[AnArKey]

Yes, I know, AnArKey is at it again.

This isn't a crazy idea, rather a borrowed one. It's pretty viable, and proven.

Basically it's having a evaporative liquid introduced before the compressor. In industrial uses (generators), it's water. For my case, methanol.

The idea is to intercool the compressor itself.

When the compressor is making boost, it's automatically making heat as a result of building pressure. Pressure acts to increase density, heat acts to reduce it. Two forces, fighting each other.

Quick lesson, term: density ratio: The relative density vs volume of air on opposite sides of the compressor, inlet vs outlet. This isn't the pressure ratio, this also takes into account the effect the temperature has upon the air.

Now if there is a liquid present in the air stream, that will vaporize as compression takes places, preventing most (maybe all) of the temperature rise, the compressor isn't having to work so hard. The density ratio, improves by over 35% by keeping the air cool during compression.

What this means is the same compressor wheel (ie turbo size) is able to make a LOT more peak power. The downside is you may wear the compressor prematurely. Also, I wouldn't try it with methanol on a car with a intercooler. I'm going to run without a IC, so that's not a concern to me.

I think it's mostly a matter of delivery. I'm sure there are some who tried shooting stream of tap water into their compressor blades and noticed wear. But methanol with a lower viscosity, far faster evaporation rate, and delivered in a fine mist, the wear rate should be low to non-existant. I have spoken with one individual who has done it and not had any major problems with it. If I wear the compressor, no big deal, they are like $75 for a new one.

Secondly, some of the methanol will vaporize before entering the compressor. In my experience, a ample supply of a fine methanol mist in a rapidly moving column of air produces near freezing temperatures, even with 90F incoming air. Compressors are rated for 25C air. By having the inlet temperature at near 0C, you have a ~10% increase in flow right there. This in in addition to the gains of "wet compression" described above.

You don't have to be the first to try it either. I'll do that. If I can get 650-700RWHP out of a compressor rated to max out at 550RWHP, that should be proof enough right?

Feel free to read around about wet compression. It works.

http://www.combustion-net.com/media_centre/2003releases/030712-cogen.htm

http://www.caldwellenergy.com/wet_compression.htm

 

[Syed Shah]

Why could it not be used on an intercooled car? This would rule it out for most of us. I would not like the idea of running without a FMIC.

Thanks

 

[Ubermensch]

Why could it not be used on an intercooled car? This would rule it out for most of us. I would not like the idea of running without a FMIC.

Thanks

I would imagine that the tortous nature of the airpath and the cooling effect would tend to condense vapor out of the airstream.

 

[kale]

what kind of flow are you looking at introducing into the compressor though? last i heard on this subject, flow would have to be of a MUCH higher volume than that of a standard MW kit, ie, good only for short periods of time before refill, or run off a HUGE tank in the back?

 

[Ckanderson]

Some Volvo guy sprayed water in before the turbo, for the cooling effect. i saw the distruction photo's, for some reason metal blades spinning at 140,000 rpm dont like water droplets, or anything liquid for that matter. I wouldent do it....

 

[Ray745]

I know the idea is patented, by Dow I believe, so I dont know what that does to any plans you had of possibly selling a kit like this if it works in the future. I've never invented anything or dealt with patents in any way so I'm not sure what that means for you, but I believe the patent deals with large turbine applications, not with cars so there may be something you can do with that. Either way good luck with this, and screw the nay-sayers

 

[AnArKey]

Syed Shah, your question was answered almost perfectly by Ubermensch. However, you could use a much smaller total flow rate and use water and be ok. You won't get as much of a boost, but it will be there. For those with hot summers, it can be a real boost.

kale, yes it will require a fairly high flow. About double the current high flow kit, and would nessitate a much more precise control over the injection rate. Still, a 5 gallon tank should be more than enough.

Ckanderson, yes that's exactly the kind of story I hear. What I don't hear, is what pressure, spray pattern, droplet size, and flow rate compared to compressor flow was he using? If you use a stream of water, uncontrolled (on/off), you will certainly cause damage. How much and in what manner it's injected makes a huge difference.

Ray745, I doubt doing this will have any coorelation to wet compression techniques on power generators. Sure the science translates, but the application is so distant I won't be breaking any patents.

