Smurfjet
Checkers erudite exposition of "Why are..." is as clear and simple as any I have seen.
Chemistry/Physics?
The controversy continues between the chemists and physicists as to which comes first and where do they start and end.
The fact that more than a few significant chemical reactions were predicted from physics ilustrates the fuzziness of this argument. Is single crystal turbine blade technology physics or chemistry. I personally tend towards the physicists because they tend to work from first principle with chemists being more empirical in their methods, but I'm sure I'll get an argument on that.
However.
One of the most fascinating thingys to me in this "engine" stuff is the combustion process or oxidising/converting hydrocarbons with O2 to produce another product with the energy produced/released providing a really useful byproduct that we use to indulge our mechanical fantasies
"Flamefront" relative to its speed and propagation and what's happening behind and in front of it in the combustion process is the operative principle.
You need to keep a few balls up in the air at the same time on this one and forgive me if I am teaching you to suck eggs mix a few metaphors here.
For example;
Light a biggish candle and carefully study the flame and the different colours emanating from the wick to the outside of the flame. They indicate different temperatures and therefore levels of combustion or chemical efficiency.
The ONLY difference between a burning candle and a substantial explosion is the SPEED or RATE at which the wax is converted to vapour and "combusted" or "burnt". This is a function of the interface or surface area available for the hydrocarbon and oxidant to interact. That defines the 'speed' of the "flamefront".
The total energy available in the candle is released over a long period of time, as the 'flamefront' or surface area of the 'flame' over which the combustion process of mixing the fuel with the O2 is occuring, is quite small and as such is quite benign and usefully beautiful.
If however you were able to vapourise the wax (hydrocarbon) from the same candle in a relatively confined space and were able to devise a method of delivering the exact amount of oxidant to each individual molecule, then you would have a infinitely large surface area/flamefront, the energy is delivered instantaneously and results in a very large explosion. Enough to flatten your and your neighbours houses yet.
Whilst we are on the subject of candles, a question for you.
In medieval times, before the invention of electricity, the local flour miller would not operate outside daylight hours.?
So taking for example Checkers "Why are.." post as a start point it is easy to see why the efforts of so many very bright engineers (F1 and aviation) and chemists have spent so much time and effort working on controlling the SPEED/RATE and efficiency of this flamefront in internal combustion and turbine engines. Both just ways of controlling the same process and converting it to mechanical energy without blowing or burning itself to bits.
The higher the temps the greater the thermal efficiency, but are harder to control. How do they control temps at the flamefront in turbines that are way above the melting point of the surrounding materials?
Another question,
Why does richening the mixture (adding fuel) have the opposite effect in a turbine engine to that of a piston?
I wont spoil the research fun by giving you all the answers but I believe that understanding the chemistry/physics of "flamefronts" is fundamental to understanding what's really happening at the end of those levers.
Some fascinating but entirely useless info, various grades of primer cord, used for example in mining applications, have a flame front capable of covering several hundreds of metres to all intents and purposes instantaneously.