Alky & Air - mass flow velocity & energy calculation . . . . .

[Jerryl]

Some of you may think this is a waste of time , . . . . but if you read the whole thing you would at least appreciate my perspective . . . .
This all started with this thread . . . . . that got me thinking . . . http://turbobuick.com/forums/threads/wot-correction-off-with-alky.370524/

There is some good discussion/info in this thread with a few variables that have not been identified/confirmed/explained in my mind.

First off here are some definitions direct from Wikipedia;
- Flash point - The flash point of a volatile material is the lowest temperature at which it can vaporize to form an ignitable mixture in air.
- Boiling point - The boiling point of a substance is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid.
- Vapor pressure - Vapor pressure or equilibrium vapor pressure is the pressure of a vapor in thermodynamic equilibrium with its condensed phases in a closed system.
- Vapor - A vapor is a substance in the gas phase at a temperature lower than its critical point.[1] This means that the vapor can be condensed to a liquid or to a solid by increasing its pressure without reducing the temperature.

So . . . based on the definitions and some simple physics, I set out for some review and came up with some “General” Facts:
· Cooler temps at constant pressure have an effect on the required time for vaporization of any liquid.
· Boost pressures raise the boiling temperature of ANY liquids.
· Too much alky with insufficient “heat” under XX pressure will results in a wet flow condition.
· The intake design is not conducive to “wet flow”.
· Air has a LOT more mass than we sometimes think about.

With these, I decided to do some quick calculations (Just for my own appreciation);
Say you have a (XXX) HP car . . . . . . what is the calculated air velocity through the stock IC TB in (XX) mph?
Why would I care you ask? Ever seen it rain in a hurricane or drive through the rain at 70 MPH? Now, think what happens with “wet flow - mass” at that velocity.
Again . . . the velocity through the stock TB for the listed HP is calculated at:

300 HP – 47 MPH
400 HP – 62 MPH
500 HP – 78 MPH
600 HP – 93 MPH

Now . . . on a 600HP set-up, you need about 60lb/min of air, and if we add mass (alcohol) to it. . . . . . we are feeding the motor +6 lbs a second (Air and meth) whish travel at +90 mph.
Let’s put this in perspective;

A baseball weights 5 1/8 ounce (0.427 lb) . . . We are feeding 14 times the weight of a baseball/sec, at +90 MPH! . . . . Think of the force required to change the direction of the inertia!
Oh . . . . 600 HP car . . . . through a 2” tube (Up pipe), the air velocity is 117 MPH.

The kinetic energy of the mass/sec = ½ MV^2 = ½ x 6lbs/sec x 90MPH^2 = ½ x 2.72 kg x 41.5^2 m/sec = 2.34 KJ = 1733 lb.ft of torsional force!
I had to do it twice to make sure I had the number correct . . . . .

Although this cacluation is inconclusive to the experienced condition(s) in the listed thread, it is interesting if you think of air and fuel traveling at mph and trying to make the turn . . . . .
Anyway . . . although Grumpy, Razor, Bison, Turbofabricator, Paul, etc . . . have already proven this to be a mute point , it is the start of “my” hypothesis . . . . .


.

 

[bison]

Great thread. Most won't understand all this but it's very obvious the effect overinjecting with too low a temp into higher intake velocities. Time to start blocking the intercooler to keep charge air temps high enough to vaporize the injected methanol.

 

[Jerryl]

Great thread. Most won't understand all this but it's very obvious the effect overinjecting with too low a temp into higher intake velocities. Time to start blocking the intercooler to keep charge air temps high enough to vaporize the injected methanol.

I have a simple idea how to resolve part of this challenge . . . .

 

[ZNix]

Very interesting.

 

[kidglok]

can we use a bottle heater on the alky tank?

 

[Jerryl]

Well . . . more calcs.
A typical Air/Air IC is about 60-70% efficient.
I am going to use 75% because of all the $$$$ spend on the IC’s.

Boost pressures raise charge temp at 11F / 1 lb boost.
Lets look at the temps before / after IC at typical boost pressures with alky (23 PSI)

If we study this model you will see that we made some assumptions.
The assumption is that the IC efficiency is constant with temp changes, and results in linear temp changes.
So, we also see that at 10F ambient, the charge temp out of the IC is still around 70F.
This the temp that the meth is initially exposed to . . . . and this happens at some volume of air that will put most vacuum cleaners to shame. (LOL!)

