Editing Diesel cycle (section)

== Applications ==
=== Diesel engines ===
{{Main|Diesel engine}}
Diesel engines have the lowest [[specific fuel consumption (shaft engine)|specific fuel consumption]] of any large internal combustion engine employing a single cycle, 0.26&nbsp;lb/hp·h (0.16&nbsp;kg/kWh) for very large marine engines (combined cycle power plants are more efficient, but employ two engines rather than one). Two-stroke diesels with high pressure forced induction, particularly [[turbocharging]], make up a large percentage of the very largest diesel engines.

In [[North America]], diesel engines are primarily used in large trucks, where the low-stress, high-efficiency cycle leads to much longer engine life and lower operational costs. These advantages also make the diesel engine ideal for use in the heavy-haul railroad and earthmoving environments.

=== Other internal combustion engines without spark plugs ===
Many [[model airplane]]s use very simple "glow" and "diesel" engines.  Glow engines use [[Glow plug (model engine)|glow plugs]].  "Diesel" model airplane engines have variable compression ratios.  Both types depend on special fuels.

Some 19th-century or earlier experimental engines used external flames, exposed by valves, for ignition, but this becomes less attractive with increasing compression.  (It was the research of [[Nicolas Léonard Sadi Carnot]] that established the thermodynamic value of compression.)  A historical implication of this is that the diesel engine could have been invented without the aid of electricity.
<br /> See the development of the [[hot-bulb engine]] and [[indirect injection]] for historical significance.