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Author Topic: Recardo graph on H20 injection  (Read 17765 times)
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jl222
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« Reply #15 on: March 11, 2009, 08:18:48 PM »

The fuel was 87 octane.

The octane rating is a measure of the resistance of gasoline to detonation (engine knocking) in spark-ignition internal combustion engines.

If the same test had been done with 119 octane racing fuel there may have been no difference with water injection. I really doubt if water injection can be of any help on a full pop racing engine.

Water injection is used to lower the temperature of the mixture to avoid detonation. If detonation is limiting horsepower, there are other ways to prevent it. At the limits of racing engines I doubt if water would allow more horsepower to be achieved.




       What water injection does [on supercharged engines] is lower the temperature of the boosted compressed air. This shrinks the air allowing more air in the cylinder. This lower temps allowes one to increase boost and make more power. WW2
AERO engines used water injection [anti detonation injection or ADI] to do exactly this and they had 115/145 octane gas and intercoolers. In the South Pacific when fresh water was short they used salt water!! Thats how important it was.
  As i've stated in another post, Formula 1 teams used water injection untill they invented their [rocket fuel] the water injection system weighed around 35lbs so the new fuel was a big advantage.
 The engines that would benefit the most are roots blowers on gas with no intercoolers.
 I'am not sure what the diesel tractor pullers [John Deer] type are doing these days, but at one point when they went to three stages [they had two turbos blowing into another turbo blowing into another] they had no room for intercoolers and injected water at 3 gallons min.


           JL222


« Last Edit: March 11, 2009, 08:22:32 PM by jl222 » Logged
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« Reply #16 on: March 11, 2009, 09:37:52 PM »

............... The engines that would benefit the most are roots blowers on gas with no intercoolers...........

We feel we owe a lot of our success in spite of some of the dumb things we have done to the water injection we got from Snow Performance with Nate's help.  One run to the 5 mile at 232 without having the cooling water turned on and the water temp pegged past 250 from about the 2 convinced me.  We warped the heads, but to not of grenaded the motor was astounding to me.  The same motor with a little freshening and the boost turned up (roots blower) using the water injection helped us move the record to 249+ the following year.  I use to think it was a gimmick, but it has made a believer out of me and if I ever get turbos on my truck I'll have it.

c ya,

Sum
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« Reply #17 on: March 15, 2009, 10:18:32 PM »

      What water injection does [on supercharged engines] is lower the temperature of the boosted compressed air. This shrinks the air allowing more air in the cylinder. This lower temps allowes one to increase boost and make more power....
OK, we have to also recognize the other big effects of water injection that are equally important, and in some engines, the dominant reasons for using it.

Yes, the water does cool the charge, IF and only IF the water evaporates before it gets to the cylinder. in many WWII aircraft engines, most of the water went into the cylinders in liquid form because of poor atomization.  So charge cooling was not the dominant effect in that era.  It was late in the war that Pratt & Whitney and Curtis-Wright figured out that injecting the air upstream of the compressor would help mechanically vaporize it, but they were more concerned with even distribution to each cylinder.

Whether the water is evaporated or not, once it is in the cylinder it will also do several other things.  First, it cools the piston crown itself as it evaporates.  As HP/in2 of piston area increases, cooling often becomes critical and pistons start to melt.  We've all seen it.  Rings weld, holes melt straight through the crown, etc.  This isn't as common in modern engines (especially imports) that have dedicated cooling oil jetted right at the bottom of the pistons.  As we boost up modern engines, we use TBC's (thermal barrier coatings) to keep the heat flux under control, water is a last resort.  Among other things, proper cooling from whatever combination of oil, TBC, and water prevents pre-ignition.  Pre-ignition is often called detonation, but it is a different effect and cooling the intake charge has a limited effect on it compared to cooling the piston.

Second, water also retards the burn rate of the end gas;  this is detonation prevention equal to cooling the intake.  It is why cooling the intake with water injection has more effect than lowering the   As the flame moves across the piston from the point of ignition, the remaining gasses compress to far higher levels than where the spark went off.  This effectively raises the compression ratio for the end gas and leads to detonation.  Water in the mix slows down the burn rate.  This actually absorbs power early in the burn and reduces engine output.  In exchange, it takes energy out of the end gas burn, often lowering its energy below the threshold for detonation.

Last, and most important for nitrous engines, small amounts of water provide a large increase in the working gas.  "Working gas" is what we call the nitrogen, CO2, H2O, and Argon that makes up the un-burnable atmosphere and the combustion products from the fuel and O2 in the air (more CO2 and H2O).  If there is more heat than the engine can handle, adding water increases the working gas and creates more pressure and less heat from a given amount of combustion.  For this effect to be dominant, the water actually needs to get into the cylinder in liquid form.

