一种基于空化数的液压元件空蚀评价方法

发布时间：2018-01-31 13:33

本文关键词： 空化数空泡空蚀 CFD　出处：《西南交通大学》2011年硕士论文　论文类型：学位论文

【摘要】：空化和空蚀对液压系统中的液压泵、液压阀等元件影响严重,是一个长期难以解决的问题。当系统的压力低于饱和蒸汽压时,低压处会产生空泡：空泡能改变流动系统的流场特性,减小流道有效面积,增加流道阻力。在空泡的初生、发育、溃灭过程中系统将产生高频噪声和压力脉动,空泡溃灭产生的微射流冲击会造成固体边壁的剥蚀破坏——空蚀。空蚀的破坏作用巨大,能严重缩短液压元件的使用寿命。论文主要利用CFD软件对Yamaguchi的空蚀实验进行建模仿真,结合仿真和实验结果,找出参数评价空蚀。论文主要包括四部分内容：(1)对实验模型的结构尺寸进行参数化,利用STAR-CD的建模命令建立参数化六面体网格模型。通过网格数误差测试,确定出最适合本文仿真计算的网格数及其建模参数。(2)分析仿真计算的结果,提出发生空蚀的假设：①速度保护：试件表面压力低,流体速度快,气泡从试件表面快速通过,气泡在试件表面破裂的数量少,腐蚀轻。②压力保护：试件表面压力高,流体速度低,大量气泡在离试件表面较远处破裂,气泡冲不进试件表面,气泡在试件表面破裂数量少,腐蚀轻。③空蚀破坏：试件表面压力不够高,压力保护不足,速度不够快,速度保护不足；大量气泡在试件表面破裂,腐蚀严重。(3)根据假设找到用空化数σ评价空蚀。对比σ分布图和实验中空蚀量的关系,得出σ的分布图能比较准确的预测空蚀的位置和程度。对比σ分布图和实验中试件空蚀图片的关系,发现。分布图预测的试件上空蚀的位置和严重程度与实验给出的试件空蚀图片一致。(4)对Yamaguchi的另一个空蚀实验进行建模仿真。按同样的方法得到发生空蚀时对应的σ值。作出σ在流场中的分布,对比实验发现σ的分布图能比较准确的反映空蚀的位置和严重程度。
[Abstract]:Cavitation and cavitation have a serious effect on hydraulic pump, hydraulic valve and other components in hydraulic system, which is a difficult problem to solve for a long time, when the pressure of the system is lower than the saturated steam pressure. Cavitation will occur at low pressure: cavitation can change the flow field characteristics of the flow system, reduce the effective area of the passage and increase the resistance of the passage. During the process of cavitation initiation, development and collapse, the system will produce high frequency noise and pressure pulsation. The micro-jet impingement caused by cavitation collapse will result in the erosion of solid side wall-cavitation erosion. The cavitation erosion has a huge effect and can shorten the service life of hydraulic components seriously. This paper mainly uses CFD software to model and simulate the cavitation erosion experiment of Yamaguchi, combining the simulation and experimental results. Find out the parameters to evaluate cavitation erosion. The thesis mainly includes four parts: 1) to parameterize the structural size of the experimental model. The parameterized hexahedron mesh model is established by using the modeling command of STAR-CD, and the error of mesh number is tested. The mesh number and its modeling parameter. 2) the results of the simulation calculation are determined. The assumption of cavitation erosion is given: the surface pressure of the specimen is low and the fluid velocity is fast. Bubbles pass quickly from the surface of the specimen, the amount of bubble rupture on the surface of the specimen is less, corrosion protection is light. 2. The surface pressure of the specimen is high, the velocity of fluid is low, and a large number of bubbles rupture in the distance from the surface of the specimen. The bubble can not penetrate the surface of the specimen, the number of bubble rupture on the surface of the specimen is less, and the corrosion is light. 3. The surface pressure of the specimen is not high enough, the pressure protection is not enough, the speed is not fast enough, and the velocity protection is not enough; According to the hypothesis, cavitation number 蟽 is found to evaluate cavitation erosion. The relationship between 蟽 distribution and cavitation erosion in experiment is compared. The distribution map of 蟽 can accurately predict the location and extent of cavitation erosion. It is found that the location and severity of cavitation erosion predicted by the distribution map are consistent with the experimental results. Another cavitation experiment of Yamaguchi is modeled and simulated. The 蟽 value corresponding to cavitation erosion is obtained by the same method, and the distribution of 蟽 in the flow field is obtained. The comparative experiments show that the distribution map of 蟽 can accurately reflect the location and severity of cavitation erosion.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：TH137.5

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