Lenoir cycle

The Lenoir cycle is an idealized thermodynamic cycle often used to model a pulse jet engine. It is based on the operation of an engine patented by Jean Joseph Etienne Lenoir in 1860. This engine is often thought of as the first commercially produced internal combustion engine. The absence of any compression process in the design leads to lower thermal efficiency than the more well known Otto cycle and Diesel cycle.

In the cycle, an ideal gas undergoes

The expansion process is isentropic and hence involves no heat interaction. Energy is absorbed as heat during the isochoric heating and rejected as work during the isentropic expansion. Waste heat is rejected during the isobaric cooling which consumes some work.

In the ideal gas version of the traditional Lenoir cycle, the first stage (1-2) involves the addition of heat in a constant volume manner. This results in the following for the first law of thermodynamics: ${\displaystyle {}_{1}Q_{2}=mc_{v}\left({T_{2}-T_{1}}\right)}$

There is no work during the process because the volume is held constant: ${\displaystyle {}_{1}W_{2}=\int \limits _{1}^{2}{pdV}=0}$

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