液压阀口二级节流特性

为了研究阀口二级节流特性，分析了U型、V型及其组合形式节流槽的几何特征，并在此基础上简化计算其节流面积，得出以阀口开度X为自变量的节流截面面积比，发现对于U型槽随着阀口开度X的变化其最小节流截面存在着转移现象，而V型槽则不存在.另外引入空化气蚀指数σ，计算以阀口开度为自变量的U型槽和V型槽空化气蚀特性函数并做出了气蚀指数曲线，分析节流槽进出口压力变化时空化气蚀特性的变化并通过试验验证，发现U型槽随着阀口开度的变化空化气蚀剧烈区的位置会发生相应的转移，而V型槽则不发生变化；当U型和V型槽的液流进出口翻转时，其气蚀指数的大小会发生明显的变化.由节流槽刚度计算式推导了U、V型节流槽的刚度理论计算式，并得出了在不同进出口压力差和不同阀口开度下的刚度曲线，研究结果为工程人员设计高性能液压阀提供了一定的理论依据.

Two-step throttle properties of hydraulic valve ports

The geometrical features of the U and V ports as well as their combinations (U-U, U-V and V-V) were analyzed, and then the throttle areas of those ports were calculated in a simplified manner so as to investigate two-step throttle properties of hydraulic valve ports. The ratio of throttling areas in terms of valve opening was obtained, and it was observed that the location of the minimum throttle area of U port varies; however, this is not true for V port. The cavitation functions of U and V ports against opening were obtained and the cavitation curves also were plotted by using cavitation number σ. According to the cavitation functions, it was observed that the severe cavitation zone in U port varies with opening, but that in V port is fixed. When the inlet and outlet of throttling port are reversed, there is an obvious change in cavitation number at the same opening. The stiffness analytical formulas for U and V orifices were derived and the stiffness curves were calculated under various pressure differentials across a port and openings. For a lower pressure differential and a smaller opening, a stiffer stiffness can be achieved.