Study On Characteristics Of Pre-stage Flow Field Of Jet Deflector Servo Valve Under Temperature Impulse

As a precise control element,the electro-hydraulic servo valve is widely used in the aerospace field.Among different kinds of them,the jet deflector servo valve is largely used for its advantages of small rotational inertia,good dynamic performance and strong anti-pollution ability.In the aerospace field,the combustion of fuel causes a severe temperature impulse within the system;and as the core part of the jet deflector servo valve,the control accuracy of the pre-stage will be greatly reduced under the influence of temperature impulse.At present,the distribution of the flow field under temperature impulse is still very scarce.Therefore,in order to improve the control performance of the deflector valve and guide its design,it is of great significance to study the distribution of the internal flow field of pre-stage under temperature impulse.This paper first divides the internal flow field of pre-stage into four parts based on the actual structure of pre-stage and the previous numerical simulation results.Combining the related jet theory and thermodynamic knowledge,the theoretical model of the flow field distribution of pre-stage under temperature impulse is established,which takes the influence according to temperature changes into consideration.The velocity and pressure characteristics of the flow field are analyzed as well.Then,based on the actual jet deflector servo valve structural parameters,the structured three-dimensional numerical model of the pre-stage flow field is established,and the transient large eddy simulation(LES)is used to simulate the pre-stage flow field.With the comparison of the results of numerical simulation and theoretical calculation,the two research methods are verified feasibly and correctly.In order to obtain the distribution of the flow field under temperature impulse,this paper rebuilds the structured two-dimensional numerical model of the pre-stage flow field,and redefines the parameters and boundary conditions of the numerical simulation using the user-defined function and dynamic grid function of the FLUENT software.Then the transient simulation of the pre-stage flow field is carried out again,using the results of the 3D LES simulation.The pressure and velocity distributions of the flow field are obtained through dynamic simulation at different displacements,and the working characteristics of pre-stage under temperature impulse are analyzed by comparing with theoretical model.Finally,this paper builds a temperature impulse prestage working characteristic test bench,which can simulate the temperature impulse environment by changing oil temperature.By this way the working pressure change of pre-stage can be determined.Through the mutual verification of theory,simulation and experiment,the feasibility of theoretical model and numerical simulation for pre-stage research is proved.This paper perfects the theoretical system of how the temperature change influences the pre-stage flow field of the deflector valve,and makes a reasonable explanation for the large decrease in the control accuracy of the deflector valve under temperature impulse.Moreover,it provides some referable research methods for jet deflector servo valve in the temperature field,and certain guiding suggestions for improving the performance as well as optimizing the design of the structure of deflector valve.