Centrifugal pump design and analysis

Aim:

• To create a 3-D model of a centrifugal pump, run a baseline flow simulation where inlet flow takes place and then perform a parametric study for different velocities.
• To plot the performance diagram and obtain the relationship between pressure ratio and mass flow rate.

Theory:

Centrifugal pump:

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 centrifugal fan is commonly used to implement a vacuum cleaner. The reverse function of the centrifugal pump is a water turbine converting potential energy of water pressure into mechanical rotational energy.

Mass flow rate:

The mass flow rate of a system is a measure of the mass of fluid passing a point in the system per unit time.

Pressure ratio:

It is the ratio between outlet pressure and the inlet pressure.

Centrifugal pump model:

Procedure:

• Create a 3-D model of Centrifugal pump taking approximate dimension in SOLIDWORKS.
• A moving reference was created between the impeller and volute to increase the accuracy of result.
• Now click on the wizard option of Flow simulation of SOLIDWORKS to perform CFD.
• Select the analysis type as internal, fluid used as water.
• Computational domain is created.
• Modify the components in the components control.
• The rotating region is selected and the speed is set to 1000 rpm.
• Set the boundary conditions, inlet boundary condition is set to environmental conditions i.e. 1 bar, outlet boundary condition velocity i.e. 10m/s.
• Mesh is created with advance refinement option turned with mesh level 3.
• Surface goals are set: inlet average pressure and outlet average pressure and mass flow rate.
• Cut plots and flow trajectories for velocity and pressure were taken.
• A parametric study was carried out for different values for outlet velocity.

Outputs:

At 10 m/s:

Velocity cut plot:

Velocity trajectory:

At 15 m/s:

Velocity cut plot:

Velocity trajectory:

At 20 m/s:

Velocity cut plot:

Velocity trajectory:

At 25 m/s:

Velocity cut plot:

Velocity trajectory:

At 30 m/s:

Velocity cut plot:

Velocity trajectory:

Parametric study results:

Graphs and Comparison:

Pressure ratio:

Pressure ratio graph:

Mass flow rate:

Mass flow rate graph:

Relationship between pressure ratio and mass flow rate:

Graph of pressure ratio and mass flow rate:

Conclusion:

• Mass flow rate is directly proportional to the velocity.
• Pressure ratio is inversely proportional to the velocity.