4. Heat engines

Heat engine are thermal energy converters: they are producing a mechanical energy from thermal energy. The Carnot heat engine (seen in Section 2.2.2.1: ) presents the maximum thermal efficiency but Real heat engines are generally not exchanging thermal energy using isothermal transformations.

1. Thermal energy is generally obtained thanks to the combustion of a fuel with an oxidizer:

• if the comustion occurs in the working fluid, we talk about internal combustion heat engines: this is the case for car engines or for gas turbines and turbojets.

• if the combuston occurs outside, it is then tansmitted to the working fluid thanks to a heat exchanger. We talk about external combustion heat engines: this is the case for Stirling engine for example.

2. As they are following a cycle, the fluid flow can be:

• Discontinuous: We talk about reciprocating internal combustion engines as for the spark-ignition engine (gasoline engines) or for the compression-ignition engine (diesel engines).

• Continuous: We talk about continuous combustion engines. This is the case for gas turbines and turbojets.

Contents:

• 4.1. Reciprocating internal combustion engine
• 4.2. Gas Turbines
• 4.3. Steam turbines
• 4.4. Combined cycles / Cogeneration