Study on the influence of structure factors of diesel engine exhaust purification muffler on transmission loss in different frequency bands

Abstract The main purpose of exhaust mufflers design is to improve the TL (transmission loss) of the target frequency band. Therefore, this paper first proposed an exhaust muffler model with foam ceramics as sound-absorbing material for a diesel engine. The finite element AML (Automatic Matched Layer) method is used to simulate the non-reflective boundary conditions and calculate the TL. In addition, the validity and reliability of the solution model are verified by comparing the experimental value and simulation value of the TL. Compared with the prototype muffler, the TL of the exhaust purification muffler has increased by an average of 6.96 dB in the frequency range of 20–4500 Hz. Finally, the influence law of structure factors m (expansion ratio), n (cavity-length ratio) and p (length-diameter ratio) on TL in different frequency bands shows that: when changing the structure factors to increase the TL value of the exhaust purification muffler, the expansion ratio should be prioritized in the low-medium frequency bands, the cavity-length ratio should be prioritized in the medium–high frequency bands, the length-diameter ratio should be prioritized in the high frequency bands.