water injection = Higher Efficiency?

[maxc]

Originally Posted by oil pan 4

The only other way water might be used to increase fuel ecomomy is to use steam in place of or in addition to EGR.
As far as I can tell no one here is about to do that.

Ive done that and increased engine power 10% with only steam on a na engine.

[mort]

Originally Posted by drmiller100

saturated does indeed follow ideal gas laws at higher temps.

Therefore, you are wrong.

Hello drmiller100,
No, the part of the steam table where the ideal gas law applies is where the steam is "dry" and at relatively low pressure. In the graph posted by t vago the blue dots are the percent error from an ideal gas. At the critical point the error is 330% But you can use the ideal gas law for supercritical steam at low pressures and accept some error. The error is away from gas properties (PV=nRT) and towards incompressibility where the volume is independent from pressure.

The problem I see with advocating for the gas law is that in terms of increasing efficiency it is a non-starter. If you want to use an ideal gas, inject air, or recycle exhaust or any other gas. All the increased power you get from the additional expansion is only equal to the amount of power it takes to pump the gas in against the pressure in the cylinder.

The putative advantage of water is that it goes from a very small volume liquid to a high volume gas. The power to pump the liquid into the cylinder should be less than the power you get back by it's expansion. This part works OK but only well below the critical temperature.
Above the critical temperature saturated steam is neither liquid nor gas. Liquid and gas properties are indistinguishable. The volume and pressure of the gas phase and liquid phase are the same. To put it in other terms, above the critical temperature compressing the "vapor" does not condense it to a liquid, and adding heat to the "liquid" does not cause it to evaporate.
Again, this is for saturated steam above the critical temperature.

However, below the critical temperature, even the phase change advantage is lost because the amount of energy as heat absorbed by the water as it expands into gas is larger than the amount of energy as expansion and pressurization due to evaporation. The phase change energy is only recovered by condensing the gas again.

Common combustion pressures run about 2 to 3 MPa and temperatures are around 2000 K. So using small amounts of water is a waste, assuming the water doesn't disassociate, it will be dry steam above the critical temperature and behave as an ideal gas. Using enough water to move into the saturated region is a waste because above the critical temperature (and below 22 MPa) steam behaves worse than an ideal gas. Adding enough water to move below the critical point is a waste because more heat goes into the phase change than you get from the expansive force, so the pressure of the water plus exhaust mixture is lower than if you hadn't added the water.

-mort

[UFO]

Thanks mort. It's refreshing to see justification and explanation for a position rather than "nuh uh".

[drmiller100]

Mort, Thank You.

What you write makes sense.

Again, I'm kind of slow, so I appreciate your patience in explaining things.

Lets say we inject enough "steam" into the intake stream to eliminate vacuum pumping losses, which I think we all agree are measurable and significant????

On the compression stroke, we are using the steam tables, and as the pressure goes up from 14 psi absolute to 140 psi absolute (assume 10:1 compression).

first, would the numbers really be 140 psi, or would some of the steam get compressed to liquid water, lowering the 140 psi pressure to something lower?

Second, when we hit ignition of the fuel air, temperatures would go up obviously.

If we have not reached the critical temps, some of the liquid would turn to vapor, causing the overall temperatures of the cylinder to be lower.

Lower absolute instantaneous temperatures means less losses to the cylinder head/piston.

When done, we lose less to the cylinder walls, perhaps with similar pressures.

Finally, a third argument. If we run steam, we can have higher effective compression ratios, yet limit oxygen.
Can we use steam to make a gasoline engine as efficient as a diesel engine - no throttle, so no throttle pumping losses, and full "compression" leading to higher absolute pressures upon ignition?

switching gears,
Perhaps another way to go about this all is to use cooled Exhaust gasses, and limit intake air by using exhaust gas, and again eliminate the throttle plate on the intake side.

[drmiller100]

I'm not following the disassociation arguments - even if we get the pressure and temp so high water disassociates, it will take energy to do that.

Then when the temps cool slighly as the piston heads down, the hydrogen will "burn" and recombine giving the energy back to the system. When done, that is all a wash.

