Water / methanol injection
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Originally Posted by bodex666
Hi all... I believe however the methanol is to stop the water freezing through the compressors and in the inlet when its extreamly cold.
Finally - and this was news to me when I first heard it: B707-100 "water wagons" used all their water tankage on TO, and the water tank(s) was purged dry during climb, to prevent freezup at altitude. Do other aircraft do this as well, or do you retain unused w/m mix and just top up on the next leg?
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On the KC-135s you used it all. You NEEDED it all. 120 seconds and you had gone through 5600lbs of water.
On the YS-11 with water/meth, after you were safely airborne, you turned off the water/meth and saved it for the next takeoff. You never got high enough to worry about ambient temps freezing the solution.
Seems like I remember also we had different water/meth solutions. It was not a standard x/x% mix.
When the airplanes left the pax fleets, the freight haulers immediately yanked out the pressurization system along with the water meth system, IIRC. Neither needed to haul boxes at night.
On the YS-11 with water/meth, after you were safely airborne, you turned off the water/meth and saved it for the next takeoff. You never got high enough to worry about ambient temps freezing the solution.
Seems like I remember also we had different water/meth solutions. It was not a standard x/x% mix.
When the airplanes left the pax fleets, the freight haulers immediately yanked out the pressurization system along with the water meth system, IIRC. Neither needed to haul boxes at night.
The Darts W/M system normally cut in thru 14,500 rpm, on power reduction after TOCA down to 14,200 and trimmed for max continuous temps. the W/M pumps were turned off. I'd like to try a W/M system on a turbocharged piston w/ a closed loop EFI system, and use a 10% hydrogen peroxide charge to see what kind of power increase you would get. Let the engineers begin!
safetypee
The BAC 1-11 did not use water/meth, it used de-mineralised water injection.
If water/meth is used it burns out the turbines.
Water injection is used for thrust augmentation and is injected into the combustion chamber to cool the flame temperature which allows more fuel to be added to the fuel/air mix thus giving a power increase.
The BAC 1-11 gained an extra 500lbs. of thrust per engine using water injection.
CC
The BAC 1-11 did not use water/meth, it used de-mineralised water injection.
If water/meth is used it burns out the turbines.
Water injection is used for thrust augmentation and is injected into the combustion chamber to cool the flame temperature which allows more fuel to be added to the fuel/air mix thus giving a power increase.
The BAC 1-11 gained an extra 500lbs. of thrust per engine using water injection.
CC
Está servira para distraerle.
pigboat's quote is spot on. I was awaiting return to my library to dig out the same information.
Operating out of FAJS (hot and high) in both the HS 748 and the F27, we often used WM for take off and always had it turned on during final approach in case of a go around.
We also used to execute a 'reduced power take off', brainchild of the then Chief Pilot.
Advance power levers to about 14,200 RPM, nip down the runway and if it looked as though you weren't going to rotate by a chosen point, advance the levers to enage WM. A lot of us thought that this was slightly dumb?
One important lesson was never to arbitrarily switch on WM during a dry take off with power levers at maximum. That would lead to expensive noises as little bits of engine tinkled out the back.
On the F 27 in England, flying for a major operator, we were forbidden to use water methanol at all, even on the hotest days. That company also had a peculiar operating policy for the fuel trimmers which ran quite contrary to Fokker and Rolls Royce's own operating manuals.
I seem to remember that both aircraft carried thirty gallons WM (US) a side. It was possible to run out of WM halfway through a take off or go around. Three wet take offs for a full tank each side was a rule of thumb. Thus, if you had five gallons a side and needed wet power for take off, it was time to top up the tanks before departure.
That's Life!!
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Water-Meth injection was used on the Allison engine fitted to the early Bell 206As. Perhaps Allison or Bell could provide info.
