Simulation and Measurement of Hot Exhaust Gas Flow Noise with a Cold Air Flow Bench

A experimental method has been developed to assess the flow noise in tailpipe noise through measurements on an acoustic flow bench with cold air. To set up this procedure, measurements were made on flow bench, engine dynamometer and chassis dynamometer. The Mach number seems to be the appropriate parameter to correlate the overall level of the radiated flow noise. If mass flow and temperature under running conditions are known, the noise level can be extrapolated for real conditions. The Strouhal or Helmholtz numbers are appropriate parameters for getting details of spectra contents.