How does a centrifugal pump work?

The basic components of a centrifugal pump are the rotating impeller and the stationary pump casing.

Before starting, the pump casing needs to be filled with the liquid to be delivered. After starting, the pump shaft drives the impeller to rotate together, forcing the liquid between the blades to rotate. The liquid in the center of the impeller is thrown to the outer periphery under the action of the inertial centrifugal force, and gains energy, so that the static pressure energy increases and the flow velocity increases. After the liquid leaves the impeller and enters the pump casing, the flow velocity of the liquid slows down due to the gradual expansion of the flow channel of the pump casing, and part of the kinetic energy is converted into static pressure energy. Therefore, the liquid with high pressure is transported to the pump through the discharge pipeline. Need a place. When the liquid in the center of the impeller is thrown to the outer periphery, a low-pressure area will be generated in the center of the impeller; since the pressure above the liquid level in the storage tank is higher than the pressure at the pump inlet, the liquid will be sucked into the center of the impeller. Therefore, the impeller continuously rotates to continuously suck in and discharge liquid.

When the centrifugal pump is started, if there is air in the pump casing, due to the low density of the air, the centrifugal force generated during rotation is small, so the low pressure formed in the central area of the impeller is not enough to suck the liquid in the storage tank into the pump, even if the centrifugal pump is started. Liquids cannot be delivered. This phenomenon is called air binding, that is, the centrifugal pump does not have a self-priming function, so the pump casing must be filled with liquid before starting, that is, the pump is primed. The function of the bottom valve installed on the suction pipe of the centrifugal pump is to prevent the liquid poured into the pump casing before starting from flowing out of the pump.