Cavitation Performance of an Oil Hydraulic Poppet Valve : Critical Cavitation Number for Various Rates of Pressure Change in Valve

Abstract

This paper deals with an experimental study on the unsteady cavitation performance in an oil hydraulic poppet valve. Experiments are carried out under two kinds of flow conditions : one is an unsteady flow in which the valve inlet pressure p₁ takes the form of trapezoid varying with time keeping the outlet pressure p₂ constant ; and the other is the flow in which the former p₁ and p₂ are interchanged, respectively. It is found that as absolute values of the rates of pressure change dp₁/dt and dp₂/dt increase the incipient cavitation number k_ci shows a tendency to decrease, and the desinent one, k_cd, shows a tendency to increase under all geometrical parameters in this test. As the absolute values of dp₁/dt and dp₂/dt further increase, the hysteresis between k_ci becomes larger for each combination of the valve and valve seat.