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# Water injection and alcohol fuel(14)

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 Slim3 (Automotive) (OP) 19 Jan 12 2:30
 Water injection-I received a DOE grant in 1980 to build an alcohol still and convert a car to run on straight alcohol. I made 160 proof alcohol and purchased 200 proof to run tests with the car. After tuning the engine (modified to run on alcohol) I ran tests on 200 proof, 190, 180 and 170 proof tuning for each mixture.I found that in 1/4 mile acceleration tests, (3 each) there was very little difference between the 200 proof and the 170 proof runs which puzzled me as I had displaced 15% of my fuel with water in the 170 proof. It was suggested that the water in the 170 was going into the combustion chamber as a liquid and turning to steam which replaced the 15% heat expansion from the fuel burn thus maintaining the power. Even though it lowered combustion chamber temp it still performed the same. I suspect that the steam expansion out performed the gas expansion.This made me install a aux water injection system on two 318 Dodge engine trucks and run the same tests and they also produced more power then just on gasoline.It was noted that the engine in poor condition raised in power more then the good engine.I made no fuel mileage tests.
 patprimmer (Publican) 19 Jan 12 3:41
 If your alcohol contains 15% water, you need to increase fuel delivery by about 15% to avoid a lean out. In that case, you burn the same amount of fuel with the water along for t5he ride.The water will effectively raise the octane rating of the fuel so you can use higher compression or more ignition advance to gain some power RegardsPatSee FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &http://eng-tips.com/market.cfmfor site rules
 Slim3 (Automotive) (OP) 19 Jan 12 10:35
 The compression ratio had been raised to make use of the higher octane rating of alcohol and the ignition timing was reset for each different proof. The dual Stromberg carburetors have metering needles so it was easy to adjust to each proof. Even though I did not conduct fuel mileage tests, I was using a small one gallon tank mounted under the hood to make all the runs. (three on each proof tested) Each proof received three full throttle 1/4 mile runs and three driving runs back and did not note much difference in fuel used between the different proofs. Before the engine modifications I made test runs in the same 1/4 mile full throttle runs, to get a bench mark of performance and using the same on gallon fuel tank.I did note more of the amount of alcohol blends was used then the straight gasoline, which I expected. However it was not the 96% more expected due to the 96% larger jet (volume not diameter). Due to the lower BTU content in alcohol. I contributed this to the higher compression ratio used on the alcohol blends producing a more efficient use of fuel coupled with the shorter time on the track (less actual revolutions of the engine through each run). I do wish I had conducted controlled fuel mileage tests. However by the time I finished the tests of the still and car, fuel prices came down and potential investors all said, "Fuel prices came down, why bother?".   http://mg-tri-jag.net
 MiketheEngineer (Structural) 19 Jan 12 13:41
 During WWII - many piston engines were equipped with water injection.  I think some high performance racing planes still do.There were some varying theories.1.  The "weight" of the water increased compression...2.  The heat from the engine actually turned the water back into hydrogen and oxygen.Never found a good answer about this.
 patprimmer (Publican) 20 Jan 12 0:19
 The real reason is the latent heat of vaporisation of the water reduces peak temperatures and suppresses detonation, so more boost or higher compression could be used. The boost and/or compression is what gave the extra power, not the water per-say. The water simply had the effect of increasing octane.Water injection is still used on high boost engines as a detonation suppressant. RegardsPatSee FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &http://eng-tips.com/market.cfmfor site rules
 Slim3 (Automotive) (OP) 20 Jan 12 1:22
 When I received the DOE Grant a company in the SC sent me several water injection add on systems to try. They said a 50/50 Alcohol/Water mix worked best on gasoline and diesel engines. I tried several combinations on a gas engine (318 Dodge). I tried straight water, 50/50 alcohol/water and straight alcohol and the results confirmed what they said. A 50/50 alcohol/water (100 proof) produced the most power when injected into the carburetor of a gasoline engine.No adjustments were made to the engine and only acceleration tests were run.The method of injection was done with a small valve and a rich mixture was injected into the intake until a stumble was noted and then the injection was leaned out until the stumble cleared up. Then the acceleration run was timed. Probably even better performance could have been achieved if I had taken advantage of an advanced ignition timing as you say.I only ran the tests as recommended by the company who sent me the systems. I was surprised as I first did not believe them about a 50/50 mix.  http://mg-tri-jag.net
 jellydonut (Marine/Ocean) 20 Jan 12 2:33
