water injection = Higher Efficiency?

[tjts1]

I gave it a shot last night and water injection definitely reduced the injector PW for a given load. I'll post the data as soon as I compile it.

[t vago]

What was your engine loading? What was your intake air temperature? What was the relative humidity of your intake air? What was the temperature of the water? What was the amount of vacuum in your intake manifold at this given load? Did you notice any temperature drop in the intake manifold air temperature when water injection was performed?

[t vago]

Originally Posted by IamIan

That water phase changed to steam ... expanded to fill the volume of the container ~39.04cc ... as any gas will do ... because there was not room for the full ~1700:1 expansion that would result at a lower ~14.7psi pressures the steam contributes a bit more than ~14.7psi ... I'm estimating ~26 psi.

Ok, so even with the assumption that 1700:1 is not changeable at all, the final system pressure is still lower than the initial system pressure.

People can disagree all they want on this point. However, it doesn't change the fact that this much-ballyhooed expansion ratio is variable.

For instance, saturated steam at 120 C has a pressure of about 20 psia. It also has a expansion ratio of 1150:1. This is directly out of the steam tables, and doesn't change at all for saturated steam at 120 C. Saturated steam at 153 C has a pressure of 75 psia, and an expansion ratio of 332:1. The original 1700:1 ratio is a firefighter's rule of thumb, developed to let people guess how much steam would be produced in the course of fighting a fire.

Again, this 1700:1 ratio is not a fixed, immutable ratio to be held holy for all time, and it certainly should not be the basis for any reasonable engineering design. It changes due to whatever temperature saturated steam is.

One other thing: I'm not saying that saturated steam at 212 F is 14.7 psia because it amuses me to do so. I'm saying that saturated steam at 212 is 14.7 psia because this figure is directly out of the steam tables, which were themselves developed during the reign of the steam engine.

[t vago]

Originally Posted by IamIan

#3> The biggest thing from my perspective often missed in a lot of the water injection type of discussions is the weight penalty of the additional device and the additional water ... even if a system does manage to increase real time efficiency from one mechanism or another ... it won't be a net benefit unless the pro is bigger than all the cons added together.

Indeed. It's all well and good to imagine, "Oh, gee! Wouldn't it be so nice to make a gasoline engine be 50% more efficient simply by squirting water into the combustion chambers?!?" It's quite another thing to lug around 50 lbs of water (that's 6.25 gallons), a positive displacement water pump to squirt the water into the chambers at at least 150 psia pressure, sufficiently strong check valves that won't leak burning combustion charge into the water lines, the lines themselves; all the while generating enough power to energize this water pump. Oh, and this must be able to last for a reasonable amount of time, like for about a year or so.

Originally Posted by IamIan

Thanks for the clarification and correction.

No problem.

[drmiller100]

some of theories I have read suggest 1/3 of the combustion energy ends up in the radiator, 1/3 ends up out the exhaust, and 1/3 makes the car "go forward."

When you dig a bit deeper, you discover the 33 percent to make the car go forward is VASTLY exagerated - 25 percent is a more reasonable goal.

It seems to me the energy going out the radiator is an opportunity for better mileage.

It seems to me if I can reduce the combustion temps, I will lose less energy to the radiator.

It seems to me if steam is HALF as efficient as the adiabatic process, but I lower the combustion temp in half while doing it, I am still ahead. After all, the radiator gets more energy then propulsion does by a fair amount.

[drmiller100]

Lets try this another way.

If we take 40 cc's of air at say 5 psi absolute. And we add the "appropriate" amount of gasoline.

someone smarter then me should be able to calculate the amount of BTU's present, and from there should be able to calculate the final temperatures and pressures assuming exhaust gasses only. Then of course we subtract 1/3 of the energy because it is lost to the container (cylinder head, piston, et al.)

Given the BTU's, a confined space, and steam tables, we should be able to calculate new pressure and temperature for steam. Like the man said, the temp will be quite a bit lower, so we will lose less to the container, and the exhaust gas temps will be lower (albeit full of water vapor).

If we can guarantee an ABSOLUTE MAXIMUM temperature of say 700 degrees combustion with water vapor, do we still need a CAT?

