Jim Thomerson

I presume you have all read Joe Wagner's engine column in the January 2004 Model Aviation. He tried running glow fuel with 20% water and upped his engine's performance by 100RPM. He had to richen the engine considerably, it did not start as well, and took 30 seconds or so before he could remove the glowplug battery. Joe is not what you would call an incrementalist!

Jim

Sport_Pilot

I tried to tell people that some time ago and got flamed for it. Lots of BS about the condensation in your fuel jug being water going around also. This is an old drag racer trick. If you are having problems with detonation in you alky engines and don't have a convenient way of lowering compression, you can add water to the fuel.

AMB

I think this was done 50 or 60 years ago with some aircraft engines using water injection as
a power boost am I right??

LearjetMech

Correct! It was called WEP, or War Emergency Power. It was usually a water or water/methanol mix!

Sport_Pilot

Actually the boost was an increase in the supercharger boost, the water or water alcohol mix was used to prevent detonation at such a high boost. When alcohol in any form is used a the primary fuel, all you have to do is add water to the fuel and richen up the mixture. This has the same effect as rasing the octane, makes the mix burn slower.

downunder

Spraying or injecting water or water/methanol mix into an engine is a totally different thing to trying to mix water in with a methanol/oil mixture. On a mild day about the most water you can mix in glow fuel is 3%...any more than that and the water drives the oil out of suspension and it falls to the bottom of the tank. The warmer the fuel is then the more water is needed before the oil seperates but you're still only talking 4-5% water.

Jim Thomerson

I wondered how Joe Wagner got the 20% water to mix. He did not say.

Jim

Homebrewer

My Feedback: (8)

Oh, I can see it now...a certain fuel manufacturer...."we used only the highest quality proprietary 99.999% pure water additive in our fuel......"

Waco Driver

I am sure that the fuel manufacturers are rubbing their hands in glee over the increased fuel sales Mr Wagner's article will generate. Fuel sales to replace the good fuel ruined by the addition of water that is. Also the engine manufacturers may get some additional sales.

After dunking my seaplane one year, I decided to run the OS 61 four stroke on the fuel that remained in the tank in order to dry out the interior of the engine. I ran it at high power for about 5 minutes. When I got home I decided to pull the head to have a look. The interior of the head, valves and top of the piston had a very even coating of shiny black carbon that looked as if it had been spray painted. It was very difficult to remove. I do not know the chemistry involved but I am sure that it was the result of water mixed with the fuel.

Let the experimenter beware!

3d-aholic

My Feedback: (7)

Its not surprising. Its a trick college physical chemistry test question.

Its a well known fact of chemistry that water increases the efficiency of combustion once an engine is up to "operating temperatures" by providing free oxygen and hydrogen scavenging in the vapor phase.

If water was the end all to end to combustion, then I suggest next time your flying at 15,000 feet in a rainstorm, you think about the amount of rain going into the jet engine on your plane.

Oh, I would not go adding water to your fuel...the trick is that the combustion efficiency increases with temperature. If the engine is cold, it squelches the combustion. You need fuel with no water at first and then switch over to water-laced fuel when the engine is at temperature.

3d-aholic

My Feedback: (7)

100.00 RPM? Gosh that has to be within experimental error and insignificant.

Hobbsy

My Feedback: (102)

Joe Wagoner couldn't get an RCV .58 to fit in a PSP engine test stand either and yet my .58 fits right in there.

LearjetMech

Hey 2Much,
Two reasons water really wont affect a jet engine in a typical rainstorm. First is most engines now are medium to Hi-bypas which means very little thrust is generated by the engine itself. Very hard to describe in words. About 70% is generated by the Fan, or N1. So 70%, if not more of that rain passes on the outside of the engine case and never sees a flame or combustion. I would suspect more than 70% due to centrifugal force. The second reason is these engines burn so hot, its not even funny. When I start a Lear 60, the start limit on the ITT (Interstage Turbine Temp) is about 960* C, or roughly 1700* F. That is the start limit and we usually never see it this high. Usually 860*C or so on start. These engines I would guess operate at cruise at about 500*C or roughly 900*F+. Now with a few rain drops which are obliterated by the fan disk and compressor stages into a mist, they are virtually non existent by the time they get to mix with fuel. Remember air is heated by compression alone. See if you can locate the engine testing video they did for the 777. They forced a virtual waterfall into the intake and she kept on chugging. Sometimes it is on TLC or discovery!! Totally freaking amazing!!

