DIAPHRAGM STIRLING ENGINES: THE HARWELL THERMO-MECHANICAL GENERATOR.

Abstract

The principle of operation of diaphragm Stirling engines is explained. In these engines, a diaphragm replaces the piston. This is done to reduce wear and the need for lubrication to a minimum and thus to design engines for operation in remote areas, unattended for many years. Suitable design and materials for the diaphragm and displacer are considered. The design of an alternator (thermo-mechanical generator), its losses, the ways to increase its power, and the operating experience is described. The field trial generators and the radioisotope generator had together totalled 126,000 machine hours of operation (equivalent to 14 years) by April 1983. None of these machines suffered any failure of the critical flexing components (the diaphragm and the displacer spring). The radioisotope heat source functions without problems and is probably the most reliable heat source conceivable.