Question

hi please elaborate axial flow pumps working principle with labelled and the flow image , application and limitation .

Answer 1

An axial flow pump is a kind of pump that consists of a propeller in a pipe, which is an axial impellar. The propeller can be driven directly by motor or petrol engines mounted to the pipe from the outside or by any rightangled drive shaft. Axial pumps are used for the promotion of incompressible fluids and are employed for large volume flows at relatively low delivery heads.

Operation:

An axial flow pump has a propeller type of impeller running in a casing. The pressure in an axial flow pump is developed by the flow of liquid over the blades of impeller. The fluid is pushed in a direction parellel to the shaft of the impeller, that is, fluid particles, in course of their flow through the pump, do not change their radial locations. It allows the fluid to enter the impeller axially and discharge the fluid nearly axially. The propeller of an axial flow pump is driven by a motor.

• Fixed diffuser vanes are used to remove the whirl component ( ) of the discharge velocity of the impeller and to convert the energy into pressure.
• The impeller vanes can be adjustable.
• The machine may be fitted with pre-entry vanes to eliminate pre-rotation and to make the flow purely axial.

Work done on the fluid per unit weight=   

where   is the blade velocity.

For maximum energy transfer,  , that is,

Therefore, from outlet velocity triangle, we have

Therefore, The maximum energy transfer per unit weight by an axial flow pump =

Applications:

• One of the most common applications of AFPs would be in handling sewage from commercial, municipal and industrial sources.
• In sailboats, AFPs are also used in transfer pumps used for sailing ballast. In power plants, they are used for pumping water from a reservoir, river, lake or sea for cooling the main condenser.
• In the chemical industry, they are used for the circulation of large masses of liquid, such as in evaporators and crystallizers.

Advantages:

• Highest flow rates (capacity).
• Can be adjusted for best efficiency at varying conditions.

Limitations:

• Low head and discharge pressures
• Not suitable for suction lift