3d-aholic

My Feedback: (7)

Yes, I've seen that Discovery show...it is amazing. I like the part where they fire the frozen turkeys out of the cannon into the running engine. Happy Thanksgiving...

Sport_Pilot

I once designed a wash to clean salt water off of low flying A-10's. A lot of the water nozzles were directed at the engines. They would park where the water was sprayed straight up in front of the wing leading edge. The engine suction would pull the water into the engine when they throttled up. They ran this way for a minute or so to rinse out the engine. A 1000 GPM or so of water going in, nothing but steam and mist going out.

Sport_Pilot

[i]Also the engine manufacturers may get some additional sales. [/i]

How so?

Sport_Pilot

On a mild day about the most water you can mix in glow fuel is 3%...

Do you know how much water was in the fuel when you started? Also could differant oils asorb more or less water?

Hobbsy

My Feedback: (102)

Fuel Companies are going to sell more fuel when guys pour water into their fuel to get more power and find out the engine won't idle and runs hot if they get it to run above idle.

Ragtop

My Feedback: (3)

Call me crazy but the point of a jet motor is to accelerate mass out the back. The more the mass, the more thrust. Water (8 #/gal) weighs more than air so..... . Internal combustion doesn't work on the "accelerated mass" idea so water don't do much.

Sport_Pilot

While true they can't throw out any more than their power. If you fly through the rain the engine will throw out water and air at a slightly lower velocity than air alone. Since the aerodynamics of the turbine blades are based on air, they will be less efficient in the rain, thus they will have slightly less power when flying in the rain.

3d-aholic

My Feedback: (7)

Actually the discover channel special says the jet engines run more efficiently in the rain....

downunder

I started off by mixing a fresh batch of fuel so the water content would have been close to zero. It was easy to cool it enough that even 0.25% of water made the oil seperate out. The results gave a virtually straight line graph for water content against temperature of seperation. This was with an 18.5% all synthetic fuel but my tests at the field were with a 20% all castor mix that seemed to show that the castor comes out more easily. I only did this to find out for myself what actually happens and I haven't done more extensive tests but it's given me a good general idea.

I've put the method and results of my tests on the web page I do for my club at http://www.holdfastmac.com.au/Waterfuel.html if anyone wants to try it for themselves.

LearjetMech

I dont think mass is the term your looking for, but rather force!

Pjtg0707

All the posts, and I suppose no one actually read and understood what he was doing.

He was saying the reason for fuel to go bad is not because of water. The main reason fuel deteriorates is becaue of oxidation. It's simple 1st year organic chemistry.

chemicals in the alcohol family have very well defined degradation paths in order of increasing oxidation states: it goes from alcohol to aldehyde to carboxylic acids. So, for methanol, it goes to acetaldehyde and finally to acetic acid. Its the presence of these products that caused the fuel to go bad, not the water, which he amply demonstrated by running engine with 20% water in his fuel. The only thing he got wrong was that brass catalyzes these degration reactions, which is pure crap.

POWERMASTER

Hobbsy
I agree 100%. If the model community could see the efforts and equipment that is
used to exclude moisture from engine fuel during manufacture, think they would think
twice about additional water in the fuel mixture. As fuel absorbs moisture during normal
usage, you will notice different needle settings, idle speeds and general operation of the
engine. The manufactures try to keep the fuel as low in moisture content as possible in
order to have a fuel that will run consistant each time that the engine is used.