Centrifugal Pump Simulation using Converge CFD
Objective
Perform a compressor pump simulation to plot the characteristic performance curve of the pump by simulating the pump for various outlet mass flow rates. The purpose of plotting said performance curve is because it indicates pressure ratio the compressor can deliver for a given mass flow rate at peak efficiency.
Introduction
Converge Studio was the software used to simulate the Compressor. The expected observations are a pressure increase across the flow path and an additional tangential velocity component to the fluid as the impeller inside is rotating the fluid and building the pressure as a consequence.
Geometry
Pump:
Impeller:
Case Setup:
The following parameters were used to simulate on converge studio:
Post-Processing:
Converge Studio plotting tools and ParaView were used to post process the results:
Variation of properties w.r.t. time:
We ran the simulation for 3 different outlet massflow rates : 130kg/s, 156kg/s and 180kg/s
Total Cells vs Time:
As we can see from the above image the total number of cells for each case is almost the same nad definitely withint the same range. This is because we have given a constant base grid and a fixed embedding which doesn\'t change the mesh with physical properties of the fluid.
Outlet mass flow rate vs Time:
As we have fixed the mass flow rate as a BC on the outlets there is no variation in outlet_mass_flow_rate with respect to time in all 3 cases
Outlet Velocity vs Time:
The outlet velocities are different for the 3 cases we have simulated and they are as follows
Case 1 : 4.97m/s
Case 2 : 5.97m/s
Case 3 : 6.88m/s
Although the above graph shows a flatline velocity graph, when looking at individual graphs with a smaller y-axis range, the observation is slightly different.
Case 1 (130kg/s):
Case 2 (156kg/s):
Case 3 (180kg/s):
We can see from the above 3 graphs that the flow accelerates slightly before the flow converges properly across the domain.
Contours
Velocity Contours:
Case 1 (130kg/s)
Case 2 (156kg/s)
Case 3 (180kg/s)
Performance Curve
A centrifugal pump performance curve is a tool that shows how a pump will perform in terms of pressure head and flow capacity. The possible combinations of total pressure and volume flow rate for a specific pump can be plotted to create a pump curve.
Total Pressure and Torque values have been obtained from Converge output files.
Data Table:
| Massflow (kg/s) | Massflow (cubic m/hour) | Total Pressure (Pa) | Total Head (m) | Hydraulic Power (kW) | Torque | Shaft Power | Efficiency |
| 130.00 | 468.00 | 511065.04 | 52.09633393 | 66.43347215 | 354.71 | 74.29108349 | 0.894232 |
| 156.00 | 561.60 | 485353.05 | 49.47533642 | 75.70939763 | 375.3929 | 78.6221 | 0.962953 |
| 180.00 | 648.00 | 450925.89 | 45.965942 | 81.16057335 | 387.63 | 81.18536224 | 0.999695 |
Total Head (m) = `(Pressure(Pa) * 1e-5)/(0.0981* S.G.)`
Mass Flow (`m^3`/hour) = Mass Flow (kg/s) x 3.6
As we can see above mass_flow has been calculated in cubin m/hour and pressure is calculated in terms of head in metre.
Efficiency Calculations:
Pump hydraulic power = `(Q*H)/367` kW
Q = Discharge in `m^3`/hr
H = pressure head in metre
P = Hydraulic Power in kW
Shaft Power = `tau * omega` kW
`tau` = Torque in
`omega` = Angular Velocity in rad/s
Efficiency = Hydraulic Power / Shaft Power
Conclusion
A pump charecteristic curve has been successfully plotted and efficiency has been calculated for all 3 mass flow\'s.