Tek-Tips is the largest IT community on the Internet today!
Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!
-
Congratulations MintJulep on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!
Why doesn’t the barrier have afterburners?
- Thread starter Thomasb91
- Start date
Lou Scannon
Automotive
My uneducated guess is it was too difficult to incorporate afterburners in the swivelling exhaust nozzles.
"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz
"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz
I think that sounds about right. The P.1154 used reheat on a conventional nozzle and 4 vectored jets like the harrier.
Edit: Nope, sorry, a central jet was one of the initial concepts. Reading further, the P.1154 used vectored reheat for the multirole VTOL airframe.
Consider that reheat is not used on a number of front line attack aircraft: A-4, A-7, SU-25, A-6, A-10... . Probably if they can but they don't then it's a matter of mission design/requirement.
Edit: Nope, sorry, a central jet was one of the initial concepts. Reading further, the P.1154 used vectored reheat for the multirole VTOL airframe.
Consider that reheat is not used on a number of front line attack aircraft: A-4, A-7, SU-25, A-6, A-10... . Probably if they can but they don't then it's a matter of mission design/requirement.
Compositepro
Chemical
moon161, why do you use the term reheat? While it is not technically incorrect, I have never heard it used as an alternative term for afterburner. Afterburner is more specific as to the source of heat, and it is the commonly accepted term that more people will understand. It is not helpful for communication to use multiple terms for the same thing in one conversation. The link you posted does not use the term reheat but rather afterburner. Actually, it mentions that on the Harrier they considered injecting fuel into the "cold" side jets, which used bypassed fan air. So in this case reheat would be incorrect.
It's also likely that anything requiring afterburners were considered to be outside the scope of the subsonic aircraft, which is primarily ground attack. The Harrier has a VERY limited combat range and it depends on having air superiority to begin with, using something like an F-22, which has about 5x the combat range.
Note that afterburner fuel burn is absurdly high; an F-16 purportedly burns 64,000 lb/hr of fuel in afterburner mode, compared to 8,000 lb/hr at full throttle.
[corrected burn rate]
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
Note that afterburner fuel burn is absurdly high; an F-16 purportedly burns 64,000 lb/hr of fuel in afterburner mode, compared to 8,000 lb/hr at full throttle.
[corrected burn rate]
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
Composite, Oh OK. Probably I remember it that way from propulsion class or thermo, treating it as 'air standard brayton cycle w/ reheat'. I've used the term as generic for burning anything outside of the combustor between the compressor and the turbine, which is incorrect too, cause you can have reheat to a nozzle or more turbine stages.
Thanks, sometimes, the fingers just don't do what the brain thinks.
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
Also...
Harriers have a relatively high by-pass fan-engine... the small core engine drives the large fan section which supplies the majority of it's thrust to the forward-2-swivel nozzles... and the core engine thrust, and some by-pass air, goes to the aft-2-swivel nozzles. Also, core-engine compressor-section compressed/hot bleed-air is 'pumped' thru Inconel tubing to the wing-tips, aft fuselage and nose for reaction controls in hover/slow-flight.
WAG on my part... for short take-offs... in addition to swivel-nozzle thrust/lift movements... bleed-air may be 'blown-over the flaps' for increased lift-effectiveness at slow speeds.
In-other-words… every bit of thrust/power is extracted thru the [4] swivel nozzles... making afterburning infeasible.
Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]
Harriers have a relatively high by-pass fan-engine... the small core engine drives the large fan section which supplies the majority of it's thrust to the forward-2-swivel nozzles... and the core engine thrust, and some by-pass air, goes to the aft-2-swivel nozzles. Also, core-engine compressor-section compressed/hot bleed-air is 'pumped' thru Inconel tubing to the wing-tips, aft fuselage and nose for reaction controls in hover/slow-flight.
WAG on my part... for short take-offs... in addition to swivel-nozzle thrust/lift movements... bleed-air may be 'blown-over the flaps' for increased lift-effectiveness at slow speeds.
In-other-words… every bit of thrust/power is extracted thru the [4] swivel nozzles... making afterburning infeasible.
Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]
verymadmac
Mechanical
There was experiments done with plenum chamber burning (basically reheat for the bypass air) but only as development work.
I guess as the Harrier is only subsonic the cost benefit didn't work plus it appears to greatly increase exhaust gas temperatures which appears to present all sorts of operational issues (anyone found a pic of a F35B operating out of a forest yet?).
I guess as the Harrier is only subsonic the cost benefit didn't work plus it appears to greatly increase exhaust gas temperatures which appears to present all sorts of operational issues (anyone found a pic of a F35B operating out of a forest yet?).
nor even the AV8B, developed by Douglas. Subsonic a/c don't need afterburners. The point of the Harrier was VTOL, not optimised for high speed flight. There were many aborted attempts and studies (for a supersonic harrier) but nothing came of them.
another day in paradise, or is paradise one day closer ?
another day in paradise, or is paradise one day closer ?
- Status
Similar threads
- Locked
- Question
