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Sound propagation in narrow tubes including effects of viscothermal and turbulent damping with application to charge air coolers
KTH, School of Engineering Sciences (SCI), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO.
KTH, School of Engineering Sciences (SCI), Centres, Centre for Internal Cumbustion Engine Research Opus, CICERO.ORCID iD: 0000-0001-7898-8643
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.

Place, publisher, year, edition, pages
2009. Vol. 320, 289-321 p.
Keyword [en]
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
URN: urn:nbn:se:kth:diva-14196DOI: 10.1016/j.jsv.2008.07.006ISI: 000262790500017ScopusID: 2-s2.0-57349114158OAI: diva2:331689
QC 20100723Available from: 2010-07-23 Created: 2010-07-23 Last updated: 2011-01-21Bibliographically 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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