 Nowadays water\methanol is used because obviously methanol is easier to sell (and no one's gonna try to drink from your tank!).Diesel enthusiasts use it to cool EGTs and allow for higher output by injecting more fuel.In the maritime sector, fuel/water emulsions are used by the large engine companies. The claimed effect of emulsion of water in the fuel is a) cooled combustion chamber resulting in lower EGTs and b) that the rapidly vaporizing/expanding water going over to steam helps to 'crush' the larger diesel globules that weren't sufficiently atomized in the injector, improving combustion and efficiency.It's all claimed, but when large, old actors like MAN (who indeed funded Rudolf Diesel and let him build his first engine) sell this for actual commercial ships, it has to have some merit. It does at least reduce NOx. From the cooling effect, if nothing else.The Crower six-stroke engine injected water to turn the engine into a steam engine for two cycles after the four fuel cycles. One would expect that injecting water that vaporizes into steam, expanding with a factor I can't remember at the moment, would provide more torque to the expansion stroke in a regular engine.
 Tmoose (Mechanical) 20 Jan 12 12:14
 I think if the energy required to turn water into steam was instead applied to heating the air (and whatever other gases are in the air fuel mix) the result would be higher combustion chamber pressure than the steamy condition.  Combustion chamber pressure is what makes torque.
 Slim3 (Automotive) (OP) 20 Jan 12 13:41
 From my tests of alcohol with 15% water in it and from all that Jellydonut points out, there is plenty enough evidence that water injection can produce a lot of power and added economy.If we had a catalyst that would truly mix at least 15% water in gasoline and not have any phase separation, that alone would decrease our use of oil nation wide.  http://mg-tri-jag.net
 patprimmer (Publican) 20 Jan 12 17:27
 Ummmmjellydonuts post falls far short of supporting your hypothesis.He is suggesting that water boiling inside large diesel droplets increases dispersion and reduces droplet size of the diesel fuel. That aids rapid combustion in that case, but does not really transfer over to petrol due to the lower boiling point of petrol and the fine mist already achieved with modern fuel injectors.Injecting more fuel into a petrol engine can make more power, but ir reduces fuel economy and increases HCs and CO in the exhaust.The Crower 6 stroke has nothing to do with water added during the first power stroke which is where it would be happening if added to the fuel.A turbo does not extract wasted energy from the exhaust and turn it into power, unless you use the turbine to drive the car rather than to drive a supercharger. Even then, while extracting the free power, you considerably increase temperature and pressure in the cylinder during the exhaust stroke, thereby using crank power to drive the exhaust stroke against higher pressure and leaving more hot residue in the chamber thereby limiting compression ratio and ignition timing, both of which hit power and economy.Technology already exists to form water emulsion in petrol.When measuring fuel economy of a water/alcohol blend injection equipped engine, you also need to count the alcohol burned as fuel burned.When you boil the water to make steam, you also cool the charge. The steam makes pressure, BUT the converting water to steam cools the charge which by itself reduces pressure, so when you do something to make pressure that absorbs pressure in the process, you quickly disappear into the same orifice as all other perpetual motion machines.   RegardsPatSee FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &http://eng-tips.com/market.cfmfor site rules
 Slim3 (Automotive) (OP) 21 Jan 12 1:48
 That all sounds good on paper but I ran acceleration tests many times and found that the alcohol with 15% water (170 proof) performed just as well as 200 Proof. I know how to tune an engine and tuned the engine on each fuel. That was a Triumph TR-7 with two Stromberg carburetors with adjustable metering needles.I also ran tests on two different Dodge 318 engine trucks using water injection added to a standard gasoline carburetor and noted improved acceleration runs with plain water and with different ratio mixtures of alcohol and water and all the mixtures improved acceleration times on both trucks and both were tuned. I am sure that the vaporization of water in a combustion chamber does tend to use some of the heat produced but possibly the expansion of steam out performs the expansion of hot air.What I do know first hand is that it works.  http://mg-tri-jag.net
 thruthefence (Aerospace) 21 Jan 12 12:19
 To further muddle the issue, here's an article dealing with water/alcohol injection in gas turbine engines, by a Pratt & Whitney engineer. In the article is also a brief description of the  forces at work in a recip as well.3Cairliners.1996.265@ohare.chicago.com%3E" target="_blank">http://www.kls2.com/cgi-bin/arcfetch?db=sci.aeronautics.airliners&id=%3Cairliners.1996.265@ohare.chicago.com%3E
 Slim3 (Automotive) (OP) 22 Jan 12 2:43
 Thanks Thrusthefence, that article by Pratt & Whitney was informative and the Piston engine part clearly explains why I got more performance from the two Dodge engines by adding water injection. I was only thinking of the steam produced and didn't think about the fact that the latent heat of vaporization of the water in the intake manifold giving the engine a condensed cool charge of intake air. A cheap turbo/super charger.  http://mg-tri-jag.net
 140Airpower (Automotive) 2 May 12 13:19
 hemi (Automotive) 2 May 12 21:54

