Improving the performance of a two-stage centrifugal pump by optimizing its flowpath

Abstract

The paper describes a technique for improving the characteristics of a two-stage screw centrifugal pump by optimizing its flow path. The technique combines the joint use of mathematical optimization software IOSO, the meshing complex NUMECA and CFD complex ANSYS CFX. First, the problem areas of the pump flow path were identified, the change of which will provide a greater impact on the parameters of the two-stage pump: low pressure impeller, transferring passage and high pressure impeller. The optimization software was used for automatic change of the geometry of the designated pump elements to find the optimal design. The investigated pump consists of two stages: a low pressure stage and a high pressure stage. The low pressure spool in turn consists of a non-axisymmetric knee inlet duct, a low pressure screw, a low pressure impeller and a transferring passage. The transferring passage is designed to change the flow direction from centrifugal to axial for the high pressure spool. The high-pressure spool consists of a high-pressure screw, a high- pressure impeller and a volute outlet duct. Considering the influence of the sensors position made it possible to improve the agreement with the experimental data: from 6.9% to 4.6% in terms of head; from 8.0% to 3.2% in terms of efficiency. The optimization aim was the increase of the pump efficiency with preservation or slight increase in the pressure head. It was found that pump with optimized geometry has greater efficiency by 3.1% and pressure head by 0.4% in comparison with the original pump variant. The obtained reserve of efficiency and pressure head can be used to boost the rocket engine, and/or to reduce the loading of the main turbine, which operates in aggressive oxidizing environment.