伺服阀前置级流场气穴现象的仿真及试验研究

针对液压阀中的气穴现象会引起液压阀的噪音、性能恶化,甚至导致液压阀失效等问题,对伺服阀前置级喷嘴和挡板之间流场中的气穴现象进行了研究.利用Pro/E软件对流场进行了三维建模,用前处理软件Gambit对三维模型进行了网格划分及边界条件设置,利用标准k-ε模型和混合气穴模型建立流场的数学模型,运用FLUENT软件对不同喷嘴入口流速下流场的分布特性及气穴特征进行了仿真分析;同时利用高速摄像机对喷嘴挡板之间的流场分布进行了观测和记录.研究结果表明,在低雷诺数流动条件下,气穴开始在喷嘴外壁和挡板前端的边缘形成;随着雷诺数的增大,在挡板弯曲的附体气穴逐渐长大并随着射流流速的增加出现云状的气穴.将不同流动条件下流场结构和气穴分布的数值计算结果与试验观测结果进行比较,两者基本吻合,说明伺服阀前置级流场气穴仿真模型和数值计算方法是可靠的.

Study of cavitiation in pilot stage of hydraulic servo valves

Aiming at the problems of that cavitation of hydraulic valve will cause the noise,performance degradation and even lead to hydraulic valve failure,cavitation phenomenon appearing in the flow field betwecn the flapper and nozzle of an electrohydraulic servo valve was studied,and the 3D flow field model was established by Pro/E software.Its grid was divided and boundary conditions were set by Gambit software prior to implementing the simulation.The mathematical models of the flow field were established,which combined standard turbulence model and gas-liquid mixture.The flow field distribution and cavitation characteristics in the different nozzle inlet velocity were analyzed by FLUENT software with finite element simulation method.Images of cavitation phenomenon in the flow field were observed and recorded through high-speed video cameras.The results indicate that at flow conditions with lower Reynolds numbers,cavitation begins to form at the nozzle outer wall and the flapper leading edge.Further increasing of Reynolds numbers,attached cavity on the flapper curved surface grows up gradually and with the jet flow velocity increasing,cloud-like cavitation is observed.Some numerical calculated results at different flow conditions are verified by the experimental data,which show the cavitation model in the flow field between the flapper and nozzle of an electrohydraulic servo valve and the numerical calculation method are reasonable.