Auxiliary power unit design for an hybrid propulsion system with ultracapacitor storage system
In this paper the design of a special auxiliary power unit (APU) will be reported; the APU, made up by a i.c. engine and an electrical generator, will be utilised as on board generator for a series hybrid propulsion system for microcar equipped with an ultracapacitor energy storage system. The special kind of storage system, characterised by high power density and low energy density, has a big influence on the design and the management of the APU. The low amount of energy stored on board avoid to run the APU at a fixed steady state and suggests to perform a more flexible management method of the power output of the APU; as consequence, the APU design have to be performed considering an area of potential work for the i.c. engine. The i.c. engine considered for the design of the APU is derived for the motorcycle market; it is a spark ignition 250 cm3 engine, liquid cooled single cylinder with four valves and electronic injection.