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A note on acoustic wave propagation in charge air coolers
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
2009 (English)In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568Article in journal (Other academic) Submitted
Place, publisher, year, edition, pages
National Category
Mechanical Engineering
URN: urn:nbn:se:kth:diva-14197OAI: diva2:331693
QS 20120315Available from: 2010-07-23 Created: 2010-07-23 Last updated: 2012-03-15Bibliographically approved
In thesis
1. Modelling of IC-Engine Intake Noise
Open this publication in new window or tab >>Modelling of IC-Engine Intake Noise
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.
Trita-AVE, ISSN 1651-7660 ; 2009:16
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
urn:nbn:se:kth:diva-10549 (URN)
Public defence
2009-06-01, Sal F3, Lindstedtsvägen 26, KTH, Stockholm, 13:15 (English)
QC 20100723Available from: 2009-05-26 Created: 2009-05-26 Last updated: 2010-07-23Bibliographically approved

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