| The hydraulic valve has been widely used in today's oil and gas field development system. But the current domestic research on valves with drilling mud as medium is inadequate, especially on valves applicable to small space in underground operations in particular. This thesis designs and analyzes directional valve taking drilling fluid as the working media on a theoretical basis, providing some experimental and theoretical reference for more in-depth study of the types of components.The project makes a study on the characteristics and mechanism of slurry directional valve by employing comprehensively experimental research, theoretical analysis, modeling and simulation. Thesis first makes an experimental and theoretical analysis about flow coefficient and flow characteristics in valve port of slurry valve. The directional valve suitable for drilling engineering requirements is designed and the designing methods are given on this basis. Finally the numerical calculation and optimizational analysis of the valves'structure parameters are made by means of system simulation and fluid simulation.Contents include:(1) Numerical simulation calculation In the region near the valve port of the cone valve commonly used in drilling fluid systems is made, based on CFD methods and gas corrosion theory, using power-law fluid constitutive equation, RNG turbulence model and two-phase flow model. The effect of angle of poppet, arc in front of poppet and chamfer of valve seat in the flow field within cone valve is investigated emphatically by analyzing the form of stream line, pressure and distribution of gas volume percentage.(2)The test program of flow coefficient is determined for the special physical and chemical properties of drilling mud media. Some related test equipments are designed and developmented and the test system is set up. Experimental investigations are made on the flow coefficient of cone valve,ball valve and plate valve taking drilling fluid used in Power-law rheological model as the working media. The data and law of flow coefficient of poppet valve for drilling fluid are obtained in various situations by measuring flow and pressure at different opening of four constructions of valve seats.(3) Several directional valves with slurry as medium are introduced from the perspective of designing difficulties, structure selection and parameter calculation. A relatively perfect set of designing methods of slurry valve is established and the main calculation formulas of parameters are given. Material selection and processing technology of slurry valve in the manufacturing process are summarized and some useful conclusions for engineering are obtained.(4) using the power bond graph theory which is outstandingly advantageous to serious nonlinear systems analysis, combined with MATLAB / SIMULINK simulation and optimization tools, according to the actual structure parameters of the designed directional valves, the corresponding valve control system is simulated and results are compared and analyzed so as to optimize the key structural parameters and to improve the slurry media directional valve performance. (5) The flow path model of slurry media directional valve is established using SOLIDWORKS. Numerical calculation of fluid dynamics of flow field in valve pocket is made using FLUENT. By analysis of pressure distribution in convection channel, velocity distribution and three-dimensional flow lines, the influencing factors resulting in the existence of negative pressure area, whirlpool areas and stream line distortion in the flow field caused by the valve structure are analyzed deeply, and the optimization and improvement measures are proposed.
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