Centrifugal pump design and analysis
Flow simulation analysis on Centrifugal pump
Aim: To determine the pressure ratio and mass flow rate of a centrifugal pump.
Objective:
- Create a centrifugal pump
- Obtain the pressure ratio and mass flow rate.
- Explain the results.
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. 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.
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. The reverse function of the centrifugal pump is a water turbine converting potential energy of water pressure into mechanical rotational energy.
In this project various aspects regarding the flow taking place in the centrifugal pump are studied.
The flow of the project is as follows
Creating a centrifugal pump. Some parts are set to transparent to be able to see through them.
Here, a zone is created around the impeller to specify a space where fluid is going to rotate at a given velocity by the impeller without actually rotating the impeller. By doing this, required output can be obtained.
After creating the centrifugal pump, flow simulation project is created by using wizard tool. Settings for the wizard tool are as below
Project name – Centrifugal pump flow
Analysis type – Internal flow
Rotation – Local region(s) (Averaging)
Liquids – Water
After setting up the flow simulation wizard, input data is given as below
Rotating Region – 146 rad/sec [(-ve) to change the direction of rotation of impeller] [146 rad/sec = 1400 rpm (approx.)]
Boundary conditions – Inlet pressure as environmental pressure and outlet velocity as 50 m/s at atmospheric pressure
Goals – Global mass flow rate, inlet and outlet average total pressure and pressure ratio
Mesh – Grid level at 3 and advanced channel refinement is checked.
Lastly, minimum iterations to be solved are specified as 500.
Results of the simulation
Velocity cut plot
Pressure cut plot
Flow trajectories of Pressure
Flow trajectories of Velocity
Next, a parametric study is created, where the values of velocity by taking 5 values between 50 m/s and 100 m/s having equal interval among them.
And then run the analysis.
RESULTS
At velocity 50 m/s
Velocity cut plot
Pressure cut plot
Flow trajectories of Pressure
Flow trajectories of Velocity
At velocity 62.5 m/s
Velocity cut plot
Pressure cut plot
Flow trajectories of Pressure
Flow trajectories of Velocity
At velocity 75 m/s
Velocity cut plot
Pressure cut plot
Flow trajectories of Pressure
Flow trajectories of Velocity
At velocity 87.5 m/s
Velocity cut plot
Pressure cut plot
Flow trajectories of Pressure
Flow trajectories of Velocity
At velocity 100 m/s
Velocity cut plot
Pressure cut plot
Flow trajectories of Pressure
Flow trajectories of Velocity
Mass flow rate
Pressure ratio
Conclusion:
As per the observations, it can be seen in the graph that as the velocity increases at every design point, the output pressure decreases. Also, the mass flow rate is not constant and un-proportional. Here, as the input pressure is kept constant, that’s why the pressure ratio and output pressure are same.
Is it also been observed that, as the velocity increases the production of unnecessary swirls occurs in the flow. This can be avoided by designing a centrifugal pump according to the standard specifications and dimensions.
Reference: