Centrifugal pump design and analysis
AIM: Perform a flow simulation on centrifugal pump and obtain relationship between pressure ratio and mass flow rate.
OBJECTIVES:
- Obtain performance diagram
- Obtain relationship between pressure ratio and mass flow rate
- Explain the result
GOVERNING EQUATION:
`"Pressure ratio = Outlet total pressure/ Inlet total pressure"`
THEORY:
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.
An impeller or impellor is a rotor used to increase the pressure and flow of a fluid. It is the opposite of a turbine, which extract energy from, and reduces the pressure, of a flowing fluid.
PROCEDURE:
Designing
Flow simulation,
Flow type – Internal
Fluid – Water
For rest default options are selected.
Mesh level 3 is selected and advanced refinement mesh is selected.
Insert,
Boundary condition – inlet opening as environmental pressure and outlet opening as outlet velocity
Surface goals – Total average pressure at inlet and outlet & mass flow rate.
Cut plots – top plane for velocity and pressure
Flow trajectories -> select inlet and outlet as boundaries -> for velocity and pressure
Baseline flow simulation
Parametric Study,
Input parameter – inlet flow velocity, total 5 scenario ranging from 10m/s to 20m/s.
Output parameter – All goals and all cut-plots
Velocity Flow Trajectories
Pressure Flow Trajectories
RESULTS:
Case 1: Inlet velocity = 10m/s
Velocity contour
Pressure contour
Velocity flow trajectories
Pressure flow trajectories
Case 2: Inlet velocity = 12.5m/s
Velocity contour
Pressure contour
Velocity flow trajectories
Pressure flow trajectories
Case 3: Inlet velocity = 15m/s
Velocity contour
Pressure contour
Velocity flow trajectories
Pressure flow trajectories
Case 4: Inlet velocity = 17.5m/s
Velocity contour
Pressure contour
Velocity flow trajectories
Pressure flow trajectories
Case 5: Inlet velocity = 20m/s
Velocity contour
Pressure contour
Velocity flow trajectories
Pressure flow trajectories
Goal plots summary
Pressure ratio summary
Pressure Ratio compared to Mass Flow Rate
CONCLUSION:
Thus, the Pressure ratio vs Mass flow rate was obtained by sketching and performing the flow simulation for the centrifugal pump. The following are observed during the analysis of the centrifugal pump:
- The increase in velocity results in an increase in mass flow rate. From the plot, we conclude that as an increase in mass flow rate, the pressure ratio value increases respectively is obtained in the above plot.
- The negative sign indicates the flow of the fluid at the outlet port.
- Generally, for the compressor pump, the pressure ratio will decrease in an increase in velocity at the outlet.
- Here the variation is not linear as because the geometry of the centrifugal pump is not sketched with the standard centrifugal pump i.e. with dimensions and values. If the standard values are used, the resulted plot will be linear and accurate i.e. the pressure ratio will decrease in an increase in velocity at the outlet.