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Modelling of IC-Engine Intake Noise
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. (MWL)
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Shorter product development cycles, densely packed engine compartments and intensified noiselegislation increase the need for accurate predictions of IC-engine air intake noise at earlystages. The urgent focus on the increasing CO2 emissions and the efficiency of IC-engines, aswell as new techniques such as homogeneous charge compression ignition (HCCI) mightworsen the noise situation. Nonlinear one-dimensional (1D) gas dynamics time-domainsimulation software packages are used within the automotive industry to predict intake andexhaust orifice noise. The inherent limitation of 1D plane wave propagation, however, limitsthis technique to sufficiently low frequencies where non-plane wave effects are small. Thereforethis type of method will first fail in large components such as air cleaners. Further limitations,that might not be important for simulation of engine performance but indeed for acoustics,include difficulties to apply frequency dependent boundary conditions and losses as well as toinclude effects of vibrating walls.

The first part of this thesis treats two different strategies to combine nonlinear and linearmodelling of intake systems in order to improve the accuracy of the noise predictions. Paper Adescribes how a linear time-invariant one-port source model can be extracted using nonlineargas dynamics simulations. Predicted source data for a six-cylinder naturally aspirated engine isvalidated using experimental data obtained from engine test bench measurements. Paper Bpresents an experimental investigation on the influence of mean flow and filter paper on theacoustics of air intake systems. It also suggests how a linear source, extracted from nonlinearsimulations can be coupled to acoustic finite elements describing the intake system and toboundary elements describing the radiation to the surroundings. Simulations and measurementsare carried out for a large number of engine revolution speeds in order to make the firstsystematic validation of an entirely virtual intake noise model that includes 3D effects for awide engine speed range. In Paper C an initial study on a new technique for the use of two-portsin the time domain for automotive gas dynamics applications is presented. Tabulated frequencydomaintwo-port data representing an air cleaner unit on the impedance form is inverselytransformed to the time domain and used as FIR filters in nonlinear time-domain calculations.

The second part of the thesis considers detailed modelling of sound propagation in capillarytubes. Thermoviscous boundary effects and interaction between sound waves and turbulencecan, for sufficiently narrow tubes, yield significant attenuation. Several components in the gasexchange system of IC-engines are based on arrays of narrow ducts and might haveunderestimated silencing capabilities. In particular the sound transmission properties of chargeair coolers (CAC) have so far gained interest from very few authors. In Paper D a detailedinvestigation of the acoustic properties of CACs is presented. As a result the first linearfrequency-domain model for CACs, which includes a complete treatment of losses in the narrowtubes and 3D effects in the connecting tanks, is proposed. Interesting low frequency dampingmost likely due to interaction between sound and turbulence is observed in the experimentaldata. A new numerical model that describes this dissipative effect in narrow tubes is suggestedin Paper E. Validation is carried out using experimental data from the literature. Finally, inPaper F the CAC-model presented in Paper D is updated with the new model for interactionbetween turbulence and acoustic waves proposed in Paper E. The updated model is shown toyield improved predictions.

Place, publisher, year, edition, pages
Stockholm: KTH , 2009. , xvi, 32 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2009:16
Keyword [en]
IC-engine, intake noise, gas dynamics, linear source data, frequency domain, 2-port, losses, air cleaner unit, filter paper, flow, FEM, BEM, charge air cooler, narrow tube
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-10549OAI: oai:DiVA.org:kth-10549DiVA: diva2:219077
Public defence
2009-06-01, Sal F3, Lindstedtsvägen 26, KTH, Stockholm, 13:15 (English)
Opponent
Supervisors
Note
QC 20100723Available from: 2009-05-26 Created: 2009-05-26 Last updated: 2010-07-23Bibliographically approved
List of papers
1. IC-engine intake acoustic source data from non-linear simulations
Open this publication in new window or tab >>IC-engine intake acoustic source data from non-linear simulations
2007 (English)In: SAE technical paper series, ISSN 0148-7191Article in journal (Refereed) Published
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.

