Cavitation and flow forces in the flapper-nozzle stage of a hydraulic servo-valve manipulated by continuous minijets

Abstract

Electro-hydraulic servo-valves play key roles in modern electro-hydraulic power systems in many industrial applications. As one of the widely used hydraulic servo-valves, cavitation in the flapper-nozzle servo-valve could produce deleterious effects of noise, flapper vibration and cavitation erosion. In this work, a numerical investigation has been conducted on the manipulation of the flapper-nozzle pilot valve using continuous minijets. Two minijets are symmetrically deployed around the main jet of each nozzle. Vapor fraction and flow forces under the effect of the continuous minijets are compared in detail between the traditional nozzle and the nozzle with the minijets. It is found that cavitation in the flapper-nozzle stage is greatly weakened under the effect of the continuous minijets. The remarkable drop in the radial jet velocity results in the suppression of the swirling structures in the annulus, which may be responsible for the cavitation reduction. The variation trend of the flow forces with the inlet pressure remains unchanged while the magnitude of the flow forces is varied slightly, depending on the various surfaces of the flapper.

Design and Verification of Two-Stage Brake Pressure Servo Valve for Aircraft Brake System

“…According to Equations ( 5) and ( 17), we get two more obvious expressions of output pressure written as Equations ( 18) and (19), as follows:…”

“…These mainly include rotary jet pipe servo valves, jet pipe valves, integrated jet pipe valves, slide valve end inclined jet pipe valves and middle jet pipe valves [7][8][9][10][11][12][13][14][15][16][17][18]. To verify the adaptability of jet pipe valves in aircraft braking systems, Yang [19] and Zhao [20] compared the performance indexes of nozzle flapper valves and jet pipe valves, and proposed that the key technical indexes of jet pipe valves meet the performance requirements of nozzle flapper valves. Zhang [21] provided an experimental method for the stability assessment of jet pipe valves with experimental projects as the background.…”

Numerical Investigation of Flow Force and Cavitation Phenomenon in the Pilot Stage of Electrical-Hydraulic Servo Valve under Temperature Shock

“…However, the experimental validation of the mechanical characteristics was not conducted to prove the efficiency of the optimized flapper shape. Then, the researchers promoted another method: the reduction of cavitation in the pilot valve is accomplished by decreasing radiation jet velocity [9], while the micro-jet can accelerate the reduction of the jet velocity [13].…”

A new simplified fluid dynamic model for digital twins of electrohydraulic servovalves

“…For instance, Urata investigated the effect of various failure modes on the behavior of hydraulic servovalves, namely, leakage flow, fringing, eddy currents and air gap asymmetry in the torque motor (Urata, 2000(Urata, , 2001(Urata, , 2002(Urata, , 2003(Urata, , 2004a(Urata, , 2004b(Urata, , 2005. Other detailed analyses of the behavior of servovalves are proposed by Yang et al (2019) and Henninger et al (2017) using computational fluid dynamics (CFD) and electromagnetic finite elements, respectively. However, these detailed simulations are generally costly, both in terms of computational time and processor workload and therefore can be unsuitable for certain tasks, whose execution is time or resource constrained.…”