Centrifugation is actually the expression of the inertia of an object, such as water droplets on an umbrella. When the umbrella rotates slowly, the water droplets will follow the umbrella. This is because the friction between the umbrella and the water droplets acts as a centripetal force for the water droplets. But if the umbrella rotates faster, this friction is not enough to make the water droplets move in a circular motion, then the water droplets will move away from the outer edge of the umbrella, just like pulling a stone with a rope to make a circular motion.
If the speed is too fast, the rope will disconnected, the stones will fly out. This is called centrifugation. The main working principle of the centrifugal pump
(1) The impeller is rotated by the pump shaft to work on the fluid between the blades. The fluid is subjected to the centrifugal force and is thrown to the periphery by the center of the impeller. When the fluid reaches the periphery of the impeller, the flow rate is very high.
(2) The pump casing collects the liquid that is thrown from between the blades, and the liquid flows in the casing in the direction in which the volute-shaped passage is gradually enlarged, so that the kinetic energy of the fluid is converted into static pressure energy, and the energy loss is reduced. Therefore, the function of the pump casing is not only to collect liquid, but also an energy conversion device.
(3) Principle of liquid suction: By rotating the impeller at a high speed, the liquid in the center of the impeller is forced to be thrown away at a high speed, so that a low pressure is formed at the center of the impeller, and the liquid in the lower tank is continuously sucked up. Air-tightening phenomenon: If the centrifugal pump is filled with gas before starting, the impeller center gas can not be formed at a sufficient vacuum when it is thrown, so that the liquid in the tank cannot be sucked up. This phenomenon is called air binding. In order to prevent the occurrence of air-tightening, the space inside the pump casing should be filled with external liquid before the centrifugal pump starts. This step is called a pump. In order to prevent the liquid poured into the pump casing from flowing into the lower tank due to gravity, a check valve (bottom valve) is installed at the inlet of the pump suction pipe; if the pump position is lower than the liquid level in the tank, no irrigation is required at the start. Pump.
(4) The guide wheel is installed on the outer circumference of the impeller to make the liquid energy conversion efficiency in the pump high. The guide wheel is a fixed bladed ring located on the periphery of the impeller. The bending direction of the blade is opposite to the bending direction of the impeller blade, and the bending angle is exactly adapted to the direction in which the liquid flows out from the impeller, guiding the liquid to smoothly change direction in the pump casing passage, minimizing energy loss, and converting dynamic pressure energy into The static pressure energy is highly efficient.
(5) The balance hole on the rear cover eliminates the axial thrust. The pressure of the liquid leaving the periphery of the impeller is already high, and some of it will seep into the rear side of the impeller rear cover, while the liquid inlet at the front side of the impeller is low pressure, thus creating an axial thrust that pushes the impeller toward the pump inlet side. This tends to cause wear of the impeller in contact with the pump casing and, in severe cases, vibration. The balance hole leaks a part of the high pressure liquid to the low pressure zone, reducing the pressure difference between the front and rear of the impeller. But this will also reduce the pump efficiency.
(6) The shaft sealing device ensures normal and efficient operation of the centrifugal pump. When the centrifugal pump is in operation, the pump shaft rotates and the shell does not move. If the annulus between them is not sealed or sealed badly, the outside air will seep into the low pressure zone at the center of the impeller, which will reduce the flow rate and efficiency of the pump. In severe cases, the flow is zero - air binding. Typically, a mechanical or packing seal can be used to achieve a seal between the shaft and the casing.
