Development of a Compact and Efficient Truck Auxiliary Power Unit (APU)

Trucks at idle have very low fuel economy and create high levels of exhaust emission. Also while on highway the main engine has to supply the power to all accessories. This is particularly important in the case of the military trucks that have a very high accessory power demand. One of the solutions to these issues is to provide a power source independent of the main engine, the Auxiliary Power Unit (APU). The APU could operate when the vehicle is parked with the main engine shut off, or work on demand while driving to provide electricity to support any utility or recreational or operational needs (refrigerator, air conditioning, TV, communication, detection etc.). This paper offers the insight on development of an APU powered by a new, high power density two stroke engine. The device comprises a unique Opposed Piston and Opposed Cylinder (opoc(trademark)) engine and a high speed rotary generator. Extensive investigation has been conducted during the engine development program to create a special uni-flow scavenging process for this two stroke engine. As the result, it realizes zero fresh charge loss with high scavenging efficiency. This paper describes the technical challenges and solutions for achieving the engine design targets and the resulting APU.