#### Quote (140Airpower):

But, auto turbo setups are indeed almost never for economy.
I respectfully disagree.  Even in the early days (not counting the very early Buick & Corvair turbos), when turbos were applied to performance applications only, that was usually in an effort to maintain performance while increasing fuel economy, in comparison to the large displacement, N/A alternative (e.g. Turbo Trans-Am, Buick Regal/GN, Mustang GT/SVO, Thunderbird Turbo Coupe).  Not that the economy quest was hugely successful, but it was driven, in part at least, no doubt by CAFE.
Today, this is even more the case.  Case in point, Ford Ecoboost.
The argument is even stronger for diesel applications.  I don't think there has been a diesel automotive application since the 90s that isn't turbocharged.  Few of these can seriously be considered performance, rather than economy oriented.
 140Airpower (Automotive) 2 May 12 23:09
 hemi, you are correct that turbo-diesels are designed generally for economy. I am not familiar with their parameters. I question if they are optimized for efficient operation of the turbo setup overall, with large scrolls and low back pressure with no wastegates. Do they often have intercoolers? The automotive requirement is for a certain minimum acceleration which tends to preclude the greatest efficiency in the turbo application. Nevertheless, a turbocharged diesel engine in an auto application can give better economy than an equivalent gas engine and that is what counts for calling it an economy engine. The other characteristics like smaller, lighter engine size compared to a non-turbo diesel of equal power may make the whole package more economical with the turbo. Even the use of an intercooler, an energy sink that lowers efficiency, can allow a smaller engine to replace a larger one and the whole package may end up being more economical. So, my statement was probably too sweeping and simplistic.The high performance cars you mentioned were not economy cars even if they got better mileage than the equivalent performing non-turbo cars and they are more like what I am talking about with respect to a non-efficient turbo installation..BTW, the earliest turbo auto engines were the Oldsmobile Jetfire (not buick) and Corvair Monza Spyder of 1962, 12 years before Porsche.
 Slim3 (Automotive) (OP) 3 May 12 1:29
 Lots of great information bouncing around here. I am now studying compressed air as a power source for an engine. I have built a Olds 215 to start on direct injected compressed air and it works well. My next project is a full operating compressed air engine. However to expect any range I had to alter the geometry of the piston engine. It looks good on paper so I will build a proto-type soon. fitzcharlesh@bellsouth.net
 dgallup (Automotive) 3 May 12 11:50
 140Airpower - I would certainly disagree with your assertion that an intercooler is an energy sink that lowers efficiency.  It's been 30+ years but when I was testing class 8 diesel engines the biggest improvement to power and efficiency I could make came from lowering charge air temp (more intercooling).  It allowed more power and better BSFC within the cylinder pressure, exhaust gas temp and NOx limits of the era. ----------------------------------------The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.
 1gibson (Mechanical) 3 May 12 12:29
 I've always thought there was something to increased mass flow through a turbo due to addition of water injection. May positively impact intake/exhaust pressure ratio, because the turbo can perform the same or more work (additional energy from mass flow) at the same or lower pre-turbo exhaust pressure.I also have this vague concept that a cylinder charge including some steam, could be slightly less compressible than cylinder charge that does not, assuming equal cylinder pressure. Which may favor increase torque?Now, somebody correct me? :)
 140Airpower (Automotive) 3 May 12 13:28
 dgallup, an intercooler dumps compression heat, energy, into the atmosphere. It is a heat, energy, sink.There is no question an intercooler is normally highly beneficial to the operation of engines. This is due mainly to combustion characteristics and operating points. In particular, decreasing charge temperature in supercharged or NA engines allows a higher total compression, from supercharging plus static CR, without detonation, a fuel issue. That generally increases thermal efficiency. This does not change the fact that an intercooler is an energy sink.A motoring cycle, where the supercharged engine is run at speed without ignition, takes more energy with an intercooler in place partly because of the restriction it poses and mostly because the lost compression heat returns less energy on the expansion stroke.Did you do any motoring cycles? This is normally not of interest.
 winfieldblue (Automotive) 3 May 12 18:45
 140Airpower, I would have thought that a cylinder filled with a larger mass of air would have more expansion given the same amount of fuel/btu's. The compression ratio would be higher with cooler air.....and that would explain why my idi diesel engine suffers a large power loss when breathing pre-heated intake air!
 hemi (Automotive) 3 May 12 19:05

