Analysis of Three-Dimensional Flow Field Inside the Pilot Stage of the Deflector Jet Servo Valve

Abstract

Current two-dimensional flow field model has some defects in describing the pilot stage’s flow field and static characteristics of the deflector jet servo valve(DJSV) because the three-dimensional(3D) jet of the flow field is ignored. In order to overcome the shortcomings, a new flow field model is proposed and the energy transfer process of the pilot stage is obtained. In this model, the flow field is divided into five regions: pressure jet region, free jet region, mixed collision region, secondary jet region and pressure recovery region. Especially, three-dimensional turbulent jet is adopted in the free jet region for the first time to describe the structure of the flow field, and the jet entrainment model is proposed in pressure recovery region to describe the coupling relationship between the pressure in the receiving chamber and the jet flow which has never been considered before. The static characteristics of the pilot stage, such as pressure-flow characteristics, pressure characteristics and flow characteristics are obtained, and the relationship between zero-position valve coefficients and the key structural parameters of the pilot stage is analyzed. The results show that main structural parameters that affect the pressure gain include the length of receiving chamber, the width of guide groove outlet and the width of the wedge; The thickness of jet-pan has the most significant influence on flow gain. The flow field structure and the static characteristics are verified respectively by finite element analysis(FEA) and experimental results, and the results show that the pilot stage mathematical model has good reliability which is beneficial to understand the working mechanism of the pilot stage provide theoretical basis for parameter optimization.