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In practical engineering we are limited in the upper temperature of thermodynamic cycle due to the material properties. So, after the max temperature is fixed, we want to make our cycle as close as possible to a Carnot cycle with the same max temperature. It is clear that the compression and expansion should be adiabatic and we are technically close to the realization of this. Also, we have to cut lower right angle of the Carnot cycle, because each next turbine stage should be larger in diameter, and building them becomes economically or technically impractical at a certain point. But the process of heat addition is a bit more tricky to understand.

Consider the case of Humphrey and Brayton cycles in the same range of temperatures:enter image description here The heat addition process is more vertical in case of faster heat addition, but according to Carnot process it should be more horizontal to be more efficient (i.e. close to isothermal). However, we do know that faster heat addition is more efficient (detonation engines are more efficient), so Humphrey cycle should be more efficient. Can't solve this puzzle...

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Ok, it seems like I understood it, writing this question still helped a lot, idk why. As we move from Brayton to Humphrey the efficiency will still rize as we approach more the form of a rectangle, which is the Carnot cycle. So, it means that even despite the line is more vertical instead of being horizontal we would still profit from reaching lower enthropy, than in the Brayton case, as we will be able to cut less of the lower right angle area as we would in Brayton case.

After all, my friends, try to burn your fuel in your combustion chambers as fast as possible! Peace

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