[mort]

Originally Posted by drmiller100

I'm not following the disassociation arguments - even if we get the pressure and temp so high water disassociates, it will take energy to do that.

Then when the temps cool slighly as the piston heads down, the hydrogen will "burn" and recombine giving the energy back to the system. When done, that is all a wash.

Hello drmiller100,
Yep. If you add extra water the energy that disassociates it comes when the temperature in the combustion process is high, and the energy you get back comes at a lower temperature so you lose thermodynamic efficiency. So it's a wash less a little bit. In the real world this happens all the time, but the energy recycled through is immeasurably small and the lost bit is a small fraction of that.
While the decomposed water is in the mix it is just a couple of gases: ideal gas law for that fraction, so no benefit.
-mort

[bazman]

Has anyone actually injected water/meth in a 50/50 mix during lean burn cruise conditions then played with timing and mixture to see if the injection of the mix enables the engine to hold speed while leaning out further or more improves mpg from better timing?

Assume the water/meth is injected at over 100psi and calibrated to achieve a desirable and atomised flow rate.

If no one has actually done this (the video of the test earlier in this thread leaves too many variables open to question) I might. The meth in the mix may just add enough fuel to assist the lean burn at maintaining speed while leaning the fuel out.

[IamIan]

My appologise to everyone else for the length of this post.

Originally Posted by t vago

In other words... you have no clue about what humidity is?

I would not agree with that.

Originally Posted by t vago

You do not know anything about the law of partial pressures?

I would not agree with that.

Originally Posted by t vago

You admit to not knowing how gases behave in a mixture?

I would not agree to that.

Originally Posted by t vago

Is this what you're saying?

no

Originally Posted by t vago

You gave a specific temperature for saturated steam. You never specified anything else.

You took the position that nothing else had any influence at all on the expansion ... this position which I already said previously I think is a VERY bold claim ... because I think weather there even is expansion at all in the first place ... and then how much expansion there will be can be influenced by other factors of a context other than just temperature ... temperature is one of them but it is not the only possible influence.

Originally Posted by t vago

I quickly gave you the data for which you were so eagerly hoping to prove the steam tables to be wrong.

Incorrect.
That was not my hope... nor my intent.

Although I anticipated the odds were against it ... This is what I was hoping for ... even if the odds seemed greatly against it.

( You might realize that VERY bold claim was going a bit too far ... even if it was just breaking down in extreme cases like relativistic speeds or at the event horizon of a black hole ... or if the object doesn't have the volume to expand that much... etc. )

I don't recall ever claiming steam tables are wrong.

However ... I also don't think they give a 100% complete picture of all the influences and factors of every single part of or step of the entire process ... which I don't think they were ever intended to go that far ... In this case you assumed the 100C temperature as a final temperature and then used the steam tables to give you other answers ... The 100C assumption by itself is not particularly harmful in the simplification ... but to then turn a blind eye to the rest of the mechanisms has seemed to lead you away from those mechanisms ... as if they don't exist ... the steam table is a net result designed to be easier to to use than working out all the individual steps and influence mechanisms ... it does not mean all those steps and mechanisms aren't there , don't happen, or don't exist.

I have been talking about one piece of the mechanism ... one part ... and it is a mechanism that is clearly understood and well established in science ... even outside of the ideal gas law that you took the wrong way when I tried to explain it using that ... off hand , it is also well established in the kinetic theory of gasses as well.

Originally Posted by t vago

You're apparently saying there is no box in the world that's big enough to contain both liquid water and water vapor at 80 C. Did I read that right?

No.

I'm saying that if any box doesn't have enough volume for 100% of the unrestricted expansion of the liquid water to gas steam ... than it can't expand that much.

For example if 0.01g of liquid water would expand the 3306.1:1 ratio you indicated when it is not restricted by the limits of the volume of the container it is in ... than sure it will expand that much ... but if the container it finds itself in does not have enough volume to fit that much expansion ... than it can't expand that much.

