Optimization Of Outlet Channel And Hydrodynamic Characteristics Of Pump Unit In A Pumping Station

Pumping station engineering,as a water conservancy infrastructure,plays a very important role in our national economy.The construction of neutral axial flow pump devices in pumping station engineering has the characteristics of large flow rate and low head,and is widely used.Mastering the hydraulic characteristics and hydraulic stability rules of the pump unit during operation is of positive significance for the economic and stable operation of the pump station.With the axial flow pump device of a pump station as the research background,numerical simulation technology is used to analyze the internal flow characteristics and hydraulic characteristics of the low hump axial flow pump device,optimize the water hydraulic design of the outlet flow channel through geometric control parameters,and analyze the pressure pulsation of the original outlet flow channel pump device and the optimized outlet flow channel pump device.The main contents are as follows:(1)Study the hydraulic characteristics of an axial flow pump device.The performance of the original axial flow pump device is predicted,and the hydraulic characteristics of each flow passage component are analyzed to study their internal flow characteristics.The results show that the flow field and hydraulic performance in the elbow inlet channel are good,which can provide good inlet conditions for the pump section;Increasing the flow rate is conducive to uniform distribution of the streamline on the pressure surface and suction surface of the impeller,and reducing and balancing the pressure distribution in the impeller section;The flow structure in the guide vane is disordered,and increasing the flow rate is beneficial to reducing the vortex structure and improving the flow pattern;The low hump outlet channel has reflux and vortex regions under low flow and high flow conditions,and the internal flow characteristics under high flow conditions are superior to other flow conditions.As the flow increases,the hydraulic loss in the outlet channel first decreases and then increases,and the kinetic energy recovery first increases and then decreases.(2)Study the optimization design of geometric parameters for low hump outlet channels.For the geometric control parameters such as hump height,hump section position,hump turning angle and diffusion section length,the Control variates is used and the scheme design is carried out respectively,and the internal flow characteristics and hydraulic performance are analyzed by numerical simulation.The results indicate that increasing the height of the hump helps to improve the flow pattern of the outlet channel and reduce hydraulic losses;Moving the hump section forward can help improve the flow pattern of the flow channel and reduce hydraulic losses;Increasing the angle of the hump section in the rising section and extending the gate section to a part of the diffusion section to increase the length of the diffusion section can help reduce hydraulic losses in the outlet channel.However,in practical engineering,the control parameters of each flow channel should consider the spatial layout limitations of pump rooms,etc.(3)Study the hydraulic stability of the original pump device and the optimized pump device.The unsteady numerical simulation method is used to analyze the pressure fluctuation characteristics inside the pump device by setting monitoring points in the pump device.The results show that the impeller inlet pulsation frequency is mainly affected by the impeller blade number and rotation frequency,and the pulsation amplitude is the largest here;In the optimized scheme,the main frequency pulsation amplitude of the monitoring points in the pump device is basically higher than that in the original scheme.The impact of pulsation on the hydraulic stability of the pump unit should be considered when designing to increase the hump height.