Cavitation performance of an oil hydraulic poppet valve. (Critical cavitation number for various rates of pressure change in valve).

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 kci shows a tendency to decrease, and the desinent one, kcd, 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 kci becomes larger for each combination of the valve and valve seat.