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.

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The cycle In the cycle, an ideal gas undergoes

V. Ganesan (2008). 9780070648173, Tata McGraw-Hill Publishing Company. . ISBN 9780070648173

(2013). 9788120346802, PHI Learning Pvt. Ltd. . ISBN 9788120346802

1–2: Constant volume () heat addition;

2–3: Isentropic expansion;

3–1: Constant pressure (isobaric process) heat rejection.

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.

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Constant volume heat addition (1–2) 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: $\{\}\_1Q\_2\; =\; mc\_v\; \backslash left(\; \{T\_2\; -\; T\_1\; \}\; \backslash right)$

There is no work during the process because the volume is held constant: $\{\}\_1W\_2\; =\; \backslash int\_1^2\; \{p\backslash ,dV\}\; =\; 0$

and from the definition of constant volume specific heats for an ideal gas: $c\_v\; =\; \backslash frac\{R\}$

Where R is the ideal gas constant and γ is the ratio of specific heats (approximately 287 J/(kg·K) and 1.4 for air respectively). The pressure after the heat addition can be calculated from the ideal gas law: $p\_2\; v\_2\; =\; RT\_2$

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Isentropic expansion (2–3) The second stage (2–3) involves a reversible adiabatic expansion of the fluid back to its original pressure. It can be determined for an isentropic process that the second law of thermodynamics results in the following: $\backslash frac\; =\; \backslash left(\; \{\backslash frac\}\; \backslash right)^$

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