【作者】 李雪松；

【导师】 马文星；

【作者基本信息】 吉林大学 ， 机械设计及理论， 2006， 硕士

【摘要】 本文结合国家自然科学基金“液力变矩器现代设计理论研究”和吉林大学创新基金“液力传动元件三维设计理论与方法研究”,利用CFD软件FLUENT对液力减速器模型的内部流场进行了数值计算,并对结果进行了分析。以此为基础计算了液力减速器的制动转矩,并与实验结果进行对比分析。全文的主要内容有以下几方面:(1)根据液力减速器的实际工作状况,提出一系列假设:①假设工作介质的密度和粘度为常数;②忽略温度影响;③假设工作腔内充满油液;④假设泵轮匀速旋转;⑤忽略各叶轮之间的液流泄漏;⑥同一工况下,同一叶轮内的每个流道的流场特性相同。(2)对所要分析的液力减速器建立三维模型。利用流体分析软件FLUENT的网格生成工具Gambit生成流道的计算网格模型,在此基础上对FLUENT中提供的湍流模型、速度-压力耦合算法和离散格式分别进行了介绍并且对比分析,从中选出适合本算例的模型和算法。(3)设定边界条件:对于计算区域内的叶片表面、外环、后壁和下壁设置成壁面边界条件;对泵轮和涡轮的交接面即进出口面采用了滑动网格理论;流道分割面设置为周期边界条件。(4)利用选择好的模型和算法对nB=3000r/min和nB=2000r/min两种转速下的速度和压力场进行对比分析,计算制动转矩并与实验结果进行对比分析。更多还原

【Abstract】 The hydrodynamic retarder derived from fluid coupling is an important kind ofelement for hydrodynamic transmission , which has been widely used in the fieldsof braking and deceleration for vehicles and some facilities. In abroad, with thedevelopment and application of the automatic transmission, some in-depth researchand application of the hydrodynamic retarder has been developed. Equipped withthe hydrodynamic retarder, the performance of the running and manipulation of bus,tour coach, heavy carrying truck, tank and camion can be greatly improved. Theearlest devices of hydrodynamic transmission in our country appeared in 1950’s.Now the hydrodynamic transmission has been paid more attention than before inour country.Some research on hydrodynamic retarder has been developed, whilethe technique is not perfect, and it is just beginning in China.There are two ways for the study of the internal flow field of hydrodynamicretarder , the test methods and the calculational methods. The purpose of this paperis simulating the internal three-dimension flow field of hydrodynamic retarder byusing the CFD software FLUENT, then the internal flow field can be achieved bysolving N-S equation directly. The braking torque is predicted on the base of theresult. The calculated results agree well with the test results. Because there aresome incomplete supposals for the software and fluid mechanics, many problemsstill need solving during calculating.The flow of fluid in the hydrodynamic retarder is three dimensional,incompressible and viscous. For the incompressible viscous flow, the continuityequation and momentum equation are called as Navier-Stokes equations, short forN-S equations. Reynolds averaging are the most basal method for simulating theturbulence. But in the Reynolds averaging equations, Reynolds stress made theequations unclosed, so the turbulent viscosity method is introduced, and then manyturbulence models are established to make the equations closed. Among them thek ?ε two-equation model is used widely, and then the control equations includetime averaging N-S equations and k ?ε turbulent equations. After comparison todifferent methods, Finite Volume Method is chosen to solve the equation, andUpwind method is the way to accomplish the space discretion. SIMPLE ,SIMPLEC and PISO are three strategies in the Press-Velocity Coupling Method.For this paper, the SIMPLE method is more favorable.The internal flow of the hydrodynamic retarder is very complex, so somesimplification and supposal are made before numerical simulation. First, thethree-dimension geometric model is finished by the UG soft, then the model isimported into GAMBIT to mesh and define the boundary conditions. The flow fieldis calculated by CFD software FLUENT. The sliding mesh theory is used duringthe simulation of unsteady flow, and the divided face of flow way is defined asperiodic boundary conditions.At last the distributing characteristic of the flow field in different rotate speedsis obtained. The results of simulation in different speeds are compared andanalyzed, and the braking torque of hydrodynamic retarder is also calculated, thenthe characteristic of braking torque is predicted. The results show that thecalculation of the braking torque which is about of 3D flow field is high precision.The calculated results agree well with the test results, and the most tolerance isonly 5%. The coherence of comparison show the calculated results is believable.The results of this paper is very valuable for the analysis of three-dimension flowfield in hydrodynamic retarder. On the base of that, some further research on thesimulation of hydrodynamic retarder can be well continued.更多还原