Research On Power Characters Of A New Type Of Pilot-Controlling Cut-Off Valve

There must be huge drive actuators when common cut-off valves used in pipe system of large diameter and high pressure, and the problem is that the opening or closing process is slow and energy consumption is high. The new type of pilot-controlling cut-off valve which utilizes pressure difference forms when fluid flows as its power can meet the industry requirements of high efficiency, environmental protection and energy saving, so the engineering application value is great. Because of the complexity of the internal flow and uncertainty of the internal pressure, there's uncertainty in the design of the structure. The power characters is summarized through simulations of the flow field with fluent technology UDF and authenticated by the experiments. The main research contents and achievements are as follows:(1) In view of the uncertainty, the general part and special part of the pilot-controlling cut-off valve design process are analyzed to find out the existent factors which is factitiously assumed and the starting point which is the pressure difference between the upper surface and lower surface of the piston-type valve core.(2) Static numerical simulations are taken by the method of RNG k-e turbulence model using 3-D meshing model which is simplified to analyze the internal flow field and validate its work principle. Pointed out that the force generated by pressure difference between upper surface and lower surface is the only power source to open the valve and its value determines the displacement of the piston-type valve core. Factors that affect the pressure difference are identified for the future study of the power characters.(3) 3-D numerical simulations show that the pressure distribution on the upper surface and lower surface is uneven, so UDF program is compiled to extract the pressure on each cell of each face and calculate its average value, and then the pressure difference is output. To obtain solutions which should be independent of grid, grid-independent verification is done which bases on the value of the pressure difference.(4) Flow field of the pilot controlling valve is simulated under different nominal diameter, piping static pressure, inlet velocity, orifice diameter and pilot pipe diameter, combined with the local resistance theory of fluid mechanics, the engineering estimation formulas of the local resistance coefficient and power value are induced. Experiments are taken under different combination of the factors. The displacement of the valve core is measured by sensor when the opening process is stable. Experimental value of the pressure difference is calculated based on its function relationship with displacement, and then compare the simulation value which is got from the meshing model under corresponding displacement with experimental value to validate the model simplification method and numerical simulation method.This research has an important academic and application value for the optimization design of the new pilot-controlling cut-off valve.