Stirling engine is an experimental source of power that someday may be used in cars, boats, and other vehicles. It runs more efficiently and produces less air pollution than do most other engines.
A typical Stirling engine has a sealed cylinder that contains a gas–either helium or hydrogen. The gas goes through a cycle of pressure changes by means of a process of alternate heating and cooling. A device called the regenerator partially heats the gas at the beginning of the cycle. A heater outside the cylinder provides additional heat by burning a fuel, such as diesel oil, kerosene, or alcohol. At the end of the cycle, the regenerator cools the gas by absorbing its heat.
The gas expands and contracts as it goes through the cycle of pressure changes. In doing so, it causes a power piston to move back and forth inside the cylinder. A rod connects the power piston to a crankshaft that converts the piston’s reciprocating (back-and-forth) motion to the rotary motion of the drive shaft. This action, in turn, causes a displacer piston to move back and forth and force the gas through the regenerator.
Robert Stirling, a Scottish minister, invented the Stirling engine in 1816. Stirling engines have never come into general use because they cost more to build than other types. The chief difficulties of Stirling engines involve their complexity, their heat exchange requirements, the sealing of their cylinders, and containing hydrogen at high temperatures.
