The Carnot engine

The laws of physics show that the Carnot cycle is the most efficient thermodynamic cycle that can be achieved. These same laws show that the Stirling cycle and second cycle Ericsson have exactly the same efficiency.

Each of the three cycles involve a succession of four thermodynamic transformations:

Carnot:         Isothermal, adiabatic, isothermal, adiabatic.
Stirling:        Isothermal, isochoric, isothermal, isochoric.
Ericsson:      Isothermal, isobaric, isothermal, isobaric.

If the Carnot engine was never built, the industry uses Stirling and Ericsson engines. I think if Robert Stirling had invented the engine described by Carnot, he would certainly have built so that if Carnot had thought about the Stirling engine, the scientific community would have said “it is impossible to build”.

Here is my explanation: if we consider the Stirling cycle the theoretical point of view we have to analyze each of the four transformations according to the methods of classical thermodynamics which consider that the processes are quasi-static close to equilibrium. We must admit also that the regenerator is perfect and there are no internal dead volumes. We conclude with absolute certainty that the Stirling engine is impossible to build. It would be the same conclusion for the Ericsson engine. The main difference between Sadi Carnot and Robert Stirling was the one built without really understanding how it works and the other understood without knowing how to build it.

If we compare these three engines seriously, we find that the simplest of them is that of Carnot. It does not need regenerator, heat exchanges take place during the isothermal transformations, widely studied for Stirling engines and Ericsson and the working gas can be moved easily without the need for valves or flaps. Strangely the engine simplest and most basic mechanical terms has never been done.

Making an engine to convert heat into mechanical or electrical energy requires a new vision of thermodynamics presented for the first time by Curzon and Ahlborn in a paper published in 1973: "Efficiency of a Carnot Engine at Maximum Power Output"  (This same result was independently obtained by Novikov and Chambadal). Since, to differentiate the theoretical Carnot cycle that describes a functional Carnot engine, some call it “the Curzon engine”. In practical terms, the Carnot engine has been more studied than the Stirling engine without ever having been made. These studies reveal the potential of this machine that will find its place in the real economic world.

For all these reasons that we will undertake its industrial production.