One thought, I have heard of some compressors being made of titanium instead of aluminum. Titanium being a LOT harder than aluminum, would probably remove all fears. Maybe I'll inquire at Garrett what compressors are available in titanium.

 

[91T4]

You have an interesting idea, however, I do not think it is possible to bypass the premature wear of the compressor wheel. As you well know, the compressor is spinning at 140,000+ rpm, and is at extremely high temperatures. Providing a methanol/water mist will drastically lower compressor wheel temperature, and since you are doing this in an 'on and off' way, you are shocking the system-heat cycling.

 

[AnArKey]

Most of the time (idle, cruise), the compressor is operating under no compression. Just free spinning. Under these conditions it's pretty much at or close to the incoming air temperature. When it starts to make boost, it goes from ambient temp at the compressor blade tips, to over 300F at the bottom of the wheel where it's throwing out compressed air. That's a pretty serious and sudden change in temperature, and that's how a turbo normally operates.

With pre compressor methanol injection, it will actually reduce the temp change, and total delta T from the top to the bottom of the compressor. In other words, it shouldn't be a factor.

 

[silvino]

The methanol won't wear on the wheel, housing or get into areas that are lubricated like into the center cartridge? Fine mist or not, I'd be worried that it'll still wear away.

I look forward to see how it goes, especially if it works .

 

[ThomsonCharm]

Syed Shah, your question was answered almost perfectly by Ubermensch. However, you could use a much smaller total flow rate and use water and be ok. You won't get as much of a boost, but it will be there. For those with hot summers, it can be a real boost.

kale, yes it will require a fairly high flow. About double the current high flow kit, and would nessitate a much more precise control over the injection rate. Still, a 5 gallon tank should be more than enough.

Ckanderson, yes that's exactly the kind of story I hear. What I don't hear, is what pressure, spray pattern, droplet size, and flow rate compared to compressor flow was he using? If you use a stream of water, uncontrolled (on/off), you will certainly cause damage. How much and in what manner it's injected makes a huge difference.

Ray745, I doubt doing this will have any coorelation to wet compression techniques on power generators. Sure the science translates, but the application is so distant I won't be breaking any patents.

One thought, I have heard of some compressors being made of titanium instead of aluminum. Titanium being a LOT harder than aluminum, would probably remove all fears. Maybe I'll inquire at Garrett what compressors are available in titanium.

I believe it is Innovative Turbos that use an Inconel Exhaust Wheel and Titanium Compressor wheels.

Their website is: http://innovativeturbo.com

Check them out I hear they use some very durable stuff on their turbos and for street use too not just Diesel.

Good Luck with your tests. I can relate with your constant "Mad Scientists" ideas as I do the same thing all the time. Just keep on experimenting and one of these times im sure youll find something useful that someone either never thought about or most likely never even bothered to experiment with. So keep on keepin on

 

[SlowEclipseGS-T]

I have a friend who used a coarse water mist into the compressor of a stock turbo'd 1G DSM, in an effort to create a crude water injection system. It didn't kill his turbo, but that might be because he only used it a couple times, since it caused him to not be able to hit any real boost numbers. He was usually running about 18 psi, but with the water going into the compressor, he couldn't get it over 10 psi.

 

[ama0787]

are you sure the methanol wouldnt combust before it did its job of cooling?

 

[earl3]

Aussie rotary owners have been doing this for years with good results. Talk to RICE RACING on rx7club.com and go for it!

 

[AnArKey]

SlowEclipseGS-T: Nice story, but I don't think those results can be used to make any conclusions really. Too many unknown factors, mainly the air: water ratio. If it was too high, which it certainly sounds like it was, it would explain the drain on the boost. Also, was he monitoring the air intake temps? It was possible he was making as much air at 10psi as 18psi before, and was just maxing out that tiny turbo at a different point on the compressor map.

ama0787:

Yes, a intake backfire is possible, but not very probable. As a comparison, consider your average carbed engine. It is constantly driving with a near stoich mix of gasoline and air in the intake. Also note that there are old turbo cars with a "draw through" carb, meaning a carb in front of the turbo, where this mix passes through a turbo.

