water injection = Higher Efficiency?

[t vago]

Originally Posted by IamIan

It isn't a fixed number.
It varies with context... temperature alone is insufficient data to determine the final expansion ratio.

If you're talking about saturated steam, then yes, it does.

Look, the example isn't perfect, and very many simplifying assumptions were made in an attempt to make it understandable. Some of these assumptions tried to give as much of an advantage to the idea of magically making steam do useful work out of exhaust heat, as was possible.

Are there flaws with the example? Sure there are! It's necessary to perform integration to more accurately reflect what would happen with this example, which is beyond the capabilities of the casual reader. Could I do the integration? Sure, but to what point? It'd just show the same thing in the end, that water injection into spent combustion gases is a dead-end idea. It'd satisfy you, perhaps, but it'd make others only more confused.

Could an example model be rigged up such that it uses integration to arrive at a more accurate final state? Sure, but I'm not going to do it. Maybe the guy with the Bachelor of Science in Mathematics could give it a whirl.

In the end, the example tries to mix together an ideal process using the ideal gas law, with real-world properties of water. Something's gotta give.

Originally Posted by IamIan

I'm saying if you agree with either the ideal gas law or the principles it is based on ... than by confining the expansion of the steam in a limited volume container , as we have in this example ... than it follows from the ideal gas law and it's principles that the partial pressure of the steam must be higher than it would be if it's expansion were not restrained by the limited volume of the container ... to claim otherwise violates the ideal gas law and the principles it is based on.

And you're missing the point here. In the real world, there wouldn't be superheated steam in the same vessel as liquid water, at least not at the given example. It leads back to that whole idea of mixing a theory based on ideal properties of a gas, with real-world data about steam.

Originally Posted by IamIan

And as you already wrote previously ... we did compression work on the system from the outside when we added the liquid water.

And I also said the amount of work performed in compressing the gas by the addition of the water was so small as to be negligible. After all, you're talking about a compression of 1.025:1.

Originally Posted by IamIan

The steam we have is the result of the energy that will be transferred from the initial gasses to the liquid water we put in ... Who's adding more than that?

You're trying to, by going by the 1700:1 thumbrule, which has already been shown to be incorrect.

Originally Posted by IamIan

In this part you quote from me ... I'm claiming the amount of partial pressure from phase changing a given amount of liquid water to steam will be effected by how the limits of the volume it can expand into ... which is what the ideal gas law requires.

And you're neglecting the real-world properties of the water.

Originally Posted by IamIan

0.96g of liquid water + 0.04 grams of steam confined to a 600cc container will not have the same pressure if the same 0.96grams of liquid water + 0.04 grams of steam is confined to a 100cc container ... the pressure will also be different if the same 0.96grams of liquid water + 0.04 grams of stream is confined to a 10cc container.

You are correct, but not for the reason you think.

Did you consider that in each of your 600 cc and 100 cc and 10 cc cases, the water and steam will adjust to fit the volume dictated by the temperature of the system? In the 100 cc and 600 cc cases, the liquid will boil off to admit more steam into the vapor part of the system. The boiling off will absorb heat from the liquid water, causing the liquid to cool. The steam will also cool so as to maintain equilibrium temperature with the water. This will cool off the system as it goes to equilibrium, which will be at a lower final temperature. This follows the properties of saturated steam. The ideal gas law does not apply here.

Similarly, the steam, now at a much higher pressure in a 10 cc vessel than in the original 40 cc vessel, will condense out into the liquid. This releases latent energy of vaporization into the system, causing the temperature of the system to rise until the system again goes into equilibrium. Again, this reflects the properties of saturated steam, not the ideal gas law.

Originally Posted by IamIan

Although the ideal gas law shows this and requires this ... the mechanism for why this happens is easier to see in the kinetic theory of gasses ... although I don't see a need to go that far into the principles the ideal gas law is based on ... I think the ideal gas law should be adequate on it's own.

Sure, for an initial condition gas that we're treating as an ideal gas for purposes of an example.

Originally Posted by IamIan

And honestly ... I don't understand why you seem to be arguing against the ideal gas law here???

Because, like I just said, water and saturated steam do not follow the ideal gas law. There are saturated steam tables for this.

