A device is disclosed herein which provides a domed cover of a combustion chamber enclosure applicable for use in Stirling Cycle engines, Ericsson Cycle engines, Rankine Cycle engines or other external combustion heat engine types which allows for the free flow of combustion air from the outer margins of the device toward the combustion air inlet in a vortexual fluid flow to achieve a more balanced stoichiometric ratio of the fuel/air mixture before ignition. This may be achieved by the employment of vanes to direct combustion air in a swirling vortexual flow as the combustion air enters the combustion chamber. Thermal barrier coatings and insulative materials may also be employed to minimize parasitic heat loss.

A device is disclosed herein which provides a domed cover of a combustion chamber enclosure applicable for use in Stirling Cycle engines, Ericsson Cycle engines, Rankine Cycle engines or other external combustion heat engine types which allows for the free flow of combustion air from the outer margins of the device toward the combustion air inlet in a vortexual fluid flow to achieve a more balanced stoichiometric ratio of the fuel/air mixture before ignition. This may be achieved by the employment of vanes to direct combustion air in a swirling vortexual flow as the combustion air enters the combustion chamber. Thermal barrier coatings and insulative materials may also be employed to minimize parasitic heat loss.

A method of operating a mechanical heat engine according to an internally reversible thermodynamic cycle may comprise four piston-cylinders, with extending connecting rods of identical stroke lengths such that three of the piston-cylinder systems have an identical bore and the fourth cylinder has a smaller bore. According to such a method, the smaller-bore piston-cylinder is connected via the piston rod to an adjacent piston-cylinder with the rods fully extended one full stroke length; and the remaining piston-cylinders are connected via the piston rod, with the rods extended less than a full stroke length.