When using nitrous, we are adding fuel and oxidizer and not adding anywhere near as much working gas.  This adds heat.  So an engine making a given amount of power with nitrous will run hotter and pre-ignite/detonate/melt sooner than the same engine on boost, all other things being equal.  In the case of nitrous, more than any other, water is an important tool to provide this working gas.

Before it is used, TBC's and proper cooling MUST be used.  Otherwise, water is just a band-aid.  About half of the air racing crowd has finally figured this out, the other half is still burning engines down no matter how much water they use.
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« Reply #18 on: March 26, 2009, 11:40:47 PM »

Blue

How much boost are the air racers using these days and can you tell us anything about boost temps before and after intercooler?

  JL222
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« Reply #19 on: March 28, 2009, 12:16:59 AM »

How much boost are the air racers using these days and can you tell us anything about boost temps before and after intercooler?
Short answer:  no data

Long answer:
The Mustangs vary from "stock" power at around 60" MAP for a low Bronze class racer to ~120" MAP for a transport case, Allison rod equipped engine called in various circles a "Mouse motor".  The 3350 radials are divided into 2 separate classes:  the DC-7 derived race engines used in Rare Bear, Critical Mass (retired), and September Fury; and the 3350-26WD Skyraider engines used in everything else.  The former run 80+" MAP, while the latter are good for far less.  I honestly don't know what the boost levels are on the R-2800 in Czech Mate or the 4360's in Furias and Dreadnaught.  "Stock" R-2800's are supposed to run 53 to 55", but I've heard of higher numbers.  One of the Yaks runs a smaller engine on even less boost and definitely holds the mph/HP edge;  I wish they had money for a hotter engine. 

While many younger tuners will allude to only-we-know-this-and-you-just-don't-know-enough-to-understand "mods", talking to the older engine builders has proved the sad fact that these engines have almost no changes from 50+ years ago other than removing limiters.  They are not equipped with any rational level of instrumentation, modern engine coatings, and still run carburators and 60 year old magnetos.

I'd love to get some data on interstage temperatures, but none of the Unlimiteds run anything but the most rudementary data acquisition.  Most don't even measure the cylinder-to-cylinder differences.  Even worse, the impellers are stock designs from 40 to 75 years ago and have far lower efficiencies than we are used to with modern compressors and turbochargers which are common in LSR.  So the temperatures are probably 10 to 30% higher than we see with modern compressors for a given boost level.  I can't prove this without proper instrumentation, however I have seen the compressor maps from these old engines and their efficiencies are HALF of modern compressors.  You're smart and you know compressor maps, draw your own conclusions.

The engines are so large (1650 to 4360 ci, 138 to 186ci/cylinder) that the water-methanol injection flows are massive;  like 2-3 GPM!  While not a firehose, it is a garden hose and aspiration is challenging.  Most teams inject the water into the compressor inlet to make the compressor aspirate the liquid because they use low pressure pumps.  What this does is scatter a lot of liquid droplets into each intake runner on the radials and simply pee it into the interstage area on the Merlins.

IF (and that's a BIG if...) the water actually evaporates in the compressor, the mass flow of the water displaces the air and less air is actually pulled into the engine.  Some of the water does, the majority goes into the cylinder in droplet form (liquid, not vapor).  This has been evidenced by opening up the upper galley of Merlins after a race and still finding standing water and fuel in the intake manifold.  Puddles.  The tuners who believe that this is normal never get outside of air racing or believe the idiocy that aircraft engines are somehow "different" from all other engines.  They are, they're older.

Be very careful of comparing old data (WWII) with new technology.  Where the water evaporates in the complete engine cycle and how the engine actually uses that latent heat and working gas varies radically.  A proper system would use high pressure injection to vaporize the water-methanol downstream of the compressor.  Done correctly, this increases the density of the downstream charge and provides a drop in pressure on the back side of the compressor, increasing efficiency and "free" boost in the compressor itself.  I have seen an optimum system and it is very different (and superior) vs. what air racers use.  The Sport Class air racers are more progressive, and several are paying attention to aspiration. 
« Last Edit: April 15, 2009, 01:05:54 AM by Blue » Logged

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« Reply #20 on: April 02, 2009, 04:58:15 PM »

My understanding is there is a trade off , cyl temp for density, steam takes up a lot of space..
not sure there is enough temp even with very fine droplet size to get evaporation and pull the heat in a NA engine
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« Reply #21 on: April 22, 2009, 05:13:25 PM »


 New Hot Rod has a 5 page article on water injection, water with nitrous - blowers -diesels and na.

