Research On The Characteristics Of Gas Axial Flow Control Valve

Flow control valves are widely used in metallurgy,chemical industry and other process industries as important pipe accessories.Among all kinds of control valves,the axial flow control valve has the characteristics of wide adjustment ratio,smooth adjustment and small disturbance to flow,and has advantages in applications requiring higher adjustment characteristics.In this work,by combining theoretical analysis,numerical simulation and experiment,the design theory and design method for axial flow regulating valve are studied,a new type of gas axial flow regulating valve with equal percentage flowrate is developed,and the flow regulating and pressure loss characteristics of the valve are studied.Main contents and results are as follows:(1)Design method for axial flow control valve and new structure design of an axial flow valve.For the requirement of equal percentage flowrate characteristics,the mathematical model for the flow of the axial regulating valve is derived,which describes the relation between the relative flow coefficient of the regulating valve and the opening of the valve.The design method of the axial flow regulating valve is put forward,and the calculation model of the slit hole of the regulating valve sleeve is established.In order to reduce pressure loss and flow disturbance of the control valve,a rear cowl is designed at the end of the axial flow valve.Referring to the structure of traditional cage sleeve valve,the structure design and calculation of new DN50 gas axial flow valve are completed.(2)Research on the numerical simulation of flow characteristics of axial flow control valve.The flow characteristics inside the control valve are studied by means of computational simulation.In the calculation process,a combination of standard k-εmodel construction and large eddy simulation model(LES)is used.Seven values were selected in a mean flow velocity range of 6m/s-30m/s(flowrate from 42.4m~3/h to 212.0m~3/h)with valve opening from 10%to 100%.The distribution of pressure field and flow velocity field are calculated,and the flow characteristics and flow regulating performance of the valve are analyzed.The results show that at the outlet of the valve orifice,swirl flow is generated,the larger velocity,the bigger size of the swirl and the longer distance to reach a stable flow.At the same flowrate,the disturbance distance downstream of the control valve decreases with the increase of opening.For all the operating conditions,the distance for the fluid flow passes through the rear cowl to reach a stable flow state is about 3-D downstream of the control valve.(3)Experimental study on characteristics of axial flow control valve.The flow regulating characteristics,pressure loss and downstream flow pressure fluctuation of the control valve were studied by experimental method.The relative flow coefficients of the control valve are obtained by testing 160 m3/h,150 m3/h and 130 m3/h flow rates and 10 valve openings.The results show that the experimental data,computational simulation data and design data are in agreement with each others,which verifies the correctness of design theory and design method.Dynamic downstream pressure tests with and without rear cowl were carried out at 100%opening of the control valve.With rear cowl,resistance loss and pressure fluctuation are reduced by 13.06%and 41.0%.