CONSIDERATIONS OF THE ALL-ELECTRIC (ACCESSORY) ENGINE CONCEPT

The concept of the all electric (accessory) engine (AEE) involves the use of an electrical machine integrated on an engine main shaft acting as a starter/generator, providing power to both engine and airframe s ystems. Through removal of the various constraints caused by the prese nt mechanical accessory drives, this concept apparently provides a num ber of advantages. However, the concept of an AEE has been around for some years and yet has not been adopted to-date. A brief review of ele ctrical machine types previously considered as internally mounted star ter/generators highlights basic problems of the concept. The reasons f or favouring the Switched Reluctance Machine for this application are then explained and some present and planned developments on this basis outlined. An approximate sizing of starter/generators to replace shaf t off-takes alone and bleed in additions in a civil turbofan applicati on is presented, showing more detailed design considerations. Other sy stem component aspects and concerns are also covered before addressing the effects on the ease of adopting the AEE concept of likely future changes to civil engines. Major differences relative to the civil case ale indicated for other engine type applications. Conclusions are the n drawn on the likely future of the AEE concept.