导轮结构对扁平化液力变矩器性能影响的研究

发布时间：2018-05-21 01:33

本文选题：液力变矩器 + 导轮结构　；参考：《吉林大学》2011年硕士论文

【摘要】：液力变矩器是自动变速器的重要部件之一,其结构形式和性能对轿车的经济性和动力性有很大影响。对于发动机前置的轿车,由于空间结构的限制,液力变矩器向着扁平化方向发展以减小轴向尺寸。导轮结构对于改变液力变矩器的轴向尺寸有着重要影响,同时会对液力变矩器的性能产生影响。研究导轮结构形式对液力变矩器性能的影响,目的在于找到适合的导轮结构,提高液力变矩器的性能。文中分别设计了两种具有不同导轮结构形式的扁平化液力变矩器循环圆,并对两个液力变矩器各叶轮叶片进行了设计,建立了两个液力变矩器的流道模型及网格模型,应用CFD软件对液力变矩器内部流动进行数值模拟,计算出内部三维流动分布和外部性能。通过对不同导轮结构的液力变矩器内部流动状态的分析和性能的对比,得到导轮结构形式对内部流动和外部性能的影响规律。针对两个不同导轮结构形式的液力变矩器性能的优劣,提出轿车扁平化液力变矩器优化方法,以提高轿车扁平化液力变矩器的性能。主要研究内容如下： (1)设计扁平率为0.8的两个扁平化液力变矩器。首先,设计两个扁平化液力变矩器的循环圆。文中采用基于椭圆的循环圆设计方法,设计扁平率为0.8的液力变矩器循环圆。为对比分析导轮结构形式对液力变矩器性能的影响,两个液力变矩器泵轮和涡轮的循环圆形状对应相同,导轮循环圆采用常用的两种结构形式,即直线导轮和圆弧导轮结构。其次,设计各叶轮的叶片。文中各叶轮的叶片均采用环量分配法进行设计。两个液力变矩器中的泵轮、涡轮和导轮分别采用相同的二次函数环量分配规律进行设计。最后,建立两个液力变矩器的计算模型并进行数值模拟。抽取两个液力变矩器的流道模型,并应用CFD软件对全流道进行网格划分,将整体网格模型导入CFD软件,选择滑动网格法进行数值模拟,湍流模型选用标准κ-ε模型,设定边界条件,采用SIMPLE算法的分离式求解法进行数值模拟。 (2)不同导轮结构形式的两个液力变矩器瞬态流场分析。对比两个液力变矩器的内部流动,主要是典型工况时流道的整体压力分布和速度分布。两个扁平化液力变矩器在起动工况和最高效率工况的压力和速度分布规律一致。起动工况时液力变矩器的循环流量最大,涡轮转速为零,泵轮出口处的压力和速度高于入口处,而涡轮则相反,导轮流道中压力和速度变化较小,受离心力及Coriolis的作用,外环压力和速度高于内环。与起动工况相比,最高效率工况的压力分布较为均匀,这是因为最高效率工况时涡轮和泵轮转速差较小,叶轮间能量交换较少,这时的离心力较大,流道外环压力明显高于内环压力。由于导轮结构形式不同,两个液力变矩器流场的压力和速度分布存在一些差别。在起动工况,圆弧导轮扁平化液力变矩器流道整体压力高于直线导轮扁平化液力变矩器,逆压区范围较小,泵轮出口涡轮入口处速度略低,导轮流道速度较高。在最高效率工况,圆弧导轮扁平化液力变矩器整体压力分布更为均匀,压力和速度都较高。 (3)对比分析了导轮结构形式对轿车扁平化液力变矩器性能的影响。转速比i0.8时,圆弧导轮扁平化液力变矩器的效率高于直线导轮扁平化液力变矩器,i≥0.8时,两个扁平化液力变矩器效率值近似相等。与效率的分布规律相同,转速比i0.8时圆弧导轮扁平化液力变矩器的变矩比较大,转速比i≥0.8时,两个液力变矩器的转矩比近似相等。对比两个液力变矩器的泵轮容量系数和循环流量可以看出,圆弧导轮扁平化液力变矩器的泵轮容量系数较大,循环流量较小。 (4)对轿车扁平化液力变矩器进行优化。针对具有两个不同导轮结构形式的扁平化液力变矩器性能的优劣,在圆弧导轮液力变矩器的基础上设计一种新的液力变矩器,具体方法就是减小圆弧导轮的轴向尺寸,其他结构保持不变,采用相同的方法进行CFD仿真分析,对比宽窄两种导轮的扁平化液力变矩器的性能。对比可以看出,宽导轮扁平化液力变矩器泵轮转矩系数高和循环流量低的状况得到改善,达到了性能优化的目的。综上所述,本文设计了具有两种常用导轮结构形式的液力变矩器,通过对两个液力变矩器内部流场的仿真分析,得到了导轮结构形式对扁平化液力变矩器内部流动及外部性能的影响规律,并通过改变导轮轴向长度,使液力变矩器的性能得到优化。
[Abstract]:The hydraulic torque converter is one of the important parts of automatic transmission , its structure and performance have great influence on the economy and power of the car .

