Acoustic Performance Simulation Analysis And Experiment Study For Muffler Air Pipe Of 4100QB Diesel

The thesis takes muffler of automobile as research object. According to related acoustic theories, using 3D number method simulating acoustic characteristic of engine's exhaust noise, and reflection the effect of eliminate noise, to find out the best project.Take 4100 QB engine as an example, base on finite element method, we establishment the 3D models and the finite element models of silencers by ANSYS software, then using SYSNOISE software calculate silencer's internal acoustic characteristics, analyze it's internal acoustic transmission loss and distribution of internal pressure, So the results of simulation are acquired.When 4100 QB engine run at the demarcated rotational speed, we launch a analysis to its exhaust noise frequency, find that between 2000Hz and 3000Hz frequency scopes, model A is still improved。Then tested these improved models. The test results indicate:between 2000Hz and 3000Hz frequency scopes, noise of improved silencer by model F is about 1.3dB lower than improved silencer by model C, about 4.2 dB lower than model A. The test results also indicate, by method of transition matrix, established the mathematical model to reduce noise is feasible, and there is the important instruction significance to the silencer design. The test results also indicate, by method of change the parameter of exhaust pipe to reduce noise is feasible, and there is the important instruction significance to the silencer design.Results indicate:the lower the diameter of exhaust pipe is, the better its elimination effect. Lengthen exhaust pipe have worse elimination effect at low frequency segment, but it get better elimination effect at medium and high frequency segment. In the condition of the same level length, the increment of eliminate noise for straight pipe more obvious than the curved pipe at medium and high frequency segment. The paper provides theories guidance for the design of muffler.