At present

the pre-stage theoretical model of jet tube servo valve usually uses flow pattern coefficient to correct the influence of jet turbulence

but does not reveal the specific influence mechanism of jet turbulence

and the influence of reflected oil is often ignored. In order to describe the pressure characteristics and flow characteristics of the pre-stage accurately

a mathematical model of the pre-stage was established based on momentum theorem

in which the specific influence mechanism of jet turbulence on the pressure recovery process of the receiving hole was revealed and the influence of reflected oil in the pressure recovery process was considered. The pressure characteristics and flow characteristics were obtained

and the flow field simulation by Fluent and mathematical model were mutually verified. The research results show that the mathematical model results are in good agreement with the Fluent simulation results. The pressure gain of the pre-stage of the jet pipe servo valve is 11.547 MPa/mm

and the flow gain is 3.270 L/(min·mm).