Centrifugal pump design and analysis

Objective: To create a Centrifugal pump design and perform analysis

Problem Statement:

For this project, 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

Theory:

A centrifugal pump is a mechanical device designed to move a fluid by means of the transfer of rotational energy from one or more driven rotors, called impellers. Fluid enters the rapidly rotating impeller along its axis and is cast out by centrifugal force along its circumference through the impeller’s vane tips. The action of the impeller increases the fluid’s velocity and pressure and also directs it towards the pump outlet. The pump casing is specially designed to constrict the fluid from the pump inlet, direct it into the impeller and then slow and control the fluid before discharge.

The impeller is the key component of a centrifugal pump. It consists of a series of curved vanes. These are normally sandwiched between two discs (an enclosed impeller). For fluids with entrained solids, an open or semi-open impeller (backed by a single disc) is preferred.

Fluid enters the impeller at its axis (the ‘eye’) and exits along the circumference between the vanes. The impeller, on the opposite side to the eye, is connected through a drive shaft to a motor and rotated at high speed (typically 500-5000rpm). The rotational motion of the impeller accelerates the fluid out through the impeller vanes into the pump casing.

There are two basic designs of pump casing: volute and diffuser. The purpose in both designs is to translate the fluid flow into a controlled discharge at pressure.

In a volute casing, the impeller is offset, effectively creating a curved funnel with an increasing cross-sectional area towards the pump outlet. This design causes the fluid pressure to increase towards the outlet.

Study Setup:

Create the part as shown.

Now using the wizard tool use the default operations and make the changes to the following windows.

Check the Rotation option with Local region(s)(Averaging).

Use the water as the fluid in this case.

Uncheck the Boss Extrude in the options given below.

Select the Calculation Control Options and follow the given below steps.

Select the Rotating Region as shown with the Parameter as 1000 rad/s.

Then add the following boundary conditions as shown.

Then add the following goal plots as shown.

Then in the results, the cut plots and flow trajectories are added as shown.

Create a parametric study with the following input parameters and output parameters.

Results:

Design Point 1:

Velocity Plot

Pressure Plot

Flow Trajectory Velocity

Design Point 2:

Velocity Plot

Pressure Plot

Flow Trajectory Velocity

Design Point 3:

Velocity Plot

Pressure Plot

Flow Trajectory Velocity

Design Point 4:

Velocity Plot

Pressure Plot

Flow Trajectory Velocity

Design Point 5:

Velocity Plot

Pressure Plot

Flow Trajectory Velocity

This plot displays the Mass Flow Rate at various different points.

This plot is a Pressure Ratio vs Mass Flow Rate plot.

Conclusion:

It can be observed from the Mass Flow rate plot that with the increase in velocity the mass flow rate increases but the plot shows it in the opposite direction because of the negative sign.

The second plot displays the plot between the Pressure Ratio vs Mass Flow Rate plot we can conclude that as the velocity increases the pressure ratio decreases making an exception for the third instance in the plot.

The velocity and the pressure plots are also created which help us in studying the characteristics of the centrifugal pump. The plots can be more accurate by increasing the mesh size but it requires higher computational power and time.

The Simulation has been successfully run, the results and plots are obtained for the various cases.

References:

https://www.michael-smith-engineers.co.uk/resources/useful-info/centrifugal-pumps