The impeller is the core component of the D-type multistage centrifugal pump and the main influence factor of work efficiency. The function of the D-type centrifugal pump impeller is to directly transfer the mechanical energy of the prime mover to the liquid to increase the static pressure energy and kinetic energy of the liquid (mainly increase the static pressure energy). The impeller generally has blades, front cover, rear cover and hub It is composed of four parts.
D-type multistage centrifugal pump impellers mainly have the following four types: closed type, front semi-open type, rear semi-open type, and open type.
1. Closed impeller means that the flow path is relatively closed, forming a closed flow path between the front cover plate, the rear cover plate and the blades. It is suitable for conveying high-growing, clean liquid occasions. The closed impeller has two structures: single-suction impeller and double-suction impeller. Closed impeller: consists of blades and front and rear cover plates. The closed impeller is more efficient and difficult to manufacture. It is most used in centrifugal pumps. It is suitable for conveying clean water, solution and other clean liquids with low viscosity without particles.
2. The semi-open impeller means that the flow path of the impeller is semi-closed. Compared with the closed impeller, there is no front cover, which is suitable for conveying liquids containing solid particles or impurities. Semi-open impeller: Generally there are two structures. One is the front half-open type, which is composed of the rear cover and the blades. The impeller efficiency of this structure is low. In order to improve the efficiency, it needs to be equipped with an adjustable gap seal ring and the other is the rear half. Open type, composed of front cover plate and blades, because it can apply the same sealing ring as closed pump impeller? The efficiency is basically the same as that of closed impeller, and besides conveying liquid, the blade also has the sealing effect of back blade or auxiliary impeller. . The semi-open impeller is suitable for conveying liquids containing suspended solids such as solid particles and fibers. The semi-open impeller is less difficult to manufacture, lower in cost, and highly adaptable. In recent years, it has been increasingly used in centrifugal pumps for refining and chemical industries, and is used to transport clear water and liquids similar to clear water.
3. Open impeller: an impeller with only blades and blade stiffeners, without front and rear cover plates. The number of open impeller blades is less than 2-5. The pump impeller is low in efficiency and has fewer applications. It is mainly used to transport high-viscosity liquids and slurry liquids.
The blades of centrifugal pump impellers are generally backward curved blades. There are two types of blades: cylindrical and twisted. The use of twisted blades can reduce the load of the blades, improve the suction performance of the centrifugal pump, and improve the anti-cavitation ability, but the manufacturing is more difficult and the cost is higher. Centrifugal pumps used in water pump impellers for refining and chemical industries require that the impellers be cast or fully welded integral water pump impellers. Welded pump impellers have been developed in recent years, and are mostly used for special centrifugal pumps made of metal materials with poor casting properties, such as iron and its alloys. The geometric accuracy and surface finish of the welded water pump impeller are better than those of the cast impeller, which is beneficial to improve the efficiency of the centrifugal pump.
