The relationship between the head and flow of the diesel water pump
The height of the head is determined by the energy loss of the pipes and valves to the water, that is, the energy value that the diesel water pump can give to the water. When the engine speed drops, the head also drops. When the centrifugal pump outlet valve is closed, because the head remains unchanged and the flow decreases, then the pump current decreases. If it is fully closed, the current is the smallest, but it is slightly larger than idling, because water has resistance. .
Current = head × flow. When the design (selection of diesel water pump) is determined, if the actual operating head of the diesel water pump is too high, it will not only reduce the efficiency of the water pump, but also seriously affect the decrease of the actual flow rate of the water pump.
Conversely, if the head of the water pump is selected too high and the actual operating head is too low, it will also affect the efficiency of the pump and cause the actual flow to be too large during actual operation. It is also likely to increase the power of the pump and exceed the rated current of the motor. fever.
The head is usually expressed by H, and the unit is m. 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 suck water up, is called the suction lift, or suction lift for short. The vertical height from the center line of the pump impeller to the water surface of the outlet pool, that is, the height at which the pump can press the water up, is called the pressure head, or pressure range for short.
Water pump head = suction head + pressurized water head. It should be pointed out that the head marked on the nameplate refers to the head produced by the pump itself, and it does not include the loss head caused by the frictional resistance of the pipeline water flow. When choosing a diesel water pump, be careful not to ignore it, otherwise you will not be able to pump water.