| Based on extensive reading about literature home and abroad, connecting with the item "the analysis and control of intake and exhaust noise" which is a branch of "863" project, this paper optimized a low-noise cooling fan for ChangAn group V805 basic vehicle. The study on engine cooling fan was using experimental method in the past, this way has many shortcomings, long design cycle, high cost and product quality was not good a1so. In this paper, the method of CFD simulation analysis is used to study low-noise cooling fan.First, this paper learned about noise hazards and the basic theory of cooling fan, summarized mechanism of cooling fan's noise; summarized the research actuality of engine cooling fan noise performance; imparted the factors which influence cooling fan noise performance; next the basic idea, governing equations and the solve of governing equations of CFD(Computational Fluid Dynamics) simulation for aerodynamic performance and CAA(Computational Aero-Acoustics) simulation for aerodynamic noise on the cooling fan are discussed. Given the reduction noise criteria of engine cooling fan--ensure the engine cooling performance.This paper simulates radiator fan and condensator fan minutely. First, using CATIA to fabricate their three-dimensional model; Later, after appropriate simplified, import them into GAMBIT,which is a preprocessor software of FLUENT and according to cooling fan experimental device to build CFD simulation model. The simulation model contains four segments, rotating fluid section, pipeline section, inlet section and outlet section. Because the simulation model is complex, mesh every segment with different size. The cell of rotating fluid section is the smallest, the cell of pipeline section is larger and the cell of inlet section and outlet section is the largest. The final model is structured/unstructured hybrid grid, and all of those segments are meshed about 300 thousand cells.Then aerodynamic performance simulation was carried out on the vehicle cooling fan using CFD software FLUENT. The cooling fan region is defined as rotate region in rotating coordinate system. Windsail is defined as static region. Multiple Reference Frame model is apply to couple between the rotate region and static region. The CFD technology based on the Navier-Stokes equations and RNG k ?εturbulence model are selected in calculation, SIMPLE algorithm and segregated implicit solver are applied to simulation. The second-order upwind schemes are used to turbulent kinetic energy equations, turbulent dissipation rate equations and momentum equations. Pressure-inlet boundary condition in the inlet and pressure-outlet boundary condition in the outlet. Numerical simulation is carried out on vehicle cooling fan's internal flow. Static pressure, dynamic pressure, and velocity distribution on the blade surface and in airflow between the fan blades are acquired; when aerodynamic performance was emulated, noise analysis uses LES model, According to FAW Technology Center《Cooling System–fan noise test methods》, the inspecting point of noise is installed at the rotating axes and the distance to the center of fan is lm.The result indicates that the error of mass flow rate and noise,both of them are smaller than 5%,so it shows that the result is reliable.Combine original cooling fan's actual situation, this article mainly carried on the fan performance along with the fan blade parameter's change relations discusses and summarizes the fan performance change regularity, simultaneously, also carry on to the fan performance along with the unequal angel layout of blade simulation analysis. The result indicated:(1) Take the condensator fan as a example, along with fan blade angle of setting's enlargement, the mass flow increases, when angle of setting is 40°, A acoustic level achieves the minimum value, so when the fan designs, some blade angle of setting may enable fan's aerodynamic noise to meet minimum. (2) Under only changing fan blade's width premise, along with fan blade width increase, this fan's mass flow increases, A acoustic level also increases along with it. Therefore in the future design of the fans, under the guarantee fan cooling performance's premise, may choose small fan's blade width as far as possible.(3) Under only changing fan blade's curvature premise, along with fan blade curvature increase, this fan's mass flow increases, A acoustic level also increases along with it. Therefore in the future design of the fans, under the guarantee fan cooling performance's premise, may choose small fan's blade curvature as far as possible.(4) Appropriate unequal angle layout of fan blades can improve the performance of fan. As six blades fan, the blades by 64.96°-50.08°-64.96°-64.96°-50.08°-64.96°layout is a good one; as eight blades fan, the blades by 50.73°-39.27°-39.27°-50.73°-50.73°-39.27°-39.27°-50.73°is a good one. According to the rules that various factors affect the performance of fan,the original fans are optimized. The result indicated that the optimized fans'performance had the remarkable enhancement compared with the original fans: under the guarantee fan cooling performance's premise, to the radiator fan, when the rotational speed is 1900r/min, A acoustic level reduces the maximum of 4.9dB (A), when the rotational speed is 2500r/min, A acoustic level reduces the maximum of 0.6dB (A). The condensator fan when the rotational speed is 2500r/min, A acoustic level reduces the maximum of 5.6dB (A).
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