Intake & Exhaust Systems: noise challenges and acoustic simulation processes



Intake and exhaust systems contribute significantly to the total noise level of ground vehicles (passenger cars,  motorcycles, heavy machinery) or any other tool equipped with combustion engines such as chain saws, for example. From a general perspective, it is possible to identify three reasons for studying the acoustic performance of these systems:

  • Noise regulations are becoming more and more restrictive (e,g, vehicles pass-by noise norms). As an example,  CNH analyzed many noise sources including the exhaust noise to meet new noise standards.
  • Passengers or users comfort is more and more becoming a marketing argument today. This does not apply only for cars, but also for heavy machinery. I quote from this New Holland brochure (page 20) "Better Comfort and Visibility. Better productivity" and "…you can enjoy all that space in the peace and quiet of the near silent 74 dB(A) level."
  • Sound Trademark: manufacturers, mainly in the motorcycle industry, look for developing their own signature. Sporty motorbikes and choppers shall be distinguished from urban two wheelers. Of course this poses new challenges when electric motors will substitute combustion engines as demonstrated in this Harley Davidson video. However, since electric motorbikes are yet in the market, studying exhaust noise is still fundamental from this perspective.

Acoustic CAE aims at enabling engineers with the capability of virtually model their product. When intake and exhaust are concerned, many acoustic, vibro-acoustic and aero-acoustic simulation challenges shall be faced. These include porous material modeling, taking into account non-uniform mean flow, complex visco-thermal dissipative occurring in catalytic converters or perforate plate for example. Moreover, their integration with the full vehicle is required to actually understand their effect with respect to pass-by noise standards.

All these aspects will be discussed in the next webinar of the Actran software suite. This will include discussions of unique modeling capabilities such as

  • anisotropic porous materials for air filter simulations;
  • leaks effect assessment;
  • full vibro-acoustic time-domain solver for transient analysis;

The presentation will include industrial case studies and finally a demo of a motorcycle exhaust will be shown.

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