How is the pump flow, head, and power expressed? What are their guiding roles?

What is the pump performance? Expressed by operating parameters, it is usually indicated on the pump nameplate and product catalog.
1. The flow rate of a flow pump is also referred to as the volume of water delivered. It refers to the amount of water pumped in a unit of time. Expressed by the symbol Q, the unit is liters/second, cubic meters/second, cubic meters/hour.
2. The head of the lift pump is the height at which the pump can lift the water. It is usually represented by the symbol H and its unit is meter. The lift of the centrifugal pump is based on the centerline of the impeller and consists of two parts. The vertical height from the center line of the pump impeller to the water source, ie the height at which the pump can draw water up, is called the suction head, or simply the suction stroke; from the centerline of the pump impeller to the vertical height of the outlet pool, the pump can press the water up The height is called pressurized head, short for press. That is, pump lift = suction head + pressure head should point out that the head marked on the nameplate refers to the head that the pump itself can produce, and it does not contain the loss head caused by the frictional resistance of the pipe flow. When choosing a water pump, care must not be taken. Otherwise, it will not be able to pull water.
3. The power in the unit time, the size of the work done by the machine is called power. It is usually represented by the symbol N. Commonly used units are: kg/s, kilowatts, and horsepower. The power unit of a motor is usually expressed in kilowatts; the power unit of a diesel engine or a gasoline engine is expressed in horsepower. The power delivered by the power machine to the pump shaft, called the shaft power, can be understood as the input power of the pump. Usually, the pump power is the shaft power.
Due to the frictional resistance of bearings and fillers, the friction between the impeller and the water during rotation, the swirling of the water flow in the pump, the backflow of the gap, the entrance and exit, and the impact of the mouth. Certain power is consumed, so it is impossible for the water pump to completely change the power input from the power machine to the effective power, which has a power loss. In other words, the sum of the effective power of the pump and the loss power in the pump is the shaft power of the pump.
There is also a difference between the matching power of the water pump and the power of the shaft. It has a larger power than the shaft. It is mainly considered that the water pump and the power machine are combined into a unit, and there must be a transmission device in the middle, and its operation will inevitably consume a part of the power. In addition, in order to ensure the safe operation of the unit and prevent overloading of the power machine, there is room for supporting power. In this way, a safe standby factor K, K=1.05-2 should be considered. In general, when the shaft power of the water pump is small, K value Take a larger one; when the shaft power is large, the K value should be smaller.