Position and placement
 

I agree with most of the preceeding statements. My intention was to have the drip step well back from the turbo inlet. I would be very reluctant to place it right up against the compressor impeller as it could create all sorts of strange effects on the compressor map, moving the surge line around and so on.

This is the mental image I formed. The injection nozzle is placed .5 -.8 meters back from the compressor inlet. Some reasonable distance down stream from that, you flare out the inlet pipe some. This slows airflow speed and encourages any large dropplets to drop out of the flow. After a short distance you began to taper back in, creating a venturi. Liquid water would tend to collect at the point the intake tract begans to converge again. The liquid would be forced to move "uphill" on the converging section. If air speed is low enough at that point it would be impossible for the liquid dropplets to run on the surface. If you place a small lip near the end of this converging section, you would stop any dropplets that try to climb the "ramp" and as they get pushed up over the lip they should get ripped into a fine mist again by the high speed airflow at the throat of the converging section.

A secondary possibility would be to place a small drain at the bottom of the wide point to allow any liquid water to drain away. This may require some form of active extraction, or simply a gravity drain with a vacuum check valve would suffice. For active extraction you could just plumb a simple windshield washer pump with its suction to this low point and its outlet back to the water reservoir or suction side of the WI pump.

For reference, Oakos Automotive on their web site ( http://www.oakos.com/wrx/installs/AEMCAI/index.htm ) did a measured air pressure drop test on a WRX. The stock intake created a 26" of water pressure drop at max flow, the high flow AEM intake reduced that to about 12" of water pressure drop. Any drain system would need to have a check valve so it did not create a vacuum leak post MAF due to the intake pressure drop but allowed the collected liquid to drain away.

My current setup (old version) had the spray injected from the outside of a horizontal 90 degree elbow, with the spray at right angles to the air flow. When I pulled the turbo out that I photographed earlier, I could see clear evidence of liquid water flow on the inside of the intake tract. There were slight but unmistakable markings left by the evaporating water as it ran on the surface. The water mark basically went downward from the jet turning down stream and then followed the bottom center of the intake tract.

In considering the physics of what was happening I remembered some old info I had picked up years ago about water flow in a stream as it enters a turn. The fast moving flow moves to the outside bank and then due to drag with the outside river bank the current turns and moves down toward the river bottom then comes back upward on the inside of the turn toward the surface. In the case of air flow in a duct you would have this same hydraulic flow in the full 3 dimensions of the tube, with the air scrubbing hard against the outside center of the duct at the point of the turn then splitting and 1/2 going up and 1/2 going down (on a horizontal bend) and curling back toward the inside of the bend a few diameters down stream. This sort of flow would carry most of the water dropplets down the bottom center of the duct. In the faint water marks on the inside of my duct I could see exactly this same type of movement. I suspect a large fraction of the liquid drop out occured during the turn on and turn off period of the spray event when atomization is not good, not to mention some after drip that I imagine every nozzle would have.

The most simple solution if you have the room would be to create a P trap intake like on a sink drain where the injection occurs on the downward section of the P and then any liquid water would collect at the bottom as it could not climb the vertical leg of the trap. Air flow would likely quickly evaporate any water collected but it would be a bad thing if a large quantity of liquid were to collect there allowing a water slug to be pulled up the intake during a hard "yump" or other violent change in direction.

I also agree that Pre-compressor injection is best reserved for use only during high airflow situations where the benefits it provides would be best used. My 10 psi turn on was too low and as mentioned above I will move that turn on point up toward peak boost where I need to maximise the compressor effeciency.

FWIW

Larry

Your diagrams still seem to show the water spraying onto the whole face of the turbine. I assume that the water erosion could be avoided by ensuring that the water didn't impinge on the tips of the blades, could this be achieved by having a narrow jet on the center line very close to the turbine? I mean within an inch or two. I'm envisaging something like a pitot tube inserted into the air intake close to the turbine.

On another tack, to stop droplets formed on the walls from hitting the tips of the blades it may be possible to pinch an idea from a Porsche crank scraper. Imagine the air intake as a vertical tube with the turbine at the bottom. Step the wall in just above the turbine, and shape the wall so it forms a gutter. Angle the gutter so it forms a spiral rather than a circle. At the 'lowest' point, put a rib taking the gutter out to the middle of the turbine, still with the gutter profile so that water has to run out to the end of the gutter and can't just drip off the sides. Assuming the air speed is high I think aerodynamic forces would be quite high compared to gravity so the water might be pursuaded to go 'uphill' towards the axis of the turbine (if you see what I mean). From point of view of air flow it would look like a straightening vane with relative little drag.

Just a thought, what do you make of it?

Oh, by the way, can anyone put any numbers to the turbine tip speed and the water droplet speed at the jet? I'm wondering whether there's any mileage in tangential injection ...

http://home.pchome.com.tw/personal/r...essorWheel.jpg

On second look, I don't think I buy this being water damage. What is your filtration? Did you run w/o a filter ever? Lose a nozzle screen ever?

i am no expert, but this looks like grit damage to me. Sorry, just that I have to question if we are chasing our tail.

