In contrast, an internal combustion engine is one where the combustion takes place inside the combustion chamber, directly involving the working fluid.
Examples of External Combustion Engines:
- Steam engines: In a steam engine, fuel is burned in a separate boiler to generate steam. This high-pressure steam is then directed into a cylinder, where it expands and pushes a piston.
- Stirling engines: Stirling engines use a closed cycle of gas (usually air or hydrogen) that is heated by an external heat source (such as a burner) and then expanded and compressed by the movement of a piston.
- External Combustion Turbines: These turbines use a separate combustor to generate hot gases that drive the turbine blades.
Advantages of External Combustion Engines:
- Fuel flexibility: External combustion engines can use a wider variety of fuels, such as heavy oils, biomass, or solar energy, compared to internal combustion engines which generally require gasoline or diesel.
- Lower emissions: Since combustion takes place in a controlled environment, external combustion engines can have lower emissions of pollutants like nitrogen oxides and particulate matter compared to internal combustion engines.
Disadvantages of External Combustion Engines:
- Lower efficiency: Due to the energy loss involved in transferring heat from the combustion source to the working fluid, external combustion engines tend to have lower efficiency than internal combustion engines.
- Larger size: The presence of a separate combustion chamber and other components often results in external combustion engines being larger and heavier than internal combustion engines.
External combustion engines are used in niche applications where specific advantages, such as fuel flexibility or lower emissions, outweigh their disadvantages. They find use in certain industries, transportation applications (such as steam locomotives in the past) and power generation.
