Research On The Modeling And Simulation Of Jet Pipe Servovalve

Jet pipe electro-hydraulic servo valve is named for its pre-stage is a jet pipe amplifier. Because of its excellent anti-pollution performance, jet pipe servo valve has been extensive used on foreign aircrafts and ships instead of traditional flapper-nozzle servo valve. For the jet flow field is very complicated, the theoretical analysis of it is not mature, and currently, the optimal design of its structure parameters is relied on a large number of experiments. In consideration of the difficulty of its processing and welding, and the requirement of high technology during the assembly and debugging, this method requires lots of manpower and resources, therefore, accurate and efficient simulation technology would be of great importance to the in-depth study on the performance and related technology of jet pipe servo valve.The numerical simulation technology has been produced with the rapid development of computer technology, which uses the numerical methods of finite element and finite volume to conduct research on the practical engineering problems. Usually, it is difficult to get analytic solution of complicated issues, but we can adopt the numerical method to solve this problem by using high accuracy approximation.In this paper, part and whole analysis of the jet pipe servo valve has been done using the theoretical analysis combined with the numerical simulation technology. The main contributions are as follows.[1] The theoretical model of the torque motor, jet pipe amplifier and armature assembly have been established on the basis of analyzing the structure and working principle of the jet pipe servo valve. In the traditional lumped parameter model, the linear equation of pressure-flow is used to simplify the modeling of flow field of the jet pipe amplifier, in this paper, conservation of energy and theorem of impulse are used to establish the model of the amplifier which are on the premise of the formula derivation of the receivers’ area distribution. The armature assembly’s mathematical model is established on the basis of analyzing the mature model of flapper-nozzle servo valve. Furthermore, used the AMESim developing tool to design the submodels of the jet pipe amplifier and the armature assembly, finally accomplished the system modeling and simulation in AMESim.[2] Used the numerical simulation technology to accomplish the 3-D modeling and simulation of the torque motor, jet pipe amplifier and armature assembly of the jet pipe servo valve. Used the finite element method to carry on the dynamic analysis of the torque motor on the bases of electromagnetic field theory, in the process of calculation, magnetic flux leakage and various electromagnetic effects are taken into consideration; Used the finite element method to carry on the static structure analysis of the armature assembly based on structural mechanics; Used the finite volume method to carry out the analysis of the flow field in the jet pipe amplifier and between the spool and sleeve on the basis of fluid mechanics. For the cavitation which can be caused by some reasons may influence the flow field, in this paper, this phenomenon has been considered by programming using UDF(user defined function) combined with multiphase flow model.[3] On the basis of above analysis, the system modeling and simulation has been carried out by two ways: one is to obtained the interpolated functions on the basis of the numerical analysis’ s results by fitting, and utilized these functions to establish model and accomplish the simulation in MATLAB; another is to use the results of the numerical analysis of magnetic field and flow field as the variable boundary conditions, and applied them on the armature assembly to carry out the dynamics simulation by programming using APDL. Furthermore some correlate characteristics of this valve are analyzed. Some key parts’ stiffness are computated, the design method of the feedback lever’s stiffness has been derived and the optimization of its structure has been carried out by numerical simulation; Modal and harmonic analysis of the armature assembly have been done to study its vibration performance; Based on the material mechanics theory, the structures of jet pipe servo valve and flapper-nozzle servo valve have been compared and analyzed; The effects of the oil pressure and the structural parameters of the jet pipe amplifier on the amplification efficiency have been studied in this paper, including the inlet and outlet pressure of the oil, the distance between the jet nozzle and receiver, the diameter of the hole, the angle and distance between the two holes.[4] In this paper the optimization algorithm is introduced for the structural design of jet pipe amplifier, two methods are designed as follow. One is based on the lumped-parameter model, the pressure differential function derived before has been used as the objective function, and the iterative optimization of multiple parameters has been accomplished by programming using proper intelligent algorithm. This method can optimize multiple structural parameters at the same time efficiently, however, due to the complexity of the jet flow field which includes some complex phenomena such as the wall jet and backflow, it is difficult to build the mathematical model accurately, and some simplifications may lead to erroneous results. Another method is the numerical optimization methods which is based on the 3-D model, the parametric model has been used to realize the automatic optimization process which includes modeling, numerical computation, optimization and updating by using the multi-software integration technology, this method effectively avoids the difficult problem of modeling the jet flow field, and this method can be used as an optimization platform for any complex flow field.[5] The erosion wear of the jet pipe amplifier may affect the performance of the whole valve. According to the computational fluid dynamics(CFD) theory and the theory of erosion, Adopted the k-ε two-equation model for the fluid and the discrete phase model(DPM) for the solid particle and used the Navier-Stokes equations combined with the plastic material erosion model to carry out the numerical simulation of the erosion rate using FLUENT, and analysed the regularities of the erosion rate’s distribution, finally used the results of the numerical analysis to estimate the service life of the valve. This research method and results has certain reference value for the fault qualitative analysis of jet pipe servo valve.