    JL222
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« Reply #22 on: May 05, 2009, 11:06:44 PM »

 Going over my WW11 engine books I had bvillercr take some fotos to post. One is on water methanol injection [ADI] or anti detonation injection.
 Most interesting to me is their octane rating for gasoline and ADI. They rated their gas with an octane number such as 100 and a performance number which would be the octane number when running rich
such as 130 or 100/130 they also had 115 octane which was 115/145,
  115/145 when used with ADI gave them 115/170.
  knowing this I never used the high price gas at Bville for many years when we had water injection and never had detonation problems and usually 25-33 lbs boost. 250  degrees after the intercooler at 33 lbs

  We use the high price stuff now and no water injection but have a much larger intercooler and lower temps.

   Ok Troy post the article grin

    JL222
   
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« Reply #23 on: May 06, 2009, 09:30:51 AM »

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« Reply #24 on: May 09, 2009, 02:18:23 AM »

Historical semantics:

"Intercooler" is a charge air cooler between multiple stages of super or turbocharging;

"Aftercooler" is a charge air cooler between one or more super or turbochargers and the engine.

I'm not sure where we crossed over into calling any charge air cooler an "intercooler", but that's now accepted practice.
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« Reply #25 on: May 09, 2009, 12:26:07 PM »

Historical semantics:

"Intercooler" is a charge air cooler between multiple stages of super or turbocharging;

"Aftercooler" is a charge air cooler between one or more super or turbochargers and the engine.

I'm not sure where we crossed over into calling any charge air cooler an "intercooler", but that's now accepted practice.

  The merlin had water passages between stages that they circulated to keep the whole blower assembly cooler.
 Bvillercr said he would take a foto after we finished the 222 car and got it loaded for El Mirage [he just showed up got to get going on car].

  I never heard of an intercooler untill the 1980s after drag racing an owning supercharged engines since 1956.

      JL222
 
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jl222
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« Reply #26 on: May 21, 2009, 01:41:31 AM »

 One cool thing about last weekend at elmo is we pitted next to Bob Button and the unlimited air racing mustang'' Vodoo'' big rig. Of course I had to ask about the engine.

  160 in of boost, thats about 65 lbs psi  shocked No intercooler and only one impeller [not 2 stageing it] and lots of ADI [water-methanol injection]

  At 65 lbs of boost my charts show 570 degree temp at 65% efficiency on a 70 degree day coming out of the blower that should evaporate a lot of adi tongue

  Bob bought Seth Hammond's modified roadster and he and their crew are fun guys.

   JL222
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« Reply #27 on: July 16, 2009, 03:10:30 PM »

I am putting a real simple water injection unit (that I experiemented with 25 years ago) on a stock '65 VW bus. No racecar, the VW is bone stock and burns regular 87 octane pump gas. The goal is to cooler temps while running the poor little thing at 4200rpm for 30hrs straight (during the upcoming Vancouver to Ensenada "Beetleball 24" Rally race, we are entered in the stock bus class) Anyhow, I should have something to report with respect to cylinder head and oil temps, but no dyno other than 'seat of the pants'.

One mechinism that I has not been mentioned is water turing to steam in the combution chamber... water expands what, an order of magnatude by volume when it changes state (liquid to gas). If done right, by happenstance or on purpose, that expanding steam could translate to an increase in power in an ICE engine (normally aspirated or supercharged), couldn't it?

Getting really far out there...  if we could just get the hydrogen to separate out from the oxygen, then into hydrogen's smaller components, duterium and tritium, get the cylinder pressure to about one million bar or so, you'd might get a small fussion event inside your engine with each pulse! The good news is you wouldn't even need another fuel (other than water) The bad news is you'd need a stronger engine just to keep the heads on and the rods in it!  shocked

Sorry... the science geek in me just had to go there  embarassed
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« Reply #28 on: July 16, 2009, 05:10:06 PM »

I don't know how to research it -- but years ago there was reference on this site to Bruce Crower's newly-invented (and patented?) 6-stroke combustion engine that relates to what you said.  Fascinating article.  His health in recent years may have contributed to his on-going research.  Someone help us out?

Stan Back
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« Reply #29 on: July 16, 2009, 06:00:06 PM »

Jack D said: 

   Re: Hayabusa Engines in Car Classes
Reply #60 on: July 30, 2007, 08:13:30 PM Quote 

--------------------------------------------------------------------------------
Look up Bruce Crower's 6 cycle diesel that uses the exhaust heat with water to extract the additional power that water to steam can provide in an otherwise idle cylinder.
Consider the expansion rate of water to steam and see if otherwise waisted heat might be useful.
It is proposed to be a High School project for next school year using one of My RX7s.
Several truck engine builders are interested in his patent.


http://www.google.com/search?hl=en&q=bruce+crower+diesel+patent

Mike
 
 
 
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