The main working principle of centrifugal pump

The main working principle of centrifugal pump:

(1) The impeller is rotated by the pump shaft and works on the fluid between the blades. The fluid is subjected to centrifugal force and is thrown toward the periphery from 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 among the blades. These liquids flow in the shell along the direction of the volute-shaped channel gradually expanding, so that the kinetic energy of the fluid is converted into static pressure energy and the energy loss is reduced. So the role of the pump casing is not only to collect the liquid, it is also an energy conversion device.

(3) The principle of liquid suction: Relying on the high-speed rotation of the impeller, the liquid in the center of the impeller is forced to be thrown away at a very high speed, thereby forming a low pressure in the center of the impeller, and the liquid in the lower tank is thus continuously sucked up.

Gas-bearing phenomenon: If the centrifugal pump is filled with gas before the start-up of the centrifugal pump, the center of the impeller after the start-up is not able to form a sufficiently large degree of vacuum at this point, so that the liquid in the tank cannot be sucked up. This phenomenon is called gas binding.

In order to prevent the occurrence of air-binding phenomenon, the centrifugal pump must be filled with the external liquid to fill the space inside the pump casing before starting the centrifugal pump. This step is called irrigation pump. In order to prevent the liquid poured into the pump casing from flowing into the lower tank due to gravity, a non-return valve (bottom valve) is installed at the inlet of the pump suction line; if the position of the pump is lower than the liquid level in the tank, it is not required to start the pump. Pump.

(4) The impeller is installed on the outer periphery 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. The bending angle of the blade is just in line with the direction that the liquid flows out from the impeller, guiding the liquid to change direction smoothly in the channel of the pump casing, minimizing energy loss, and converting dynamic pressure into energy. Static pressure energy is highly efficient.

(5) Balance holes on the rear cover eliminate axial thrust. The pressure of the liquid leaving the periphery of the impeller is already high, and some of it will seep behind the rear cover of the impeller, and the front inlet of the impeller is at a low pressure, thus creating an axial thrust pushing the impeller towards the inlet side of the pump. This can easily cause wear of the impeller in contact with the pump housing and, in severe cases, vibration. The balance hole leaks some of the high-pressure liquid to the low pressure area, reducing the pressure difference between the impeller and the front and back. However, this will also reduce pump efficiency.

(6) The shaft seal device ensures the normal and efficient operation of the centrifugal pump. Centrifugal pump in the work is the rotation of the pump shaft and shell does not move, if the gap is not sealed or sealed, the outside air will infiltrate the low pressure area of ​​the center of the impeller, so that the pump flow rate, efficiency decreased. Severe flow is zero - gas tied. In general, mechanical seals or packing seals can be used to achieve the seal between the shaft and the shell.