The temp after the methanol will drop significantly if the charge temp is high.
My real life data collection shows about 40-45% temp reduction on a non-IC’d set-up.
The better the IC, the less the delta temp.

Ambient - 50
Boost -23
IC Efficiency -75%
Charge temp Before IC -303
Charge temp after IC - 112

Ambient - 40
Boost -23
IC Efficiency -75%
Charge temp Before IC -293
Charge temp after IC - 102

Ambient -30
Boost -23
IC Efficiency -75%
Charge temp Before IC -283
Charge temp after IC - 92

Ambient - 10
Boost -23
IC Efficiency -75%
Charge temp Before IC -263
Charge temp after IC - 72

 

[bison]

It should be noted that the air speed through the engine is relative to the displacement and speed of the engine. Not necessarily the power.

 

[Jerryl]

It should be noted that the air speed through the engine is relative to the displacement and speed of the engine. Not necessarily the power.

Bison,
Absolutely correct!

Spoke to my one of my engineering managers . . . long shot and probably will not happen . . but . . .
If someone on this board is willing to complete a 3d drawing of the intake, we will run a complete CFD and I promise to publish it.

 

[kidglok]

so if the flash point of methanol is 52*F, and in 10* ambient conditions, the charge temp after the IC is still 72*, which mean the IAT shouldnt affect the atomization of the alky.

correct? what am i missing here?

 

[bison]

so if the flash point of methanol is 52*F, and in 10* ambient conditions, the charge temp after the IC is still 72*, which mean the IAT shouldnt affect the atomization of the alky.

correct? what am i missing here?

You aren't getting full vaporization period. Not even close. The manifold pressure will further Increase The vaporization temp. If it's 10* you charge air temp isn't going to 70* unless you have really poor heat exchange anyway. Furthermore the latent heat of vaporization if the methanol is so high that it will drop the temp so rapidly it will work against itself if over injected.

 

[Jerryl]

so if the flash point of methanol is 52*F, and in 10* ambient conditions, the charge temp after the IC is still 72*, which mean the IAT shouldnt affect the atomization of the alky.
correct? what am i missing here?

When the methanol flashes, the temp will drop.
What the temp drop is depends on many factors; Pressure, air flow, temp, methanol volume.

When the temp drops, “if” the pressure is constant, there is a chance of fuel drop-out.
Razor stated that a low 11 sec car uses about 1oz/sec. . . . . (Something like that . . .)

“IF” you can vaporize ALL the methanol, the calculated temp drop is around 110F.
This all theoretical . . . . because the temp can not drop below xxF.
At 300F you can drop the temp much futher than ar 120F.

So how much can you spray? Don’t know . . . that depends . . . . . but you should spray just enough to get to . . . . huh, say 60-70F (Gut feel) . . . . I pulled that number out of the air . . . . I am sure someone will prove me wrong, which would really be cool.

 

[bison]

The most powerful my car ever was with alky injection was in 95* air with a 50 shot of N2O. Charge air temps were in the 60's-70's

 

[kidglok]

so what would be a better way of measuring the volume of alky injected?
measuring the pressure, or the amount of iat reduction?

 

[big reazon]

So what ambient temp is too cold to use alky?

 

[kidglok]

ive run it in 50* weather, but i was only making high 11 sec power at the time

 

[tonka]

So what ambient temp is too cold to use alky?

Ambient temp isn't really the issue, the temperature/pressure conditions existing within the intake, with methanol present, is what can get you into trouble

 

[murphster]

After reading some of this I decided to actually read up on some of the science of what is going on and have provided some links for reading.

First off, the most important thing we are dealing with here is atomization. This is the process by which the liquid methanol is spread into tiny droplets, an aerosol. The boiling point of methanol is 149F, so we are not dealing with vaporization. The flash point has to do with flammability and not with the methanol distribution.

The most important factors affecting atomization is the nozzle size and design along with the pressure and velocity of the fluid coming out of the nozzle. Too big of a nozzle will create larger droplets and less atomization and smaller nozzles will produce smaller droplets and hence better atomization. However, increased flow requires larger nozzles so there is a balance between nozzle sizes and flow for a given application. Increased pressure and velocity will produce smaller droplets and better atomization but the droplets will stop becoming smaller after a certain pressure so there is no benefit in running even higher pressures past this saturation pressure for a given nozzle size.

