In an external combustion engine, a separate burner or combustion chamber is used to heat a fluid, typically water or steam. This heated fluid then enters the engine cylinder and expands, driving the piston and generating power. The used fluid is then discharged from the engine.
A notable advantage of external combustion engines is that they can accommodate a wider variety of fuels, including coal, natural gas, or heavy fuel oils.
Examples of external combustion engines include:
Steam engines: In steam engines, coal or other fuels are burned in a boiler to create steam. The high-pressure steam is then directed into the cylinders, driving the pistons and generating power.
Stirling engines: Stirling engines utilize a closed cycle where a working fluid, such as hydrogen or helium, is repeatedly heated and cooled in separate parts of the engine. The expanding gas generates power by moving the pistons.
Hot air engines: These engines operate based on the expansion and contraction of heated air. Air is heated in a cylinder by an external heat source, causing it to expand and drive the piston. As the air cools, it contracts, creating a vacuum that pulls the piston back.
It's worth noting that external combustion engines are generally less efficient than internal combustion engines due to additional heat losses. However, they can still find applications in specific areas, such as large power plants or specialized vehicles where the fuel flexibility and reliability of external combustion engines are beneficial.
