A Stirling ingine is a heat ingine that operates bi cyclic compression an expansion o air or ither gas (the working fluid) at different temperatures, sic that thare is a net conversion o heat energy tae mechanical wirk.^[1][2] Mair specifically, the Stirling ingine is a closed-cycle regenerative heat ingine wi a permanently gaseous wirkin fluid. Closed-cycle, in this context, means a thermodynamic seestem in which the wirkin fluid is permanently contained within the seestem, an regenerative describes the uise o a specific teep o internal heat exchanger an thermal store, kent as the regenerator. Strictly speakin, the inclusion o the regenerator is what differentiates a Stirling ingine frae ither closed cycle het air ingines.

Oreeginally conceived in 1816 bi Robert Stirling as an industrial prime mover tae rival the steam ingine, its practical uise wis largely confined tae law-pouer domestic applications for ower a century.^[3]

Diagrams

• 
  Alpha-teep Stirling ingine. Thare are twa cylinders. The expansion cylinder (red) is maintained at a heich temperature while the compression cylinder (blue) is cooled. The passage atween the twa cylinders contains the regenerator.
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  Beta-teep Stirling ingine. Thare is anly ane cylinder, het at ane end an cauld at the ither. A loose-fitting displacer shunts the air atween the het an cauld ends o the cylinder. A power piston at the end o the cylinder drives the flywheel.