【作者】 李松；

【导师】 邵雪明；

【作者基本信息】 浙江大学 ， 流体力学， 2008， 硕士

【摘要】 节流阀是电液伺服系统的重要部件。当入流口和出流口的压差较大时,通过阀口的油流速度非常大。常见的机械油粘度也较大,因此油液的粘性加热显著。这会导致阀芯膨胀,使阀被卡死而失效。针对这一现象,本文选择了工程应用中典型的节流阀,采用了CFD方法模拟了阀内的油流温升现象,分析了U形节流阀槽口结构参数、进出口压差及槽口类型对油流温升的影响。然后基于CFD模拟得到的温度场,采用FEA方法,对U形节流阀阀芯变形进行了模拟。通过对数值模拟结果的分析,发现:U形节流阀的槽口深度越大,其最高温度随质量流量变化的速率越小;U形节流阀的最高温度随进出口压差的增大而增大,并基本成线形关系;节流阀的油液从槽口流出后形成射流,U形节流阀的射流出射角随着阀口开度的增大而减小,而V形节流阀的射流出射角保持不变;U形节流阀阀芯的局部高温分布在槽口轮廓线附近,而V形槽口节流阀的局部高温集中地出现在槽口底面上。研究阀芯变形时,发现槽口半径小的U形槽,其阀芯最大的径向变形容易发生在槽口两侧的壁面。这种情况下,阀芯最大径向变形随着质量流量增大的速度逐渐减小。槽口深度大的U形槽,其阀芯最大的径向变形容易发生在槽口半圆壁面。本文发现的有关节流阀油流温升及阀芯变形的规律,为改善节流阀的槽口温度分布,防止被卡死,提供了新的设计思路。本文首次采用的CFD和FEA结合的方法,也为相关领域的研究提供了参考。更多还原

【Abstract】 The thesis presents a numerical analysis of the viscous heating and spool deformation of throttle valves. The CFD method is used to simulate the temperature distribution around the notch of the throttle valve, due to the viscous heating effect caused by high speed flow of large-viscosity hydraulic oil. Basing on the CFD result, the FEA method is used to simulate the spool deformation of the throttle valve due to the high local temperature, which is supposed to be the causation of the jam fault.Temperature distributions of U-shape and V-shape throttle valves are simulated. The influence of three factors on the temperature distributions are investigated, including the U-shape notch structure parameters, the pressure drop and the notch type. Several conclusions are obtained: with the depth of the U-shape notch increasing, the increasing rate of the maximum temperature to the fluxes is decreased; and there is a linear relation between the maximum temperature and the inlet-outlet pressure drop; the high local temperature of U-shape throttle valve appears near the contour lines of the notch, while that of V-shape throttle valve occurs on the bottom face of the notch.In order to study the spool deformation, the heat transfer and thermal stress on the spool of U-shape throttle valve are simulated. It is observed that the peak radial deformation of the U-shape notch spools of small radii are occurred in both side walls of the notch, and that of big depth are occurred in the semicircle wall. In the former situation, the increasing rate of the maximum radial spool deformation to the fluxes is decresed.The thesis provides a deep insight into the jam fault problems. These conclusions presented above are important for improving the design of throttle valves to get rid of the jam fault. The experience of application of the coupling CFD and FEA provides a reference for the research of the heat transfer and deformation.更多还原