Three-dimensional Numerical Simulation Of Flow In Labyrinth Control Valve

As a kind of actuator, control valve is a very common and essential terminal control component in a control system of process control industry. In practical applications such as power engineering and chemistry industry, control valves are required to work reliably under high temperature and high pressure. In this paper, ANSYS CFX is used to simulate the flow characteristics of a natural-gas control valve and a minimum flow valve. The simulational results can be taken as a reference upon designing and optimizing these valves. The main results are as follows:(1) In this thesis, the MX-6"L25W1V-0-type minimum flow valve was simulated under a steady condition. It was found that depressurization process mainly occurs at the disc and an increase in flowing rate within the plates is helpful to improve the capacity of depressurization. Besides, the surface roughness is demonstrated to have a negligible influence on depressurization effect. Given the mass flow of89kg s-1, the pressure difference is20.664MPa when the roughness is3.2μm while the pressure difference increases to21.068MPa when the roughness is32μm. And when the valve opening level reaches ten plates, cavitation phenomenon appears in the minimum flow valve. The cavitation occurs in the upper region close to the valve outlet.(2) The linear flow characteristics of the MA-3"L25R2C-type natural-gas control valve were verified. The gas physical parameters were calculated using P-R state equation. The throttling effect was analyzed in case of natural gas as the flowing medium. As a result, the temperature at the outlet is much smaller than that at the inlet. When the pressure difference between the inlet and outlet is34.497MPa, a smaller opening level leads to a larger temperature difference, that is, the temperature difference increases from68.22K to100.27K as the number of plates decreases from12to2in this paper. Also, when the valve fully opens, the temperature difference increases from39.486K to74.283K as the flow increases from5kg/s to50kg/s. The temperature difference decreases when increasing the temperature at the inlet. The temperature difference is62.809K when the temperature at inlet is313.15K while the temperature difference decreases to54.944K when increasing the temperature at inlet to373.75K. It is found that critical flow occurs at the valve outlet.