Research on low cavitation in water hydraulic two-stage throttle poppet valve

Abstract

Cavitation has important effects on the performances and lifespan of water hydraulic control valve, such as degrading efficiency, intense noise, and severe vibration. Two-stage throttle valve is a practicable configuration to mitigate cavitation, which is extensively used in water hydraulic pressure relief valves and throttle valves. The pressure distribution inside a medium chamber located between two throttles of a two-stage throttle valve is investigated through numerical simulations. The effects of the passage area ratio of the two throttles and the inlet and outlet pressures on the pressure inside the medium chamber are examined. The simulation results indicate that (a) the pressure inside the medium chamber is not constant, (b) the locations of maximum and minimum pressures inside the medium chamber are both fixed, which will not vary with the passage area ratio or the inlet and outlet pressures, and (c) the ratio of the pressure drop across the front throttle to the total pressure drop across the two-stage throttle valve is nearly constant. The critical cavitation index of the two-stage throttle valve is then established. A semiempirical design criterion is obtained for the water hydraulic two-stage throttle valve. The correlation between the critical cavitation index and the passage area ratio of the two throttles is investigated. Relevant validation experiments are conducted at a custom-manufactured testing apparatus. The experimental results are consistent with the simulated ones. Further analyses indicate that (a) the large backpressure can improve not only the anti-cavitation capability but also the total load rigidity of the water hydraulic two-stage throttle valve, (b) an appropriate passage area ratio will be beneficial for improving the anti-cavitation capability of the water hydraulic two-stage throttle valve, and (c) the water hydraulic two-stage throttle valve with a passage area ratio of 0.6 would have the best anti-cavitation performance with the lowest risk of cavitation.