The part I've written several times now ... it seems you keep skipping ... and I'll try again ... the energy that is responsible for that unrestricted expansion doesn't disappear if the container isn't large enough ... the force that pushes the molecules apart can be countered by a counter force of a container ... if the container is able to push back as much as the gas tries to push out in it's expansion than the expansion stops ... the energy what would have 'fueled' that expansion instead goes into other manifestations ... heat and pressure are common.

Originally Posted by t vago

So you did not actually say this?

That I wrote ... and despite several attempts to date at explaining your misunderstanding of it ... you continue to misunderstand... oh well.

Originally Posted by t vago

Or can you tell me the substantial difference between that statement you made above, and this one?

"since no gas exactly follows the ideal gas law, we can still treat steam as an ideal gas"

I've already done so several times ... but sure ... let me try again... but at this point I have extreme doubts you will correctly get my position this time after getting it wrong so many times already.

In your fictitious quote you change the claim to "we can still treat steam as an ideal gas" ... I didn't claim this ... I claimed the principles and relationships shown in the ideal gas law still apply.

Here is the difference to me between your incorrect impression of my position and my actual position.

#1> If I take a given amount of saturated steam in a piston ... and apply an external force to compress it into a much smaller volume ... this will result in an increase in pressure inside the piston ... this basic relationship between a change in volume and change in pressure which is shown in the ideal gas law will also happen if done to saturated steam ... I am not claiming it is a 1:1 exact match to what the ideal gas law would predict from just ideal gasses ... because it isn't ... it isn't an ideal gas , and there are other non-gas influences effecting the net results ... the interaction with the liquid water , etc... but basic relationship still hold.

#2> If I take a given amount of saturated steam in a piston ... and apply an external source of heat energy to raise the temperature of the system ... If the piston is not allowed to move the pressure inside the piston will go up ... again this is the same basic relationship shown in the ideal gas law ... and it is what will happen to the saturated steam ... and again as above it is not a 1:1 exact match to what the ideal gas law would predict from just ideal gasses... because it isn't just gasses involved , and the gasses that are involved aren't ideal... etc.

#3> etc ... continue the above #1 and #2 trends for all the basic relationships shown in the ideal gas law ... none will be 1:1 because it isn't just gasses and the gasses present are not ideal.

#4> the part about "since no gas exactly follows the ideal gas law" is not just about this case with saturated steam ... As I've tried to explain many times now ... What the heck ... one more try ... even if it might be winning the lottery type of odds ... liquid gasoline + air in a container with changing pressure and temperature will also not 1:1 exactly follow what the ideal gas law would predict from just ideal gases ... because again ... they are not just gasses ... and the gases we do have are not ideal ... there are other non-ideal gas law influences ... even if I used Hydrogen gas and Oxygen gas ... both being gasses would still not 1:1 exactly match what the ideal gas law would predict from ideal gases ... they too can auto ignite at certain temperatures and pressures ... and they two are not ideal gasses and they too have other influences.

#5> I am not claiming we can treat steam as an ideal gas ... as you wrote ... I am claiming the basic principles and relationship of the ideal gas law do still apply.... see above.

Originally Posted by t vago

Give me an explanation that substantially differentiates what you said and what I put in quotes.

See above.... not that I expect this latest effort of mine to make any better progress than the previous efforts ... but oh well.

Originally Posted by t vago

Show me the substance whereby you can justify your being offended.

At this point I doubt anything me or anyone else said would justify it to you ... you seem convinced you've done nothing wrong ... And I doubt anything me or anyone said would change that... but oh well.

#1> To me it isn't complicated ... if someone writes a quote and passes that quote off as coming from me or someone else ... I expect it as a quote ... to actually be a quote from that person ... if it isn't than it isn't ... If someone intends to incorrectly use quotation marks not to mean a quote but to mean something different ... than to me at the very least there should be some type of disclaimer before or after the incorrect use of the quotes to indicate that it is not actually a quote ... something along the lines of ... do you mean? ... or are you saying? ... which is not what you did either ... what you wrote to me clearly seemed to infer that the part in the quotes was a quote from me ... only it wasn't ... you made it up.

