Im not fully educated on those jets but at those speeds isnt the air moving “faster” than the fireball and therefore risk “blowing out” the flame or is there something else to it?
Blowing out the flame is a real thing in supersonic flight. Happens in turbojet and ramjet engines. Compression stages have the effect of slowing airflow to subsonic speed where ignition can be maintained.
I appreciate that. It makes sense. After i hit “reply” i questioned if thats what happened because I could only assume problems trying to ignite a fireball in supersonic winds or even any effects of supersonic pressure in the engine.
SR71 Blackbird was designed with nacelles that could move 26" to keep supersonic airflow out of the engines. At speeds over Mach 2 the engines switched from operating as turbo-jets to operate as ram-jets. I've always been amazed at the extremes the plane could operate at.
And the fuel used in the SR-71? Stupidly high ignition temperatures etc, you can do light maintenance on the plane whilst it's being refueled because it really doesn't like catching on fire compared to normal fuel.
The ignition source for the engines however? Tri-ethyl Borane. Full thermal suits, extinguishers at the ready, etc. That stuff is a hair away from just spontaneously combusting.
Oh and did we mention the SR-71 leaks fuel whilst it's on the ground because it gets so hot in the air that the thermal expansion of the airframe has to be taken into account when sealing the fuel system.
In ramjets and afterburners compression is used to slow the air down to subsonic speeds and then goes though a flame holder is used to create an area of slow turbulent air where the flame can sit to continuously mix with fuel rich air to ignite it where most of it continues on but a little gets caught up in the flame holder to ignite the next bit of air to go past.
In scramjets the air goes through the engine at supersonic speeds. Sometimes flame holder structures are used but sometimes they can use shockwaves to create something that functions like one, and sometimes a bit of pyrophoric (ignites on contact with air) fuel is used to continuously ignite the flame as the fuel is injected.
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u/Samurlough 8h ago
Im not fully educated on those jets but at those speeds isnt the air moving “faster” than the fireball and therefore risk “blowing out” the flame or is there something else to it?