| Electro-hydraulic servo valve plays a key role in aerospace equipment.As a kind of them,the jet deflector servo valve has characteristics of simple structure and strong anti-pollution ability which promotes its wide application.However,it's key component,jet deflector mechanism,has complex and tiny structure,and internal dynamic characteristics of the flow field are difficult to be described by an accurate mathematical model.In order to guide the design and production of the jet deflector servo valve,it is crucial to study the internal flow stability and flow noise of the jet deflector mechanism.By analyzing the complex structure of the jet deflector mechanism,the internal jet flow field is divided into four stages.The 3D mathematical model is established which can accurately describe the velocity as well as the pressure distribution inside the flow field,based on the jet theory,the wall jet theory and the impinging jet theory.What's more,the positions of cavitation are predicted by evaluation parameters of cavitation.In addition,an accurate 3D numerical model is established.It is structurally meshed to ensure the maximum accuracy of the simulation results.Then the transient two-phase simulation of the model is carried out,and the changes of cavitation generation and collapse during the whole jet process are obtained,which provides a powerful basis for analyzing the internal flow noise.Besides the transient Large Eddy Simulation(LES)simulation is carried out on the model to obtain the dynamic as well as the stable distributions of the flow field in the whole jet process.At the same time,the simulation results and the theoretical calculation results are mutually verified.Finally,the characteristic test bench for the jet deflector mechanism is designed to measure the flow field pressure distribution under different displacement conditions of deflection plate.The experimental results show that the 3D mathematical model and numerical simulation of the jet deflector mechanism can effectively describe the jet characteristics of the jet deflector mechanism.The thesis establishes the first 3D mathematical model,which can accurately describe the spatial flow characteristics of the jet deflector mechanism.Then a more accurate 3D numerical model is established,and the complex model is structurally meshed.Grid quality reaches a high level to ensure the accuracy of the simulation results.So transient LES and transient two-phase simulation of the model can be used to accurately analyze the flow characteristics of the internal flow field.More importantly,the thesis perfects the theoretical system of the flow field characteristics for the jet deflector mechanism and provides a more perfect theoretical basis for the study of the electro-hydraulic servo valve.Moreover,it of offers a worthy research method for future researchers and guiding significance for the design and production of electro-hydraulic servo valves. |
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