Experimental and statistical analysis of the flap gate energy loss and pressure fluctuation spatiotemporal characteristics of a mixed-flow pump device

A Flap gate is an essential device that cuts off the water flow, reduces energy consumption and ensures the safety of the pump unit. The characteristics of the flap gate energy loss and pressure fluctuation of the pump device are investigated based on the high-precision test rig. The results show that the residual circulation at the outlet of the pump section is one of the essential reasons for the energy loss of the flap gate. When the cut-off angle reaches 60 degrees or above, the influence of the flap gate on the energy loss can be ignored. The pressure fluctuation at the inlet and outlet of the impeller and guide vane outlet with the flap fully open under multiple flowrates is mainly monitored. The probability density distribution of pressure fluctuation is close to normal distribution. Induced by the dynamic and static interference between the impeller and the guide vane, the blade passage frequency, shaft frequency and harmonic frequency are the main frequency components. The guide vane outlet has high fluc-tuation amplitude, maximum peak-to-peak value, and continuous 100-250 Hz high-frequency components. The high-frequency components may synchronize with the natural frequency of the pump unit, which will induce hydraulic resonance.