This engine is a compromise between the alpha engine and the beta engine. In a cylinder the displacer assumes its function. In the other cylinder, the operating piston controls the variations of the global volume and recovers energy. This type of engine is frequently used to take advantage of small differences in temperature between cold source and hot source.
Compared to the ideal cycle described in the page "The principles", the different phases of the cycle of a gamma engine are less differentiated. However, the following drawings seek to represent them.
During this phase, the engine piston moves slightly, the overall volume is minimal. In contrast, the displacer carries out a long race and the gas is heated.
The displacer moves little. In contrast, the operating piston carries out more than 70% of its race. It recovers energy.
The displacer carries out most of his race: the gas is cooled. The operating piston moves little.
The displacer remains at the top: the gas is cold. However, the piston engine performs the majority of its race: it compresses the gas by yielding mechanical energy
The following animation shows the complete cycle of a gamma engine:
This diagram is characteristic of the engine described above.
The calculations were made with TM = 290 K (17°C) et Tm = 348 K (75°C) .
The volume covered by the operating piston is 5 times lesser than the one covered by the displacer.
The theoretical efficiency would be 17%.
One can see that this cycle is clearly different from the theoretical cycle.
The important thing is to have the gray area as large as possible. It is representative of the work recovered during a cycle (see the page ."the principles").
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