Keyword
Acoustic noise measurement, Acoustics, Computer simulation, Engine cylinders, Engines, Exhibitions, Frequency domain analysis, Intake systems, Time domain analysis
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-14191 (URN)10.4271/2007-01-2209 (DOI)2-s2.0-84877431697 (Scopus ID)
Conference
Noise and Vibration Conference and Exhibition; St. Charles, IL; United States; 15 May 2007 through 17 May 2007
Note

QC 20100723

Available from: 2010-07-23 Created: 2010-07-23 Last updated: 2017-12-12Bibliographically approved
2. Prediction of IC-engine intake orifice noise using 3D acoustic modelling and linear source data based on non-linear CFD
Open this publication in new window or tab >>Prediction of IC-engine intake orifice noise using 3D acoustic modelling and linear source data based on non-linear CFD
2008 (English)In: Proceedings of the 5th International Styrian Noise, Vibration and Harshness Congress, in cooperation with SAE International, Graz, Austria, 2008, 2008Conference paper, Published paper (Refereed)
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-14194 (URN)
Conference
SAE International, June 4-6, 2008, Graz
Note
QC 20100723Available from: 2010-07-23 Created: 2010-07-23 Last updated: 2010-11-11Bibliographically approved
3. A study on acoustical time-domain two-ports based on digital filters with application to automotive air intake systems
Open this publication in new window or tab >>A study on acoustical time-domain two-ports based on digital filters with application to automotive air intake systems
2011 (English)In: SAE International Journal of Passenger Cars - Mechanical Systems, ISSN 1946-3995, Vol. 4, no 2, 970-982 p.Article in journal (Refereed) Published
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 CO 2 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.

Place, publisher, year, edition, pages
SAE International, 2011
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-14195 (URN)10.4271/2011-01-1522 (DOI)2-s2.0-84859366619 (Scopus ID)
Note

QC 20100723

Available from: 2010-07-23 Created: 2010-07-23 Last updated: 2017-01-10Bibliographically approved
4. Sound propagation in narrow tubes including effects of viscothermal and turbulent damping with application to charge air coolers
Open this publication in new window or tab >>Sound propagation in narrow tubes including effects of viscothermal and turbulent damping with application to charge air coolers
2009 (English)In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 320, 289-321 p.Article in journal (Refereed) Published
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.

Keyword
Acoustic wave propagation; Acoustic wave transmission; Aerodynamics; Air engines; Architectural acoustics; Boundary layers; Catalytic converters; Cooling; Cooling systems; Damping; Hydrodynamics; Internal combustion engines; Lattice vibrations; Ports and harbors; Tanks (containers); Three dimensional; Turbulence; Turbulent flow, 3d effects; Acoustical society of america; Air temperatures; Analytical solutions; Approximate solutions; Charge air coolers; Circular cross-sections; Complete treatments; Cooling tubes; Dimensional effects; Experimental datums; Finite element schemes; Finite element solutions; Flow conditions; Frequency dependents; Internal combustions; Linear frequencies; Mean flows; Narrow pipes; Narrow tubes; Outlet ducts; Petrol engines; Sound propagations; Sound transmissions; Transmission losses; Transmission properties; Turbulent boundary layers; Turbulent damping; Turbulent shear layers; Uniform mean flows; Volumetric efficiencies, Tubes (components)
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-14196 (URN)10.1016/j.jsv.2008.07.006 (DOI)000262790500017 ()2-s2.0-57349114158 (Scopus ID)
Note
QC 20100723Available from: 2010-07-23 Created: 2010-07-23 Last updated: 2017-12-12Bibliographically approved
5. The effect of turbulence damping on acoustic wave propagation in tubes
Open this publication in new window or tab >>The effect of turbulence damping on acoustic wave propagation in tubes
2010 (English)In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 329, no 22, 4719-4739 p.Article in journal (Refereed) Published
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.

National Category
Mechanical Engineering Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-14193 (URN)10.1016/j.jsv.2010.05.018 (DOI)000280929700011 ()2-s2.0-77955418374 (Scopus ID)
Note
QC 20101130 ändrad från in press till published 20101130Available from: 2010-07-23 Created: 2010-07-23 Last updated: 2017-12-12Bibliographically approved
6. A note on acoustic wave propagation in charge air coolers
Open this publication in new window or tab >>A note on acoustic wave propagation in charge air coolers
2009 (English)In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568Article in journal (Other academic) Submitted
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-14197 (URN)
Note
QS 20120315Available from: 2010-07-23 Created: 2010-07-23 Last updated: 2017-12-12Bibliographically approved

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