Mechanical and thermal design of an aeroengine starter/generator

The paper describes the mechanical and thermal design of a high speed, high power density synchronous permanent magnet machine for an aero engine starter generator system with a power rating of 150 kW and maximum speed of 32,000 rpm. The electrical machine is designed to minimise the weight and maximise the efficiency so both mechanical and thermal aspects are considered. The cooling strategy adopts an inner stator sleeve for enhanced cooling of the stationary components whilst minimising the windage loss. Finite Element Analysis (FEA) is used for the static structural analyses of critical components of the machine and the dynamic performance of the rotating shaft. Heat transfer phenomena are also investigated by the means of Computational Fluid Dynamics (CFD) and Lumped Parameter Thermal Network (LPTN) for the optimisation of the proposed cooling arrangement and prediction of the machine temperature distribution.