NR2272

NEWS RELEASE                                                                                        SEPTEMBER 2016

Growing Need for Better Silencers and Sound Enclosures for Stationary Reciprocating Engines

We have entered the age of distributed power. Gas engines providing electricity heat and light are now used for base load, standby, or emergency power for hospitals, data centers and many locations in close proximity to residences and areas with high population density. Engines are inherently noisy.  The exhaust is only one of six noise sources. McIlvaine is now providing a continuous analysis of sound attenuation options.  This includes a recent interview with Dennis Aaberg. Dennis has recently retired from Cummins Power Generation after a thirty-seven-year career in noise and vibration control.  He is a recognized expert on the subject and the author of articles appearing in Gas Turbine, Reciprocating Engine Decision Guide.  During his career, which began with Onan Corporation before it was purchased by Cummins, Inc. and became Cummins Power Generation, he worked within the Applied Technology Group to reduce product noise levels and improve sound quality on small gas and diesel engines, generator sets, garden tractors, welders and a variety of other engine-driven applications.  Dennis has also worked integrally with customers to solve community noise issues and application noise issues.

Several of the questions addressed in the interview deal with the need for customization. Dennis explained that to provide fairly accurate insertion loss predictions (i.e. within 1-3 dB(A) or better) for a given internal combustion engine-driven product, the silencers must be custom made for each engine-driven application because a given muffler will perform differently for each different engine it is integrated with.

Exhaust silencing systems act as a system with the engine, so any modeling work must include physical internal dimensions of the engine exhaust system and engine; along with all the engine operating parameters.  That is partially why when you look in exhaust silencer manufacturer catalogues you typically see a 10 dB(A) expected exhaust noise insertion loss range, because it can vary greatly from engine to engine.  Therefore, to custom design a product to meet a strict noise level, several iterations of modeling, analysis, test and validation typically need to be made.  This can be time-consuming and expensive, but perhaps necessary in critical noise control applications; which are becoming much more common globally.

Since the speed of sound changes with temperature, this can also complicate the expected insertion loss of the muffler for any particular engine because the broadband effectiveness of the silencer can vary as the engine exhaust temperatures change as the silencing effectiveness at various frequencies can change as the engine and silencer temperatures change.

The interview and coverage of sound attenuation in the Gas Turbine Reciprocating Engine Decision Guide includes the use of sound enclosures and other sound attenuation options.  The complete interview is found in 59D Gas Turbine and Reciprocating Engine Decisions.   The forecasts of the worldwide markets for sound attenuation for engines and turbines are found in 59EI Gas Turbine and Reciprocating Engine Supplier Program.