Impeller

The impeller not only refers to the wheel disc equipped with moving blades, which is a component of the impulse steam turbine rotor, but also refers to the general term of the wheel disc and the rotating blades installed on it. Impellers can be classified according to their shape and opening and closing conditions.

Closed impeller: consists of blades and front and rear cover plates. Closed impellers are more efficient and difficult to manufacture, and are used more in centrifugal pumps. It is suitable for conveying clean water, solution and other clean liquids with low viscosity without particles.

Semi-open impeller: Generally, there are two structures: one is the front semi-open type, which is composed of a rear cover and blades. The impeller efficiency of this structure is low, and an adjustable gap sealing ring is required to improve efficiency; the other is The rear half-open type is composed of a front cover and blades. Since the same sealing ring as the closed impeller can be applied, the efficiency is basically the same as that of the closed impeller, and the blades not only transport liquid, but also have a sealing effect. 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, low in cost, and highly adaptable. It is gradually used in centrifugal pumps for refining and chemical industries and is used to transport clear water and liquids similar to clear water.

Open impeller: There are only blades and blade stiffeners, without front and rear cover, the number of open impeller blades is less than 2-5. The impeller has low efficiency and few applications. It is mainly used to transport liquids with higher viscosity 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 on 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 refining and chemical industries require the impeller to be cast or fully welded integral impeller. Welded impellers have been developed and are mostly used in special centrifugal pumps for chemical industry made of metal materials with poor casting properties. The geometric accuracy and surface finish of the welded impeller are better than those of the cast impeller, which helps to improve the efficiency of the centrifugal pump.