Centrifugal pump design and analysis (Flow Simulation using Solidworks)

Aim: To make a 3D model of Centrifugal pump and perform flow analysis to obtain a performance curve by plotting the Pressure ratio vs mass flow rate graph.

Theory: A centrifugal pump used to transport fluid by converting kinetic energy to hydrodynamic energy of the fluid flow. It sucks fluid through its eye(inlet) and through impeller the kinetic energy is converted to hydrodynamic energy and sends fluid through the outlet greater pressure. The impeller is backward-facing designed with increasing area radially outward to decrease fluid velocity and increase pressure.

For the flow analysis, only the wet end of the centrifugal pump is designed i.e. those parts which dictate the hydraulic performance of the pump. This includes an impeller and a volute. For this experiment, a single-suction centrifugal pump is designed. Its impeller is the open type with backward-curved blade design. For the sake of convenience, a nondiffusing type volute is designed i.e. the volute and impeller are concentric. Following are the given dimensions:

Volute:

• Inlet diameter = 40mm
• Outlet diameter = 20mm
• Volute diameter = 140mm

Impeller:

• Impeller diameter = 100mm
• blade thickness = 2mm
• Number of blades = 5

A pump performance curve indicates how a pump will perform in regards to pressure ratio and flow. The pressure ratio is the ratio of outlet pressure to inlet pressure. The mass flow rate is measured in the outlet. It is negative since mass is flowing out. The pressure ratio is on the y-axis while the mass flow rate is on the x-axis. Inlet pressure is set to 101325 Pa and the impeller is given 1000 rad/s rotation speed in an anti-clockwise direction. To obtain performance diagram, a parametric study is done with input variable of outlet velocity 10,15,20,25,30m/s. Inlet pressure, outlet pressure, and mass flow rate is set as output results.

Observations:

Pressure Distribution:

• For outlet velocity = 10m/s.
• For outlet velocity = 15m/s.
• For outlet velocity = 20m/s.
• For outlet velocity = 25m/s.
• For outlet velocity = 30m/s.

Flow trajectory at outlet velocity = 20m/s.

Ouput Data:

It is observed that with an increase in outlet velocity mass flow rate also increased. With an increase in the mass flow rate, there is also a decrease in outlet pressure.

The decrease in outlet pressure is due to increased outlet velocity.

Performance diagram: 

This curve shows an increased flow rate as the pressure head decreases.

Conclusion:

• Outlet pressure decreases due to increased outlet velocity according to Bernoulli's principle and mass flow rate increases.
• With increase in mass flow rate, there is a decrease in pressure ratio which suggests that the pumping capacity decreases with increased flow rate.
• With increased flow rate the height up to which water can be pumped decreases.