In collaboration with EMS – Mekorot Projects Ltd, NUMFLO performed a multi-point CFD optimization of one stage of a hydraulic bowl pump. The target was to increase efficiencies for two high massflow operating points, while keeping other coefficients (head and power) in a prescribed range around the reference values.

The optimization, performed with NUMECA FINE™/Design3D optimization environment provided around a 1% increase of efficiency for both operating points.

The optimization process is performed in 4 main steps:

- a reference performance curve is computed. Both rows (impeller and diffuser) are meshed using high quality structured methodology, with AutoGrid5™ software;

- based on the reference geometry, a parametrical model is built using Autoblade™ software to replace the actual geometry with parametrical curves and surfaces that can be automatically modified to create new geometries;

- a database of 200 CFD simulations is generated with FINE™/Design3D and Minamo™ Module;

- finally, the database is used to generate a surrogate model (“Tuned Radial Basis Function”) that is exploited by the optimization process in order to converge to the optimum geometry.

A new performance curve is launched on the optimized geometry showing a global increase of the efficiency. The efficiency is decreased for the low massflow, but no objectives or constraints were imposed for this working condition during the optimization process. The goal of the optimization was to increase efficiency for high massflow ranges. The optimized case was manufactured by EMS – Mekorot Projects Ltd and tested experimentally in order to be compared to the original geometry. The experimental results show that the results predicted by the CFD optimization are reproduced, providing the expected gain in efficiency.

The pictures show the geometry of the bowl pump, the entropy field before and after optimization and the performance curves obtained during experiments for the original and the optimized pump.



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