Head, flow, and power are important parameters for investigating the performance of the pump and are the basis for the technical engineer to select the pump
1. The flow rate of the centrifugal pump is also called the water delivery volume. It refers to the amount of water delivered by the pump in a unit of time. Expressed by the symbol Q, the unit is liter/second, cubic meter/second, cubic meter/hour
2. The pump head refers to the height of the pump can lift water, usually expressed by the symbol H, the unit is meter.
The head of the centrifugal pump is based on the center line of the impeller and consists of two parts. The vertical height from the center line of the pump impeller to the water surface of the water source, that is, the height at which the pump can draw water, called the suction head, referred to as suction lift; the vertical height from the center line of the pump impeller to the outlet water surface, that is, the pump can press the water up The height is called the pressurized water head, referred to as the pressure range. That is, the pump head is equal to the sum of the suction head and the pressurized head. The head indicated on the nameplate refers to the head that can be generated by the pump itself, and it does not include the loss head caused by frictional resistance of the pipeline water flow. When choosing a water pump, be careful not to ignore it.
3. The amount of work done by the machine in a unit of time is called power. The symbol N is usually used to indicate the commonly used units: kg·m/s, kilowatt, horsepower.
The power unit of the motor is usually expressed in kilowatts; the power unit of the diesel engine or gasoline engine is expressed in horsepower. The power transmitted by the power machine to the shaft of the pump is called the shaft power, which can be understood as the input power of the pump. Generally speaking, the pump power refers to the shaft power. Due to the friction resistance of the bearing and the packing; the friction with the water when the impeller rotates; the vortex of the water flow in the pump, the backflow of the gap, the inlet and outlet, the impact of the port, etc. Part of the power is inevitably consumed, so it is impossible for the water pump to completely change the power input by the power machine into effective power. There must be a power loss. That is to say, the sum of the effective power of the water pump and the lost power in the pump is the shaft power of the water pump.
The pump head has no relationship with the power, and it is related to the diameter of the pump impeller and the number of stages of the impeller. The pump with the same power may have a head of hundreds of meters, but the flow may be only a few squares, or the head may be only a few meters, but the flow may be One hundred parties. The general rule is that under the same power, the flow rate of high head is low, and the flow rate of low head is large. There is no standard calculation formula to determine the head.