Contrast And Simulation Of Different Ventilators On The Automobile

Automobile has become very important in People's daily life of transport, when brings convenience for our life, it also have had a profound impact to our environment. Noise pollution and air pollution has influenced people healthy living environment, and fan noise is one of the main components of automobile noise.Based on the national―863‖project named as―intake and exhaust noise analysis and control‖, Changan, Fox, and Golf cooling fan and Changan, Golf condensing fan were experimented and simulated on flow and noise.This thesis summarizes the fan noise classification and generating mechanism and calculation method of spectrum prediction, introduces the design method of fan development process, theory of present situation and the domestic and foreign optimization method, discusses the basic theory of acoustic noise and computational fluid dynamics calculation principle, the basic knowledge of aeroacoustics noise and noise classification was introduced in the thesis. According to the Lighthill acoustic formula, wind tunnel noise calculation method was deduced. Fan noise include fundamental frequency noise and eddy current noise, that belong to the dipole noise, so this thesis pointed dipole noise optimization theory basis.Flow and noise of cooling fan and condensing fan was measured under the same speed. Limited by the equipment, the flow and the noise lack of correspondence, in this position, they can be revised by each other when one of them would be considered as standard. The experiment conclusion are as follow : speed and flow process linear relation;in the cooling fans, the performance of Fox fan is the best in the low speed, and the performance of Changan fan is the best in the high speed; in the condensing fan, Changan'performance is better. Cooling fan and condensing fan were modeled respectively by PRO/E. Fan wind tunnel test model established by GAMBIT and boundary conditions were set by FLUENT. The flow and noise simulation result compared with the experimental result showed that the feasibility of this method. Through the contrast of the flow figure (static figure, vector diagram and the total pressure figure) of fans, the analysis as follow: fan performance quality mainly depends on leaf area, installation angle and curvature. Larger the leaf area as well as installation angle and curvature, stronger the fan's power capability.The noise optimization based on the double fan wind tunnel model. This thesis applied dipole noise generating mechanism and noise reduction theory to optimize. The windshield was set on the axis of the model to optimization to reduce eddy current noise in the purpose of reducing the noise. Simulation noise results show that the distance of windshield and fans have a direct effect to optimization. Three distances were considered in the thesis, the noise fell down 2.6dB at most after optimization. It was shows that an optimal distance exists between windshield and fan, that could reduce noise to a minimum. This method is indirect method, it could reduce noise without changing the process, and has the advantage of low cost, applicability and high feasibility.