( 1 ) Two flat hydraulic torque converters with a flat rate of 0.8 are designed .

Firstly , the circular circle of two flat hydraulic torque converter is designed . The circular circle of hydraulic torque converter with the flat rate of 0.8 is designed by the circular design method based on the ellipse . In order to analyze the effect of the guide wheel structure on the performance of the torque converter , the circular shapes of the two torque converter pump wheels and the turbine are the same , and the circular circle of the guide wheel adopts the common two structural forms , namely , the linear guide wheel and the circular arc guide wheel structure .

secondly , the blades of each impeller are designed ; the blades of each impeller are designed by adopting a ring quantity distribution method ; and the pump wheel , the turbine and the guide wheel in the two hydraulic torque converter are respectively designed by adopting the same quadratic function ring quantity distribution law .

At last , the calculation model of two torque converter is established and the numerical simulation is carried out . The flow path model of two torque converter is extracted , and the whole flow channel is divided by CFD software , the integral mesh model is introduced into CFD software , the sliding grid method is selected for numerical simulation , the turbulent model selects the standard kappa - 蔚 model , the boundary condition is set , and the numerical simulation is carried out by using the separated solution method of SIMPLE algorithm .

( 2 ) Transient flow field analysis of two hydraulic torque converter in different wheel structure forms .

The internal flow of two torque converter is compared , which is mainly the overall pressure distribution and velocity distribution of the runner during typical operating conditions .

Compared with the starting working condition , the pressure and velocity of the turbine and the pump impeller are smaller , the pressure and the speed of the outer ring are higher than the inner ring .

Due to the different forms of the guide wheel structure , there are some differences between the pressure and the velocity distribution of the flow field of the two hydraulic torque converter . In the starting condition , the integral pressure of the arc guide wheel flat hydraulic torque converter is higher than that of the linear guide wheel flat hydraulic torque converter , the range of the reverse pressure area is small , the speed of the inlet of the pump wheel outlet turbine is slightly lower , and the rotation speed is higher . Under the maximum efficiency condition , the integral pressure distribution of the circular arc guide wheel flat hydraulic torque converter is more uniform , and the pressure and the speed are higher .

( 3 ) The effect of guide wheel structure on the performance of flat hydraulic torque converter is analyzed .

When the speed ratio is higher than that of the linear guide wheel flat hydraulic torque converter , the torque ratio of the two hydraulic torque converter is approximately equal . When the speed ratio is more than or equal to 0.8 , the torque ratio of the two hydraulic torque converter is approximately equal . Compared with the pump wheel capacity coefficient and the circulating flow rate of the two torque converter , it can be seen that the capacity coefficient of the pump wheel of the circular arc guide wheel flat hydraulic torque converter is large , and the circulation flow is small .

( 4 ) To optimize the torque converter of the flat hydraulic torque converter with two different guide wheels , a new torque converter is designed on the basis of the arc guide wheel hydraulic torque converter . The method is to reduce the axial dimension of the circular arc guide wheel , the other structure remains the same , and the performance of the flat hydraulic torque converter with the same method is compared .

In conclusion , the hydraulic torque converter with two kinds of common guide wheel structures is designed in this paper . Through the simulation analysis of the internal flow field of the two hydraulic torque converter , the influence law of the guide wheel structure on the internal flow and external performance of the flat hydraulic torque converter is obtained , and the performance of the torque converter is optimized by changing the axial length of the guide wheel .
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：TH137.332

【参考文献】