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- Fairbrother, R., et al.
(författare)
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Linear acoustic exhaust system simulation using source data from non linear simulation
- 2005
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Ingår i: SAE technical paper series. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191.
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 4. |
- Glav, Ragnar, 1960-, et al.
(författare)
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Application of the folded resonator
- 2003
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Ingår i: Proceedings of the Tenth International Congress on Sound and Vibration. ; , s. 3203-3210
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Konferensbidrag (refereegranskat)abstract
- A folded side-branch resonator has been designed and tested on a heavy truck. The design procedure is based on numerical simulations of the complete exhaust line and cold flow measurements of resonator inlet resistance and end-correction. A reduction in exhaust noise of as much as 7dB relative to the standard exhaust system shows the potential of the suggested technique to handle low frequency problems without increased volume or backpressure.
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| 10. |
- Glav, Ragnar, 1960-, et al.
(författare)
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Exhaust and Intake Noise and Acoustical Design of Mufflers
- 2008
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Ingår i: Handbook of Noise and Vibration Control. - Hoboken, NJ, USA : John Wiley & Sons. - 9780471395997 ; , s. 1034-1053
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Bokkapitel (refereegranskat)abstract
- A muffler or silencer is a device used in a flow duct to prevent sound from reaching the openings of the duct and radiating as far-field sound. Reactive silencers do this by reflecting sound back towards the source while absorptive silencers attenuate sound using absorbing material. They are necessary components in the design of any exhaust or intake system for internal combustion (IC) engines. No car or truck can pass the standard noise tests required by legislation or compete on the market without them. There are three basic requirements for a modern exhaust systems; compact outer geometry, sufficient attenuation and low pressure drop. The aim of this chapter is to discuss acoustical design and analysis of IC-engine exhaust and intake systems. The specific problems of modern intake systems made from plastic material with non-rigid walls are not discussed because not much has been published on this subject. The theory and techniques presented can be used also for other applications such as compressors and pumps and to some extent also for air-conditioning and ventilation systems.
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