water injection = Higher Efficiency?

[t vago]

Originally Posted by drmiller100

Could you point me to the page which says 17:1 is the max efficiency

Volume 2, Chapter 5, page 181, figure 5-7. The discussion begins on page 179, near the bottom.

Originally Posted by drmiller100

in all cases?

I didn't say that. You did.

[t vago]

Originally Posted by bazman

This guy uses colorful language at times and does not speak well of his competition, that aside he is allegedly a qualified mechanical engineer not just a mechanic... he uses a mechanical pump and his Rotarys make a lot of power with his water injection...

His videos do show a nice spray pattern. I'd love to see the pump.

[drmiller100]

Originally Posted by t vago

Volume 2, Chapter 5, page 181, figure 5-7. The discussion begins on page 179, near the bottom.



I didn't say that. You did.

the graph shows a CURVE. this means it changes depending on different conditions.

Further, never does the curve he shows get near 17 to 1 - max is about 16.6 to one.

Further, the book was written back in 60's before Lean Burn was used much. Lean burn gets you down 20:1 range, and is even more efficient.

Have a great day !

[mort]

Hi drmiller100,
So traveling back in time...

Originally Posted by drmiller100

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????

OK, for some numbers, imagine a 2.5 liter Otto cycle at 1500 rpm cruise, the air consumed is about 625 l/m and the volume swept by the pistons is 1875 l/m. To eliminate pumping across the throttle requires 1250 l/m of steam. The saturated steam table says that at 100 C. we can just get to 1.7 l/g. That gives us 735 g/m. The mass of air, 625 l/m is about 590 g/m. The fuel consumption is about 40 g/m. Without testing I can tell that adding 18 times more water than fuel will prevent ignition. If you deliver only as much water as fuel ignition will be difficult, and at that point you only reduce pumping by about 5% Water injection systems used to cool high boost engines often start misfiring at about 20% of fuel flow.
Anybody with a big water tank can try it, but I'm not hopeful that reducing pumping is achievable.

Also on this:

Originally Posted by drmiller100

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

Lower peak temperature reduces thermodynamic efficiency faster than it reduces heat loses through the cylinder walls. Higher compression ratios are more efficient, even though heat through the cylinder increases.
-mort

[IamIan]

Originally Posted by t vago

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

correction ... you did fabricate a fictional quote.
What your claims here of your personal preferred method of presenting a false quote doesn't change that.

Originally Posted by t vago

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

Incorrect ... that's why they are called quotation marks.

Originally Posted by t vago

This is getting to be ridiculous.

I agree ... you made a mistake ... it you stopped launching attacks as some kind of offensive method to justify yourself this needn't have gone past you just admitting your typo / phrasing error.

I see no good reason I should just sit by while you launch attacks at me ... I think it is reasonable for me to be able to present my own 2 bits in defense of myself against your continued attacks.

Originally Posted by t vago

I've just reported you, by the way.

Interesting ...
You fabricate a fictional quote ... and when I call you on it politely ... so far from where I sit your reaction to being called on what you did actually do has been: ( just off the top of my head )

• Insult me as a person for calling your on what you did.
• Justify what you did as not being wrong.
• Suggest something is wrong with me for take offense to you being offensive.
• Suggest there is not real difference between your fictional quote and what I actually wrote.
• Suggest something is wrong with me for not knowing what you intended was different from what you wrote.
• Try to incorrectly represent definitions of paraphrasing ignoring the grammatical distinction between paraphrasing and quoting.
• Try to suggest it is my fault for not knowing how you prefer to present a fictional quote.
• Incorrectly make claims about what quotation marks mean.

I think given the constant attacks and offensive you have been putting out ... that I have been responding to your attacks and offensive behavior in a reasonably civil manner to address the attacks you have been launching against me.

Originally Posted by t vago

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.

And I was saying that :
Like the pressure cooker ... if the volume of the container does not have enough room , so that it restricts the expansion of that steam formed to less than it otherwise would have been ... the pressure will go up in that container.

Which despite your resistance to the idea ... and your attacks and insults ... is exactly what happens.

You want to stop .. fine ... but ... if you continue to launch more attacks ... I think it is reasonable I am allowed to respond to your attacks.

[bazman]

Genius is always in action a wise man once said

[drmiller100]

Originally Posted by mort

Hi drmiller100,
So traveling back in time...


OK, for some numbers, imagine a 2.5 liter Otto cycle at 1500 rpm cruise, the air consumed is about 625 l/m and the volume swept by the pistons is 1875 l/m. To eliminate pumping across the throttle requires 1250 l/m of steam. The saturated steam table says that at 100 C. we can just get to 1.7 l/g. That gives us 735 g/m. The mass of air, 625 l/m is about 590 g/m. The fuel consumption is about 40 g/m. Without testing I can tell that adding 18 times more water than fuel will prevent ignition. If you deliver only as much water as fuel ignition will be difficult, and at that point you only reduce pumping by about 5% Water injection systems used to cool high boost engines often start misfiring at about 20% of fuel flow.
Anybody with a big water tank can try it, but I'm not hopeful that reducing pumping is achievable.