The temperature affects the surface tension of the liquid and hence the atomization, but this seems to be relatively minor in comparison. A change from 32F to 90F changes the surface tension of methanol by about 10%.

Atomization gets better with an increase in the pressure of the gas it is being introduced into, in our case boost. Introducing a low pressure liquid into a very high pressure gas will atomize it on its own, but this would take higher pressures than the boost we run. Heating the liquid to just below its boiling point will increase atomization at lower pressures. For methanol that would be 149F. Maybe this could be doable but it would only be needed for low pressures or very large nozzles to see any benefit.

I read through a lot of papers and documents trying to see the effects of temperature and atomization. All I found were some references that the effect is relatively minor and mostly mentioned the surface tension, which is why I tried to give a number to it above. With all the papers on atomization, water injection, etc I don't any mention of a liquid being atomized and then it being reversed (puddling) due to colder ambient temperatures. If anything, the temperature of the methanol has a larger effect and even that is minor.

The biggest factors are the nozzle size and pressure and any puddling present would likely rise from having too big a nozzle and/or too low of a pressure. This leads me to believe potential problems from alky/meth injection come from two areas: 1) Not enough pressure and 2) Too lean of an A/F ratio. Number 1) can be caused by quite a few different things as I've encountered all of them over the years. The most likely suspects are a leaking pump or lines. I've had both multiple times and my pressure tester has confirmed the lost pressure in the lines resulting from leaks. This low alky pressure leads to both less atomization (poorer distribution) and less alky flow which can obviously be harmful. Another source of low pressure can be the alky bottle cavitating under high acceleration. I saw this when I started logging alky pressure. Filling the tank to the top between runs cured this. To help prevent this I rotated my alky tank so that the drain line is now facing the rear and will log the results soon. A final source of low pressure is failure to prime the alky pump within a reasonable amount of time before a WOT run. Alky pressure logging shows a considerable amount of time to full pressure if the pump has not been primed or run before WOT. These low pressure situations are all potential sources of failure and my alky pressure, A/F, and knock on my logs clearly show this.

Too lean of an A/F ratio, Number 2), can happen as the cars gets faster and richer A/F ratios are not used as the amount of methanol being injected goes up. Another debated topic that can come into play is the thought that #1 becomes the weak link in the stock fuel supply setup with the #1 injector being the last stop in fuel delivery line while also being next to the inline fuel regulator. After having issues with #1 leaning out a few years ago I went to an external regulator and a dual fed fuel rail setup and have gone much faster with no issues since. I can't say 100% that it was the solution but I've definitely ruled it out.

Here are some links to info on atomization:

A good introduction to atomization
-http://www.elliottequipment.com/ask/ATOMIZ_1.PDF

A more detailed study
-http://w3.wtb.tue.nl/fileadmin/wtb/ct-pdfs/Master_Theses/Master_Thesis_CEMIL_final.pdf

A good decription of water injection and effects of pressure
-http://downloads.hindawi.com/journals/jc/2012/718202.pdf

Some relevant atomization info of similar nozzles and pressures that we run
- http://pakjas.com.pk/papers\447.pdf

Surface tension vs temperature for methanol
-http://ddbonline.ddbst.de/EE/110%20SFT%20%28Surface%20Tension%29.shtml

 

[we4Mateo]

Great stuff

 

[kidglok]

arite, im throwing in the towel

gonna leave the damn knob on 6 untill it knocks, then i'll move it to 7

 

[bison]

After reading some of this I decided to actually read up on some of the science of what is going on and have provided some links for reading.

First off, the most important thing we are dealing with here is atomization. This is the process by which the liquid methanol is spread into tiny droplets, an aerosol. The boiling point of methanol is 149F, so we are not dealing with vaporization. The flash point has to do with flammability and not with the methanol distribution.

