Me and a pal is going to do some research about the effect of water injected into a turbine...!
The famous F9F Panther had 60 litres of water for this purpose, and this gave 25-30 % increase of effect.

One liter of water gives 1800 m3 of moist ( like the clouds, not steam).
Only a tiny spray from a OS 10 FSR carburetor will do the job.
Chamberpressure at full speed will be enough to give this fine spray directly into the compressor.
Have to be careful conserning the amount, or the compressor will be damaged..

Imagine what the right amount of water will do tho the pressure wich also lowers the temperature!!
Some experiments is ofcourse nessacery, but we estimate around 30% increase.
Anybody else with some thoughts around this?
I`ll be cack after the first rounds to let you know.


Regards

Gudmund

this will increase fuel consumption too then ?

Not at all, rather less consumption.
This is what we theoretically ecspect, but we`ll see. The water will help to get the max on the ECU, and therefore reduce
the fuelflow.
Interesting theory?[8D]

Btw, is the Liebetrau site nonop?[:-]
How much for a F-16 from them? And wich scale gear do they deliver?

The first tests would be done during the next week.[>:]

Regards

Gudmund

AV-8's carry water on board. I'm pretty sure they use it when they are in a hover or any other situation they need to use it. I think it is injected in the plenum chambers or not but I'm pretty sure the use water.

Harriers do certainly carry water. Only enough for about 90 seconds from what I believe. Just enough for a vertical landing at the end of a sortie on a hot day.

I understand that the principle is to increase the mass flow and hence the power. The reduction in temperature is an extremely useful side effect.

The water injection should work. It will probably require more fuel to get the higher thrust, but temps should be lower. If the spray is very fine, and injected near the center of the compressor, it shouldn't hurt anything.

I was discussing water injection with Scott Shockley (driver of the famous Super Shockwave jet truck) just last weekend. He siad the jet car guys have known about water injection for years, but it tends to make their afterurners unreliable, so they don'y use it. After all, most of their show is the afterburner flame and smoke.

Are you testing on a thrust stand? Be sure to record ambient temp/pressure to allow you to adjust for non-standard conditions, as well as exhaust temp, water flow rate, etc.

I'd be very interested in seeing your results!

Bob C.
Silent Wings Airshows

I remember the KC-135's when I was in the Air Force used water injection. They injected about 750 gallons into their four engines for a dramatic increase in thrust that lasted about 120 seconds. I don't think that they injected them into the compressors stages or the combustion chamber, but rather into the exhuast section. Also, if memory serves me correctly-the fuel flow from each engine jumped from about 7,000 pounds per hour of fuel to about 12,000 pounds per hour. Since water turns to steam when vaporized and expands greatly I would be concened about injecting into the compressor area. Seems as if you could blow up the engine that way. But if it vaporized when injected in the exhuast area the sudden expansion of the vapor would be pushed out the back resulting in an increase of the thrust. On full scale aircraft they also used deionized water to prevent mineral deposits in the engine-I think distilled water would serve the same purpose.

Perhaps someone on the forum was, or knows an old engine mechanic from the military that that could give them more factual advice on how this concept works.

Don`t forget the turbine is controlled by either pressure or rpm. A pressure ECU won`t work, but a rpm ECU would.
The fuel flow is expected to be redused, we`ll see.

Regards

Gudmund

I'll be interested in seeing how it works for you. An interesting idea-and all great things start with interesting ideas.

I may be wrong but the water injection I know about was actually alcolhol. Some early DC8's and 707s used it.

Normally, the (de-ionised) water is injected just upstream of the combustion chamber, but downstream of the compressor. It lowers *** (Turbine Inlet Temperature) and JPT (Jet Pipe Temperature), thereby allowing the engine to run at a higher RPM for any given ***/ JPT. There is also a very small thrust increase due to the water/steam in the flow, but the real purpose is to supress the ***.

I believe that with water/methanol injection, this was injected somewhere in the compressor stages, and the evaporation of the methanol caused the temperature of the air to drop, thereby inceasing it's density and mass flow rate, thereby increasing thrust. I don't think the methanol was burned directly.

As long as we are limited by bearing life and a physical compressor and turbine RPM limit, rather than running on the JPT limit, I don't see that we would be able to use any potential benefit of water injection. Interesting experiment though.

Paul

I would hate to be in the plain of those bearings and blades when they come apart!!!!
I dont understand why we try and get more out of these engines then they are designed for. Maybe Im way too concervative but I think manufacturers place limits for reasons. Good luck with it, but dont be surprised if it comes apart. i would love to see it work!!
I ran a water methanol injected engine for about 4000 hrs worth of flight time and NEVER used. It was not recommended for normal use, and its limit was for less than 5 minutes. it was a Garrett TPE331-10. For reasons that I have learned in some 12,000 hours of flight time operating turbines I just cant see the benefits outweghing the possible consequences. Like I said before Good Luck...I hope it works.

Pete

There are several reasons for me to check this out.

Some of us have models wich could take some moore power, or after some time when you are familiar to a new model, you would always say yes to a bit moore punch without messing with the ECU?.
IF the effect is as estimated, I know alot of guys who could take benefit of this in their Eurosport.. 3D can be possible with the same engine as before.
I might be dreaming, but I think this is worth a try...?

Not for myselves, as I have what I want, but sharing the experience with others.
Turbines are expensive, and if such a simple thing as water-injection can help someone to get moore out of it, then why not? Besides, this is a untouched subject in model- turbine operation.
I`m sure many modellers have though of this idea before, but I don`t know if anybody actually have tried this.