In comparison, my application will use methanol, which has almost a FAR higher ignition temperature (867F vs 496F for gas). The methanol:air ratio going in will also be far less than stoich, varying from 20:1 at activation, to about 12:1 at full boost, which is still half that of stoich. Methanol is not ignitable until there is a 7.3% volume concentration. At half stoich, it will be at aprox 6.5%, under the flammability limit. Only going to use enough to keep the process cool. Also consider the methanol will only be going into the turbo at WOT, 95% of the time the engine is running the methanol is totally off. Lastly, I'll probably add a little bit of water to the mix (10-20%), which significantly reduces the ignitability. You could probably have a open flame in the intake and it wouldn't fire, not that I would suggest trying that.

Basically, it's 10x less likely to suffer a intake backfire as any given carbed car.

earl3: I think I'll do that. Thanks for the info.

 

[John H]

Ok, all this talk about injecting methanol might spook some people, so I have an easier way to test this compressor cooling theory.

*Keep in mind this is by no means has the same overall goal of injecting methanol, but it would help prove the theory.*

What if you introduced nitrous oxide into the air path before the turbo? A relatively small shot - say 30-50hp worth. This should cool down the compressor well below what water or methanol could do. It should be vastly safer to the compressor than water or methanol because it's introduced as a gas, not liquid. If this should provide a 10+% gain as Derek suggested, why does everyone introduce nitrous oxide well after the turbo? Obviously the setup before the turbo would be dry (just nitrous oxide) with fuel being added later.

Would spraying a dry shot of nitrous before the turbo pose ANY negative effects at all? Of course keeping in mind that a proper amount of fuel would be added after the turbo of course (possibly through the injectors themself). And say if the nitrous was introduced BEFORE the MAF or IAT, would the ecu help by adding fuel on it's own? Obviously not enough fuel on it's own as nitrous oxide has a higher percentage of oxygen, but still - it would add fuel right? Then again the percentage of oxygen in the air varies with altitude and the stock ecu adjusts, so would it possibly compensate with enough fuel?

John H

 

[AnArKey]

By all means, nitrous should be before the turbo! It will make the most use there.

I did some calculations, I had NO IDEA how cold nitrous made things. From what I have read, nitrous flow is aprox 1LBM nitrous per 10HP. So a 50 shot, should use about 5LBM of nitrous. The latent heat of vaporization is about 161Btu/lb. That means it will absorb 5*161=805 Btus/min of cooling. If there is 55LBM airflow, which it rather high (near the top end), that should drop the air temp about 61F! If it's 90F out it will be freezing going in! When you activate nitrous, it's usually at a much lower airflow, say only 20LBM. That should drop the total air charge temp down 167F! I'd be worried about ice particles forming from the air that will be condensed out then frozen. Would they be very fine and soft like tiny snow or hard particles that would destory the impeller? You won't get the full temp drop, as some to a lot of energy (depending on intake humidity and temp) will come out of the water.

So to answer your question, the max HP a given turbo can make should be about 10-15% more (plus the size of the nitrous shot), with than without nitrous. You get two advantages to nitrous when injecting in FRONT of the turbo:

1. Increased horsepower through oxygen enrichment
2. Increased flow capability of turbo through pre-compressor charge air density increase.

When injected AFTER the turbo, and after the intercooler:

1. Increased horsepower through oxygen enrichment
2. Increased horsepower from charge air density increase in the intake.

So it's a trade off. If you need a little extra flow from your turbo, it should go in front. But the final air temp won't be lowered as much, because the turbo heats it up, and then the intercooler stabilizes it toward ambient. With the nitrous after the intercooler, you get colder final air into the motor, but the turbo doesn't get the boost.

EDIT: I missed a detail, which I have since realized. When injected pre-turbo, the turbo has to pump the added volume of gas. NO2 in gas form is about 1.5x the density of air. So we are increasing what the turbo can pump, but at the same time diluting the air stream. By injecting on the pressure side, the work of getting the NO2 is done by it's own physical properties of expansion, rather than having to be recompressed in the compressor after being allowed to fully expand in the intake.

The rough math I have run shows a pretty close relation to the air displaced by NO2, verses the air density increase from the cooling. It seems very close to cancelling each other out, with a slight net gain from the cooling.

Where as methanol, you gain 2-3x as much from cooling as you lose to vapor content in the air.

So it would seem, there isn't much of a benefit to putting it in front of the turbo, only the possible damage of ice beating up the compressor.

Methanol still seems to be the better choice.