How To Improve The Capacity Loss Of Centrifugal Pump

Sep 03, 2021

At present, the efficiency of most models of centrifugal pumps is generally about 70-80%, and the efficiency of a few large flow models is about 90%. The main reason affecting its efficiency is the energy loss in the pump, which is mainly mechanical loss, hydraulic loss and volume loss. The mechanical loss mainly refers to the friction loss between the impeller cover plate and water and the friction loss on the bearing and shaft seal of the centrifugal pump. The hydraulic loss mainly refers to the impact or vortex caused by the change of the movement speed and direction of water in the pump, the friction loss between water and each channel in the pump and the internal friction loss of water flow, The volume loss is mainly caused by the leakage of high-pressure water in the pump to the low-pressure area. The proportion of each loss in the total loss varies with the specific speed of the pump, and it is these losses that reduce its efficiency. Its efficiency has not improved much for decades from the last century to the present, and it is basically in a state of standing still.

The reason for this situation is that no method has been found to significantly reduce the energy loss in the pump. As a general-purpose machine with a long history, it is generally considered that it has been developed more mature, the loss in the pump has been basically reduced to the minimum, and there is not much potential to be tapped. But this is not the case. The existing centrifugal pump, especially the centrifugal pump with closed impeller, which is most used, still has a lot of potential to reduce the energy loss in the pump.

At present, the common methods to improve its efficiency at home and abroad mainly include the following:

(1) Improve casting accuracy; Improve the smoothness of the runner surface of the impeller cover plate and the inner wall of the pump shell, and reduce the water flow friction loss.

(2) Improve the machining accuracy, reduce the sealing clearance or process the sealing ring into a labyrinth shape to reduce the volume loss in the pump.

(3) Reasonably calculate the clearance between the impeller cover plate and the inner side of the pump body to reduce the friction loss of the disc.

(4) Reasonably determine the inlet and outlet angles of flow passage parts to avoid dead zone, sharp angle, sudden change, etc. in the flow channel and reduce the hydraulic loss in the pump.

(5) Mechanical seal structure is adopted to reduce the friction loss of shaft seal.

The above methods are beneficial to improve the efficiency of centrifugal pumps. Some of them have different effects on different types of centrifugal pumps, but in general, these methods do not play a significant role in improving the efficiency.