Page 71 - Piston Engine-Based Power Plants

Stirling Engines and Free Piston Engines 63

Figure 6.2 Alpha Stirling engine with regenerator. Source: Wikimedia.

Compression Expansion
Piston
space space
Displacer

Beta engine

Regenerator
Cooler Heater

Figure 6.3 Beta Stirling engine. Source: Wikimedia.

hot source at one end and a cold sink at the other. One piston is a con-
ventional power piston and seals the chamber to the atmosphere. The
second is a loose fit within the cylinder so that as it oscillates the work-
ing fluid can move past it from bottom to the top of the cylinder and
vice versa. A simplified version is shown in Fig. 6.3. The stages of the
cycle are essentially identical to those of an Alpha engine.

In addition to these two main types there are a wide range of other
Stirling engine designs. These include a gamma Stirling engine a varia-
tion of the Beta engine but with a separate cylinder to the second piston,
a flat Stirling engine and a number of free piston Stirling engine designs.

ENGINE TECHNOLOGY

The Stirling engines differ in several ways from a conventional internal
combustion engine and have different mechanical and material