Centrifugal is actually the performance of the inertia of an object, such as the water drop on an umbrella. When the umbrella rotates slowly, the water drop will rotate with the umbrella, because the friction between the umbrella and the water drop serves as the centripetal force for the water drop. But if the umbrella spins faster, the friction isn’t enough to keep the droplet moving in a circle, and the droplet will break off and move toward the outer edge, much like a string pulling a rock in a circle. If it moves too fast, the string will break and the rock will fly out. This is called centrifugation.
Main working principle:
(1) The impeller is driven to rotate by the pump shaft and works on the fluid between the blades. The fluid is thrown to the periphery from the center of the impeller by centrifugal action. When the fluid reaches the outer circumference of the impeller, the flow rate is very high.
(2) The pump shell collects the liquid thrown from the blades, and the liquid flows in the shell along the gradually expanding direction of the volute channel, so that the kinetic energy of the fluid is converted into static pressure energy and energy loss is reduced. So the pump shell is not only a liquid collection, it is an energy conversion device.
(3) The principle of liquid suction: relying on the high-speed rotation of the impeller, forcing the liquid in the center of the impeller to be thrown away at a high speed, so as to form a low pressure in the center of the impeller, and the liquid in the low trough is continuously sucked.
Gas binding phenomenon: if the centrifugal pump is filled with gas before starting the shell, the center of the impeller can not form a large enough vacuum at the place when the gas is thrown after starting, so that the liquid in the tank can not be sucked up. This phenomenon is called chi binding.
In order to prevent the occurrence of gas bound phenomenon, the centrifugal pump should be filled with external liquid before starting the pump shell space. This step is called irrigation pump. In order to prevent the liquid poured into the pump shell from flowing into the low slot due to gravity, the inlet of the pump suction pipeline is equipped with a check valve (bottom valve); If the pump position is below the level of the liquid in the tank, no irrigation pump is required during startup.
(4) The regulating wheel is installed around the impeller to make the liquid energy conversion efficiency in the pump high. The guide wheel is a fixed bladed ring located at the outer edge of the impeller. The bending direction of these blades is opposite to the bending direction of the impeller blades, and the bending Angle just ADAPTS to the direction of the liquid flowing out of the impeller, guiding the liquid to change direction smoothly in the channel of the pump shell, making the energy loss minimum and the efficiency of dynamic pressure energy conversion into static pressure energy high.
(5) The balance hole on the rear cover plate eliminates axial thrust. The liquid pressure leaving the periphery of the impeller has been high, and part of it will seep into the back side of the impeller rear cover, while the liquid inlet in the front side of the impeller is low pressure, resulting in the axial thrust that pushes the impeller to the pump inlet side. This is easy to cause the impeller and pump shell contact wear, serious vibration will also occur. The balance hole makes part of the high pressure liquid leak to the low pressure area, reducing the pressure difference before and after the impeller. But this will also cause a reduction in pump efficiency.
(6) Shaft seal device to ensure normal and efficient operation of centrifugal pump. Centrifugal pump at work is the pump shaft rotation and shell does not move, the annular gap between them if not sealed or sealed well, the outside air will penetrate the impeller center of the low pressure area, so that the pump flow, efficiency decline. Severe flow is zero – gas tied. Usually, a mechanical seal or packing seal can be used to seal the shaft to the housing.
Post time: Apr-15-2022