液控换向阀内流场及动态特性的数值模拟

Numerical simulation of flow field and dynamic characteristics of pilot operated directional valve

摘要:

为获得阀口型式对液控换向阀内流场和动态响应的影响，利用CFD和Matlab Simulink数值模拟软 件对该阀进行了分析．阀内流场模拟采用两相混合流和标准k-8模型；滑阀动态响应研究是基于滑阀运动 的物理方程在Matlab Simulink平台上开展的．对3种阀口流场进行稳态和瞬态分析，得到流量系数、入流射 流角度和滑阀所受轴向力．分析结果表明：阀口开度越小、流量越大，轴向力和气穴产生的可能性都增大；滑 阀运动速度越大，开阀过程产生气穴可能性越大，闭阀过程相反；阀口开度为2 mm，流量在35 L/min以下不 产生气穴；液动力方向始终为开阀方向，常用公式计算结果与实际不符．动态特性研究表明：K或V型阀口的 滑阀响应较快，但系统工作速度主要由阀口流量系数决定，应限制滑阀位移以避免振荡．阀口型式对液控换 向阀内流场和动态特性均有显著的影响

Abstract:

To obtain the effects of notch type on the flow field and dynamic response characteristic of the pilot operated directional valve, the simulations of steady and transient flow with three kinds of notch based on CFD and Matlab Simulink software are carried out, and the discharge coefficients, the efflux angles into the notch and the axial forces on the spool are obtained. Two-phase Mixture flow model and standard K-epsilon model are used in the flow field simulation. The results show that the smaller the notch opening and the larger the flow rate, the greater the transient axial forces and the possibility of cavitations. When the moving speed of the spool increases, the possibility of cavitations increases during the notch open process, and decreases during the notch close process. There are no cavitations generated with the notch opening 2 mm when the flow rate is within 35 L/min. The direction of flow forces is to open the notch, and the flow forces calculated from Con- ventional Formula do not comply with the real ones. The results from dynamic analysis for the spool show that the spool with K or V notch responds quicker; the working speed of the system mainly depends on the dis- charge coefficient of the notch; and the spool displacement should be limited to avoid oscillation. In conclu- sion, the type of the notch impacts the flow field and dynamic response of a piloted directional valve a lot.