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Centrifugal water pump optimization project

This project deals with the optimized design of a centrifugal pump to operate in a certain operating range, evaluating different modifications to maximize the performance of the equipment.

The new design is based on an already operational centrifugal pump, whose characteristics are the following:

• Nominal working range: flow 13-17 kg / s, head 53-57 m.

• Average efficiency in nominal working range: 0.72%.

• Power consumed in nominal working range: 9.5-11.5 kW

• Angular speed: 1798 rpm

• Operating fluid: water at room temperature.

To facilitate pumping tasks in the installation where the equipment is located, a new pump is required that handles the same flow, but can provide greater head:

• New nominal working range: 13-17 kg / s flow rate, 60-63 m head

• New average efficiency in nominal working range: maximum possible based on studies carried out.

• New power consumed in nominal working range: minimum possible based on studies carried out.

To carry out CFD studies, first, a parametric 3D model is built that allows an exhaustive evaluation of the maximum number of possible geometric modifications. Creating a parametric model makes it possible to modify any dimension immediately, without having to redesign everything.

As can be seen in the previous image, the parameterized characteristics are the following:

• Total diameter of the rotor.

• Total suction diameter.

• Total discharge diameter.

• Upper volute radius

• Lower volute radius

• Horizontal length of the blade.

• Outlet pipe length.

• Rotor outlet width.

• Total width of the rotor.

• Blade width.

• Number of blades.

Of all the possible modifications, this project only considers the number of blades and their width. Of course, it would be possible to evaluate any of the other modifications, but due to the restrictions imposed on this work, it is not done.

When modifying the number of blades, the main objective is to ensure that the pump is capable of driving the water to the new head, so it is logical to think that this number will have to be increased. In this case, its increase from 7 to 12 is studied, the original number being 6.

As can be seen in the previous image, the number of blades must be increased to 9 if it is desired to reach the required head with a certain margin of safety. From here, increasing the number does not just provide more height, so 12 can be considered sufficient.

Once it has been ensured that the head operation criterion is met, it is necessary to analyse which number of blades would provide the best performance. It is clearly observed how the use of 9 of these elements achieves higher performance values in the new equipment option range. This result agrees quite well with what is expected, since if from 9 the pump barely managed to provide greater head (in short, the transmitted hydraulic power is approximately constant) but the motor has to move more elements, the required power will increase and the performance will decrease. The number of blades of the new design is therefore defined as 9.

Once this number has been determined, the second variant of this project remains to be analysed, the width of the blades. Two possible modifications of double and triple width are studied, starting now with the new 9-blade model.