Vaporised Alcohol Injection

[Simpler=Better]

Tomorrow I'll finish grabbing a second set of manifold to play with, I'll be installing boost/intake temp/EGT/EGP sensors along with rebuilding the turbo.

As part of an independent study I am working with retrofitting existing diesels to use ethanol air stream injection to reduce diesel consumption/increase performance(in bursts). Why ethanol? Another student is working on a system for farms to make ethanol from waste silage, and this will tie in with it.



As for performance; why couldn't you add a nozzle to squirt alcohol/water into the exhaust PRE-turbo? This could in theory causing it to spool up on-demand giving you more off the line. Match that with injection in the air stream, and in theory you've got a nice little boost.

I was thinking of adding either one nozzle at the EGR port, or 5 evenly spaced along the manifold. I'll probably do both and record measurements, they call it a study for a reason, right?


As for fuel economy, we are assuming that the alcohol is homebrewed and around $0.75/gal worst case scenario


I need more holes in my project, so let loose with any/all comments!

Originally Posted by Simpler=Better

As for performance; why couldn't you add a nozzle to squirt alcohol/water into the exhaust PRE-turbo?

Because its horribly polluting to inject raw fuel into the exhaust. Injecting a cold liquid into a hot cast iron manifold is a great way to crack it.

Sounds like Simpler≠Better any more.

[Simpler=Better]

Originally Posted by ForcedInduction

Injecting a cold liquid into a hot cast iron manifold is a great way to crack it.

Ah, I kinda forgot about that. I guess I'll have to make a titanium one/buck up and do the VGT route for low end boost.

In my book, it counts as simple until a computer controls my engine(Long live Rube Goldberg!)

[h2odiesel]

I have to say I can't quite figure out what water/alcohol pre hot side turbo injection would do to increase performance, unless you are expecting spontaneous ignition. You might achieve that by injecting straight alcohol in sufficient quantities at moderate engine loads. As far as providing an economical performance boost I doubt it. It might be fun though. ethanol combustion is very clean,
C2H5OH + 3O2 → 2CO2 + 3H2O + heat
It might well reduce NOx emissions in diesel exhaust though that is already fairly low. Simple can often be better and more reliable. Personal attacks during a discussion often only expose ones limited thinking.

[argus445]

Originally Posted by h2odiesel

I have to say I can't quite figure out what water/alcohol pre hot side turbo injection would do to increase performance, unless you are expecting spontaneous ignition. You might achieve that by injecting straight alcohol in sufficient quantities at moderate engine loads. As far as providing an economical performance boost I doubt it. It might be fun though. ethanol combustion is very clean,
C2H5OH + 3O2 → 2CO2 + 3H2O + heat
It might well reduce NOx emissions in diesel exhaust though that is already fairly low. Simple can often be better and more reliable. Personal attacks during a discussion often only expose ones limited thinking.

It would make tons more sense to me to throw it in before where it can be burned. There really couldn't be any fuel economy improvements since your talking about the exhaust side by cooling it assuming it's not excessive would actually slow the turbine and cause less work to be done on the other end. Most turbo's do there best when pushed towards there max. safe limits cause they grow and fit more closely most one's i've seen.

Originally Posted by argus445

There really couldn't be any fuel economy improvements since your talking about the exhaust side by cooling it assuming it's not excessive would actually slow the turbine and cause less work to be done on the other end.

Exactly. The water would cool the hot exhaust gasses, significantly reducing the exhaust volume and the turbo's efficiency.

[h2odiesel]

I don't really have a dog in this fight. I just think it might be fun. I'm sure you've seen the homemade jets using turbos. The auto ignition temperature for ethanol is around 450C. If you were injecting straight ethanol in front of the hot side the gases would be expanding across the turbine. If you could manage the timing of the injection with regard to egt and back pressure it could really cut down on your spool up time!

Energy is absorbed to transform liquid into a gas.

You would be much better off having a 200psi tank in the trunk and using the compressed air to increase volume in the exhaust manifold.

[h2odiesel]

The whole concept is a bit bazaar, but if the exhaust temp were sufficient to ignite the ethanol >450C the small amount of heat absorbed at phase transfer would be insignificant. The problem would more likely be damage to the turbine blades or over speeding and surging. It would be an interesting few minutes though!

[argus445]

Originally Posted by h2odiesel

The whole concept is a bit bazaar, but if the exhaust temp were sufficient to ignite the ethanol >450C the small amount of heat absorbed at phase transfer would be insignificant. The problem would more likely be damage to the turbine blades or over speeding and surging. It would be an interesting few minutes though!

Yah they make Jet engines out of old turbos on youtube better to watch than to do. I think they use propane or something tho till it over-runs and makes a huge explosion and 250,000-300K rpm turbine blades come out at who knows how fast at you lol i can see one exploding coming thru the hood?
If you do make sure to video tape it for us.

[Simpler=Better]

I might not have been clear before: I would like to do alcohol injection into the air intake, with the nozzle(s) attached to the pressurized manifold(so not to risk damaging the turbo's blades)

The secondary injection part would be(theoretically) into the exhaust stream, pre turbo. The theory is that the exhaust gas is hot enough to ignite the alcohol, and create more pressure fueling the turbo. I see how it could cause damage to the manifold if too much was injected, or if it wasn't properly misted (I could see soot gumming up a nozzle pretty quick)

The idea stemmed from hearing about some race cars where they would drip gas into the manifold to maintain boost while off-throttle.

[KarTek]

On the intake side, you may be able to gain some power/efficiency by adding alcohol if it is properly vaporized, similar to adding propane. You would have to check the flash point and make sure it's not too high otherwise it can be pretty hard on the engine.

The downside of this is that the cost of the suplementary fuel usually offsets the gain in power/effeciency.

[Simpler=Better]

Originally Posted by KarTek

The downside of this is that the cost of the suplementary fuel usually offsets the gain in power/effeciency.

Yeah, but we're assuming that the supplementary fuel is being homebrewed from waste silage, etc.

Lets say you're supplying 20% on the go pedal; how much ethanol could you add to the intake before the octane raised to the point of non-combustion?

Thats a trial and error question, there is no answer.

Alcohol/methanol injection is known to work, just not very well in street applications (Drag racing and towing are different). I had a 50/50 water/methanol injection system pumping 300cc/min and I only gained 2hp at the wheels (dyno tested, there is a thread on it) and no significant change in MPG. I abandoned it since it was more hassle than it was worth.