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Boost for turbines

"War Emergency Power" for continuous burn engines
  [vote for,

One common thing in WWII Planes (as in, most of them had it) was a WEP (war emergency power) function which allowed a temporary power boost for takeoff or that extra edge in combat. This was typically achieved via water injection.

Also note that in turbine engines it is more often the exhaust temperature that limits the power. They can develop 110-120% of rated power for a *very* short time without damage.

Also note that water takes a large amount of energy to heat and then boil, and it expands to 1200 times its original size (1ml water becomes 1.2L steam). When injected into a stream of uber hot air (just after the burner in a turbine) the water will instantly boil, cooling the exhaust gases significantly, and thanks to the steam, not significantly reduce it's volume.

My idea should become evident after reading the last three paragraphs: To inject water into the pre-turbine exhaust stream, allowing higher overall airflow levels without the extra heat normally associated with the extra power. So you have a WEP or overboost function for your turbine that is sustainable until you run out of water. The downside is probably reduced thermal efficiency, and the steam trail you leave.

Thoughts? Ben

BLSTIC, Sep 08 2009

Oxygen toxicity http://en.wikipedia...iki/Oxygen_toxicity
Nasty stuff - powerful oxidising agent </sarcasm> [AbsintheWithoutLeave, Sep 08 2009]

Roumeliotis I, Mathioudakis A. Applied Energy 2009 http://www.scienced...4a876089b5d07d546ad
Latest research [lurch, Sep 09 2009]


       Do you mean like the water-injected turbojets (Pratt&Whitney J57's) on KC-135s and B-52s?
lurch, Sep 08 2009

       Harriers do this.....
8th of 7, Sep 08 2009

       // stand by my previous assertion that LOX is the most ideal boost amplifier//
I stand by my assertion that LOX is a toxic and corrosive, difficult to handle commodity.
AbsintheWithoutLeave, Sep 08 2009

       //Oxygen is toxic.// Yes. At a partial pressure equivalent to the bottom of a deep swimming pool, oxygen is deadly.
That's what I'm saying.
You don't want to be breathing 100% even at 1 bar for too long.
AbsintheWithoutLeave, Sep 08 2009

       //Oxygen is toxic.// Ya' better believe it. Your body makes use of it in a pretty narrow range around common temperatures and pressures, but you get outside of that and it does non-biological things to you real fast.   

       And when you're talking about LOX, you better hope it's not LOX when you breathe it. That LOX converter is a Criticality 1 system: it fails, the next-of-kin sue.
lurch, Sep 08 2009


       "My idea should become evident after reading the last three paragraphs"
normzone, Sep 08 2009

       What is (marked-for-tagline) supposed to mean normzone?   

       Oh, and one thing about water as opposed to liquid oxygen. It's uber-cheap.   

       Lurch - Probably, but I can't find any information on them (in my 24.47 seconds of looking). Even if this idea is baked I wouldn't mind finding how well it worked and what downsides there are.
BLSTIC, Sep 08 2009

       [BLSTIC], if you'd be interested in the study I linked, I could try to get it for you. Go to my user page, get my email, and drop me a note.   

       I can't guarantee I can access it (odds are around 40%, I'd guess; it would be higher if it were medical stuff) but I'll certainly give it a try. <edit>100%. Got it.</edit>   

       (Oh, and about water being "cheap" - when used in jets, it was ultra-purified, de-mineralized, de-ionized water - and probably cost as much as jet fuel.)
lurch, Sep 09 2009

       //I'm sorry, but toxicity cannot seriously be considered a factor in the context of using it for an engine boost.//
Excellent, we'll use fluorine then. We could get rid of igniters too that way.
coprocephalous, Sep 09 2009

       // One common thing in WWII Planes (as in, most of them had it) was a WEP (war emergency power) function […]. This was typically achieved via water injection. //   

       So this is baked?
notexactly, Jan 28 2016

       [BLSTIC] (who I haven't seen for a while) knew of its use in piston engines; he didn't realize it was already used in jets.
lurch, Jan 28 2016

       Ah. I might want to use this, actually. I wonder if it would work for a ramjet…
notexactly, Jan 28 2016


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