launches the

Stirling engine and regenerator design forum

This site is committed to fostering progress of the Stirling engine towards widespread commercial reality. The air- or nitrogen-charged variant is emphasised. 

The site will evolve with the aim of providing:

*    potential for coordination and focus: At the present time, design experience and 'know-how' are spread between a large number of organizations and individuals, much of it under proprietary restrictions. Despite half-a-century of modern technological development, not a single power-producing Stirling engine is  available off-the-shelf as a result of this way of doing things. There is now an alternative: the WWW offers the means to propose and agree a specification (configuration, power, swept volume, charge pressure, rpm,  etc.) and to coordinate effort to design, build and develop to that specification.

*    insight as a basis for communication, for discussion and for eventual resolution of performance bottlenecks. This will eventually be supported by access to a portfolio of computer software (simulations of the gas process etc.).

*    links to relevant literature, design data and sources of materials

*    (as the engine specification develops) engineering drawings dimensioned and toleranced  to ISO standard, allowing inter-changeability

The aims themselves will no doubt be revised as site and project take shape. A series of Articles will address issues considered crucial to the achievement of performance potential. Two of the most urgent are anticipated below:

HEATING PROVISION: Through much of the two-century evolution of the Stirling engine the heating provision has been the natural-convection flame - in many cases the open flame. The alleged versatility the air engine is still 'demonstrated' with reference to un-pressurized, table-top models powered by a spirit lamp or candle flame. Sophisticated pressurized engines are little better, discarding exhaust at temperatures in the region* of 250 - 300^oC. In the 21st century the design problem is not phase angle or volume ratio, but delivering the chemical energy of the fuel to the working fluid. A Heating Provision page (under construction) will describe a technology which has demonstrated dramatic reduction of exhaust heat wastage.

REGENERATOR DESIGN:   Flow and heat transfer data on open access extend little further than wire screens, and are to C_f vs R_e format. This  derives from, and is consistent with, pipe flow. Flow though the gauze stack is not pipe flow: fractional pressure drop dp/p is adversely affected by values of M_a/R_e ≥ 10^-4. Correlations to traditional format are fundamentally unsuitable for exploring and extending the performance envelope of air- (and N2-) charged engines. Article #1 demonstrates why.

*Hargreaves  C  The Philips Stirling Engine. Elsevier, 1991