[IamIan]

Originally Posted by drmiller100

some of theories I have read suggest 1/3 of the combustion energy ends up in the radiator, 1/3 ends up out the exhaust, and 1/3 makes the car "go forward."

When you dig a bit deeper, you discover the 33 percent to make the car go forward is VASTLY exagerated - 25 percent is a more reasonable goal.

It seems to me the energy going out the radiator is an opportunity for better mileage.

It seems to me if I can reduce the combustion temps, I will lose less energy to the radiator.

It seems to me if steam is HALF as efficient as the adiabatic process, but I lower the combustion temp in half while doing it, I am still ahead. After all, the radiator gets more energy then propulsion does by a fair amount.

what your describing is the 6 stroke engine ... theory works ... application is harder than it seems, and has issues... feel free to read up on it and the issues involved.

[IamIan]

Originally Posted by t vago

Again, this 1700:1 ratio is not a fixed, immutable ratio to be held holy for all time, and it certainly should not be the basis for any reasonable engineering design. It changes due to whatever temperature saturated steam is.

correct ... and there are no real ideal gases either ... so?

Originally Posted by t vago

One other thing: I'm not saying that saturated steam at 212 F is 14.7 psia because it amuses me to do so. I'm saying that saturated steam at 212 is 14.7 psia because this figure is directly out of the steam tables, which were themselves developed during the reign of the steam engine.

ok ... and? ... I don't get what's the point you are trying to make?

My only guess right now is ... maybe you are indirectly trying to suggest my higher value I got from using the ideal gas law is incorrect ... I am not certain what your point is there???

If the volume is not restricted it expands @212F & 14.7psi by about ~1,700:1 ... but unless I missed something the ideal gas law requires the partial pressure from the steam to go up if you confine the expansion of the same amount of steam in a limited volume ... add more heat energy and you phase transition more liquid water to steam in the fixed volume the steam expansion keeps increasing the pressure ... yes as the pressure goes up so does the phase transition point ... etc ... but if you want to account for that then the final system temperature is not the 212F or 100C you listed either ... it raised with the higher phase transition temperature of the higher pressure the liquid water is under ... which has effects on the available heat energy that can be transferred across the dT difference between the liquid water temp and the initial hot gas temp... etc... etc... like you said we can keep making it more and more complicated if we want to.

[t vago]

Originally Posted by IamIan

ok ... and? ... I don't get what's the point you are trying to make?

My only guess right now is ... maybe you are indirectly trying to suggest my higher value I got from using the ideal gas law is incorrect ... I am not certain what your point is there???

What exactly is this expansion ratio for water at 212 F? 1700:1?

I certainly don't think so.

The specific volume of liquid water at 212 F is 0.016715 ft^3 per lbm.

The specific volume of saturated steam at 212 F is 26.80 ft^3 per lbm.

Divide the specific volume of steam at 212 F by the specific volume of liquid water at 212 F, and you get... wait for it... 1603.35.

That's right! 1603.35:1, not 1700:1! You're willing to continue this discussion on the basis of a rule-of-thumb figure that was not even meant for any sort of engineering at all.

Originally Posted by IamIan

If the volume is not restricted it expands @212F & 14.7psi by about ~1,700:1 ... but unless I missed something the ideal gas law requires the partial pressure from the steam to go up if you confine the expansion of the same amount of steam in a limited volume

Yah, you did miss something. I just addressed part of it, but here's the other part.

Unless there's work done on that gas after the steam is added to it, the system presented in this example will only have saturated steam. How can it possibly be otherwise? 99.9% of the water in the final system is still a liquid! And if the liquid water and the steam are at the same temperature, which must happen due to conservation of energy because no outside heat was added apart from injection of water at 100 C, and due to the fact that no compression work was performed on the system from the outside, how could there possibly be more steam added?

[t vago]

My final point is this:

There are too many people here who buy into the siren song of "there's something out there for cars that's oh-so-much more efficient than the 'obsolete' 4 stroke internal combustion engine, but we just didn't figure it out how to make it work yet." This is pushed by true believers who don't have one lick of actual knowledge of the theory behind either the wonder-engine or the internal combustion engine as we know it, and is then supported by people who would and should know better, yet show a disturbing lack of curiosity.

Good luck getting your magic devices to run using steam, folks. You're only hurting the cause of ecomodding.