humid is better in turbines

[ae2598 at wayne.edu]

Tell me about it.  A friend of mine experimented with liquid-water
injection on his quad-4 after a heavy rainstorm..  Funny how when the
piston can't reach TDC, you get lots of extra crankcase ventilation!

 On Thu, 23 Aug 2001 jll at edge.net wrote:

> I sure hope that the liquid is being flashed off as a gas vapor prior to entering
> the combustion chamber. Positive displacement gas compressors tend to come apart
> when an incompressible liquid is introduced into the compression chamber.
> JL
> 
> >KasaRyan at aol.com wrote:
> >> 
> >> Whoo Whee! opened up a can o worms on this one!
> >> 
> >> Ok, one of the reasons I put in the explaination I did was that I knew that
> 
> >> some early jet aircraft, the 707 among them, would dump hundreds of gallons
> 
> >> of water into the combustion chambers of the engines on takeoff.  This
> >> probably lowered the temp slightly, but more importantly dramatically
> >> increased the volume of what was coming out the back of the engine, and also
> 
> >> pushing on the turbine to compress more air.  The more force you chuck out
> 
> >> the back, the more the plane goes forward!  Sir Issac had that one down,
> as
> >> far as Harry ricardo goes, I dont have his book on combustion chamber design,
> 
> >> but I do believe he plugged away at it for a while.
> >> 
> >> Roger, you seem to have the thermo book handy, so I would like this
> >> calculated.  If you have one gram(or cc) of water at 100C, and you add enough
> 
> >> energy to vaporize it into gas, how much energy does this take, and at 1
> ATM,
> >> how much volume does it take up once vaporization is complete?  If you take
> 1
> >> cc of air at 100C, and you add the same amount of energy, is the resulting
> 
> >> volume increase more or less than for the water which goes thru the state
> 
> >> change.  (IS this PV=nRT? or something of that sort)
> >> 
> >> I believe I was wrong on the water being in a liquid form on a humid day,
> but
> >> what if you use injection, and have liquid water in the combustion chamber.
> 
> >> 
> >> If this goes on too long, i will probably have to dust off the books and
> look
> >> it up myself.
> >> 
> >You might need to, I won't be able to run the numbers until tonight.
> >
> >I believe you have 2 test cases, all closed systems, I don't believe
> >humidity enterns in to it as water vapor acts as an ideal gas.
> >
> >	case #1: 1 mole an ideal gas at 50C with xx joules then 
> >		added to it what is the ending pressure.
> >	case #2: 1 mole (minus a small amount for the water) of an ideal
> >		gas and 1 mole of water (18ml) at 50C with xx joules added
> >		to it, what is the ending pressure?
> >
> >I suspect strongly case #2 (same physical volume starting) will produce
> >a higher ending pressure, this requires that you get the water into the
> >combustion chamer as a liquid, and then add enough energy to convert it 
> >to an ideal gas.    If it goes inth the combustion chamber as a gas, it 
> >will act pretty much like an ideal gas, and no gain is made, and also it
> >would have displaced some oxygen coming in so reduced the amount of energy
> 
> >that you could add to things.   I am pretty sure the Harrier jets do
> >this trick also to increase thrust, though only for short periods of time,
> 
> >I suspect that the water is weight inefficient so you don't want to use
> >it for long times (only use to hover (harrier) and takeoff and other
> >emergencies).
> >
> >				Roger
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