Centrifugal pump design and analysis

1. AIM

To design and analyse a Centrifugal Pump.

2. OBJECTIVES

1. To create a 3D model of a centrifugal Pump.
2. To obtain the relationship between Pressure ratio and mass flow rate (Performance diagram.)

3. INTRODUCTION

A pump is a device that moves fluids (liquids or gases), or sometimes slurries, by mechanical action, typically converted from electrical energy into Hydraulic energy. 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.

The Main parts of Centrifugal Pump are:

1. Impeller
2. Casing
3. Delivery Pipe
4. Suction Pipe with Foot Valve Strainer

Pressure ratio = Outlet total pressure/ Inlet total pressure

4.CAD GEOMETRY

5. FLOW SIMULATION

SOLIDWORKS Flow Simulation is an intuitive Computational Fluid Dynamics (CFD) solution embedded within SOLIDWORKS 3D CAD that enables you to quickly and easily simulate liquid and gas flows through and around your designs to calculate product performance and capabilities.

The major tabs in Flow simulation

PARAMETERS

1. Internal flow simulation
2. Steady state study
3. Pressure: 101325KPa
4. Temperature: 293.2K
5. Medium : Water
6. Rotation : On
7. Wall conditions: Adiabatic with 0 micrometer roughness,

Boundary conditions

1. Inlet pressure : 101325KPa
2. Outlet velocity at exit: 10m/s

STEPS

1. Model the system using solidworls sketch, boss extrude, sweep and revlolve tool.
2. Lids are created at the inlet port and outlet of pump to make the model water tight.
3. Activate the flow simulation plugin of solidwokrs in add-ins tab.
4. Select wizard and input respective details including medium as per parameters given above to set the project. Add rotation in the wizard settings.
5. Set the computational domain to 3D and set the domain in such a way that the silumation result is not affected.
6. Redefine the gloabal mesh for more accurate results.
7. Insert boundary conditions at inlet and outlet as given above.
8. Insert cutplot of top plane for velocity and pressure.
9. Set surface goals on the lid for Average input and output pressure, also mass flow rate at outlet.
10. A new parametic study is created. Input is given as outlet velocity wihich vary from 10 to 50 in a step of 10. Output are all the surface goals and cutplots. Set iteration = 500 and uncheck all options under calculation control option. Hit run.

Boundary settings

Parametric study settings

6. RESULTS, OBSERVATIONS AND CONCLUSIONS

Velocity = 10m/s

Velocity = 20m/s

Velocity = 30m/s

Velocity = 40m/s

Velocity = 50m/s

In every case we can see a low velocity and pressure near the impeller. This is due to pushing of water from there due to the rotation of impeller. The mass flow rate is considered as positive here. The negative results is due to the sign convetion of water going out of the fluid domain.

Performance curves

Animation

Conclusion

1.Outlet velocity is inversly propotional to pressure as outlet velocity increased, total average outlet pressure value gets decreased. This can be seen in the contour plots clearly.

2.It is not the perfect performance curve as pump geometry is madeup geometry. Do small vortex is created near the exit of the flow as it is not exactly tangential. This shows as how important the need to keep the outlet in a tanget position.

3.With increase in Outlet Velocity the Average Mass Flow Rate showed a linear variation in the negative direction and hence it increases.

4.With increase in the outlet velocity, the mass flow rate also increases.

5.But for pressure ratio is high for low velocity and pressure ratio starts to decrease when the velocity increases.