Experimental Study Of Acoustic Performance Of The Intake System And Its Optimization

The noise level is one of the important performance indices to evaluate vehicles’rank level. As one of the main noise sources, the intake noise attracts great attentions. Reducing the intake noise becomes an urgent problem for engineers. Since the experiment method has advantages of directly, reliability and substantivity, it is an indispensable method for research study and engineering practice. In this thesis, the intake system of a domestic vehicle, whose intake noise appears too large, has been improved by experiment method. Under the premise of unchanging the appearance and arrangement of intake system, the full speed section intake noise has been decreased by applying a new permeable material woven insert pipe. Meanwhile, in order to make the measurement results correspond the original intake noise, the measurement methods of intake noise have also been explored.Through the static acoustic performance experiments of intake system and silencer elements in semi-anechoic room, the new permeable material woven pipe had a good noise attenuation effect. When this material was installed as the air inlet pipe, it can reduce the noise of original intake system at the frequency range of300Hz to1500Hz. When it was installed in the air filter as an insert pipe, this material can also improve the acoustic performance, compared to tradition plastic insert pipe. By juxtapose the static transmission loss experiment results of different punched holes combinations at the position of medium and rear of air inlet pipe, the transmission loss of different punched holes combinations all increased with the increasing of the punched hole area.To evaluate the effects of different punched holes combinations at the position of medium and rear of air inlet pipe on intake noise and surrounding environment noise, the engine bench experiments in semi-anechoic room have been done.The scheme of punching holes at the rear of air inlet pipe had a most significant effect to reduce intake noise, on the other hand, this scheme did not increase the surrounding noise. The scheme of punching holes at the medium and rear of air inlet pipe did not have an expected effect. As a consequence, punching holes at the rear of air inlet pipe is an optimization scheme to reduce intake noise of vehicle AD1.8T.To evaluate the effects of plastic insert pipe and permeable material woven insert pipe on intake noise and vehicle interior noise, the stationary vehicle experiments and vehicle tests on road have been done. Applying insert pipe had a significant effect to reduce the intake noise of vehicle AD1.8T at all speed sections. Besides, applying permeable material woven insert pipe can reduce the vehicle interior noise to some extent. The experiments on vehicle AC1.8T showed similar results. Therefore, applying permeable material woven insert pipe is another optimization scheme to reduce intake noise of vehicle AD1.8T.