#2> You reaction to being caught doing this has been to go on the offensive ... when I first made the effort to politely tell you about it ... you come back not with an apology ... but by telling me to grow up ... as if all grown ups create fictional quotes about others like you did in that case... as if to infer that there must be something wrong with me because I pointed out your fictional work and I didn't like it.

Originally Posted by t vago

Include in your explanation that I explicitly stated you did not actually say the words that I arranged and placed in quotes, both in the post you responded to, and in this very post.

Yes after you made up the fictional quote and tried to pass it off as from me ... and after I called you on it ... and after you went on the offensive for me calling you on it ... yes ... then you admitted I didn't actually write that quote ... just as you then went on to claim that what I actually wrote was close enough to what you tried to pass off as what I actually wrote , so that you seemed not to seem any issue at all with the fictional fabrication you did or the way you presented it.

Even now you are still on the attack about it... continuing to try and put me down for calling you on what you did.

Originally Posted by t vago

What are you, some sort of politician now?

nope.

Although ... come to think of it ... you might do well at that yourself ... this whole divert attention from your errors by attacking the victim of your errors seems like a common tactic in politics.

Originally Posted by t vago

You also have faulty reading comprehension skills. I have explicitly stated that you did not actually say the phrase I put in quotes, both in that other post that you responded to, and this here post.

I am aware of that ... see above ... and yet your self justification and put down attacks to me continue ... as you seem to continue to try and defend the thing you did as if it wasn't really wrong ... and you seem to continue to try a diversion as if even if it was wrong there must be something more wrong with me for calling you on it.

If when I politely called you on it you just admitted the error and stopped there this part of the discussion would have ended there ... but no ... your attacks ... put downs continue.

Originally Posted by t vago

That you take offense to being paraphrased is rather remarkable.

It is not being paraphrased that I find offensive.
I was offended by it when you were not passing it off as paraphrasing ... then you only made that distinction after being called on what you did ... but you didn't just make that distinction ... you continue to go on the offensive about it... so you continue to be more offensive.

Originally Posted by t vago

It's called paraphrasing.

You might want to read your own link.
You missed the parts that describe what I wrote above about indicating the paraphrase... which you did not do.

a paraphrase is usually introduced with a verbum dicendi​—​a declaratory expression to signal the transition to the paraphrase. For example, in "The signal was red, that is, the train was not allowed to proceed," the that is signals the paraphrase that follows.

Notice Bellow I don't see any effort to do that at all.

Originally Posted by t vago

2. You're flat-out wrong about using "since no gas exactly follows the ideal gas law, we can still treat steam as an ideal gas."

Originally Posted by t vago

Give me the definition of saturated steam.

I might be wrong ... but it is my understanding that saturated steam means that the steam gas and the liquid water are both in thermal equilibrium ... or the steam itself which is in contact with the liquid water has not been heated past the phase chage point of the liquid water under those conditions ... sense the phase change point from liquid water to gaseous steam changes with pressure ... this can be at many different points ... be it 80C, 100C , 120C , etc.

Originally Posted by t vago

Okay. You're adding heat to a container containing both liquid water and saturated steam at a given temperature. So what?

I was trying to make the explanation in the entire point ... not each sentence of it.... see bellow.

Originally Posted by t vago

And at the end of the day, in your vessel containing both liquid and water vapor, if there's still liquid water present, then there's still saturated steam present! It doesn't matter what the temperature is (as long as it's below 373 C). It doesn't matter what the pressure is (as long as it's below about 22 MPa).

Once again you misunderstood.

The pressure is higher when the steam does not have enough volume in the container to expand into as much as it would have otherwise ... ie ... in the pressure cooker ... the pressure is lower in the open container that does not restrict the expansion of the steam.

