| The deflector servo valve has excellent performance in stability,speed and anti pollution ability,which makes it widely used in aerospace and other fields requiring highprecision control.The deflector jet assembly is the core of the deflector servo valve,and the flow field and noise characteristics are its important characteristics.The structure of the deflector jet module is precise and irregular,and its working conditions are complex.Small structural changes and different working conditions will have a great impact on its performance.Therefore,it is very important to study the flow field and noise characteristics of the deflected jet module and the influence of its structure and working conditions on its performance.In the research of flow field characteristics,firstly,combined with the theory of fluid mechanics and jet theory,the flow field of the deflected jet assembly is analyzed in stages,the valve equation of the deflected jet assembly is established,and the important performance parameters and influencing factors of the deflected jet assembly are obtained.Secondly,the steady-state flow field and cavitation are simulated,and the changes of pressure,velocity and cavitation under different offsets are analyzed.The pressure characteristics of two-phase flow are obtained,and the differences between two-phase flow and single-phase flow are obtained through comparative analysis.The influence of wedge fillet and deflector outlet fillet on the flow field characteristics is investigated,and the structural optimization direction based on the flow field characteristics is obtained.Then,the transient flow field is simulated,the pressure and cavitation changes at different times are analyzed,and the dynamic characteristics of cavitation and pressure fluctuation in the key parts of the deflected jet assembly are obtained.In the research of noise characteristics,firstly,according to the fluid noise theory,the noise radiation modes and measurement modes of different noise sources in the deflected jet module are analyzed,and the sound wave generation equation of multiphase flow is established.Secondly,the noise distribution is simulated in the steady flow field,and the noise area distribution and the noise changes under different offsets are obtained.The influence of the two structural changes of the receiving cavity fillet and the deflector outlet fillet on the noise characteristics is explored,and the optimization direction of noise reduction is put forward.Then,the noise spectrum simulation of the transient flow field is carried out,and the noise frequency variation in the main noise area is studied,and the noise spectrum characteristics of the deflected jet components are obtained.The pressure fluctuation in the noise area is monitored,and it is concluded that the factors such as pressure fluctuation and cavitation are the important influencing factors of noise frequency variation.The influence of different working pressure conditions on noise spectrum is studied,which provides a reference for the selection of working pressure when considering the influence of noise.In the aspect of model test,based on the similarity theory,the experimental model of the deflected jet assembly is designed,the experimental system is built,the model tests of the flow field characteristics,cavitation characteristics and noise characteristics of the deflected jet assembly are carried out,and the theoretical analysis and simulation research are verified by experiments.This thesis perfects the research on the flow field and noise characteristics of the deflected jet assembly,puts forward a new structural optimization direction to improve the flow field performance and reduce the noise,obtains the dynamic characteristics and pressure fluctuation characteristics of the key local cavitation in the deflected jet assembly,studies the noise characteristics of the deflected jet assembly from two aspects of the noise region distribution and noise spectrum,and analyzes the main influencing factors of the noise,The basis for selecting the working pressure considering the influence of noise is established,which provides a certain reference and guidance for the performance research and structure optimization of deflected jet components. |
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