The impeller of centrifugal pump mainly has the following four forms: (1) closed; Semi-open type; (c) rear half-open type; open
1- impeller; 2- Rear cover plate; 3- wheel hub; 4- Front cover plate; 5- impeller sealing ring; 6- Stiffening rib
enclosed impeller
It consists of blades and front and rear cover plates. Closed impeller is widely used in centrifugal pumps because of its high efficiency and difficult manufacture. Suitable for conveying clean liquids with low viscosity and no particles, such as clean water and solution.
Unshielded impeller
Generally, there are two structures: one is semi-open, which consists of a rear cover plate and blades. The impeller with this structure has low efficiency, and a sealing ring with adjustable clearance is needed to improve the efficiency; The other is the rear half-open type, which consists of a front cover plate and blades. Because the same sealing ring as the closed impeller can be applied, the efficiency is basically the same as that of the closed impeller. Besides conveying liquid, the blades also have the sealing function (of the rear blade or the auxiliary impeller). Semi-open impeller is suitable for conveying liquid containing suspended solids such as solid particles and fibers. The semi-open impeller has the advantages of small manufacturing difficulty, low cost and strong adaptability. Centrifugal pumps, which are gradually used in oil refining and chemical industry, are used to transport clean water and liquids close to clean water.
Unshielded impeller
Impeller with only blades and blade stiffeners without front and rear cover plates (the number of open impeller blades is less than 2-5). Impeller has low efficiency and less application, and is mainly used to transport high viscosity liquid and slurry liquid.
The blades of centrifugal pump impeller are generally backward curved blades. There are two kinds of blades: cylindrical and twisted. The application of twisted blades can reduce the blade load, improve the suction performance of centrifugal pump and improve the cavitation resistance, but it is difficult to manufacture and costly.
Centrifugal pumps used in oil refining and chemical industry require all-welded casting or welding of impellers. The development of welded impellers is mostly used for chemical centrifugal pumps made of metal materials with poor casting performance (such as iron and its alloys). The geometric accuracy and surface smoothness of welded impeller are better than that of cast impeller, which is beneficial to improve the efficiency of centrifugal pump.