Abstract: A precise and complete mathematical model for the flow field in the pre-stage of jet deflector servo valve is established for the design and research of pilot-stage servo valve. The jet process is divided into four stages: initial jet, deflector pressure recovery, secondary jet, and pressure recovery at receiver opening. In the process of two jets in the pre-stage, the different theoretical models are adopted to build the complete mathematical model of flow field in the pre-stage, and the evolution of jet pattern is described in detail. It is found through analysis that the oil enters the flow field in pre-stage and impacts on the side wall of deflector, and then the flow pattern changes, one part of oil flows out of the deflector along its side wall, the flow velocity of the other part of oil decreases, and a high pressure zone is formed downstream. The oil is affected by the flow divider when it flows out of the deflector, and flows into different channels. The flow and pressure characteristic equations are used to derive the pressure gain, and a mathematic relation between load pressure and deflector offset is established. In the process of numerical simulation, the different turbulence models are adopted to analyze the pressure distribution of flow field in the pre-stage. The effectiveness and rationality of the proposed model describing the jet characteristics is verified by comparing and analyzing the numerically simulated results, the external characteristic experimental results and the calculated results of jet model.Key

Key words: jetdeflectorservovalve, flowfieldmodel, turbulentjet, turbulencemodel