Centrifugal pump design and analysis - Solidworks CFD

1. AIM:

- To design a centrifugal pump and simulate the flow inside it using Solidworks CFD

2. 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 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.

3. OBJECTIVES:

- To plot the performance diagram i.e. to obtain the relationship between Pressure ratio and mass flow rate with explaination.

4. FLOW SIMULATION SETUP:

    1. Create a CAD model of the centrifugal pump in solidworks.

    2. Enable Flow Simulation from the add-ins menu.

    3. After that, the flow simulation wizard is used to set up all the parameters of the mathematical model.

    4. Steps for wizard: (Note that rotation is checked, i.e. there is rotation of fluid involved in this study):

    5. Give a suitable project name.

    6. Select a proper unit system, preferably SI system.

    7. Select a flow type. In our case, the flow of the fluid, i.e water, is through the inlet of the pump. Hence, it is an internal flow.

    8. Select the proper fluid that is used in the simulation. Also, select the proper flow type, depending on the nature of the flow i.e laminar, turbulent or mixed.

    9. Set wall conditions as it is. Do not make any changes as far as the challenge is considered.

   10. Since this is an internal flow, the boundary conditions are needed to be set up. The typical boundary conditions used in this simulation are:

   11. Environmental Pressure at inlet, equal to 1 bar, i.e 101625 Pa.

   12. Velocity at outlet, initialed to a value of 15 m/s.

   13. Check the computational domain after setting up the flow simulation. If the size of the domain is adequate, leave the size as it is.

   14. The size of the mesh for this simulation was set to 4 due to hardware limitations of the laptop. Also make sure that the advanced channel refinement is selected.

   15. Once the grid is selected, set the local surface goals. In our case, the main goal is to find out the mass flow rate at outlet, pressure at inlet and outlet respectively.

   16. Finally, create the lids as the inlet and the outlet must be perfectly closed.

   17. Run the simulation using parametric study as follows:

         - Select the input variable as the outlet velocity normal to the face of the outlet pipe. Enter the range of the velocity and the number of iterations for which the simulation must be run.

          - Select the output parameter as the main surface goal, i.e the mass flow rate, outlet pressure, inlet pressure, required cut plots and flow trajectories.

          - Check the scenario tab and run the simulation.

5. OBSERVATIONS, RESULTS AND CONCLUSION:

1. The outputs obtained after running the simulations are as follows:

2. The cut plots obtained for oulet pressure for the 6 iterations are animated below in a GIF format

Flow trajectory:

    3. The performance curve of the pump was obtained, i.e. a plot of pressure ratio on the Y-axis and Mass flow rate of the fluid in kg/s on the X-axis.

    4. The following graphs were also obtained after the simulation:

        - Mass flow rate

        - Average total pressure at outlet

        - The plot data obtained after running the simulation is shown below:

 Conclusion:

1. From the results we can see that the pressure is decreasing with the increase in velocity.
2. Mass flow rate has a negative sign because it is coming out of the system(lid in this case).
3. Also, we can observe from the flow trajectory that there is a significant loss due to eddy formtion which makes the outlet mass flow rate lesser than the inlet mass flow rate.