Elimination Of Hump Characteristic Of An Axial Flow Pump By Adapting Axial Grooves At The Wall Of Inlet Pipe

The hump characteristic is the main factor that inhibits the stable operation of the axial flow pump.The concrete manifestation of the hump characteristic is that when the axial flow pump runs to a small flow rate,the axial flow pump head drops significantly.Prior to this,the axial flow pump vibration and noise and the cavitation inside the pump has already occurred,which seriously affects the safe operation of the pump group.The numerical simulation method was used to deeply study the hump phenomenon and internal turbulent flow characteristics of the axial flow pump.The internal flow characteristics that caused the axial flow pump to degrade under low flow conditions were analyzed.At the same time,corresponding improvement methods are proposed for the hump phenomenon under partial conditions,as well as the internal de-running,vortex and pressure pulsation in the pump.The specific conclusions of this paper are as follows:When the pump runs away from the design condition point,the impulsion angle of the impeller inlet increases,resulting in the occurrence of turbulent flow phenomena such as de-flow and vortex within the impeller channel,which reduces the hydraulic performance of the pump.In this paper,the internal flow field of the axial flow pump is studied by using the fluid mechanics analysis method.The results show that there is a clear hump area when the pump departs from the design condition point and enters the low flow condition operation.The head pump's head curve and efficiency curve show a significant downward trend.Under the condition of critical stall,the suction surface of the blade inlet suction surface near the rim and the blade outlet is close to the hub;in the deep stall condition,the development of severe flow,And together with the flow to form a stable vortex structure,blocking the entire flow channel.In order to reduce the angle of attack caused by the pre-rotation of the blade inlet under axial pump stall conditions and increase the lift in the case of small flow conditions,this paper applies an axial pump inlet slotting technology,namely in the inlet wall of the axial pump.One week in the axial direction slot,analysis of its impact on the axial flow pump flow field and hump phenomenon to improve the role.The research shows that under small flow conditions,the axial slotting can reduce the ring inlet and the angle of attack of the impeller,and can reduce the back flow of the blade back.The hump phenomenon is significantly improved.At the same time,it is found that the groove depth is one of the important factors to improve the hump phenomenon of the axial flow pump with small flow rate.When the groove depth and the impeller diameter ratio K=0.02,the channel vortex inside the impeller is almost completely eliminated,and the axial pump head and efficiency are improved.All have been improved,and low-frequency pressure fluctuations have been weakened,thereby eliminating the hump phenomenon of the axial flow pump and ensuring the safe and stable operation of the axial flow pump.This article focuses on the study of the axial groove depth of the axial pump performance improvement,at the same time,it was found that not only the depth of the axial groove affects the hump phenomenon of the axial flow pump,but also the number and length of the axial grooves influence the performance of the axial flow pump to some extent.Studies have shown that as the number of axial grooves increases,the effect of eliminating the hump phenomenon becomes more pronounced,but the pressure pulsation becomes more severe.