Larry, you have the same turbo, yes? You had nothing like this, correct?

greenv8s

I am not able to envision what you have described.

But, for it's simplicity, I like the center-mast stream, or narrow cone (preferred) idea. But again, anything located close to the blades will be an airflow disruption, and I think a good rule is to keep at least 2 diameters away from it. Then pray your install never get's loose! For many, there is a bend in the intake close to the blades (considered bad design) and that may limit how close you can get anyway.

If only someone can come up with an easily serviced coaxial alignment. The wall nozzle has that advantage. Someone can do it, to make this idea practical.

I've been using K&N cone filter for years, and never run without it.

I do hope, too, this is not caused by the injection, but now I hesitate.

And I remember Larry had a similar picture here somewhere. The damage was not so severe, though.



Michael,

Why don't you try it yourself & see how it goes? :twisted:
Maybe you'll have better luck :wink:

My pictures
 

My compressor erosion pictures are on page three of this thread. My damage is less severe and I KNOW that some of my damage was due to dirt ingestion during a couple unfiltered drag strip runs.

Yes it is likely it can, you just discribed the setup used by one guy that has been running pre-turbo spray for years. He injects directly on the compressor shaft nut with a narrow jet. The rapidly spinning shaft nut simply blasts the water stream into a fine cloud. I suspect the effect is not dissimilar to a 1000 psi impingment fog nozzle. The advantage of that system is as you say little or no chance to wet the intake tract walls, and the water is ejected tangientially outward inline with the compressor blades so little relative speed difference should exist. This is also very similar to the configuration used in WWII combat aircraft where they injected both fuel and WI "into the eye of the compressor".

The problem with that setup is it is not easily setup on many systems as the available space near the compressor inlet is quite limited in many cars, and service (ie to change jet size) would be quite difficult.

One of the things that may have limited my compressor damage is that I set the system up with a constantly pressurized system and the flow was controlled with a solenoid only about 4 inchs from the jet, so after drip would have been essentially eliminated, and rise time to full spray pressure at the jet should have been very short. Mine was also a continuous spray rather than a modulated spray as you would get with the HSV turning the spray on and off for folks using that style of system.

I also had a manual test spray button that at times I would briefly test the spray at low rpm to confirm my system was working. Based on this discussion, I now consider that to be a bad practice and will avoid it in the future, unless the engine is at a fairly high air demand, so that intake velocity would be likely to keep the plume from heavily wetting the intake walls.

Larry

Would this method work?

http://www.aquamist.co.uk/forum/sleeve3.gif

Nice Richard,

Would it "splice" into the conduit? Can the plumbing be routed within the support structure?

Haven't thought that far yet. It wil be quiet a simple fit, just slice it between the inlet hose and turbo flange, possibly with a few slots on the ring so it can be tightened up.

Do you think it could be used on different size ducting?

For universality (all diameters) and ease of maintenance:

how about a device that can be inserted in a standard size hole drilled into the conduit? Insert, and then have a band clamp of sorts on the opposite side that would pull it tight around the periphery, for a seal. Would also minimize drag interference I think.

Re: My pictures
 

Larry,

Is it possible to have a picture about how he install the whole thing?
I guess it'd be pretty similar to Richard's proposal above.

But, how can we deal with the restriction to the airflow & the fixing reliability?

Yet another idea, the supporting spoke can be designed as a set of "wings" to be a fixed turbine. Can this be done, or has any advantages? (sorry for the naive imagination on the aerodynamic)

hub injection
 

I've never seen the installation but it is explained in some detail in another forum : (posts are about 2 years old)

http://www.eng-tips.com/viewthread.cfm?qid=72284

Look for the posts made by " turbododge " --- I haven't figured out a way to invite this guy over here yet, as I don't see any sort of a private messaging system on the eng-tips forum --- maybe I'm missing something, but I would like to see him join this thread if he happens to browse this forum under a different username.


================== quick summary of his key posts ======

turbododge (Automotive)
30 Oct 03 19:51
I just got referred to this thread by a friend and being a long time user of water injection thought you all may be interested in what I have personally seen over the years. I run a twin turbo, now EFI (was carb), twin turbo 340 Mopar in a 70 Cahllenger, strictly street, 14 psi boost, intercooled.

I use an old Edelbrock Varijection system that has been altered for instant on under boost conditions at 7 psi. It varies the amount of water based on rpm and absolute manifold pressure. It does not have adequate pressure to spray directly into a pressurized intake manifold, so I spray directly on the turbine blades. The turbos are lower than the inlet ducting to the throttle body, so even if I have a valve failure, I cannot water slug the engine. I have run this system for over 15 years on carbed and EFI turbo engines, and would not go without water injection. I can run 8 to 1 compression at 14 psi on 92 octane all day without worrying about detonation.