Also on this:

Lower peak temperature reduces thermodynamic efficiency faster than it reduces heat loses through the cylinder walls. Higher compression ratios are more efficient, even though heat through the cylinder increases.
-mort

Hi Mort,

Again, THANK YOU. At least now I have some idea how to go about figuring out some of this stuff.

And not to pick nits, but now that I have your numbers, I'm seeing 1.2 grams per liter for air, and you look like you are calculating 1.2 liters per gram? Which obviously makes the numbers even worse.

An interesting thing to consider is we are not adding 14 times as much WATER - we are adding 14 times as much STEAM.

Steam is an inert gas, already vaporized, just like exhaust gas in EGR systems is an inert gas.

I don't understand why the extra water/vapor would hurt anything?

Also, FWIW, no one said this has to be a total loss system, and as you pointed out earlier, burning gasoline produces water.

The water tank might not be nearly as big as you are thinking!

[bazman]

Allegedly - normally the engine will start to stumble if more than 20% by volume water is added as fuel. If that is correct and you add water at 20% by volume as fuel right through the driving range then you'd need your water tank to be no bigger than 20% of your fuel tank. I know Ricardo was supposed to get as much as 50%.... but you will have other problems if you start trying to maintain that kind of ratio - lubrication being one of them.

[IamIan]

Originally Posted by drmiller100

The above statement is probably true under certain conditions, but many more examples abound where it is untrue.

Just my 2 bits

Honda's Lean Burn in the Gen-1 Insight does go significantly above this ... been independently tested to go as lean as 25.8:1 ... I suspect Honda ICE engineers have a firm grasp on ICE engineering ... ie they wouldn't have gone that lean 25.8:1 as a peak or as lean as the 22:1 they have published for this engine as a more general case lean burn AFR ... if it was going to hurt net ICE operating efficiency.

While that by itself might lead someone to think that Honda's leaner lean burn is automatically evidence of leaner is better efficiency ... I would caution against that kind of direct leap... this specific ICE could very well be an exception to a more general ICE rule of thumb ... and there might have been other engineering motivations to design this than for higher peak efficiencies.

There are a variety of reasons they might have done that to improve the net operating vehicle efficiency ... some of them are for better conversion efficiency ... but better under specific conditions might not be the peak efficiency point for a given ICE .... or from another perspective ... it might be used as a method to mitigate other potential sources of low efficiency.

Raising the efficiency of a low efficiency point in the operating range for a ICE might still not be the peak efficiency point for that ICE ... thus the peak efficiency might not be increased ... even if the efficiency at a specific low efficiency point is increased ... or even if it allows for the net operating efficiency is increased.

Just because it allows for the net operating efficiency to be increased ... does not mean these leaner AFRs being run all the time would also increase the net operating efficiency over the entire ICE operating window.

In the Honda Gen-1 Insight case ... the ICE was designed for it ... AFR changes , the timing changes, V-Tech on/off, etc ... they didn't pick one thing for the whole ICE operating band ... they made a very dynamic system that can change the operating characteristics of the whole engine significantly ... and a lot of those dynamic changes they are making are happening fairly quickly ( by human standards ) and automatically in the background.

So while 17:1 AFR may or may not be the peak ICE AFR for highest net operating efficiency always for all contexts and conditions and for all straight gasoline engines ... unless you want to get a lot more complicated in a custom designed and built ICE with a more dynamic system ... it might be a good enough rule of thumb for a significant majority of most cases... which in this context of aftermarket mod of a OEM ICE , might not be a bad place to start.

[user removed]

My thinking is primarily around the idea that in order to see any benefit from water injection, the whole engine design would have to be altered to incorporate water injection under specific conditions, principally at loads that would exceed normal operation parameters.
This is what they did in the aero engines. War Emergency Power conditions meant life expectancies measured in minutes, sometimes even seconds. Remember these aero engines operated at altitudes where atmospheric pressures were less than 1/3 of that at sea level. Running two atmospheres of boost at 30,000 feet versus two atmospheres at sea level is a completely different scenario for power and engine life expectancy.
What I doubt it that there will be a combination of power, economy, and longevity, that any manufacturer would consider selling to the general public.
Now if you went with 16 to one compression on pump gas and supplied just enough water to stabilize combustion at WOT and max vacuum advance you may see a benefit, but the benefit would be a partial throttle openings when the actual in cylinder compression was significantly lower that the maximum available.
I think this is what Mazda is doing with the SKYACTIV engine technology, but instead of water they are using cooled egr to allow much higher compression ratios where part throttle loads can use valve timing and extra egr to minimise pumping losses.
I just wish they would spend as much time and effort at eliminating reciprocation losses.

regards
Mech