Aerodynamic And Noise Rsearch Of Intake System

Air intake system should try to reduce the pressure loss when filtering impurities as the engine power will be reduced with bigger pressure loss. At the same time, the air intake system should have a good NVH performance.This paper studied the air intake system of one A-class vehicle through model establishment by CATIA, aerodynamic performance, anti-snow performance and NVH performance analysis by CAE, and relative tests.For the aerodynamic performance, the structure was optimized based on the flow field analysis results of air intake system. There was a good consistency between simulation and test after experimental verification.The difficulty for the development of anti-snow performance is the flow characteristics of snow, which is different from air and rainwater. Snow has large range of particle diameters,will flow with air, and can be affected by its gravity and inertial force, which are difficult for the simulation to locate its entering route accurately. Front-loading air intake was adopt by the vehicle studied, which is benefit for the air suction but higher requirement for the design of anti-snow structure due to the easier entering. Air intake temperature, intake resistance,filtering efficiency and other parameters must be considered for the design of anti-snow structure. Based on the factors above, the balance between anti-snow and system performance was achieved through design, simulation and experimental verification.For the acoustics development, the acoustics performance of multihole muffler was obtained through tests. For the 4-order noise at 2800r/min, an anti-noise resonant at 186 Hz was used to forecast and verify, which finally met the requirements of intake noise and radiation noise of filter housing.For the throttle noise, simulations and tests were done from occurring mechanisms,transmission routes and optimization plans. After tests, it can be confirmed that the noise from throttle was wide-band and distributed between 400 Hz to 2000 Hz. The noise reduced to less than 1000 Hz when went through body with noise absorption function, and can be perceived easily.When accelerating quickly, “chichi” noise will appear in the throttle before the accelerating noise from engine. But there’s no obvious noise in the intake and cockpit, which means that air intake system is not the main transmission route of “chichi” noise. When the throttle covered with noise absorption cotton, the radiation noise from the throttle housing will be reduced, and the whistle noise can be reduced correspondingly. So, the radiation fromthrottle housing is the key transmission route of throttle noise. Cover the throttle with noise absorption cotton can reduce noise, which means that shielding throttle noise from transmission route is a better way.