I find the talk about atomization, hummidty, where the water evaporates, etc to be very interesting, as I have watched my system extensively over the years. When I spray on the turbine blades, the water (with 50% isopropyl) vaporizes instantly, before it even touches the blades. I have 50K mile turbos that show no erosion at all, and even the intercooler does not get any significant amount of moisture in it. The ductwork all stays dry. The low pressure area at the turbine inlet easliy evaporates the water spray. I found no difference with EFI or blow thru carb in this respect.

When I was running a suck through carb setup, I was spraying directly into the carb throat with the water, and found that the carb venturi would vaporize the water right along with the fuel from the venturi. Subsequent running through the turbo also further atomized both elements. All was good unless the inlet ducting was cold enough to condense out the fuel and slug the engine.

In an N/A engine, you would spray straight into the carb with most systems like a Spearco. An Aquamist you could go into the manifold below the carb as they atomize better, but most folks don't do that. Unless you are dumping very large amounts of water into the carb, it will atomize, if it did not, it would build up in the intake and give a big slug to the engine when you turned, etc, and probably thermal shock or hydraulic the engine to distruction. I think it would be a very risky business to try to get, or count on getting unvaporized water into the cylinder.

As far as the power is concerned. As I mentioned before, my setup is instant on, off a pressure switch, or an override switch in the cockpit. I have done lots of testing at boost levels to 12 psi (max without detonation without water) with the water on and off. I give people rides and turn the water on and off, then off and on to see if they can feel the accelleration rate change. I can tell you that no one has ever not been able to tell that the water came on and the accelleration rate increased. It is very significant. I would be surprised, however, if you would be able to readily feel the difference in an N/A engine, as when I turn the water on and off while holding the boost down with the throttle, I cannot feel a difference at all, in my low compression engine.

My net conclusion is that on a boosted car above 10 psi, water injection is necessary if you want to be able to run decent compression, timing, and mixtures, plus you will get more power do to charge cooling, even if you are intercooled. On an N/A car, I would use water only if you need it to kill detonation because of high compression, bad gas, etc. I don't believe it would give you enough more power to notice.

==========

turbododge (Automotive)
31 Oct 03 0:18
Turboice: You are absolutely correct in that one big factor with water injection is killing the detonation to allow you optimize other conditions. It is very common in the turbo crowd to try to drown the detonation with extra fuel, even down to 10 to 1 A/F. All it does is cost power and give minimal results. The is a very good chart in the Hugh MacInnis book Turbochargers on the affects of water on detonation, boost level and air fuel ratio. One look at the chart and you can become a water booster for life.

Concerning the non erosion of my blades, it may have to do with the fact that my water only comes on when I really need it, so it is on a very small % of the time, but I am also very carefull to send the nozzle stream (it is not atomized) at the CENTER of the compressor shaft so that any impact is on a slower speed, less critical area, and the water flow moves out the blade rather than impacting it. Also, with Varijection, there is less water at lower rpms and boost levels and more at higher speeds and boost. A single output volume, set to deliver enough water at full load, like a Spearco, can easily overwhelm a turbo spinning at lower rpm and impact the blades harder. With the EFI controlling spark and A/F (12.5 A/F under boost)and careful tuning of the water we normally will only use a gallon of water per 1 to 2K miles of street driving, as we are good to 10 psi very safely without any water, (and 12 if the gas is good). So putting is enough water to get to 14 psi is pretty easy.

==============
turbododge (Automotive)
31 Oct 03 12:40

...

The erosion of the blades discussion is very interesting, and may apply to others differently than me. I am running plain old T04, oil cooled turbos, and have been for many years. The newer turbos with the aforementioned lighter blades and perhaps more brittle alloys may be more of a problem. With those I have no experience. There was a post that mentioned someone who had a friend who did get blade erosion (post probably gotted whacked because it referenced another site). Was this person, by any chance, running a water/methanol mix in his system? From what I have seen and heard, methanol will take out turbine blades, throttle body plates and bearings, and can even corrode the tips of fuel injectors enough to cause pattern problems. That is why I use Isopropyl in mine.

============
In thread http://www.eng-tips.com/viewthread.cfm?qid=82878


turbododge (Automotive)
5 Jan 04 18:51
I have been injecting water/isopropyl alcohol on the turbine blades of my twin turbo 340 Mopar for 15 years now. This kind of system was very popular in the past, as it was much more difficult then to inject into the boost stream because of the high pressure. The blade erosion issue has always come up in discussion, but the only ones I have seen that had problems were either on stationary units that ran the injection constantly, instead of only under boost like in a street car, or if they used methanol in the injected liquid. Methanol is much more corrosive than isopropyl. My turbos have over 40K miles on them with no signs of erosion at all. I use about 1 gallon of water/isopropyl mix per 1000 miles. My system is also variable with speed and boost, so I don't overload the airstream with too much liquid at any time. It also atomizes better if you aim a single spray nozzle directly at the shaft of the turbine, the liquid usually is totally vaporized by the time it is 1/4" from the nut on my setup.

