| As a kind of self-control valve, the performances of Pilot-diaphragm Steam PRV (pressure reducing valve) which can use energy of steam to adjust and control the pressure of pipeline is the key to determine whether the entire steam system is safe and stable operation or not. Due to complex structures、harsh changing conditions and high requirements about control accuracy, the methods of general static theoretical calculations, the traditional prototype testing, experience optimum design can not meet the user’s requirements that steam PRV is stable and fast response. Meanwhile, with industrial production showed a large capacity, high-parameter, high efficiency and low consumption trends, the flow-induced vibration, noise issues into the steam PRV are highlighted, which seriously affect the health and life safety equipment and operating personnel. In response to the above problems, taking DN50、PN25Pilot-diaphragm Steam PRV developed by Lanzhou University of Technology and Gansu Hongfeng Machinery Co.Ltd as study object, following a series of studies are carried out:(1) The coefficients and critical pressure ratios of different choking flow orifice of Steam PRV were calculated as a basis for mathematical modeling by using numerical simulation method of flow field. The complete dynamic model of the Pilot-diaphragm Steam PRV from the gas source to the load was established. The actual conditions of real gas effects and steam throttle pressure of Joule-Thomson effect were taken into account, which laid the theoretical foundation for establishing dynamic simulation model diagram of Matlab/Simulink system.(2) On the basis of the analysis of pressure and flow characteristic, the feasibility of the program that whether the structural parameters would impact the dynamic characteristics was verified. Impact of the adjusting spring stiffness, damping area of Pilot valve, diaphragm area of the main pilot valve, low pressure chamber volume of the main valve, load chamber volume of the main valve and other key structural parameters of the dynamic characteristics of the valve were carried out by using simulation comparative study. Objective function and Genetic Algorithms were used to optimize and design the main structural parameters of the Pilot-diaphragm Steam PRV, which made greatly improvement of the Pilot-diaphragm Steam PRV’s dynamic performance.(3) By using computational fluid dynamics (CFD) to simulate the three-dimensional turbulent unsteady pressure fluctuation characteristics of steam PRV, and based on the two methods of time-average flow analysis and large-eddy simulation, seeking the flow field incentives of flow-induced vibration and noise internal valve. Modal analysis of steam PRV’s body was carried out by using the finite element analysis software ANSYS. Acoustic modal of the structure which combined with the steam chamber PRV、inlet and outlet pipeline was carried out to analysis by applying acoustics software, to get frequency range and mode shapes of PRV which may be acoustic resonance.(4) The sound field internal steam PRV was solved by using vibro-acoustic coupling method of solid structure, flow field and sound field. Explored the radiation law of aerodynamic noise outside the body based on analysis the results of the sound field simulation. By improving the main valve spool, the seat structure and so on to compare and analysis the influence law of aerodynamic noise, which provided a new way of thinking for Pilot-diaphragm Steam PRV design and solving vibration and noise problem.Through the studies of the above problems, these provide references for the future design of the Pilot-diaphragm Steam PRV serialized product with stable operation, strong anti-interference ability and low noise. |
PDF Full Text Request