Dept. of Mech. Eng. and Appl. Mech., 120 W. E. Lay Automotive Lab., Univ. of Michigan, Ann Arbor, MI 48109-2121
The reactive silencers installed in the induction and exhaust systems of production vehicles involve a compromise between the noise reduction and the flow efficiency. The present study considers venturi tubes as low flow-loss elements and investigates their acoustic attenuation performance in terms of two approaches: the first one combines the solutions of one-dimensional wave propagation in conical reducers and diffusers, and straight ducts; while the second one approximates the variation in the cross-sectional area by a series of stepwise contractions and expansions. The results from both approaches are shown to agree well for a number of venturis constructed for the experimental validation. Transmission loss predictions are then compared to the data obtained from an extended impedance tube setup. Finally, the acoustic attenuation and the flow performance are presented for one of the constructed venturi tubes against a limit configuration: a contraction chamber with the diameters defined by the duct and throat dimensions of the venturi tube.