The only problem I see, is the setting limitations on the ECU..
Higher pressure is higher rpm, and higher rpm was not the idea. It might be possible as the temp goes down, but only if the ECU allows it to happen. This again means you have to set a higher max rpm for full speed to allow it to use the increased performance...
Like a dog biting itselves in the tail.
When the evaporated water enters the chamber, there will be a significantly higher pressure.
The ECU will reduce the flow to ceep it not above the max, but where is the gain then??[:-]
IF the engine allows a higher pressure within the desired max rpm (as before and without water), then i will say this is a success.
IF a higher max rpm is nessacery to give the injection it`s purpose, it would be a (highly) reduced sucsess, because the only gain would be a lower temp ( the engine has already a GO for increased performance).

We don`t know nothing about the effect yet, none has ever done it before, do I need to say moore?

It might end like these faces tell us...[X(] , [8D] , [&o] , [>:] , !!

Regards

Gumund

Just do it! And post results, it doesn't mattery why! Hell of an idea!

Although in the harrier, I'm pretty sure that the water is simply used to cool the engine rather than boost performance. The hottest our turbines run is when we're running them on the ground. Stationary turbine runs the hottest and that's why the harriers carry the water for vertical non forward movements. 90 seconds of this cooling water is all they can carry.

density of water is about 1000 times the density of air!! this means 1000times the force on the blades so be carefull!

I know you are not here in the USA, but I think I remember the AMA turbine rules specifically prohibit afterburners and water injection. Anyone remember that? So we can't do it here in the USA, but we can still wait with interest for your results! Best of luck and please tell us all about it.

Quote:
I don't think that they injected them into the compressors stages or the combustion chamber, but rather into the exhuast section. Also, if memory serves me correctly-the fuel flow from each engine jumped from about 7,000 pounds per hour of fuel to about 12,000 pounds per hour. Since water turns to steam when vaporized and expands greatly I would be concened about injecting into the compressor area. Seems as if you could blow up the engine that way.

My oppinion is that the compressor will complete the job the small carburetor could`nt do.
Nearly atomizing the water before it reaches the combustion chamber.
This must be the ideal recepe for the injection as I see it.
Axial turbines operate at a much higher pressure, and on such engines I agree the right point for injection would be the exhaust area.
To inject water in our engines in the nozzle area, would not give any effect after my oppinion...
Just my thought.

Regards

Gudmund

Correction: 800 times, and yes we want to continue this great sport, so we will take any precautions needed.
To compare it with 800 times the force on the blades is not really the truth, I think,
as we have no plans to run it on water only

Thuesday is the D-day, so I`ll be back then to give the answer to this 1000 Dollar question.
Still no replys to my question about the Liebetrau F-16. Anybody?

Regards

Gudmund

If memory serves, Eddie Weeks was either present or had reports of a hose being shot into an OLY with no ill effects.

I think it was a Peggy-Sue, but yeah, it ran and took it up until a point at which it was way too much water and put her out. But no damage. It was Hans from AMT that was doing it, I think.

Reading JSF-TC's post was informative. When I was in the Air Force I worked on Instrument Systems, not jet engine and maybe it all makes a little more sense to me know. On the KC-135 when the hit the switch for water injection the fuel flow almost double. If I understand what he said the water cooled the exhuast allowing a higher rate of fuel to be burned without overheating the engine, thus more thrust. Make sense.

This topic was discussed in this forum previously - here's a link to the prior discussion including a coule of very informative posts from Andre (BMT): http://www.rcuniverse.com/forum/m_17.../tm.htm#173764

Gordon

As someone who worked with jets using water injection for over 20 years, i can tell you the textbook answer for what water injection does: increases mass airflow through the engine. The B-52G carried 1200 gallons of DEMINERALIZED water, and the boost lasted for 120 seconds. The KC-135 used the same J-57 engines, carried 600 gallons, and it also lasted for 120 seconds. Gave about 6000 pounds more thrust per engine, which was about 30% increase. The fuel flow did increase, and the engine pressure ratio increased by a bunch also. Don't remember what we trimed them to now, but the 135's really screamed, and if you were going to have an engine failure it would happen during water. These engines put 1/3 of the water into the inlet, and 2/3 into the diffuser cases. The F-105 used water injection, and an afterburner, and I don't know of any problems with the burner connected to the water injection. I don't know how our little engines will react to water. Maybe the ECU will just pump in more fuel to put the egt back in the ballpark, but I would be very careful! The fuel controls on the big engines had a seperate trim system for dry and wet thrust. Also we couldn't use water below 40 deg. on the B-52 because of the temperature drop in the inlet. The tanker had water heaters to get the water temp to 70 deg, then you could take off wet down to 20 deg. Hope this makes sense. Remember, demin or distilled water. The impurities in the water would eat the full size compressors.

I used to work with a guy that flew F105s. He told me a story one day. He said that the opening on the Jet fuel tank intentionally had a very different shape than the opening on the tank for water injection. That was, of course, so some numb-nut could not possibly put jet fuel into the water tank. Well, one day he was sitting writing a report in his office that had a window facing the runway and suddenly a big BOOM and the concussion almost shattered the window. An F-105 blew up on the runway apparently just as the pilot cut in the water injection system. Seems they found their numb-nut. Some guy fueling the aircraft was positive he was supposed to put jet fuel in that tank with the funny nozzle, so he scrounged until he found enough gear to make some weird adapter so he could get it in!

Very interesting! I heard that one should user methanol/water mix.. Any comments on that?