The most important factors affecting atomization is the nozzle size and design along with the pressure and velocity of the fluid coming out of the nozzle. Too big of a nozzle will create larger droplets and less atomization and smaller nozzles will produce smaller droplets and hence better atomization. However, increased flow requires larger nozzles so there is a balance between nozzle sizes and flow for a given application. Increased pressure and velocity will produce smaller droplets and better atomization but the droplets will stop becoming smaller after a certain pressure so there is no benefit in running even higher pressures past this saturation pressure for a given nozzle size.

The temperature affects the surface tension of the liquid and hence the atomization, but this seems to be relatively minor in comparison. A change from 32F to 90F changes the surface tension of methanol by about 10%.

Atomization gets better with an increase in the pressure of the gas it is being introduced into, in our case boost. Introducing a low pressure liquid into a very high pressure gas will atomize it on its own, but this would take higher pressures than the boost we run. Heating the liquid to just below its boiling point will increase atomization at lower pressures. For methanol that would be 149F. Maybe this could be doable but it would only be needed for low pressures or very large nozzles to see any benefit.

I read through a lot of papers and documents trying to see the effects of temperature and atomization. All I found were some references that the effect is relatively minor and mostly mentioned the surface tension, which is why I tried to give a number to it above. With all the papers on atomization, water injection, etc I don't any mention of a liquid being atomized and then it being reversed (puddling) due to colder ambient temperatures. If anything, the temperature of the methanol has a larger effect and even that is minor.

The biggest factors are the nozzle size and pressure and any puddling present would likely rise from having too big a nozzle and/or too low of a pressure. This leads me to believe potential problems from alky/meth injection come from two areas: 1) Not enough pressure and 2) Too lean of an A/F ratio. Number 1) can be caused by quite a few different things as I've encountered all of them over the years. The most likely suspects are a leaking pump or lines. I've had both multiple times and my pressure tester has confirmed the lost pressure in the lines resulting from leaks. This low alky pressure leads to both less atomization (poorer distribution) and less alky flow which can obviously be harmful. Another source of low pressure can be the alky bottle cavitating under high acceleration. I saw this when I started logging alky pressure. Filling the tank to the top between runs cured this. To help prevent this I rotated my alky tank so that the drain line is now facing the rear and will log the results soon. A final source of low pressure is failure to prime the alky pump within a reasonable amount of time before a WOT run. Alky pressure logging shows a considerable amount of time to full pressure if the pump has not been primed or run before WOT. These low pressure situations are all potential sources of failure and my alky pressure, A/F, and knock on my logs clearly show this.

Too lean of an A/F ratio, Number 2), can happen as the cars gets faster and richer A/F ratios are not used as the amount of methanol being injected goes up. Another debated topic that can come into play is the thought that #1 becomes the weak link in the stock fuel supply setup with the #1 injector being the last stop in fuel delivery line while also being next to the inline fuel regulator. After having issues with #1 leaning out a few years ago I went to an external regulator and a dual fed fuel rail setup and have gone much faster with no issues since. I can't say 100% that it was the solution but I've definitely ruled it out.

Here are some links to info on atomization:

A good introduction to atomization
-http://www.elliottequipment.com/ask/ATOMIZ_1.PDF

A more detailed study
-http://w3.wtb.tue.nl/fileadmin/wtb/ct-pdfs/Master_Theses/Master_Thesis_CEMIL_final.pdf

A good decription of water injection and effects of pressure
-http://downloads.hindawi.com/journals/jc/2012/718202.pdf

Some relevant atomization info of similar nozzles and pressures that we run
- http://pakjas.com.pk/papers\447.pdf

Surface tension vs temperature for methanol
-http://ddbonline.ddbst.de/EE/110%20SFT%20%28Surface%20Tension%29.shtml

You still need vaporization. Like I already mentioned you aren't getting 100%. There isnt enough heat there and too much pressure to get 100% but you better be getting some or you're going to be in trouble when you start making a lot of power. Atomization is very important because a higher surface area of the injected liquid is exposed to the air stream and will heat faster since it's not insulated as much by surrounding liquid. The atomization is the same when I inject 20gph at 100* as it is if I inject 20gph at 60* through the same nozzles. the big difference at 100* charge air is a much higher % vaporizes and is part of the air stream. I would not even try to run my 80* alky tune at 40* in an 800hp engine. I know the result and it isn't a good one. High temps will tolerate a higher volume since more becomes a gas and the mass flow of the engine is less so it will tolerate more timing too.