Evaluating Cavitation Erossion Of Hydraulic Component By Using Cavitation Inception Number

Cavitation and erosion is a long difficult problem to solve, and have serious impact on hydraulic component such as hydraulic pump, hydraulic valve. Cavitation is generated at low pressure site in hydraulic system when system's pressure is below the saturated vapor pressure; bubbles produced by cavitation can change the flow characteristics of hydraulic systems, and can also reduce the effective flow area of flow channel and increase the flow resistance. During the process of bubble's generation, development and collapse, hydraulic system will produce high-frequency noise and pressure fluctuation. Bubble collapse generates micro-jet which impact on solid boundary can result in denudation——cavitation erosion. Cavitation erosion has great destructive effects on hydraulic system which can seriously shorten the service life of hydraulic components.In this paper, the major work is using CFD software to modeling and simulating Yamaguchi's cavitation experiments, and also combined simulation and experimental results to find out the parameter to evaluate cavitation erosion. This thesis consists of three parts: (1)Designing the structural dimensions of the experimental model to be parameter; using STAR-CD's modeling command to establish parametric hexahedral mesh; testing the simulation error of different number grids to decide which grid number should be used. (2)Analyzing simulation results, proposed the hypothesis when cavitation erosion happens:①Velocity protection:on specimen surface, the velocity is quickly, the pressure is low, bubbles passes specimen surface quickly and little bubble explode on specimen surface, cavitation erosion is light.②Pressure protection:on specimen surface, the velocity is slow, the pressure is high, a large number of bubbles explode on distance away from specimen surface and bubbles can't flow to specimen surface, cavitation erosion is light,③cavitation damage:on specimen surface, pressure is not high enough, pressure protected is not enough, the velocity is not quickly enough, the velocity protection is not enough, a large number of bubbles explode on specimen surface, cavitation erosion is serious. (3)According the hypothesis of cavitation erosion, find that cavitation inception number a can be used to evaluate cavitation erosion. Drawing the a distribution counter over the entire flow field; comparing the location of a distribution cloud and the mass loss of cavitation erosion got from experiment; find that, a distribution cloud can be used to predict the location and extent of cavitation erosion. Comparing the a distribution cloud with the specimen's cavitation erosion picture that get from experiments, find that, the location and extent of cavitation erosion were the same between experiment and the prediction of a distribution cloud. (4)Modeling and simulating Yamaguchi's another cavitation erosion experiment, using the same method to obtain theσvalue when cavitation erosion happens. Drawing the a distribution counter over the entire flow field, comparing theσdistribution cloud with experiment results, found that,σdistribution cloud can be used to evaluate the extent and location of cavitation erosion.