I can run with or without the water very easily, and if I am holding a boost level and turn on the water, you feel a very positive increase in accelleration. I am also running an intercooler, so this is beyond the intercooling affects.

If you do a good job of setting up the system, I would not be afraid to inject ahead of the turbo, as I have seen very good results that way.


============
turbododge (Automotive)
7 Jan 04 0:01
Yes definitely on the compressor wheel, poor phraseology on my part.

I am not up on the viscosity/vapor pressure etc with methanol vs isopropyl, but I know I have seen methanol systems corrode the compressor wheel, but never an isopropyl setup do the same. Downstream corrosion is even more of a problem with with methanol, and I have even seen corroded throttle shafts stick in the carb base. Intercoolers will also sometimes condense out a small amount of water or alcohol in cold weather and the methanol will also go work on the intercooler. I would guess that the compressor gets wet enough with the methanol someplace along the line, either at cold start, cold idle or such. The corrosion I have seen covered more of the depth of the blade than impingement damage which tended to be very close to the entrance edges of the blades.

The other thing that goes with this is that all the other systems that had problems with corrosion also were on/off, non variable, systems, which can heavily overload the compressor at low rpms, cool air conditions. I have literally seen liquid drip from the compressor housing hose connections after a run.

I am sure there are lots of folks that have successfully run methanol in their setups, but for me the isopropyl makes it much easier and more reliable, with very little downside.

===============

turbododge (Automotive)
7 Jan 04 20:36
Overrange: We drive the car a lot, but spend a very, very small percent of the time at throttle positions that would turn on the water. If we do a 500 mile "cruise" through the countryside, it is very possible that we will not use any water at all. My system does not come on until 8 psi of boost, (out of 14psi maximum),and since the system matches water flow to boost and rpm, water flow at that point is quite low. I can tell you that a 340 CID V8 will accellerate very quickly at 7 psi, and it is easy to stay within that range by controlling the throttle. To use the full 14 psi on the street requires a very good road in a remote area as the tires can go loose at any time, in any of the first 3 of 5 gears, depending on the traction. Even if the water does come on, it is only on for 10 or so seconds per use (maximum) before you are way over 100 mph. If I am testing and tuning, I have used a much as a quart in a day.

Although I did not mention it earlier, as the question I was addressing was the feasibility of injecting into the compressor, is that my system is not primarily used for inlet charge cooling, as I have an intercooler for that. My system is to allow me to run decent boost, without detonating, on 92 octane pump gas. Without the water I will get detonation at 10 to 12 psi, depending on the gas and weather conditions. It takes much less water to reduce detonation (as long as you have an intercooler to cool the air) than it does to cool the air enough to make power. That said, if I run up to 10 psi with the water turned off, and then turn it on, you can feel the car pull harder, so I am either gaining from cooling of the air further, or because of a better combustion process in the cyliders. I don't know what it is, but you sure can tell if the water is on or off.

The car also has a very good cold air system on it that takes air in through the boxed wheelwells that a fed from spoiler ducts, with only 6" of ducting before the turbos, after the large K & N filters.

===============

As you can see by the above he sprays a solid stream directly on the compressor shaft nut, and allows the spinning compressor nut to beat the stream into a microfine mist moving radially outward. His system is in my estimation an ideal case of wet compression as there is no time for the water mist to evaporatively cool the air stream before it arrives at the compressor, but it will modify the compression due to the high presence of water in the air flow.

I on the other hand needed to maximize the density increase due to air charge cooling pre-compressor to get the most out of my undersized turbo.


I might add that I am not too concerned with his observations about methanol corrosion as he was obviously talking about setups that grossly over injected fluid and kept the intake tract wet all the time. Any system like mine that only comes on intermittently at high air flow demands will quickly dry out any condensate in the intercooler etc. That is one of the reasons I turn my system off in cold weather. I don't need the detonation suppression when the weather is cold ( I don't run high boost when its snowy and icy out ).

Perhaps a little of both would be best one very small spray jet well back from the compressor with some sort of a dropplet trap to keep any but smallest dropplets from passing into the compressor, and a hub injection setup to get the advantages of wet compression.

The other obvious question is are some of us willing to consider the turbo compressor a wear part and to plan on replacing it on a regular basis? I know many of the hard core performance nuts upgrade turbos on a very frequent basis, and for them replacing a $40 compressor wheel (or what ever they cost) every 2 years would not be a big deal in exchange for the performance advantages. I'm sure the WRC folks or people that compete in similar levels of competition would have no problems at all with that sort of replacement cycle. Serious drag racers might go through several clutches, a couple rear ends and a motor or two every year. A little R&R on the turbo compressor is not that big a deal in the grand scheme of things.



Larry

Re: hub injection
 

[quote="hotrod"]I agree, why don't you get your density contribution post IC instead of pre-turbo, the convention? I am planning a 2 stager. Variable post IC, plus the boost activated 2nd stage pre-turbo (for when you just can't have enough!)

