bearfoil,
IF I follow your way of describing things... what you describe is what happens at low speed, when indeed a 'cone' of air is sucked into the inlet.
Once supersonic, to use the popular old-fashioned way of describing it: there no longer is any "warning" for the air ahead of the intake, and the intake neatly slices a squarish "pipe" from the arriving airflow and performs its magic.
bjornhall, b377, et al,
This thread really started off on the problem of getting ones mind around the question on how an
intake could actually produce
thrust.
We seem to have that sorted out to a large extent.
What happens to the energy actually being liberated by the burning fuel is a slightly different story, and there your reasoning is perfectly right... some ends up being used to power the engine accessories, some ends up as hot air, literally, some ends up as noise
At Mach 2, most of it is still used to move the aircraft.
CJ