Centrifugal pump design and analysis
AIM: To design a centrifugal pump and perform a parametric study on it.
OBJECTIVE: To find the relationship between Pressure ratio and mass flow rate.
Pressure ratio = Output total pressure / Input total pressure
PROCEDURE:
- Create geometry of the centrifugal pump
- Save the part
- Open flow simulation
- Setup the lids at both ends
- Open wizard
- Set the flow type as internal, steady state
- Set fluid as water
- Define the operating conditions and wall parameters
- Finish wizard
- Setup the rotating zone correctly
- Set a mesh
- Set the boundary conditions as follows:
- Inlet: Environmental pressure
- Outlet: Velocity outflow (10-25 m/s : parametric study variable)
- Set all the surface goals (inlet total pressure, outlet total pressure, outlet velocity)
- Set all cut plots
- Set the flow trajectories
- Modify the convergence criteria to 750 iterations only
- Run the simulation
- Check if the results are physically coherent
- Else, modify the mesh and re-run
- Setup a parametric study for 5 values in between 10-25 m/s and run the simulation(s)
RESULTS AND DISCUSSIONS:
Design point 1
Design point 2
Design point 3
Design point 4
Design point 5
|
Outlet pressure |
Inlet pressure |
Velocity outlet |
mass flow rate |
Ratio |
|
|
463226.02 |
112091.83 |
10.133 |
0.0002865 |
6.93276E-05 |
|
|
481986.53 |
117362.43 |
13.866 |
0.000392047 |
9.54625E-05 |
|
|
274536.37 |
108634.8 |
17.648 |
0.00049898 |
0.000197448 |
|
|
153046.55 |
101325 |
21.359 |
0.000603904 |
0.000399817 |
|
|
218208.6 |
119522.36 |
25.104 |
0.00070979 |
0.000388783 |
From the parametric study for the centrifugal pump it is found that the ratio of Pressure ratio to the outlet velocity displays a parabolic relation upto design point 5 and then loses its relation which defines a choking condition for delivery. Which indicates that the pressure at outlet decreases with increase in outlet velocity, which is physically correct, as the flow has to satisfy the Bernoulli’s equation.
The incoming fluid appears to be recirculating in the suction pipe and the one leaving has none which indicates that the suction pipe geometry requires modification, whereas the delivery pipe is fine.