Water Hammer Analysis Of Safty Membranes System In High-head Hydropower Station

Using safety membranes instead of surge tank in hydropower is a new technology. Especially, applying in high-head hydropower has considerable economic benefits and promoting this technology has realistic value.Water hammer analysis for safety membranes system is of great significance to protect pressure piping systems and perfect system. Analysis the effect of numbers of safety membranes and setting pressure for the stability of pressure pipeline system also play an important role on guiding. Traditional model test methods of safety membranes system's advantages are visualized, but it may be spend a considerable amount of time and money.With the using of numerical calculation widely and the developing of computer's performance, the numerical simulation method will improve work efficiency greatly.The project, Kaiyuanâ…¡hydropower station Power Plant of Jiuquan City in Gansu province, has applied this technology. An analysis of Water hammer phenomena of Safety Membranes system is significant to protect the pressure piping systems and improve membranes systems. The number of membranes and setting pressure also has a significant impact on the stability of the system pressure.A strong contraction of expansion joints was observed when the membranes were bursting as well as closing the eccentric center butterfly valve. Considering this phenomenon as a starting point, the author has done following tasks.Firstly, brief research introduction of water hammers and safety membranes were presented at home and abroad.Moreover it summarized the CFD theories for the following numerical simulation. Fluent software is used to simulate eccentric center butterfly valve under different opening both steady state and transient. Numerical simulation results indicate that using transient dynamic meshing method to simulate the drag coefficient of triple eccentric butterfly valve superior the steady-state simulation results, and its flow characteristic is linearly better than ordinary symmetry medium-pressure butterfly valve.Secondly, the water hammer calculation method and its numerical solution were introduced. Based on reasonable assumptions with one-dimensional software-Flowmaster simulated water hammer phenomena of the safety membrane system. It provides a new approach for selection and design of safety system. Based on the simulation results of safety membranes system, we selected a reasonable setting pressure and membranes diameter.300mm-diameter safety membranes were adapted in this project. It analyzed situations under different setting pressures. By comparison, safety membranes of two 300mm diameter which setting pressure are 1.1&1.2 times that of work pressure respectively,it's pressure fluctuation curves is more smooth than two machine of 1.1 times that of working pressure situation.To prevent cavitation occurred, we consider using orifice plate to enhance the pressure after the triple eccentric butterfly valve. The flow area of the orifice plate size will affect the security of the system. So calculate reasonable orifice circulation area should ensure that the pressure pipeline is safe.This paper combined the use of Fluent with Flowmaster software, which can get micro flow field distribution, macro water hammer pressure value and obtained useful conclusions and recommendations in engineering design and operation management.