Thermodynamics review.

[Jon E]

I want to figure out how to calculate the intake charge temperature reduction for propane, water and nitrous oxide. Knock / detonation characteristics aside I still want to know how much each of these are reducing an intake charge temperature.

If my research is correct (please correct me if Im wrong) then:

Propane:
Vaporization temp= -44*F
Specific heat= .3885 cal/gram

Water:
Specific heat= 1.0 cal/gram

Nitrous:
Vaporization temp= -129*F
specific heat= .2098 cal/gram

If water has a caloric content 2.5 times greater than propane, will it require 2.5 times as much propane to have the same cooling effect as 1 unit of water? On average what is the volume of water or propane injected? (grams/min?) What about the latent heat of vaporization? Since nitrous and propane are already a vapor, will water absorb even more energy (temp) from vaporization in the combustion chamber? How do I calculate in the vaporization temperature for each?

Have any of you ever calculated this?

Or am I thinking about it way too hard?

 

[cool 84]

Can't help too much with the math but in the real world when the alky kicked in it knocked charge air temps down from 120 degrees to 70 degrees which was close to ambient.

 

[Turbo__Tim]

cool 84 has it right. He got his answer through measurement. That is the right way to go IMO. So many variables...

Cooling the intake charge with alchy/water mix reduces the volume of the water that would normally be in the air by converting (condensing?) this water content to tiny droplets. This allows oxyget to take it's place, leaning the mixture somewhat, and allowing the opportunity to add a bit more fuel to the intake. These water droplets, (and the water you added to the intake stream) are used in the combustion process as an agent to carry excess heat out of the cylinders, reducing hot spots that cause pre-ignition.

So alchy injection works as a 2 pronged solution. Allowing more oxygen in, and removing dangerous heat from the cylinders.

Propane does not cool the intake (in the vapor form that we use) rather it reacts with the fuel to insure a uniform burn. The result of this is a better controlled cylinder temperatures due to not leaving large amounts of un-burned fuel behind to 'pollute' the next charge with higher temperatures, and partially burned fuel.

As cool84 has done, the best way to find the intake temps is to measure them. Humidity and the percent (and type) of alchy in the mix will affect temperatures, so a temperature probe is needed for accurate results.

I'm not sure, but humidity as well as ambient temperature and intercooler type should affect nitrous intake temperatures. Of course the amount of nitrous injected would affect this as well.

As far as water reducing the intake temps nobody on tis board has injected pure water and measured this as far as I know. Pure water injection requires lots of pressure and several nozzles to get the super fine mist that the engine can ingest without flooding the spark. For reasons unknown, import guys have done this with success without the high pump pressures using the Aquamist system. I don't know why they can do this and we can't, but 50-50 mix seems to be the most water percentage run here, and that is by a very few, using 2 stage systems, and very high timing levels. Pure water, like alchy, carries heat and un-burned fuel out of the cylinders.

A lot of unanswered questions remain, I hope to have answered some, or helped out with some theory...

 

[cool 84]

This may be a little off topic.. I had a friend with a hotair GN that injected pure water upstream of the turbo. While going through school, this was his only option, he ran 87 octane and straight water, couldn't afford any more. On 87 octane the car would detonate at anything >7psi. With the water he could run stockish boost levels, ~13psi with no knock. I'm wondering if this worked because the turbo "misted" the water as it went through.

 

[DavzGN]

based on the numbers, it sounds like water injection and propane injection would be the best combination. Water for the best cooling and propane for the octane.

David
87GN

 

[Jon E]

Originally posted by DavzGN
based on the numbers, it sounds like water injection and propane injection would be the best combination. Water for the best cooling and propane for the octane.

Thats what Im thinking about doing. I dont see any reason why it wouldnt work as long as they are both used in small ammounts.

In this case shouldnt 1+1=2 ?

 

[mycarsucks]

There is another thread that we are discussing this in as well. Its called Propane AND Alcohol. Jay C mentions that it should be safe to do it. It sure looks like it could have some potential.

 

[Turbo__Tim]

Originally posted by cool 84
This may be a little off topic.. I had a friend with a hotair GN that injected pure water upstream of the turbo. While going through school, this was his only option, he ran 87 octane and straight water, couldn't afford any more. On 87 octane the car would detonate at anything >7psi. With the water he could run stockish boost levels, ~13psi with no knock. I'm wondering if this worked because the turbo "misted" the water as it went through.

cool 84 that is exactly why. Only thing is how long will the turbo hold up? Why don't we put our heads together and make a 'mister' for alchy systems. I was thinking of using the alternator as a power source. Have it power a gear box with step down gears to spin a fan blade really fast...

 

[DMan]

I used to inject water only - I found I could get up to 21 psi boost with a high timing chip before I ran into knock problems. I think if you have adequate fuel delivery you can probably go alot further than I did with just water.

 

[Turbo__Tim]

That's interesting! You are the first one I've heard that has done this. Did you use a powerfull pump and small nizzles to do this? What kind of timing was involved there?

It's not fair to tell us just that little bit

 

[DMan]

No problem..in fact I might even have some old DS runs stored.

