Study On Discharge Capacity And Opening Mechanism Of Safety Valve By Experiment And Numerical Simulation

The discharge capacity of safety valve is one of most important reference parameter ofits performance. This paper is under the guide of Patent “A safety valve with integratedreal-time test system” to study the discharge capacity measurement method and related flowmechanism during dynamic opening process. The detailed study is summarized as follows:1.Depending on the fundamental fluid equation and the theory about nozzle flowcharacteristics, we make use of isentropic flow equation of ideal gas to induce the dischargecapacity of safety valve when it is opening to relief the overpressure. In addition, systemsummarizations about different factors which affect the safety valve discharge capacity aregiven in the paper. The paper also point out that overpressure gas flow interaction mechanismand especially for its gas dynamics changing pattern.2.The CFD software was adopted to investigate three dimensional model of safety valvedynamic opening process. Through the numerical simulation analysis, it is concluded that thesafety valve flow parameters would vary with the time. The results also show that thesubsonic and supersonic flow near the valve port and the valve exit has occurred.“StreamlineAnalysis Method” is used by the paper to investigate the flow parameters interactionmechanism at different time and different location variations. Flow field parameters mutationpoints in flow channel has been found and studied..In a word, the locations are somegeometric mutation cross-sections, and the flow characteristic of the mutation is not onlyrelated with the cross-section structure, but also with flow sate itself.3.The relationship of non-standard discharge capacity measurement value and numericalsimulation is to be studied. More, four kinds of discharge capacity numerical simulationmethods and numerical simulation definition about discharge coefficient (Kd,num) are alsointroduced in this paper, and advantages and disadvantages of various methods are carefullydiscussed. It shows that the pressure difference between inlet and outlet, outlet diameter, thevalve chamber back pressure may affect the discharge capacity and its flow dischargemechanism.4.For experimental study, we have taken disc sensor and detection flange sensor to testthe safety valve discharge capacity and other related parameters. The experimental test results are well conformed to2D and3D numerical simulation. So, properly numerical simulationmethod is able to predict the discharge capacity and the special sensor developed is usefuland operational to measure the discharge capacity.