The miniature Stirling engine model is a very cool desk gadget. This little model is exciting to see in action, and figuring out how it works, can offer plenty of joy of discovery.
Miniature Stirling engine models are popular desk gadgets. There are several different types of Stirling engines, but they are all external combustion engines, which means that the combustion takes place outside the cylinder. The heat source can be anything from sunlight to burning alcohol or even a cup of coffee. This miniature model in the top picture can successfully use a cup filled with warm coffee as a heat source. Like any other type of Stirling engine, this model uses the property of gases to expand and contract. The gas (air) between two plates, the lower of which is located on top of a heat source (for example, a cup filled with hot coffee), heats and cools cyclically. This expansion of air can be turned into mechanical work and make the flywheel rotate. Because this Stirling engine model can work using a fairly low-temperature heat source, it is also called a low-temperature Stirling engine.
This miniature Stirling engine model consists of a smaller power piston and a larger displacer piston attached to the crankshaft. A larger displacer piston displaces air in a larger cylinder, which is placed above the heat source. Because, there is a temperature difference between the upper and lower plates of the cylinder, the air in the cylinder heats and cools cyclically. When the displacer piston displaces the warm air in the larger cylinder, the warm air expands and pushes the power piston, which spins the flywheel. When the air has cooled, the displacer piston moves the air around the warmer end of the cylinder, and it starts to heat up again. The whole cycle takes only a fraction of a second, and the flywheel starts spinning very quickly.