Redesign of an Aero-Engine Fuel Pump Impeller

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Introduction

The client is a major supplier of various products for the aerospace industry. In this project they asked Advanced Design Technology to help with the redesign of an aero-engine fuel pump impeller which were suffering from severe erosion caused by cavitation after a certain period of operation.

The impeller redesign was subject to both geometrical and hydraulic constraints in order to fit the impeller in the existing casing and to meet the required head at take-off and cruise condition.

Cavitation pattern in the original impeller (left) and the redesigned impeller (right)

An impeller geometry was reached which exhibits an improved cavitation pattern at cruise condition.

Given the fact that most of in-operation service of the fuel pump is at cruise condition, a detailed cavitation simulation was performed at cruise condition for the existing impeller. The results showed that the cavitation pattern in the impeller and trajectory of vapour phase streamlines can predict the erosion on a qualitative basis as shown. The focus of the redesign was then to improve the cavitation performance by application of TURBOdesign1 while maintaining an acceptable level of efficiency and required pump head over the complete operating range.

After a few design iterations an impeller geometry was reached which exhibits an improved cavitation pattern at cruise condition. This was achieved through specification of an appropriate blade loading which allows to control the pressure field in the impeller. The new impeller has a sheet-cavitation type which is anticipated to cause much less erosion damage as most cavitation bubbles do not collapse and will be carried away downstream by the main flow.

Complex distribution of the blade loading at hub (1) and shroud (2) allows for better control of cavitation behaviour

 

Further CFD investigation by means of both single-phase and two-phase flow shows that the new impeller also meets the take-off head with a minute penalty in the pump efficiency.

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