【作者】 耿丽珍；

【导师】 袁兆成；

【作者基本信息】 吉林大学 ， 动力机械及工程， 2008， 硕士

【摘要】 本文在广泛阅读国内外文献的基础上,结合项目组承担的国家“863”项目“轿车动力总成悬置系统、进排气及车内外高频噪声分析与控制术”子项“进排气噪声分析与控制”,以发动机冷却风扇的降噪准则—以确保发动机冷却性能(扇风量)为前提条件,对长安V805基础车发动机冷却风扇进行了低噪声优化设计研究。本文首先介绍了发动机噪声及其危害,讨论了冷却风扇噪声的产生机理及降噪的常规措施,归纳总结了冷却风扇国内外研究现状及风扇噪声性能的各种影响因素;总结分析了汽车冷却风扇气动性能CFD仿真和气动噪声CAA仿真的基本思想、控制方程和控制方程的求解方法;运用商用软件FLUENT对发动机冷却风扇进行了流场和声场的仿真计算分析。本文主要对风扇性能随风扇叶片参数的变化关系进行深入探讨并总结出风扇性能变化的规律,为风扇的优化设计提供参考,同时也对叶片不等节距布置的风扇进行了详细的仿真分析。对每种因素的仿真结果都以图表的形式绘出,主要总结出风扇的叶片结构尺寸对其性能影响的规律。在此基础上,对发动机散热风扇和冷凝风扇进行了优化设计,在保证冷却性能的前提下,均达到了降低风扇气动噪声的效果。更多还原

【Abstract】 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).更多还原