Research On Characteristics Optimization And Key Technology Of Pilot Pressure Relief Valve

Pressure relief valve is an important equipment in the steam system.But many problems occur in the use of domestic pilot pressure relief valve such as instability,short life,high failure rate,vibration and noise.In this dissertation,based on a widely used pilot pressure relief valve,simulation and optimization work is carried out.The contents include: system simulation of pilot pressure relief valve,characteristics optimization,numerical simulation of the pressure valve flow,and fatigue life prediction of the diaphragm.Based on the analysis of working principle of the pressure relief valve,the mathematical model of the valve system is established,and the system simulation and analysis are carried out on the platform of Simulink.By analyzing the demands of static and dynamic characteristics of pressure relief valve in the steam system,the influence of different structural parameters on the static and dynamic characteristics of the pressure relief valve is simulated and the feasible parameters are selected.By setting the evaluation function,multi-objective particle swarm algorithm is used to optimize the characteristics.After comparing with the output pressure curve without optimization,the feasibility of the optimization is verified.In order to study the vibration and noise of the pressure relief valve,it is necessary to simulate the flow of steam inside the pressure relief valve.Based on the static simulation of the internal flow of the main valve chamber of the pressure relief valve,the dynamic grid is used to simulate the internal flow of the main valve chamber in transient way.The internal flow information is analyzed and the reason of induced vibration and noise is studied.The pressure pulsation data is obtained by monitoring the key position of the flow field.At the same time,the finite element simulation of the structural modals and acoustic modes of the pressure relief valve is carried out,and the modal frequency and modal modes of the structure and the vocal cavity are obtained respectively.The obtained pressure pulsation data is transformed into frequency spectrum and compared with the frequencies of structural modals and acoustic modals.The possible resonant frequency is analyzed.For the most vulnerable metal diaphragm during the use of the pressure relief valve,the fatigue life study is carried out in this dissertation.The finite element method is used to analyze the heat and structural coupling problem and the stress distribution on the diaphragm.Facing the problem of using one diaphragm or two diaphragms in the product,the nominal stress fatigue life analysis method and the linear cumulative fatigue damage theory are used to compute the fatigue life of the two cases.And the fatigue life of the two cases is also predicted and compared with the design life of the pressure relief valve.To conclude,this dissertation provides the theoretical support for the development of the pilot relief valve,and also provides a reference for the improvement and serialization of the pressure relief valve products.