Numerical and experimental investigation of leakage behavior at null position of high-pressure electro-pneumatic servo valve

Abstract

The high-pressure electro-pneumatic servo valve (HESV) is a core element of the high-pressure pneumatic servo system. The annular clearance and the rounded corner of the spool-sleeve can cause the leakage at null position, thereby affecting high-precision control and stability of the servo system. This paper investigates the effects of the clearance structure on leakage behavior at null position of the HESV. A numerical approach was employed to evaluate the effects, and then a mathematical model was established to obtain the variation law of leakage flow rate at null position. The results indicate that the leakage flow rate at null position varies linearly with supply pressure and rounded corner radius, and is nonlinear as a quadratic concave function with annular clearance. The leakage flow rate of the annular clearance and the rounded corner varies with the valve opening in an invariable-nonlinear-linear trend. A test rig system of leakage behavior at null position of the HESV was built to confirm the validity of the numerical model, which agrees well with the conducted experimental study.

Keywords

high-pressure electro-pneumatic servo valve / clearance / leakage flow rate / null position

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