Centrifugal pump design and analysis
Centrifugal pumps are a sub-class of dynamic axisymmetric work-absorbing 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 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. A centrifugal fan is commonly used to implement a vacuum cleaner. The reverse function of the centrifugal pump is a water turbine converting the potential energy of water pressure into mechanical rotational energy.
3D model of centrifugal Pump:
OBJECTIVE: This study aims to design and develop a model of a centrifugal pump and analyze the various parameters such as the velocity, pressure at the outlet and inlet, mass flow rate, etc.. And also we simulate the flow of water through the centrifugal pump evaluating pressure and the velocity of the flow. And finally, we end up calculating the pressure ratio based on the pressure at the outlet and inlet and result in developing a performance diagram (plot of mass flow rate v/s pressure-ratio).
PROCEDURE: Create a centrifugal pump of outer volute radius 0.045m, the impeller of 0.04m radius, and an eye of 0.02m radius with the number of impeller vanes = 6.Now create an inlet runner of 0.03m in diameter and 7cm in length and an outflow casing of 0.01m in diameter.Then set-up the rotational domain just outside the impeller blades, where we are going to simulate our rotation. Now specify the boundary conditions and set-up the goals for pressure, mass flow rate, and the pressure ratio and run the flow simulation for results.Now setup the cut plots for velocity, goal plots, and flow trajectory.Then start a new parametric study and provide input variables as velocity varying from 10, 15, 20, 25, 30.Setup the output parameters as cut plots and goals.Run the parametric study to get results for varying velocity.
PLOTS AND GRAPHS: Velocity plot at 10 m/s:
cut plot:
Flow trajectory:
Velocity plot at 15 m/s :
Flow trajectory:
Velocity plot at 20 m/s :
Flow trajectory:
Velocity plot at 25 m/s :
Flow trajectory:
Velocity plot at 30 m/s :
Flow trajectory:
Pressure Ratio = {Outlet total pressure / Inlet total pressure} Pressure ratio values: Pressure ratio at a velocity of 10 m/s = 9.22. Pressure ratio at a velocity of 15 m/s = 9.95. Pressure ratio at a velocity of 20 m/s = 10.09. Pressure ratio at a velocity of 25 m/s = 9.05. Pressure ratio at a velocity of 30 m/s = 8.85. Table showing values of different parameters:
Graphs of Pressure ratio and the mass flow rate versus velocity :
Graphs showing variation in total pressure (inlet and outlet), mass flow rate and pressure ratio at various velocities:
Performance diagram: Graph of mass flow rate versus pressure ratio:
Results: From the above study, it is observed that the outlet total pressure is almost 9-10 times more than the inlet pressure i.e., the pressure ratio varies between 9 and 10, in most of the situation (for outlet velocities ranging from 10 to 30). Outlet pressure is more than the inlet pressure as the area of the cross-section at the outlet is less than the area of cross-section at the inlet. The mass flow rate increases uniformly with an increase in the outlet velocity. And, as the outlet velocity increases the outlet average total pressure decreases. Finally, the pressure ratio increases gradually and remain constant (varying between 9 and 10) then decreases with an increase in the mass flow rate.