The working point of the vane pump is determined by the intersection of the water pump performance curve and the water pumping device characteristic curve. When selecting and using a water pump, the performance parameters of the pump working point often deviate from the highest efficiency point. It does not meet the actual needs, resulting in reduced work efficiency, serious overload or underload of the power machine, too large or too small water output of the water pump, too high or too low lift, cavitation, etc. At this time, it is necessary to change the water pump performance curve or The method of pumping device characteristic curve moves the operating point to make it meet the requirements. This method is called the adjustment of the pump operating point. Commonly used adjustment methods include variable speed adjustment, variable diameter adjustment, variable angle adjustment, pitch change adjustment and shunt adjustment. \r\n1. Variable speed adjustment\r\nChanging the speed of the water pump can change the performance of the water pump, thereby achieving the purpose of adjusting the working point of the water pump. This adjustment method is called variable speed adjustment. \r\nThere are two ways to change the speed of the water pump. One is to use a variable speed power machine, and the other is to use a variable speed transmission equipment. The speed of the internal combustion engine can be automatically adjusted according to the load; the main methods of electric motor speed change include frequency conversion, variable resistance, variable voltage, variable capacity adjustment, etc. \r\n2. Diameter adjustment\r\n Turning the outer diameter of the impeller of a centrifugal pump or mixed flow pump can change the performance of the water pump, thereby adjusting the operating point of the water pump and expanding the use range of the water\r\n This adjustment method is called variable diameter adjustment, also known as turning adjustment or cutting adjustment. Turning adjustment has been widely used in water pump manufacturing. In order to expand the scope of use of water pumps, most of the single-stage single-suction cantilever centrifugal pumps and double-suction centrifugal pumps manufactured in my country, in addition to standard diameter impellers, also have one or two variants with smaller impellers (A, B) . If necessary, the user can also cut the impeller by bicycle to adjust the working point of the water pump. \r\n3. Variable angle adjustment\r\nThe axial flow pump has a low lift and a narrow high-efficiency area. A slight change in its working lift will cause a significant drop in work efficiency. Neither throttling adjustment nor turning adjustment is suitable for axial flow pumps. But the axial flow pump has a huge hub, which facilitates the installation of adjustable blades. The method of changing the installation angle of the axial flow pump blades to adjust its operating point is called variable angle adjustment\r\nIV. Variable valve adjustment\r\nFor a water pumping device equipped with a gate valve in the water outlet pipeline, when When the gate valve is closed, the pipeline characteristic curve becomes steeper due to the addition of a local resistance to the pipeline resistance. Therefore, the operating point moves along the curve of the water pump towards the upper left direction where the flow rate decreases. The smaller the gate valve is closed, the greater the additional resistance and the smaller the flow rate becomes. This method of changing the position of the water pump operating point by closing the gate valve is called variable valve adjustment or throttling adjustment. \r\n5. Diversion adjustment\r\nConnect a branch pipe or bypass pipe to the water pump outlet pipe to lead out part of the water flow to change the operating point of the water pump, which is called diversion adjustment\r\n. The principle of split flow adjustment is exactly the same as that of vane pump on branch pipeline. It only unleashes the potential of the machine and improves pumping efficiency. However, such an adjustment requires the installation of an additional pipeline, so calculations must first be made to verify the economical efficiency of the adjustment. This situation is the same as a water pump supplying water to outlet pools with different heights. The axial flow pump unit and the centrifugal pump unit working in series should apply split flow adjustment during startup to avoid overload and vibration of the power machine.