Stirling Engine

Large gamma-type Stirling heat engine with fan attached.

Demonstrate the functionality of a stirling engine and the principles of heat engines. Shows that heat engines can be run in reverse by changing the direction of the thermal gradient.

• Stirling Engine
• Alcohol burner
• Plexiglass shield
• Lighter or matches
• Liquid nitrogen and styrofoam container (Optional)

1. Place the burner under the engine and light it. You'll probably have to refill this with ethanol before you start.
2. Let the burner warm up the cylinder for 5-10 minutes.
3. The engine then needs to be started by hand. Spin the blades counterclockwise (from the front) and if it's hot enough it'll continue spinning under it's own power. You can also try starting it before it's ready- as the engine heats up, the amount of resistance to rotation diminishes until it finally goes on it's own. There's an arrow on the front that gives it's direction of rotation. If you find it difficult to get it started a drop of all-purpose lubricant oil in the pistons may help.

Alternatively, the engine may be run in reverse by applying the opposite temperature differential.

1. Fill the styrofoam container with liquid nitrogen and place it under the engine so that a substantial part of the cylinder is in the LN2. This container may have to be refilled.
2. Give it a while to chill.
3. The engine must then be started by hand. Note that since we're running the engine in reverse by giving it the opposite heat differential the fan will also run in reverse. To start it, spin the blades clockwise (when looking from the front).

If the lamp is empty, refill it with ethanol. Do not use lamp oil.

A plexiglass shield was recently made for the bottom of the engine, as in some lecture halls there may be a strong enough breeze to put out the burner.

Placing the burner on a wooden block to bring the flame closer to the cylinder will help the engine heat up faster.

Useful Links: How Stuff Works provides an excellent description of Stirling Engines and some physical concepts behind them: http://auto.howstuffworks.com/stirling-engine.htm American Stirling Company is the place to go if one was interested in purchasing a Stirling Engine that can run using the heat of your monitor! http://www.stirlingengine.com/ For those interested in creating their own Stirling Engine, perhaps Koichi Hirata can help out. http://www.bekkoame.ne.jp/~khirata/