Types

Stirling cycle engines have the ability to provide power and efficiency better than most diesel engines. Even better is their potential for lower life cycle cost, less weight, far less noise and vibration, and almost no emissions. This engine is quieter, smoother and much cleaner than conventional I.C. engines mainly due to the engine’s continuous external combustion.

A Stirling engine is a closed-cycle, regenerative heat engine which uses an external combustion process, heat exchangers, pistons, a 'regenerator' and a gaseous working fluid contained within the engine to convert heat to mechanical work (motion).

An important feature of the Stirling is the 'regenerator' to store energy as the gas passes thru on the way to the cooler (low temp. heat exchanger) and gives it up as the gas flows back through the regenerator going to the heater (high temp. heat exchanger).

There are two obvious types of Stirling cycle engines, the kinematic which has the pistons attached to a drive mechanism which determines the phase angles and converts the linear motion of the pistons to a rotary motion and the free piston which uses harmonic motion mechanics to determine the cycle phases.

There are hundreds of variations of types in these two categories. Particularly the kinematic is divided into Alpha (two pistons), Beta (piston and displacer in one cylinder) and Gamma (piston and displacer in separate cylinders). Then there are the double acting engines which are alpha engines in series. These can drive either a crankshaft drive or a swashplate drive. The swashplate has a cousin the wobble drive. The examples of the state of the art in both categories are from Stirling Thermal Motors for the kinematic drive (double acting alpha, high pressure hydrogen, pressurized drive-case) and Sunpower, Inc for the free piston machines which include both prime movers and refrigeration units.

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