The temperature of the still liquid water when it is at a phase change temperature already of 100C , doesn't go above 100C ... the reason the pressure cooker is able to get the liquid water hotter than 100C ... is because it is able to first increase the phase change temperature of the liquid water ... the phase change temperature changes with pressure ... The water also has a specific heat / thermal mass ... which means even after that minimum quantum of pressure energy needed to increase the phase change temperature point of the liquid water by ~0.1C ... the water can't instantly increase in temperature ... it still must first absorb enough thermal energy joules to raise the mass of the water from the old 100C phase change temperature up to the new ~100.1C phase change temperature before it can do any further phase changing of liquid water to gaseous steam.

The temperature increase follows after the increase in pressure ... because it is the increase in pressure that first changes the phase change temperature point of the still liquid water.

Originally Posted by t vago

I'm going to keep beating you over the head with this:

See above ... No harm to me ... there is a difference between them ... and your continued efforts at trivializing what you did or to attack me only serve to dish out more offense with no substance.

Originally Posted by t vago

Steam mostly does not follow the ideal gas law, and saturated steam definitely does not follow the ideal gas law. If you were to take saturated steam in a constant volume at 100 C, raise the temperature of that steam to 120 C, and then try to use the ideal gas law to guess the new pressure, then you'd definitely get a wrong answer.

See above for the distinction and difference you are missing here.

- - - - -

Although at this point , I still think the odds are better at winning the lottery than getting you to get my position correct.

I'll try again anyway.

Maybe I will have a bit more luck with your own calculations ... although I doubt it.

How much does your temperature only point of view show you the liquid water will expand in the 40cc example? ( Bold Added )

Originally Posted by t vago

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.

But how much room does the 40cc limited volume of the container allow for that liquid water to expand into gaseous steam? ( Bold Added )

Originally Posted by t vago

Let's look at that 0.04 grams of water that flashed into steam. It formerly occupied 0.04 cc of volume, but now it occupies the entire 39.04 cc of volume occupied by the gas, because it is itself a gas now. For that tiny amount of liquid, we just saw a 975:1 expansion factor,

hmmm ... by your own calculations ... temperature alone it should have expanded 1603.35 ... but it only had enough room in this limited volume container to expand to 975:1.

The context of the situation imposed a limit to the amount of expansion the phase change from liquid water to gaseous steam could do... this will have other influences on the system ... the pressure will go up ... which allows the phase change point of the still liquid water to go up past 100C ... the pressure's change of the phase change point happens before the water increases from the old lower phase change point ... heat energy from the initial hot gasses still trying to transfer to the still liquid water at that point are not creating more steam until they first raise the thermal mass of the remaining liquid water up to the new higher phase change temperature ... the steam tables would show a higher than 100C temperature and a higher pressure ... if we wished we could continue with the corrections even further we could also adjust the amount of joules of energy the initial hot gasses will transfer as the liquid water raises in temperature the temperature gradient reduces and less and less joules of heat energy will transfer to the still liquid water ... etc ... etc ... and as we said before continuing to try and make the model more and more close to real world can get more and more complicated with diminishing returns ... but the mechanisms of these changes are still there.

Just looking to a steam table and ignoring the mechanisms that are there I think should be done carefully ... especially to avoid overlooking these mechanisms and how they will effect the net results.

Each of the mechanisms / steps do not themselves disagree with the steam table nor prove it wrong ... they are why the steam table is what it is ... but by turning a blind eye to them you can end up misusing the steam tables ... beyond the scope of their abilities.

I suspect that is what has happened here.

[t vago]

Originally Posted by IamIan

At this point I doubt anything me or anyone else said would justify it to you ... you seem convinced you've done nothing wrong ... And I doubt anything me or anyone said would change that... but oh well.

Hey! If I would have wanted to falsely quote you, I would have used [ quote ] and [ /quote ]!

Originally Posted by IamIan

#1> To me it isn't complicated ... if someone writes a quote and passes that quote off as coming from me or someone else ... I expect it as a quote ... to actually be a quote from that person ... if it isn't than it isn't ... If someone intends to incorrectly use quotation marks not to mean a quote but to mean something different ... than to me at the very least there should be some type of disclaimer before or after the incorrect use of the quotes to indicate that it is not actually a quote ... something along the lines of ... do you mean? ... or are you saying? ... which is not what you did either ... what you wrote to me clearly seemed to infer that the part in the quotes was a quote from me ... only it wasn't ... you made it up.

