Centrifugal pump design and analysis

Introduction:

Centrifugal pumps are used to transport fluids by the conversion of rotational kinetic energy to the hydrodynamic energy of the fluid flow. The rotational energy typically comes from an engine or electric motor. They are a sub-class of dynamic axisymmetric work-absorbing Turbomachinery The fluid enters the pump impeller along or near to the rotating axis and is accelerated by the impeller, flowing radially outward into a diffuser or volute chamber (casing), from which it exits.

Common uses include water, sewage, agriculture, petroleum and petrochemical pumping. Centrifugal pumps are often chosen for their high flow rate capabilities, abrasive solution compatibility, mixing potential, as well as their relatively simple engineering. A cenntrifugal fan is commonly used to implement a vaccum cleaner. The reverse function of the centrifugal pump is a water turbine converting potential energy of water pressure into mechanical rotational energy.

Working of a Centrifugal pump:

Like most pumps, a centrifugal pump converts rotational energy, often from a motor, to energy in a moving fluid. A portion of the energy goes into kinetic energy of the fluid. Fluid enters axially through eye of the casing, is caught up in the impeller blades, and is whirled tangentially and radially outward until it leaves through all circumferential parts of the impeller into the diffuser part of the casing. The fluid gains both velocity and pressure while passing through the impeller. The doughnut-shaped diffuser, or scroll, section of the casing decelerates the flow and further increases the pressure. It is important to note that the water is not pushed radially outward by centrifugal force, but rather by inertia, the natural tendency of an object to continue in a straight line when traveling around circle.

Volute:

Inlet diameter: 20mm

Outlet diameter: 10mm

Volute diameter: 45mm

Impeller:

Minor diameter: 20mm

Major diameter: 40mm

Number of Blades: 6

The Parametric study is conducted with different inlet velocity of fluid from 10m/s to 30m/s

Outlet velocity contours are viewed by the cutplots, all these cutplots are obtained by the parametric study.

Velocity cutplot at 10m/s:

Velocity cutplot at 15m/s

Velocity at 20m/s

Velocity cutplot at 25m/s:

Velocity cutplot at 30m/s

Flow trajectories are obtained from the same paramteric study

Flow trajectory at 10m/s

Flow trajectory at 15m/s

Flow trajectory at 20m/s

Flow trajectory at 25m/s

Flow trajectory at 30m/s

The Outlet Pressure plot is given as below:

Conclusion:

As we can see From the above plots and cutplots, as inlet velocity increases the outlet pressure decreases.

The flow trajectories are little messy and unevenly followed, thats because the geometry is not a defined geometry. its just a madeup geometry.