Influence of pre-stage cavitation on performance of double-nozzle flapper pressure servo valves

Cavitation is common in electrohydraulic servo valves and often adversely affects their performance. This study explores the influence of pre-stage cavitation on the performance of double-nozzle flapper pressure servo valves. The mechanism of cavitation is theoretically studied, a dynamic model of cavitation bubble motion is deduced, and the main factors affecting the development and variation of cavitation are determined. The software ADINA is used to establish a servo valve pre-stage fluid–structure interaction (FSI) model using the finite volume method. Cavitation is introduced to the model to conduct an FSI simulation of the influence of pre-stage cavitation on the performance of double-nozzle flapper pressure servo valves with nozzle diameters of 0.5, 0.55, 0.6, and 0.7 mm. An experiment on the servo valve is carried out to verify the simulation results. The simulation and experiment show that a nozzle diameter that is too small or large weakens the performance of a servo valve, and 0.6 mm is an ideal diameter; asymmetric double nozzles may reduce or improve the performance of a servo valve, and a combination of 0.6 and 0.55 mm nozzles is optimal; pre-stage cavitation influences the performance of a servo valve by changing the size and pressure gain of the dead zone; and excessive cavitation strength decreases or increases the dead zone and increases the pressure gain.