How to solve the problem of pump high lift?

(1) The existing impeller of the pump must be replaced with an axial impeller with a lower specific rotation speed (with the power unchanged, increase the head and reduce the flow). As the head of the impeller is increased, the speed or the momentum moment of the impeller outlet increases, so the expansion and derotation functions of the outlet guide vane are required to be stronger. At present, in domestic large-scale vertical axial flow pumps with impeller diameters of 2.8 meters or more, the guide vanes are fixed in the reinforced concrete of the outlet flow channel, so it is very difficult to replace the guide vanes when changing the impeller. According to the working principle of the horizontal centrifugal pump, after the impeller head is lifted, the absolute liquid flow angle of the guide vane inlet (the guide vane inlet installation angle) cc3 decreases, and the curvature of the guide vane increases. If the guide vanes are not replaced, at the same flow rate, the water flow will form a vortex area on the back of the guide vane inlet, which will cause the pump efficiency to decrease and the outlet pressure to fluctuate. If it is difficult to replace the guide vane, it is better to cooperate with relevant research units and try to find improvement measures under the conditions of the existing device. The final improvement plan of the superior should be determined by model test.

(2) Increasing the speed of the pump is known from a similar law. Increasing the speed of the pump can increase the flow and head of the pump, but the shaft power of the water chestnut increases and the power machine needs to be increased. For pumping stations with very high heads, the key to adopting this method is the choice of speed-increasing method and variable-speed equipment. Due to the small unit, the small-scale drainage and irrigation pump station is easy to achieve variable speed (such as adjusting the oil intake of the internal combustion engine, changing the diameter of the pulley, etc.). For AC motors, the synchronous speed can be adjusted (stepless variable frequency speed regulation and stepped variable frequency speed regulation), or the slip can be adjusted (for asynchronous motors, the motor stator voltage can be adjusted, and the series winding can be changed. The additional resistance of the linear motor rotor circuit, etc.) two adjustment methods. The former is energy-saving, and the latter is energy-consuming. Large and medium-sized agricultural pumping stations are subject to certain restrictions due to their large unit capacity and expensive speed control equipment.

(3) The new problems brought about by the increased speed of the water pump may include problems such as cavitation, structural strength of the unit, bearing life, and verification of critical speed. The pump speed increase may also change the flow pattern of the inlet flow channel, making the flow velocity and pressure distribution at the inlet of the pump uneven, thus aggravating the vibration of the unit.