I just took a look at trying to get close to the diesel turbo, not going to be easy. There is a 90 only 5 inches from the blades. The upside to not requiring fine atomization, is that the nozzle doesn't have to be finely engineered. Mybe that will prevent some clogs???

special case
 

There are two reasons!

1.) In the first case when I started experimenting with this, I was trying to maximize the performance of a stock undersized turbo just to see what was possible. The only way to increase mass flow in a system in choke flow, is to increase the upstream density. It will still be choked to the local sonic air speed at the critical flow point, but with the increase in density, mass flow will still go up slightly.

2.) Due to my living at 5800+ ft altitude (and can easily reach over 12,000 ft altitude in an hour or so of driving) every turbo that is currently on the market is working far outside its design compressor map at these altitudes. At max boost, I am not on the far right side of the compressor map, I am completely off the page to the right. The intake cooling and wet compression pushes my operating point back toward the left.

Larry

Re: special case
 

:lol:

Re: special case
 

Larry do you feel you have been successful in humidifying the slug of air in the 50 milliseconds it spends between filter and turbo inlet? Can you support that?

just my opinion that with these coarse sprays, and so little residence time, that nearly no evaporation actually occurs, especially considering the low water/alc temps used. Maybe you can change my mind.

Flash swirl sounds like what you need to explore. What do you think? swamp cooler?

evaporation
 

Interesting question --- My short answer is enough to make a useful difference.

The objective is NOT to humidify the air, the objective is to increase engine (and in this case turbocharger performance) due to the sum of multiple effects. One of which happens to be evaporative cooling.

After considering you question for a while here's my view.

First very very small amounts of evaporation are all that are necessary to make a major change in the inlet conditions of the turbocharger. The specific heat of the intake air is .25 Cal/gm deg C (give or take a bit) while the latent heat of evaporation of water is 540 Cal / gm.

The maximum intake air flow on the stock WRX turbocharger is approximately 360 CFM or about 25.2 lbs / min ( 0.42) lb/sec or about 191 grams /second.

If you are spraying at a rate of 4 gallons / hour that is approximately 4.2 grams/second of water.

If you lower the intake air by 11 degrees Farenheight or about 6 deg Centigrade you increase the air density by 1% which will give you an increased mass flow through the turbocharger of approximately the same and give a net power increase (all else being about equal) of 1%. On a 250 hp engine then, each 6 deg C drop in intake temp is worth about 2.5 hp.

Given the ratio between the specific heat of air and the latent heat of water you have to evaporte only a very small fraction of the water to bring down the intake air temp significantly. Lots of people have recorded intake air temp drops on the order of 30 - 50 deg F (17 - 28 deg C) with initial air temps near 105 deg F (40 deg C).


So just to persue your question lets look at what we know. The air flows at a rate of 360 CFM max in an intake tube of 2.5 inch ID --- this gives a peak air speed at redline of about 176 ft/second (120 mph). The spray nozzle is about 2 ft away upstream so flight time for the dropplets are on the order of 11.4 milliseconds.

Now how many drops are in that air column and what is their surface area?

One cubic centimeter of water in the form of 50 micron dropplets (if my numbers are right) consists of about 424 million dropplets with a total surface area of about 333.3 cm^2. We are spraying at a rate of 4 gal/hr or 4.2 cm^3 / second so we are putting about 1,780 million dropplets into the airstream per second, they have an effective lifetime of 11.4 milliseconds in the air column, so the air column at any moment contains about 0.0477 cm^3 of spray or 20.44 million dropplets with a total surface area of 15.9 cm^2. Plus we also have the evaporation that occurs off the wetted interior surface of the tube, which would amount to 1216 cm^2 of surface.

How much water evaporates every 11.4 milliseconds, from 1232 cm^2 of water surface when exposed to a 120 mph wind ??

That intake air column has an air volume of only 0.068 cubic ft, which converts to about 2.166 grams of air, it obviously only takes a miniscule amount of evaporation during that 11.4 millisecond flight time to make a huge change in the temperature of a slug of air that only weighs 2.166 grams.


To lower that 2.166 grams of air 6 deg C, you only require .54166 calories of energy per deg C. To get that amount of cooling by evaporation of water you only need to evaporate 0.001 gm of water in 11.4 milliseconds/ deg C, or 0.08799 grams per second/ deg C which equals .5279 grams of water evaporated per second for a 6 deg C intake air temp drop.

{ all this ignoring the higher volatility of the alcohol component and its lower latent heat of evaporation but --- lets keep it simple for discucussion sake}


The interesting thing about this exercise is that it is obvious that the wetted surface of the intake tract dominates the evaporative cooling process by a large margin over the cooling that takes place at the dropplet surfaces.

Your swap cooler comment is right on target, and I have been considering similar ideas. It might be useful to intentionally maximize the wetted intake surface both to gain this cooling and to capture large mist dropplets.

