Centrifugal pump is a kind of energy conversion machine. The energy conversion process must be accompanied by the loss of energy. Efficiency is the measure of this conversion. How to improve the efficiency of centrifugal pump and reduce the loss of energy? It is necessary to understand the loss of energy in the pump. The energy loss in the pump mainly includes the following three aspects:
1. Hydraulic loss of centrifugal pump
The fluid flow in the flow passage part of the pump (from the inlet to the outlet) must have the loss caused by the change of velocity and direction, which is the hydraulic loss. In order to reduce this part of the loss, in addition to improving the smoothness of the overflow components, the best hydraulic model should be selected as far as possible.
2. Mechanical Loss of Centrifugal Pumps
It is mainly the friction loss (also called disk loss) of the outer surface of the front and rear cover plates of the liquid and impeller and the pump chamber. Disk loss accounts for a large proportion, even up to 30% of the effective power. Experiments show that the loss of disk is proportional to the cubic power of rotational speed and to the quintic power of impeller outer diameter. Therefore, the larger the outer diameter of the impeller, the greater the disc loss. Although the loss of the disk is proportional to the cubic of the rotational speed, the outer diameter of the impeller decreases accordingly with the increase of the rotational speed at a given head (it can be considered that the increase of the rotational speed of the pump doubles and the outer diameter of the impeller reduces by half), and the loss of the disk decreases in a quintic proportion. Therefore, with the increase of the rotational speed, the loss of the disk does not increase. On the contrary, it declined, which is one of the reasons for the development of high-speed pumps.
3. Volume loss
A part of the liquid in the impeller leaks back to the impeller inlet through the clearance of the sealing ring of the impeller, and can not be effectively utilized, resulting in loss. Therefore, the clearance of the sealing ring should be as small as possible, but due to processing and assembly reasons, too small clearance may form eccentric wear or jam, the national standard has made special provisions for the clearance of various types of pumps.
Measures should be taken to improve the efficiency of centrifugal pumps:
1. When selecting new pumps, the pumps produced by large manufacturers should be selected to ensure the high efficiency of centrifugal pumps. Replace inefficient centrifugal pumps. When replacing, the centrifugal pump, which is close to the actual operating conditions, is selected to ensure that the replaced pump always operates in an efficient state. After replacing the low efficiency and high consumption centrifugal pump, the pump efficiency can be increased by about 10%.
2. In strict accordance with the operating rules of centrifugal pumps, the disc pump should be carried out before starting the pump, the inlet valve should be opened, the outlet valve should be closed, and the exhaust gas should be exhausted to check whether the inlet pressure of the pump meets the requirements. To prevent pump cavitation caused by low hydraulic pressure and insufficient flow.
3. Application of frequency conversion energy-saving technology. For centrifugal pumps whose design parameters are larger than the actual operating conditions, the centrifugal pumps always run in the high efficiency area after installing frequency conversion speed regulating device.
4. Promote the application of new energy-saving products such as high-efficiency and energy-saving permanent magnet speed-regulating motor and dual-power motor on the main centrifugal pumps.
5. Clean the filter cylinder regularly and check the pipeline connection to ensure the smooth flow of the centrifugal pump intake pipeline.
6. Pump efficiency testing of centrifugal pumps should be carried out regularly. For pumps with low pump efficiency, the causes should be found in time and corresponding measures should be taken to solve them.
7. Maintenance of centrifugal pumps.
(1) The seal of the shaft end of centrifugal pump should be checked and adjusted regularly to reduce the volume loss;
(2) When the centrifugal pump runs for 10,000 hours, it should be overhauled to restore the pump efficiency; the bellows sealing technology should be popularized in centrifugal pumps to eliminate the leakage of centrifugal pumps and improve the volumetric efficiency.