Gabriel
Topic Author
Posts: 25
Joined: Sun Dec 18, 2005 12:17 am

How Does Work The Water Injection System?

Fri Aug 18, 2000 8:11 pm

Hi,

I ever heard about the water injection system to increase the engines power in take off (such as in the Boeing B52 Stratofortress), but never knew hod does it work...

Anyone can explain it to me?
Thanks
Gabriel  
 
JT8DJET
Posts: 196
Joined: Fri Jul 07, 2000 12:28 am

RE: How Does Work The Water Injection System?

Fri Aug 18, 2000 9:38 pm

"The injection of water into the gas path causes heat transfer. When the fluid evaporates, heat in the air will be transferred into the fluid droplets, cooling the air and making the gas flow more dense. Water injection in a gas turbine engine is then a means of augmenting engine thrust. Augmentation can be thought of as occurring in two ways. First, addition of water to air in the compressor increases compression and mass flow. second, water cools the combustion gases which allows additional fuel to be used without exceeding maximum temperature limits during takeoff. Increases in these three engine parameters results in a thrust increase in the range of 10 to 15 per cent." - taken from Aircraft Gas Turbine Powerplants Handbook.
 
Buff
Posts: 1066
Joined: Fri Mar 16, 2007 1:29 pm

RE: How Does The Water Injection System Work?

Fri Aug 18, 2000 10:25 pm

Sometimes referred to as "Water-Meth" (Methanol) or "Wet Take-Off Power". The methanol is included as an inert agent to prevent the water from freezing, either in the tank, or during the heat transfer referred to above.

A few years ago in northern Manitoba, Canada, an HS-748 was getting ready to depart a small strip. Normal procedure is to arm the water-meth injection prior to throttle up. In this case though, the arming wasn't done until late in the takeoff roll or just after airborne (I can't remember the specific details). Unfortunately, when asked to fuel the airplane earlier, the new fueler mistook the water-meth tank for a fuel tank.

When the kerosene entered the compressor section of both engines, one flamed out, the other exploded in the exhaust section. The plane was deadsticked into a dry river bed with no serious casualties.

Best Regards,

Buff
 
prebennorholm
Posts: 6418
Joined: Tue Mar 21, 2000 6:25 am

RE: How Does The Water Injection System Work?

Fri Aug 18, 2000 10:42 pm

Also early 747 clasic airliners had the ability to use water injection. It was only used occationally under hot&high conditions, or at MTOW on marginally short runways. I don't think it is used any more on commercial planes. It gives a terrible smoke.
Also piston engines have used water injection. Especially during WW2, but also later carrier fighters etc.
We are not talking about a few bottles of water. A B-52G could carry 10,000 lbs of water for take-off. It would last only one and a half minute, so the party ended at about 200 feet altitude.
Best regards, Preben Norholm
Always keep your number of landings equal to your number of take-offs
 
Gabriel
Topic Author
Posts: 25
Joined: Sun Dec 18, 2005 12:17 am

RE: How Does Work The Water Injection System?

Mon Aug 21, 2000 7:36 pm

thanks for the replies  

gabriel

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