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The impeller not only refers to the disc equipped with moving blades, which is an integral part of the impulsive steam turbine rotor, but also refers to the general term of the disc and the rotating blades installed on it. The impellers are usually cast or welded, and the material is selected according to the working medium. Main function: The function of the impeller is to convert the mechanical energy of the prime mover into the static pressure energy and dynamic pressure energy of the working fluid.

Classification of impellers
According to the blade form, it is divided into three types: open impeller, closed impeller and semi-open impeller.
The closed impeller is composed of front and rear cover plates and blades;
The semi-open impeller is composed of blades and rear cover;
Open impellers have only blades and part of the back cover or no back cover.

According to the working mode, it is divided into single-suction impeller and double-suction impeller.
A single-suction impeller means that the impeller sucks liquid from one side.
The double-suction impeller means that the impeller sucks liquid from both sides, and has excellent anti-cavitation performance.

According to the structure: flow channel type (single flow channel, double flow channel), blade type (closed type, open type), spiral centrifugal type, swirl type four. the
1. Runner type impeller:
The channel impeller is a curved channel from the inlet to the outlet, which is suitable for conveying liquids containing large particles of impurities or long fibers. Because this type of impeller has excellent anti-clogging performance. But its disadvantage is that its anti-cavitation performance is weak.

2. Blade impeller:
The semi-open and open impellers in the vane impeller are easy to cast, and easy to maintain and clean up the impurities blocked during the conveying process. However, its disadvantage is that the gap between the inner wall of the pressurized water chamber and the vane increases under the abrasion of solid particles during transportation, which reduces the operating efficiency of the pump, and the stability of the flow state of the liquid in the flow channel is damaged due to the increase in the gap. , so that the pump vibrates, this type of impeller is not easy to transport medium containing large particles and long fibers. The closed impeller has high operating efficiency and can run stably for a long time. The axial thrust of the pump is small, but the closed impeller is easy to be entangled, and it is difficult to transport the sewage medium containing large particles or long fibers.

3. Spiral centrifugal impeller:
The spiral centrifugal impeller has twisted blades, and the delivered liquid will not hit any part of the pump when passing through the blades, so there is no damage to the pump and no damage to the delivered liquid. Due to the propulsion effect of the screw, the suspended particles have a strong passability, so the pump with this type of impeller is suitable for pumping media containing large particles and long fibers.

4. Swirl impeller:
The swirling impeller is all or part of the impeller is retracted to the flow channel of the pressurized water chamber, which has good anti-clogging performance. The flow of particles in the water pressure chamber is driven by the eddy current generated by the rotation of the impeller. The movement of suspended particles does not generate energy itself, and the energy is exchanged with the liquid in the flow channel. During the flow process, the suspended particles or long fibers do not contact the worn blades, the blades are more worn, and the gap does not increase due to abrasion. It is suitable for pumping media containing large particles and long fibers.