Pump performance curve to change the method of variable speed regulation, cutting impeller cylindrical and so on. 1, variable speed regulation: is in the pipe curve unchanged, with variable speed to change the pump performance curve, thereby changing their working point. When the speed changes, the head and flow will change, and with the speed increase, qv and H will be increased, with this method to adjust the flow and lift, will not produce additional energy loss, so this method is the most Economy. However, the original motivation put forward new requirements, that is, the prime mover should be adjustable speed, such as steam engine, internal combustion engine, etc., or additional transmission, due to large investment in transmission, the general small and medium-sized pumps rarely used. 2, cutting the impeller cylindrical: impeller diameter smaller after cutting, you can change the pump qv-H curve, the pump operating point also changes. Using this method to adjust the flow rate, a basic centrifugal pump can be equipped with several different diameter impeller, when the flow changes regularly, according to need to select. Using this method is more economical.