Research On High Pressure Pilot Operated Axial-flow PRV Model Simulation And Performance Optimization

This thesis is supported by cooperate program. Natural gas pilot operated pres-sure reducing valve is a kind of self-controlled valve used for pipe line system andpressure regulating station to guarantee the equipment works normally. A series ofbasic theory such as fluid mechanics, engineering thermodynamics and automaticcontrol are involved to study the valve’s performance. To improve the performance ofthe valve, it is necessary to study the dynamic characteristics shown by pressure re-ducing valve under different combinations of components parameter, to simulate thedisturbance under actual working conditions of outlet pressure fluctuations, to de-scribe the impact of different flow structures for the pressure reducing valve flowcharacteristics and noise prediction. Research on these issues was carried out, pro-viding reliable theoretical bases for further study.Based on structure parameters and working principle of natural gas pilot operatedpressure reducing valve, using the Simulink toolbox of Matlab software, the equationsof motion, the gas state and flow equation and the cavity pressure control model wasestablished, as well as the system block diagram. Focusing on the subsystem and theS-function, the system dynamic characteristics was obtained and the state at each timeof the natural gas pilot operated pressure reducing valve under the condition of thedynamic flow changes was calculated. The response curves of the dynamic character-istics were drawn in different inlet pressure, the spring stiffness as well as gas dis-charge. And optimization of the natural gas pilot operated pressure reducing valvestructure parameters was carried out using the Gatool toolbox of Matlab software. Anoptimized mathematical model was established using output pressure as objectivefunction according to different design variables. The best fitness and the mean tra-jectory were gained based on the theory of genetic algorithm, obtaining the combina-tion of optimal dynamic performance of the natural gas pilot operated pressure re-ducing valve.The three-dimensional modeling of the natural gas pilot operated pressure re-ducing valve internal flow passage was found using Solidworks software. Import theflow channel model into meshing in CFD software based on the internal flow channelgeometry and flow characteristics. Using the compressible fluid model of the ideal gasof natural gas, the inlet pressure and outlet pressure were setting as boundary condi-tions. Improved RNG k-Epsilon model was used to solve the pressure and speed dis- tribution as well as other flow related parameters of the natural gas pilot operatedpressure reducing valve. The flow fields of the pressure reducing valve with differentvalve plug shape were analyzed. Changes of valve plug shape were made to improvethe performance of the valve.On the basis of the flow field analysis, the theoretical prediction and calculationof the noise generated by high-Mach number natural gas pilot operated pressure re-ducing valve was carried out using the standard IEC60534-8-3-2009"Indus-trial-process control valves. Part8-3: Noise considerations. Control valve aerody-namic noise prediction method". Improvement requirements for the noise exceededthe standard limits were put forward, pointing out the direction for future research.