Centrifugal pump design and analysis
Project Title: Centrifugal pump design and analysis
Objective:
1. Study the centrifugal pump
2. Study the rotating reference frame.
3. Study the performance curve of the centrifugal pump
Theory:
Centrifugal Pump
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 exists.
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.
Working of pump
Like most pumps, a centrifugal pump converts rotational energy, often from a motor, to energy in a moving fluid. A portion of the energy goes into kinetic energy of the fluid. Fluid enters axially through the eye of the casing, is caught up in the impeller blades, and is whirled tangentially and radially outward until it leaves through all circumferential parts of the impeller into the diffuser part of the casing. The fluid gains both velocity and pressure while passing through the impeller. The doughnut-shaped diffuser, or scroll, section of the casing decelerates the flow and further increases the pressure.
Problem Statement:
For this project, you will have to show the following
Performance diagram. Obtain the relationship between Pressure ratio and mass flow rate and explain your results.
Pressure ratio = Outlet total pressure/ Inlet total pressure
Solution:
Modelling:
1. Impeller
2. Outer casing
3. Inlet pipe of the pump
Outlet pipe of the pump
Assembly of centrifugal pump
Cut section view of centrifugal pump
Inlet lid
Outlet lid
Flow setup
1. Analysis type
flow is taking place inside the pump so internal flow simulation is considered.
the impeller is rotating so the rotation model is turn on.
Working fluid
In this simulation working fluid water considered.
Initial condition
Pressure 101325 Pa
Temperature of water 293.2K
Computational domain:
Rotating domain
the impeller is rotating so the rotating domain is created around the impeller.
Rotating speed of the domain is 1000 rpm.
Boundary condition
Inlet
Environmental Pressure is given.
value of pressure is 1.1325 Pa
Outlet
At the outlet, the velocity boundary condition is given
value of outlet velocity is 10 m/sec
Mesh:
Hex mesh is used in this simulation.
Hex mesh is more accurate than triangular mesh
Global mesh setting
Results:
Parametric study
1. Input parameter
outlet velocity is considered as the input parameter.
there are 6 design points are generated from 10 to 20 m/sec
Output parameter
Avg total pressure is considered as outlet parameter in a parametric study
Pressure and velocity at the cut plane is selected to visualize the flow pattern.
The scenario of all design points
Design point 1
velocity 10 m/sec
Pressure
Velocity
Design point 2
velocity 12 m/sec
Pressure
Velocity
Design point 3
velocity 14 m/sec
Pressure
Velocity
Design point 4
velocity 16 m/sec
Pressure
Velocity
Design point 5
velocity 18 m/sec
Pressure
Velocity
Design point 6
velocity 20 m/sec
Pressure
Velocity
Effect of pressure ration on the mass flow rate
Conclusion:
1. the velocity is less so the mass flow rate is less when the velocity increases the mass flow rate increases.
2. we can see that the pressure ratio is high for low velocity and pressure ratio starts to decrease when the velocity increases.
4. Velocity plots have a proper indication of outflow velocity as assigned.
5. Mass flow rate reduces as the pressure ration increases.