************
Heat engines
************

**Heat engine** are *thermal energy converters*: they are producing a mechanical energy from thermal energy.
The *Carnot heat engine* (seen in :numref:`Sec:chap2:Carnot`) 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*.

.. toctree::
  :maxdepth: 1
  :caption: Contents:

  chap4_1RICE
  chap4_3GasTurbines
  chap4_4SteamTurbines
  chap4_5Cogeneration