| Multi-stage pressure-reducing regulating valves are widely used in power stations and petrochemical industries,and play a key role in the reliable operation of the entire system.Under the severe conditions of high pressure and large flow,the regulating valve has inherent problems such as unstable pressure reduction and speed control,serious cavitation and cavitation.With the support of the national key R&D project "Research and Application Demonstration of Key Technologies for High-Performance Special Control Valves"(2018YFB2004001),this paper proposes a new type of space ant nest type multi-stage pressure-reducing control valve.Through the combination of simulation analysis and experimental verification,the composite depressurization principle of the throttling element is studied,and its structural design method is established.The main research contents and conclusions are:(1)To deal with the phenomena of cavitation and cavitation,severe vibration and noise during the pressure reduction process of the regulating valve under the condition of high pressure and large flow,a multi-stage pressure reduction regulating valve with space corner ant nest was proposed,and the CFD simulation software Fluent was used for numerical calculation.The principle of compound pressure reduction in the hedging,turning angle and other links inside the throttling element,as well as the internal flow characteristics of the throttling element,are studied.The variation law of the interstage pressure and velocity of the throttling element with the valve port pressure and the number of depressurization stages is analyzed in detail.Through simulation analysis,it is found that the gradually shrinking structural design makes the entire step-by-step pressure reduction process of ATE close to linearity,and the pressure drops smoothly.(2)The cavitation characteristics of the throttling element are studied by Fluent twophase flow simulation calculation.It is found that the cavitation of the throttle element mainly occurs in the last stage,and with the increase of the pressure drop at the valve port,the cavitation degree in the throttle element increases exponentially.The cavitation margin of the throttling element is set as the gas phase volume fraction of 0.1%.By calculating the critical pressure of the throttling element with different pressure reduction stages,it is found that the critical pressure and the pressure reduction stage are linear.This mathematical model provides a reference for the selection of the appropriate step-down stage for the throttling element,avoiding the occurrence of cavitation and improving the service life of the regulating valve.(3)The influence of changing the structural parameters of the ATE throttling element on the internal pressure reduction characteristics of the element is analyzed by numerical calculation.Change the stage spacing of the throttling element,the variation form of the punching through hole,the depth of the waist groove and the form of the outlet sink,and analyze their influence on the flow rate and cavitation characteristics.It provides the basis for the selection of the structural parameters of the throttling element.(4)Build an experimental system to measure the interstage pressure and flow of throttling elements with different pressure reduction stages under different valve port pressure drop conditions.The experimental data was compared with the data obtained by the simulation calculation.The data with the pressure difference between the stages less than 5%between the experiment and simulation accounted for 96%,and the average interpolation value of the flow between the experiment and simulation was 10.2%.The experimental data are in good agreement with the simulation data,which verifies the accuracy of the simulation model. |
PDF Full Text Request