[SlideWRX]

Originally Posted by t vago

Yes, water injection will allow people to safely run with a leaner-than-normal charge mixture. Ordinarily, leaner mixtures tend to have slower burn rates, which would be handled in olden times by advancing the ignition timing. This would allow all of the usable heat energy to be turned into mechanical work. However, with today's cars, ignition timing cannot be adjusted. As a result, some of that otherwise available heat energy is left in the exhaust gas. This heats up the engine block more than normal, and if left unchecked, will create conditions that will cause engine destroying detonation and pre-ignition.

Water injection will serve to cool off the charge mixture to be burned in the engine. This will lower peak combustion temperature, and will move the engine away from detonation/pre-ignition conditions. For this reason, water injection is sometimes considered to be an anti-knock additive (another term for detonation is spark knock).

The bolded part is incorrect. Ignition timing changes are the heart & soul of the aftermarket performance industry. Even when you have a commuter car that the performance industry hasn't cracked the ECU, There are interception/replacement options for ignition timing. Part of the reason to use water injection is to advance the timing to get to Minimum Best Timing, the start of the range of ignition timing for a given operating condition that produces the most torque/power. Most turbo engines cannot hit MBT without knock, even with premium gas when under full boost.

Regardless of the timing, a lot of heat is lost to the exhaust. The data I've seen on operating engines says at light loads 30% of the thermal energy is lost to the exhaust and coolant *each*. Under heavy load, A higher percentage goes out the exhaust, because the cooling system generally hits a limit.

[drmiller100]

Originally Posted by t vago

Fixed it for ya.

no u didn't.

Personal attacks, and posts to "real world" discourage the good folks from trying to help.

Screaming loudly does not make you right.

[drmiller100]

Originally Posted by 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?

waiting.......

[t vago]

Originally Posted by drmiller100

this site has a LOT of tailgunners. Tailgunners are bar stool racers who discourage others from doing things - if someone were to do something, or TRY something, their lives would be less complete.

Originally Posted by drmiller100

Personal attacks, and posts to "real world" discourage the good folks from trying to help.

Originally Posted by drmiller100

You are an idiot. I bet you are an engineer.

Originally Posted by drmiller100

Screaming loudly does not make you right.

[drmiller100]

t_vago, I'm sorry for calling you an idiot.

I shouldn't have done that as it was mean.

[t vago]

Originally Posted by drmiller100

waiting.......

Originally Posted by drmiller100

You are an idiot. I bet you are an engineer.

Originally Posted by drmiller100

My education was more theory then practice, for which I am better suited. I'm trying to get one of the engineer types to help me with the practical side of things, but so far we haven't had a good engineer come along and run some numbers for us which reflects the reality of the experiment.

[t vago]

Originally Posted by drmiller100

t_vago, I'm sorry for calling you an idiot.

I shouldn't have done that as it was mean.

I am afraid I am unable to accept your apology. You've managed to insult all of the engineering types here with this thread, and with your DIY tricycle thread, and other places on this board.

We've tried to offer you help and constructive criticism and explanations as to how things work in the real world. So far, you've responded with a condescending holier-than-thou attitude, particularly in regard to us engineering types.

You need to do better than that.

[drmiller100]

Originally Posted by t vago

I am afraid I am unable to accept your apology. You've managed to insult all of the engineering types here with this thread, and with your DIY tricycle thread, and other places on this board.

We've tried to offer you help and constructive criticism and explanations as to how things work in the real world. So far, you've responded with a condescending holier-than-thou attitude, particularly in regard to us engineering types.

You need to do better than that.

I'm sorry engineers are taught to point out flaws and all the negatives in everything they see.

I'm sorry engineers are trained to copy the previous guy's work, and to never think outside the box.

I'm sorry my existence, thought processes, attitudes, attempts, and comments piss off educated degreed engineers to no end.

I'm sorry I have created many successful projects despite the best advice from oh so many engineers.

I'm sorry engineers can count the trees in a forest, but miss the importance of the raging forest fire on the horizon.

I'm sorry you think I am condescending with a holier then thou attitude.

I'm sorry for calling you an idiot, for you are an educated, licensed engineer who demands the full respect your continued efforts deserve.

[drmiller100]

Oh.

And I'm sorry my givea**** broke last week.