A Lumped-Parameter Dynamic Model of a Thermal Regenerator for Free-Piston Stirling Engines

This paper uses lumped parameter dynamic equations to model the mass flow, piston dynamics, and control volume behavior inside a free-piston Stirling engine. A new model for a Stirling engine thermal regenerator that incorporates a dynamically changing temperature gradient is presented. The use of graphite as a regenerator matrix material is justified despite its limited background by comparing the functional requirements of regenerators to heat exchangers where graphite use is commonplace. Experimental results are used to characterize a graphite regenerator and validate the dynamic model.