Like I said, truck would need to be fitted with a boiler, and all the controls, feed pump you name it. No one with out a ticket should be even thinking about it.
I already have the high pressure pump and computer controls, all I'd need to put the water into the manifold is a solenoid, steel line and nozzle... Interesting idea.
This is very good discussion IMO. Now, we both agree that the most heat is absorbed from the liquid to gas transition. My ASSUMPTION is that no matter how cold the water going into the cylinder is, there is enough heat inside the cylinder when it is firing that there's NO way the water can make it out of the cylinder without being a gas. Therefore, the benefit of heating it up before is negated. It is hard for me to imagine the liquid being in direct contact with the combustion process and not getting translated to the vapor state. Remember, a diesel cycle takes much longer to occur than an Otto cycle (gas engines, for those wondering). This means the water has more opportunity (or time) to vaporize. In a gas engine, there's basically one big POP! and the combustion is done. In this case, the water may not be exposed to the flame long enough to transition if it enters cold. This scenario may yield better to pre-heating IMO.
I've studied Thermodynamics and the laws of Heat Transfer extensively in school, and without doing a calculation, this is my intuition about it. Actually, if I can dig up some of my old books I can better answer this question. Putting some hard numbers on it would actually be pretty easy using the RPM (piston speed), fuel flow, water flow, and water inlet temperature.
The critical temperature of water is 700 degrees and the critical pressure of water is 3200 PSI. This means that above 700 degrees, water is ALWAYS vapor. Above 3200 PSI, water is ALWAYS liquid. And above 700 degrees and 3200 PSI, it's a supercritical fluid with liquid and vapor qualities.
Does supercritical fluid compress?
I wouldn't imagine that liquid water in the power stroke would be a problem; the piston is moving down on the power stroke, so a non-compressible fluid shouldn't cause rod bending.
Having liquid water in the compression stroke has to be dangerous. If cylinder pressures on compression stroke reach over 3200 PSI, than any water present, ambient humidity included, will condense and become liquid.
How much boost pressure do we need before we start seeing that cylinder pressure?
The part that I find weird is how fast injected water can change intake temperature through convection. If we take a 300 degree air charge, inject 32 degree ice water into it, then eight inches down the air intake, the intake air sensor is registering 120 degree charge air. On an engine moving at a decent RPM, we have to be talking milliseconds of time for the water and air to transfer that much heat. Yet, we know it happens that fast. I can't really believe that fast temperature drop is a result of water accumulating onto everybody's IAT probes over the last 20 years and misleading people. So I guess it's a great demonstrator of the amazing capabilities of atomization.
So short of mass misinterpretation of IAT gauges, there's no doubt that ice water cools down charge air greatly and rapidly. And that is very effective in increasing mass flow into a cylinder and reducing EGT's, so that's the operating understanding most people have.
If we heat the water, we could force it to phase change, rapidly.
But does ice water ever undergo a phase change before TDC compression? If we use the "temperature equilibrium" theory, and assume that all of the finely atomized water droplets are the same temperature as the intake gas, then we know that it doesn't usually phase change in the intake, since the intake is usually kept below the boiling point of the water at that pressure. Pressures and temperatures increase as a piston compresses;
does cylinder air temperature ever increase above water's boiling point at a given cylinder pressure? That'd be a calculus problem best graphed out on a TI-89, I think that the answer is "yes" though. It seems like cylinder temperatures can exceed 700 degrees while being less than 3200 PSI.
If finely atomized water can absorb sensible heat fast enough to remain in "temperature equilibrium" with the cylinder air, then absorbing sufficient heat during compression to keep on the gas side of the phase diagram seems possible. If atomized water does absorb heat that fast, than the only danger is that there is so much water in the cylinder that there isn't enough heat to keep it all gaseous. Or that the water is not atomized finely enough to absorb heat fast enough. Or that cylinder pressures exceed 3200 PSI.
If the water is liquid at the BEGINNING of compression, only then would it be a big deal for rods bending. The problem would come if you vaporize the water, then the compression turns it back into liquid at the top of the stroke.
I would argue that by controlling EGTS, you are effectively ABLE to make more horsepower. By lowering the EGT's with water, you can do things like run bigger injectors, or turn up duration to allow for more fueling. Water is an INDIRECT power adder.
If we heat water before injection, it will have to absorb less heat to turn into a gas, so it will be less likely to condense into liquid at any pressure below 3200 PSI.
The question is whether it would be beneficial, and it doesn't seem like more, hotter water would be better than less cold water, provided that the cold water has time to absorb sufficient heat, which it seems like it does.