I have considered putting pieces of fine mesh brass or stainless steel screen wire placed at extremely oblique angles to the air flow. (intention to give a very large open surface area but little or no direct path through the screen) Any dropplets that couldn't make the "jog" due to their large size, as they approached a screen wire would be broken up and wet the screen wire surface. Smaller dropplets would simply pass through the screen unmolested.

In a perfect design the screen would be treated so it wetted well with water alcohol mixes and had high capillary attraction to pull liquid water up off the floor of the intake and into the air stream. This is basically what is done inside heatpipes.

Larry

I started down the road to verify your numbers and it suddenly occured to me... I'll get to that. First, nice quantifiable arguments, as always. What I say in no way detracts from your well explained facts, but something is left out. Nowhere really do you represent where there is a reason for the liquid to evaporate. There is no "driving force" equation representing the change of state. You could have a billion droplets at -500 C and all the exposure in the world will still require an ice-age of time to evaporate (sublime) them.

Yes we have heard of 30-60 F drops, but not with ambient air, heated air (that is also dry). Ambient air at 80F will evaporate water at 80F, and if the air is 60% RH, it may take minutes, not milliseconds, to change state of a fraction of it. Perry's or the CRC might be worth looking at. See in an environment where compressed heated air (post-IC) is plentiful at 5% RH, there is a much greater force evaporating the liquid. But what you said, about the wall exposure was brilliant, and maybe breakthrough.

Here in Sunny Phoenix, I can lose 1/2" of water out of my 90 degree pool on a windy 115 F DAY. Yet not notice any loss, after a week of calm winter weather, with 50 degree air and water temps. Naturally if the water was at boiling, air at 100C, I could evaporate the whole pool in hours.

What quickly became obvious to me is this: a lightweight droplet, entrained in a moving column of moist cool air, is going nowhere (except through the compressor). Ah hah! The moisture on the wall has nowhere to go but to humidify. (the assumption that the entire conduit wall is wet is optomistic without a system settup to make it wet, one nozzle isn't up to the task, agree?) Without some nice dry hot air blowing past the drop, it quickly retires to a fate of drift, until it is exposed the hot, dry, dynamic conditions that are waiting downstream.

Keeping clear that anything that increases the apparent restriction in the plumbing is not going to work. It WILL kill the performance sought in the form of pressure drop. Screens and such in the column will not be a solution, without drasticly changing the conduit dimensions. 176 ft/s is not the place to add any kind of change, since as we know, most hood ornaments will be cast off at that speed, certainly flies don't survive it.

FWIW, I grant some evaporation can occur post filter, but this must be so miniscule as to be negligible. Swamp cooling that much air, done in a conventional way requires square meters of wicking material, and a puller fan that will wreak hovoc on your alternator. The pressure drop across swamp cooler pads is significant, and the process is not an on-off process. It takes minutes to wet the pads befor they start providing the desired result, etc.

What does come to mind, is along what he have discussed, with a twist. A 1/8" perforated SS tube that runs the much of the length of the conduit, concentrically. Ever seen a soaker hose? each .008" perforation a pseudo-nozzle, maybe 10-20 of them depending on flow requirements. You could even put a nozzle on the end of it, pointed into the blades.

What it might do for you is keep the wall lightly wetted, and still provide for airborne mist, and a direct inject nozzle. Manufacturing it, without significant restriction, will have to be a different book.

Real world conditions.
 

Well your comments are interesting, but I feel there is plenty of driving force.

Typical conditions here at the strip or on a hot summer day, outside air,measured well away from the pavement 85 deg F, at 12% humidity. I frequently measure actual intake air temps above 105 deg F.

That puts the intake air humidity as it passes the spray nozzle in the dry air catagory with a dew point of less than -39 deg F.

At dew points like that with pure water your wetbulb temperture would be about 53 deg F. (ie this is the temperature the air would cool to if you raised it to 100% RH by evaporation of water)

This is ignoring the issue of alcohol evaporation or the lower air pressure which makes the water have a higher relative vapor pressure.

The relative air speed between the dropplets and the intake air being in the 100 mph plus range will result in a nearly instantanous evaporation of enough water to drop the air temp by 10's of degrees F.

Its difficult to measure the true air temp because of problems caused by wetting of the surface of the temperature probe, but there is absolutely no doubt that there is a very large driving force for evaporation when the dry air and the rapidly depressurized water dropplets first encounter each other at high relative velocities.


If you want to dig through Perry's or CRC handbooks to figure out the realtive vapor pressures and all that ---- please do ---- I have neither the time or the interest in trying to validate what is obvious to me based on my experience. When going to the pre-compressor water spray, my midrange boost onset was so dramatically improved I had to change my driving style to keep from running over people when accelerating from stop lights. I'd come into boost so quickly I had to change my boost controller settings (turn them down) for daily driving.

Simple proof of driving force for water evaporation when your car is mass flow limited for air by the choke flow capacity of the turbo.

Without water spray in the intake car goes x mph in 1/4 mile, with water spray pre-compressor car goes y mph in 1/4 mile.

x is > than y ----- spray must work!