Hey! If I would have wanted to falsely quote you, I would have used [ quote ] and [ /quote ]!

Originally Posted by IamIan

#2> You reaction to being caught doing this has been to go on the offensive ... when I first made the effort to politely tell you about it ... you come back not with an apology ... but by telling me to grow up ... as if all grown ups create fictional quotes about others like you did in that case... as if to infer that there must be something wrong with me because I pointed out your fictional work and I didn't like it.

Hey! If I would have wanted to falsely quote you, I would have used [ quote ] and [ /quote ]!

Originally Posted by IamIan

Yes after you made up the fictional quote and tried to pass it off as from me ... and after I called you on it ... and after you went on the offensive for me calling you on it ... yes ... then you admitted I didn't actually write that quote ... just as you then went on to claim that what I actually wrote was close enough to what you tried to pass off as what I actually wrote , so that you seemed not to seem any issue at all with the fictional fabrication you did or the way you presented it.

No. "Putting things within quotes" is not the same as passing something off as what somebody else said.

I've just reported you, by the way. This is getting to be ridiculous.

Originally Posted by IamIan

Even now you are still on the attack about it... continuing to try and put me down for calling you on what you did.

Hey! If I would have wanted to falsely quote you, I would have used [ quote ] and [ /quote ]!

Grow up.

Oh, and by the way - I'm done talking with you. You want to keep on arguing from ignorance? Fine. All I was saying re: saturated steam at a set temperature had a set pressure. You somehow managed to vastly obscure the issue, both by confusing dynamic and equilibrium conditions, and by getting your panties in a knot when I said you were mistaken by trying to tie the ideal gas law to steam tables.

Enough is enough.

[bazman]

Originally Posted by bazman

Has anyone actually injected water/meth in a 50/50 mix during lean burn cruise conditions then played with timing and mixture to see if the injection of the mix enables the engine to hold speed while leaning out further or more improves mpg from better timing?

Assume the water/meth is injected at over 100psi and calibrated to achieve a desirable and atomised flow rate.

If no one has actually done this (the video of the test earlier in this thread leaves too many variables open to question) I might. The meth in the mix may just add enough fuel to assist the lean burn at maintaining speed while leaning the fuel out.

Guys - though we appreciate the science - it'd be more useful to discuss what might work in a car on the road.

Let's get back to that. This thread has potential if we make this all real.

Again - has anyone played with timing and lean burn while injecting high pressure water/meth?

I've never found anyone that has yet. I've come across meaningless experiments, and those that have tried injecting straight water without a custom tune hoping the water would do something magical. But who has actually tuned mappable water/meth injection under lean burn conditions?

Anyone?


....I hear the sound of crickets lol

To me, the obvious thing to do is try it if no one has. My tuner can change my timing and air fuel to anything the engine can take, and the potential lean limits go up if we drop the O2 sensors.

My current water/meth is pre Throttle body and not mapped so I'd need to get an additional mapped version I can inject under vacuum and control the flow.

re the science of water and efficiency: The water does not NEED to add mpg directly - all it has to do is enable the engine to tolerate a leaner mix while maintaining enough hp to keep the car at the same speed. If water + leaner mix and optimized timing (and 50% meth to the water to aid combustion) all help the engine run leaner than it can without water/meth - THEN it will get more mpg.

Will the increase be enough to justify the added cost of the meth? Hopefully. Would the increase justify the cost of the injection setup itself? likely not - but if you run boost then that cost is justified for other reasons.

Thoughts?

I believe a 50/50 mix of water/meth MIGHT help and for me it is easy as I run that mix anyway and have a sizable tank in the trunk to store it. All I need is another water injection kit to supplement the one I have (or replace it if I can vary the flow from very low at cruise to very high at boost). I'd never run water all the time, only under boost or under lean burn conditions. My tune kicks lean burn in after 7-8 seconds of steady light throttle cruise, then off if I poke the throttle.