formalism for representation of the multi-ports based on the admittance relationship between the ports is presented. From this the first linear frequency domain model for CACs, which includes a complete treatment of losses in the cooling tubes and 3D effects in the connecting tanks is extracted in the form of a two-port. The frequency dependent transmission loss is calculated and compared to the corresponding experimental data with good agreement.

  • 7.
    Knutsson, Magnus
    et al.
    KTH, School of Engineering Sciences (SCI), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO.
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO.
    The effect of turbulence damping on acoustic wave propagation in tubes2010In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 329, no 22, p. 4719-4739Article in journal (Refereed)
    Abstract [en]

    The attenuation of sound due to the interaction between a low Mach number turbulent boundary layer and acoustic waves can be significant at low frequencies or in narrow tubes. In a recent publication by the present authors the acoustics of charge air coolers for passenger cars has been identified as an interesting application where turbulence attenuation can be of importance. Favourable low-frequency damping has been observed that could be used for control of the in-duct sound that is created by the engine gas exchange process. Analytical frequency-dependent models for the eddy viscosity that controls the momentum and thermal boundary layers are available but are restricted to thin acoustic boundary layers. For cases with cross-sections of a few millimetres a model based on thin acoustic boundary layers will not be applicable in the frequency range of interest. In the present paper a frequency-dependent axis-symmetric numerical model for interaction between turbulence and acoustic waves is proposed. A finite element scheme is used to formulate the time harmonic linearized convective equations for conservation of mass, momentum and energy into one coupled system of equations. The turbulence is introduced with a linear model for the eddy viscosity that is added to the shear viscosity. The proposed model is validated by comparison with experimental data from the literature.

  • 8.
    Laurantzon, Fredrik
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics. KTH, School of Engineering Sciences (SCI), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO.
    Örlü, Ramis
    KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO.
    Segalini, Antonio
    KTH, School of Engineering Sciences (SCI), Mechanics, Stability, Transition and Control. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Alfredsson, P. Henrik
    KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Engineering Sciences (SCI), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO.
    Time-resolved measurements with a vortex flowmeter in a pulsating turbulent flow using wavelet analysis2010In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 21, no 12, p. 123001-Article in journal (Refereed)
    Abstract [en]

    Vortex flowmeters are commonly employed in technical applications and are obtainable in a variety of commercially available types. However their robustness and accuracy can easily be impaired by environmental conditions, such as inflow disturbances and/or pulsating conditions. Various post-processing techniques of the vortex signal have been used, but all of these methods are so far targeted on obtaining an improved estimate of the time-averaged bulk velocity. Here, on the other hand, we propose, based on wavelet analysis, a straightforward way to utilize the signal from a vortex shedder to extract the time-resolved and thereby the phase-averaged velocity under pulsatile flow conditions. The method was verified with hot-wire and laser Doppler velocimetry measurements.

  • 9.
    Rämmal, Hans
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Engineering Sciences (SCI), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO (closed 20101231).
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Engineering Sciences (SCI), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO (closed 20101231).
    Testrig for characterization of turbo-compressor acoustic properties2008In: 14th AIAA/CEAS Aeroacoustics Conference (29th AIAA Aeroacoustics Conference), 2008Conference paper (Refereed)
    Abstract [en]

    The aim of this paper is to present a description of a novel experimental facility designed for the acoustical characterization of turbochargers. The facility is created to determine both the passive (scattering) and active (source) acoustic properties of automotive turbochargers. In this paper the experimental procedures for the determination of the scattering data for automotive turbo-chargers at realistic operating conditions will be described. The first experimental results obtained for a Volvo passenger car turbo-compressor are presented for several operating conditions.

  • 10.
    Tiikoja, Heiki
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Flow acoustics. KTH, School of Engineering Sciences (SCI), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO (closed 20101231). KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Rämmal, Hans
    KTH, School of Engineering Sciences (SCI), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO (closed 20101231). KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Åbom, Mats E G
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Flow acoustics. KTH, School of Engineering Sciences (SCI), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO (closed 20101231). KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Bodén, Hans
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Flow acoustics. KTH, School of Engineering Sciences (SCI), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO (closed 20101231). KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Test-rig for complete acoustic characterization of turbochargers2010In: 16th AIAA/CEAS Aeroacoustics Conference (31st AIAA Aeroacoustics Conference), 2010Conference paper (Refereed)
    Abstract [en]

    The aim of this paper is to present description of a novel experimental facility designed and set up in KTH Cicero Centre for complete acoustic characterization of turbochargers. The facility is created to determine both the passive (scattering) and active (source) acoustic properties of automotive turbochargers. In this paper the currently most accurate experimental technique to determine the passive acoustic effect of the turbocharger is described. A detailed overview of the test-rig is given together with the mathematical procedures followed to obtain the acoustic 2-port data for turbochargers. The results, including transmission loss and scattering matrix elements, are presented for the compressor and turbine side of a typical automotive turbocharger working in a number of different operating conditions. The influence of the operating conditions on the passive acoustic effect of the device is studied and summarized.

  • 11. Vuorinen, V.
    et al.
    Larmi, M.
    Fuchs, Laszlo
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO (closed 20101231).
    Large-Eddy Simulation of particle size distribution effects on turbulence in sprays2008In: 46th AIAA Aerospace Sciences Meeting and Exhibit, 2008Conference paper (Refereed)
    Abstract [en]

    In this work Large-Eddy Simulation and Lagrangian Particle Tracking methods are used to improve understanding of the dynamics of sprays for a range of particle loadings (i.e. 0.001 - 0.002 of volume fraction). We consider a subsonic particle laden round gas jet at Re = 104 and Ma = 0.3. The initial slip velocity between the particulate and the carrier phases is +0.25Uexit. The computational particle sizes are distributed in a range of Stokes numbers, 0.1 < Stp < 10. Thereby, interaction between the turbulent flow and the particle spectrum can be studied. Two particle mass loadings ψ = 0.3 and 0.6 are investigated corresponding to strong and very strong two-way momentum coupling. The results demonstrate that the mean Stokes number of the particle size distribution and the mass loading have a significant role in the observed dynamics of the jet. The relationship between the probability distribution function of the particles to gas slip velocities and the observed intermediate and large scale behaviour including mixing is pointed out.

1 - 11 of 11
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf