Low power Stirling engine for underwater vehicle applications

The selection and design of a power system for any form of underwater vehicle is an extremely complex and difficult task. The system must be capable of providing the vehicle with the required mission performance in terms of power and energy and also be volumetrically and gravimetrically compact. When the vehicle to be used is a newly designed US Navy Diver Propulsion Vehicle (DPV), other power system constraints are highlighted. These constraints include limited vehicle diameter, high performance operation, low power requirements, safety and a nonmagnetic signature. Of the many power systems available, very few can fulfil the design criteria for the DPV. One system that can is the hydrocarbon fuelled Stirling engine-a dynamic heat engine using an external combustion system. This paper describes the application of the Stirling engine for underwater duties, and in particular the selection, design and development of a Stirling engine powered DPV. Details are given of the specialist vehicle requirements, engine selection and design and the development of a combustion gas recirculation system to enable pure gaseous oxygen to be used as the combustion oxidant. In addition, details are given of the restrictions imposed on component design and manufacture by the low vehicle power requirements