Larry

OK, I buy it. What do you think of the spray bar/tube idea?

soaker hose
 

I'm not fond of the soaker hose idea, --- seems to be too much complication, and an absolute gurantee that you would end up with liquid water running down the bottom center of the duct. By the time you get that long tube supported so it does not fatigue fracture and go through the turbo I think your drag losses in the intake would go sky high.

At this point I think some controlled tests on a test rig would give us more useful info in 2 days than we could glean from months of brain storming.

I just need some time to cobble together something that will allow some pictures and measurements to be made.

New job it keeping me busy. ;)

Larry

Oh well, a revelation for me alone then, I guess.

Hope I was clear. Each pseudo nozzle in the SS line would be much smaller flow than any w/i nozzle presently marketed. Large droplets would wet the wall, small mass droplets entrain in the stream. It has the advantage of saturating using all means, given the short residence time before turbo.

Not sure why a SS line would be in danger of coming loose. Of course, this is unconventional, out of the box thinking. That is, no doubt where the solution is for such a challenge.

Perhaps you have seen the loops that are fastened to high speed fans at football games, for quick cooling on the sidelines. I'll find one and post it.

wow interesting read. some thoughts i had that im not sure were covered though..

i think there is always a step from turbo inlet pipe to compressor housing (unless the rubber pipe flares out just at the compressor inlet).

if im running one pump and 2 hsv, what happens with the pressure difference at the nozzels?
say i start injecting the main jet (after the intercooler) at 18psi and the pre-compressor jet at 23psi. engine running a max of 28psi.

would the water be more likely to travel to the compressor jet as there may be a vacuum in front of that one and +23psi in front of the main jet?

Drew

Any progress Larry? Or anyone else?

Larry I was wondering what size nozzle you are running pre-compressor. If I remember correctly you have a Shurflo pump, correct?

Do you have post-turbo injection as well?

Drew I have also thought about what will happen when I run a dual stage set-up (1 pre, 1 post compressor) when I change to a pre-compressor injection nozzle. I wonder if the Shurflo pump can maintain pressure so the nozzles continue to atomize correctly. I know lowering the pressure of the system by adding a second nozzle decreases the amount that the nozzles each flow, but what is the effect on atomization?

I currently run a dual-stage post-turbo WI setup with no problems. I just worry about changes to the atomization when I move one of the nozzles to spray in front of my soon to be new turbo :? .

I have a turbo with turbine wheel damage from a manifold cracking and throwing chunks downstream, so I am willing to sacrifice it in the name of science :wink: . The only problem is that I am continuing my year long travels in SE Asia and will not return to Colorado until October 2005, so we will have to wait until then.

Craig (currently in Cambodia)

i was thinking of maybe adding one of those inline check valves in the pre-comp line.

something along the lines of if i got 15+ psi after the intercooler, i could try and balance the flow between the 2 jets with a 15psi valve at the compressor.

although just read aquamist's website..
http://www.aquamist.co.uk/sl/plist/p...8/806-248.html

maybe thats what your supposed to do anyway.

Drew

I would like to see a 70-90 psi crack pressure in a check valve. That would help prevent inneficient atomization for the critical pre-comp stage.

...or a solenoid run by a presssure switch on the water line, etc...

setup
 

Well at the moment I'm getting ready to re-configure things. My old setup was pre-compressor only and a 3 to a 4 gal/min nozzle. That was too much water in retrospect so I decided to rebuild the system.

I will be adding pre-throttle body nozzles and reducing the pre-compressor nozzle size probably to a 2 gal/hr or a 1 gal/hr rate.

My system uses a shurflo 100 psi pump and a shurflo 24 fluid ounce accumulator (pn 181-203) and the trigger solenoid sits within inches of the nozzle, so the turn on time is very short, with a large accumulator at 80-90 psi feeding the solenoid.


Larry

I have been thinking about how I can get rid of pooled water in the intake pipe during pre-compressor injection. One idea I thought of is creating a place for the water to pool, like bottle cap sized addition to the intake pipe that is lower than the compressor intake. Here you could place a small check valve that would close while you are WOT, but open when you let off the gas, allowing some of the pooled water to drain out.

I don't know what kind of check valve would open so easily that water could drain out, but I'm up for ideas. I also don't know for sure that there would be adaquate time between shifts and low enough suction in the intake pipe to allow the valve to open.

Here is my other idea.... You could use the vaccum from your throttle body to suck out the water from the pooling area (for lack of a better term) into a small catch can or something.

The only thing I worry about with the pooling area is that huge drops of water would be sucked out of it because of the high speed of the air in the intake tube. I think the depth of the pooling area would be the only way to reduce this. I also don't know if the pooling area would create a bunch of turbulence directly in front of the compressor. I guess it depends on its design.

I would appreciate any feedback that people have to offer.