I used the Shurflow pump with Aquamist nozzles. Injection pressure about 100 psi. I found I could get to about 21 psi with 4 large aquamist nozzles, before I started running out of fuel. Thats where the alky helps. Timing was high - I don't know the exact number but it was a Thrasher 108 chip. Sunoco 94 in the tank.

If you pore over some SAE papers on water injection, you'll find the cooling effect that comes from the water is equivalent to about 20-25 octane points, depending on the ratio of water to fuel (which is the main reason I think that if you're already doing water-alky, propane is irrelevant). Based on that, I figured I could get away with just water. Alcohol does seem to make the car 'angrier' though. Anyway I went to 50 lb injectors to try to prove that I could go just as far with only water, but electrical glitches got in the way of the proof, then I sold the injectors to Grumpy as part of the troubleshooting and ahhhh...yada yada.

So anyway I'm back to blue tops and 50/50 water alky. BUT, I would like to go to 55 lbers, perhaps even bigger and try just injecting water. I see a lot of people out there with big injectors and water alcohol. You need half as much gasoline as you do alcohol for the same BTU content. It wouldn't be a big deal to recalibrate for water only. I'd like to see some other people try to push the water-only envelope. [Stock fuel pump and stock injector-ed cars need not apply!]

 

[Turbo__Tim]

4 1 mm Aquamist nozzles is what aquamist reccomends, and is close to what others are using with 2 stage kits. To just cool with water requires atomization meaning a good pump and maybe .5 mm Aquamist nozzles.

When the Buick engineers tested this they used a 50-50 mix with methanol. This is why I think chasing a pure water injection is going to require a lot of work.

If you ever did get it to work, it would be very inexpensive, and the water would last a while between fill-ups.

I still believe propane/alchy will work for reasons already expressed. There is only one way to know for sure.

BTW I have gotten the electrical problem solved with my car. Finially! One of the interupter rings on the crank pully was bent, and just grazing the crank sensor. After running it that way for 5 minutes the heat build up on the sensor was causing it to fail.

Sheesh! One month of looking for that one...

Now it's time to try my little theory on combining the 2 systems. Should be interesting! Should know something by saturday night.

 

[DMan]

Originally posted by Turbo__Tim
4 1 mm Aquamist nozzles is what aquamist reccomends, and is close to what others are using with 2 stage kits. To just cool with water requires atomization meaning a good pump and maybe .5 mm Aquamist nozzles.

4 1mm nozzles huh? I wonder where they got that bit of engineering advice?

Here maybe?
http://www.aquamist.co.uk/dc/coollinks3/index/street/smdex/smdex.html

Click on the GN

Turbo_Tim, 2 questions: 1. Do you use Aquamist nozzles? The 1.0 nozzles atomize just fine. 2. Are you going to the Nats?

 

[bob86gn]

We really need to know the heat of vaporization the materials see, that is the heat absorbed (cooling the air) by changing phase from liguid to vapor. I left my chemical reference manual at work I can look them up tomorrow.

 

[Steve Hill]

for the vaporization of water I think the textbook answer is like 540 calories per gram (at 100C, naturally).
What is not usually considered, however, is the affect of more than one bar atmosphere on this process. This will make Dmans head hurt ;-)

 

[Turbo__Tim]

He he Steve, well said

Here is thread I found using vaporization as a search word. It's good to keep in mind that many of the topice discussed here have been discussed before. If you need information there is a wealth of it in the archives.

Look for Steve Woods' response here:

http://www.turbobuick.com/forums/showthread.php?s=&threadid=31021&highlight=vaporization

Dman- Yes I like the aquamist nozzles for the price, and the ease of tuning. I have no plans for the Nats yet, but I've been building up to going there for 3 years now. This might be the year that's all I can say right now...

Steve, it's always good to hear from you!

 

[DMan]

Originally posted by Steve Hill
for the vaporization of water I think the textbook answer is like 540 calories per gram (at 100C, naturally).
What is not usually considered, however, is the affect of more than one bar atmosphere on this process. This will make Dmans head hurt ;-)

Dman's head always hurts. And I think more atmospheric pressure means it requires even more calories to vaporize.

I think the real question now is how many Krispy Kreme doughnuts would you need to eat to match the calories required for vaporization of water injected into your turboBuick?

 

[Jon E]

Originally posted by Steve Hill
What is not usually considered, however, is the affect of more than one bar atmosphere on this process.

So the higher the boost, the more calories required to vaporize the water? Which equals a greater reduction in temp? How much is the vaporization temp raised for each bar?

 

[Steve Hill]

Jon, Dman, he he I posted that as a thinking exercise. Yes my head hurts too!
So lets exprapolate, and, remember we are talking about a phase change:
of course the boiling point is raised, but is the energy required to exicte the molecules into a gas also increased??

 

[Turbo__Tim]

My religion forbids extrapolation, exasperation, and other forms of self abuse. It's all there in the sixth commandment.

Keep it up and you will have to get glasses one inch thick to correct them crossed eyes!