Alpha Stirling engine relates to external combustion engines.it means the ability to work from any heat sources. The engine operation principles are based on the circulation of air between the areas of heating and cooling. This leads to a change of volume and pressure inside the cylinder, whereby the piston motion occurs.
Usually Stirling engines have two pistons. One is to move the gas between the areas of heating and cooling. The second one is a working piston and serves to convert the air pressure energy into mechanical motion. This engine also has a cylinder filled with a porous mass, which is used to save energy and to transfer it to gases that circulate inside the system.
The beta-Stirling engine as its analog engine alpha- Stirling , is an external combustion engine. That allows it to work on any kind of fuel and even solar energy.
A distinctive feature of beta-Stirling engine is that it has only one cylinder. Displacing and working pistons are on the same axis inside the cylinder. The rule of pistons motion is determined by the peculiarities of two gears system and a rhombic drive construction.
This interactive 3D model shows the principle of beta-Stirling construction and operation.
Here is another example, of a fairly common Stirling engine representative. It became widespread for the reason that having a large area of heating and cooling it can work even been put on a mug of coffee or a piece of ice. The demo of its functioning at small temperature differences is very impressive.
The principle of operation is based on the movement of hot air from the heating sphere to the cooling sphere and vice versa by displacing (large) piston. This causes an increase or decrease of pressure inside the system. The change of pressure, in turn, moves the working (smaller) piston.