Impeller refers not only to the wheel equipped with moving blades, which is an integral part of the impulse turbine rotor [1], but also to the general term of the wheel and the rotating blades mounted on it. Impeller can be classified according to shape and opening and closing condition. Centrifugal pump impeller mainly has the following four forms, (a) closed; (b) front half open; (c) back half open; (d) Open.
In addition to the main impeller, some turbines have secondary blades. The so-called auxiliary impeller hydrodynamic seal refers to the installation of an open impeller in a coaxial opposite direction near the back of the pump impeller rear cover plate. When the pump works, the auxiliary impeller rotates with the main shaft of the pump, the liquid in the auxiliary impeller will also rotate together, the rotating liquid will produce an outward centrifugal force, the centrifugal force on the one hand against the flow of liquid to the mechanical seal, reducing the pressure at the mechanical seal. On the other hand, prevent the solid particles in the medium from entering the friction pair of the mechanical seal, reduce the wear of the mechanical seal grinding block, prolong its service life.
In addition to the sealing effect of the auxiliary impeller, it can also play the role of reducing the axial force. In the submersible sewage pump, the axial force mainly consists of the differential pressure force of the liquid acting on the impeller and the gravity of the whole rotating part. The direction of the action of the two forces is the same, and the resultant force is the addition of the two forces. It can be seen that under the condition of the same performance parameters, the axial force of the submersible pump is larger than that of the general horizontal pump, and the balance is more difficult than that of the vertical pump. Therefore, in the submersible sewage pump, the reason for the easy damage of bearings is also closely related to the large axial force.
And if the auxiliary impeller is installed, the direction of the pressure difference force of the liquid acting on the auxiliary impeller is opposite to the resultant force of the above two forces, which can offset a part of the axial force, and also play the role of extending the life of the bearing. But the use of auxiliary impeller sealing system also has a disadvantage, that is, in the auxiliary impeller to consume a part of the energy, generally about 3%, but as long as the design is reasonable, it can reduce this part of the loss to a minimum.
Artison is a supplier of aerospace components; Products include impeller, turbine, combustion chamber, fastener, etc.
If you have any questions or needs, please contact us. Here is our contact information:
Price Inquiry：sales.lily@superalloyparts.com
Technical Support：eng.daisy@superalloyparts.com
Quality Control：qc.jason@superalloyparts.com