-Craig

If you can design something that will evacuate excess, and not reduce pressure in the inlet tract, that would be interesting. Anything that sucks out water, is going to cause a performance degrading pressure drop I think. Also, can't have unfiltered air infiltration when no water is present.

Sorry i am not more help.

just inject into the centre of the turbo.

Drew

I was thinking that the suction would only happen when you let off the gas, as to not greatly affect the MAS "counted" air mass during WOT.


-Craig

WOW! I made it through all 13 pages! Great forum here!

Now this forum doesn't apply to me very directly, since my compressor is oversized for the boost/flow I'm currently running. However, my engine setup would be perfect for pre-comp injection, hardware-wise. I currently run a very large K&N cone filter(~6" diameter and 9-10" long) attached directly to the turbo inlet(4")

I got to thinking of all the ideas I've read here. If I had an injection nozzle in the end of the filter(pointing directly at the impeller) then any spray hitting the walls would be hitting the filter element(read swamp cooler filter) and since the filter has a large step where it necks down to the turbo it'd be about impossible for non-atomized water to flow down the turbo inducer(besides the small amount that hits it directly)

So what I'm saying is that you should all ditch your MAFS, buy a Megasquirt kit(or other MAP-based system if you like wasting money) and put a large cone filter directly on your turbo inlet. :D

Anyhow, thanks for the extremely interesting reading!

BTW, what ever happened to the MX5 tester guy? As has been said before, a few simple tests would be worth more than all 13 pages of this thread!

Edit: Pardon the obnoxious first post :wink:

I've been thinking more seriously about how to mount a WI nozzle aimed into my compressor blades.

How do you guys think a nozzle and the hardware to keep it in place will affect the tornado like flow of air entering the turbo?

It seems like you would not want to disrupt this swirl as that would make the turbo have to work harder to suck air in.

Any thoughts?


-Craig

An interesting article on pre-compressor WI for gas turbines:

http://www.alphapowersystems.nl/NewOrleans.pdf

"By injecting atomized water in the compressor of a gas turbine the parasitic work of the compressor is reduced due to quasi-isothermal compression.

Approximately 2% water to the mass flow results in a significant increase in the gas turbine?s power output.

... round-the-clock water injection could cause problems with erosion, water separation etc. The droplets must therefore be small.

The water to be sprayed is pressurised and heated up. Then, as it spouts out-of a swirl nozzle, explosive flashing takes place. The result is a surprisingly fine hot plume of tiny water droplets, ready to evaporate as they enter the compressor.

By using a swirl nozzle and by supplying pressurised hot water, the combination of spraying and flashing results in droplets roughly ten times smaller in diameter and thousand times smaller in volume and weight than the droplets of a normal swirl spray device.

The amount of heat extracted from the compressor air by evaporation is much greater than the amount added through the hot water spray. As a result, the temperature drops and the compressor discharge temperature is reduced. This results in less parasitic work of the compressor ..."


Seems the higher the pump pressure & the finer the atomizing, and the warmer :shock: the injected water, the best.

I searched more about these "SwirlFlash Nozzles" and it sounds like you have to pressurize the heck out of the system to get the droplet size they have. 40-150 Bar!! :shock:

Here is a quote:
-----
The patented SwirlFlash? technology is based on a simple but robust principle. A liquid is pressurized (typically 40-150 bar), heated-up to about 200 C and fed to a swirl nozzle. Due to the swirl movement the liquid (for example water) spouts out of the nozzle in a typical spray pattern which has the shape of a cone. The droplets size is about 25 micron. However, when the water is significantly above the boiling point at the ambient pressure, it starts boiling violently (flashing). As a result each droplet of 25 micron explodes in a thousand fragments, each having the size of about 2.5 micron. The typical spray cone of a swirl nozzle changes as a result of partial flashing to a parabolic shape. The ultra fine spray ensures almost instant evaporation and cooling.
-----

Here is where it was:
http://www.alphapowersystems.nl/swirl.htm

I apologize if this is what is contained in the pdf file, but the computers over here in China (travelling now) will not let me open it up. :roll:

Has anyone used these SwirlFlash Nozzles?

-Craig

(edited for clarity)

Quite a while ago, someone has posted this "SwirlFlash" here somewhere (sorry I don't remenber who).

I think the key is not at the nozzle, but the pressure & temp. These two are also the hardest portion for us to deal with. :cry:

And the whole system is definitely bigger & heavier than what we are using now. That would be a bad thing. Maybe sometime it's the difference of doable & mission impossible. Especially in a crampped engine bay like mine.

not so undoable... run pure water in your radiator fluid and run a 30 lb cap. tap the aquamist feed from the radiator so now you have heated water 180-220 degrees f and its also pressurized to 30 psi above atmospheric. to fill the system just keep the overflow can filled to spec.

That's really a good idea!

But (a big one), it's too "agressive" for a road car, isnt't it?

I don't need anti-freeze in where I live, that's alright, but I do need anti-corrosion & lubrication from the coolant.

Seeing rust in the injected water would freak me out.