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Research of the Flow Characteristics of the Jet Flow Field in Prestage of Hydraulic Servo Valve

Author: ZhangShengZhuo
Tutor: LiSongJing
School: Harbin Institute of Technology
Course: Mechanical and Electronic Engineering
Keywords: Flapper-nozzle servo valve Jet flow field Pressure oscillation Flow visualization
CLC: TH134
Type: Master's thesis
Year: 2011
Downloads: 109
Quote: 0
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Abstract


The jet flow in the flapper-nozzle prestage of hydraulic servo valve has a few characteristics, such as high speed, cavitation, shear flow and so on. The instability of the jet flow field often results in high frequency pressure oscillation and noise when the servo valve works, even influences its life. So in order to improve the performance of the servo valve, it is essential to build the mathematical model and study the distribution of the jet flow field.In this paper, the mathematical models of the jet flow field in a servo valve are established, which is accompanied by the continuity equation, the momentum equation, suitable turbulence model and the near wall calculating method. The 2D flow field model near the flapper nozzle is established and meshed by CAD and GAMBIT software, and simulated by FLUENT software with different shapes, different zone of wake and different location of the flapper. The corresponding distributions of pressure and velocity are simulated. Then the condition and the law of the high frequency pressure oscillation are summarized. The jet flow field is observed by a digital microscope and a high speed video camera with different inlet pressure and shooting frame number. The shear flow oscillation period is estimated by observe the edge motion of the jet flow. The results are compared with the simulation.In this paper, the mathematical models in the flapper-nozzle prestage of hydraulic servo valve are built based on the current state of the jet flow field research and the fluid mechanics theory. The finite element analysis of the jet flow field with different shapes and different boundary conditions are carried out. The pressure oscillation is measured, and the jet flow field is shot, by doing this the period of the jet flow oscillation is estimated. These works provide some theory basis for the research of the jet flow field characteristics and the mechanism of the high frequency noise.

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CLC: > Industrial Technology > Machinery and Instrument Industry > Mechanical parts and gear > Control parts
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