John...
I should have been more clear. I was talking about ram effect on a basic turbojet (subsonic) engine which would provide a slight rise in compression at the entrance to the engine which would produce more thrust as it went through the burner stage.
The Concorde engine is quite a bit different than a basic turbojet. I don't fully understand the engine but it's quite interesting! I'll have to read through some of those Concorde threads... there are some very knowledgable people on here.
Lyman...
To be precise, the J58 is at no time a "ramjet".
Reference this:
Ramjet - Wikipedia, the free encyclopedia
You will see this quote: "The SR-71's Pratt & Whitney J58 engines act as turbojet-assisted ramjets at high-speeds (Mach 3.2)."
Another reference:
Factsheets : J58 Turbojet Engine
It's a turbo-ramjet. A ramjet won't function when there is no airflow. The turbojet is what propels the airplane up to speeds that will have the ramjet part of the engine function. The J58 is essentially a turbojet inside a ramjet.
The 80% thrust referenced above is not combusted air, but intake air, isolated from the turbo machinery and the after burner.
Not what I've read. That hot, compressed intake air is fed to the afterburner section.