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OBJECTIVE
- To Create a 3D Model of Centrifugal Pump and to run a Flow Simulation.
- To Obtain a relation between Pressure ratio and Mass Flow rate.
INTRODUCTION
Centrifugal Pumps are the sub class of the Turbomachinery. 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 electric motor. 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 where it exits.
ISOMETRIC VIEW OF CASING
ISOMETRIC VIEW OF THE IMPELLER
ISOMETRIC VIEW OF THE CENTRIFUGAL PUMP
GRID DEPENDANCY TEST
For this test I have set the input variables as output velocity and the values are 10 m/s , 15 m/s , 20 m/s , 25 m/s , 30 m/s. The Level of mesh is set as 3. The number of Iteration for the solver is set as 700 in the calculation control option.
ressure variation plot for various values of outlet Velocity obtained from the Parametric Study
Pressure variations inside the centrifugal pump as seen from the front sectional view for velocity at the outlet 10m/s and 15m/s respectively
Pressure variations inside the centrifugal pump as seen from the front sectional view for velocity at the outlet 20m/s and 25m/s respectively
Pressure variations inside the centrifugal pump as seen from the front sectional view for velocity at the outlet 30m/s
Velocity variation plot for various values of outlet Velocity obtained from the Parametric Study
Velocity variations inside the centrifugal pump as seen from the front sectional view for velocity at the outlet 10m/s and 15m/s respectively
Velocity variations inside the centrifugal pump as seen from the front sectional view for velocity at the outlet 20m/s and 25m/s respectively
Velocity variations inside the centrifugal pump as seen from the front sectional view for velocity at the outlet 30m/s
Flow Trajectories at 10 m/s
Flow Trajectories at 15 m/s
Flow Trajectories at 20 m/s
Flow Trajectories at 25 m/s
Flow Trajectories at 30 m/s
Pressure ratio is the ratio between the outlet pressure and the inlet pressure.
Pressure ratio = Outlet total pressure/ Inlet total pressure
Inlet pressure remains the same for all the cases but the outlet pressure varies. When the flow rate at the outlet is high the pressure reduces at outlet which results in the decrease in the pressure ratio.
Plots related to the above discussions are below
Pressure ratio Verses Mass flow rate
Pressure ratio verses the outlet velocity
Pressure ratio with respect to the design ponits
Pressure ratio, Mass flow rate with respect to the design ponits
CONCLUSION
- From the First plot we can see that initially the velocity is less so the mass flow rate is less when the velocity increases the mass flow rate increases.
- From the Second plot we can see that pressure ratio is high for low velocity and pressure ratio starts to decrease when the velocity increases.
- From the Third plot we can see that for lower mass flow rate the pressure ratio is high when the mass flow rate increases pressure ratio decreases.
- A pump does not create pressure it only creates flow.Pressure is a measurement of the resistance to flow.
- First resistance is created by volute casing of pump which catches the liquid and slows it down. When liquid slows down in the casing some of its kinetic energy is converted into pressure energy.
- That's why velocity increases pressure decreases and velocity increases mass flow rate increases.