The principle of centrifugal pumps
In daily life, we often observe the following phenomenon: on rainy days, when spinning a rain umbrella, water droplets fly out tangentially along the edge. The rotating umbrella imparts energy to the water droplets, and the centrifugal force generated by the rotation flings them away. This is an example of how centrifugal force can add energy to water. centrifugal pumps are designed based on the principle of flinging water through centrifugal force. By utilizing the high-speed rotation of the pump impeller, the centrifugal force flings the water, increasing its energy. The energized water then flows out of the pump through the pump casing and outlet, and is subsequently transported to its destination via the discharge pipe. This is the working principle of a centrifugal pump.
The working process of a centrifugal pump is as follows: Before starting, the pump casing and suction pipe should be filled with water (a foot valve is installed at the bottom of the suction pipe to prevent backflow). Then, the motor is driven, causing the impeller and the water inside it to rotate at high speed. At this point, the water is thrown out of the impeller by centrifugal force, flows through the casing passage, and enters the pump outlet. From there, it flows into the discharge pipe. Meanwhile, a vacuum is created at the center of the pump impeller as water is thrown out, allowing water from the intake pool to flow into the impeller inlet under the action of external atmospheric pressure. As the impeller continues to rotate, water is continuously thrown out and drawn in, creating a continuous pumping effect.
Before starting a centrifugal pump, if it is not filled with water, the impeller can only rotate the air. Since the mass per unit volume of air is very small, the resulting centrifugal force is minimal, making it impossible to expel the air from the pump and the discharge pipeline. This prevents the formation of a vacuum inside the pump, and water cannot be drawn up. The working process of a centrifugal pump is essentially one of energy transfer and conversion, where the high-speed rotational mechanical energy of the motor is transformed into the kinetic and potential energy of the water. During this energy transfer and conversion process, significant energy losses occur. The greater these losses, the lower the efficiency of the centrifugal pump.