#### Quote (140airpower):

BTW, the earliest turbo auto engines were the Oldsmobile Jetfire (not buick) and Corvair Monza Spyder of 1962, 12 years before Porsche.
Yes, those were the two I had in mind, I mistakenly wrote Buick since the Olds 215 was simply a derivative of the Buick 215.  Thanks for pointing that out.
I guess our common ground is that the early (2nd gen, 70's) auto turbo applications I was alluding to (turbo Trans Am, Buick Regal, Ford 2.3 e.g.) were attempts at economical performance, not economy cars per se, which is all I was trying to say.
 hemi (Automotive) 3 May 12 19:08

#### Quote (winfieldblue (Automotive)     3 May 12 18:45):

140Airpower, I would have thought that a cylinder filled with a larger mass of air would have more expansion given the same amount of fuel/btu's. The compression ratio would be higher with cooler air.....and that would explain why my idi diesel engine suffers a large power loss when breathing pre-heated intake air!

winfieldblue, can you give us the P-V and T-S diagrams for that?
 140Airpower (Automotive) 3 May 12 19:35
 1gibson, water, H2O, is a lighter molecule than either nitrogen, N2, or oxygen, O2. To the extent that water vapor replaces air, the charge becomes lighter by mass. Furthermore, the replacement of an amount of air by water vapor lowers power by that exact amount.The mechanisms by which water helps have been measured, calculated, surmised and speculated on by many authors.From what I can tell....The benefit of water as a VAPOR is that by replacing some air it lowers combustion pressure from charge dilution. At high enough temperatures its specific heat increases above that of the burned and unburned parts of the charge, thus reducing temperature and pressure and it also begins to dissociate, absorbing even more heat. The presence of water vapor then tends to slow the burn and reduce the peak temperatures and pressures. It is a good anti-knock agent with any and all fuels in an SI engine. It has somewhat different beneficial effects in diesel engines and jet engines. Water introduced as a LIQUID, sprayed into the manifold or direct injected, will absorb a LOT of heat from its very high heat of vaporization. In the manifold, it will cool the charge air to the extent that it evaporates (charge air has to be hot) and will thereby increase the charge density. What water that does not evaporate in the manifold or if it is direct injected it will retard the temperature and pressure rise on the compression stroke from the heat it absorbs while evaporating and then reduce the maximum temperature and pressure during combustion from the mechanisms described above.Water is usually measured as a percent of fuel by weight. Popular water injection systems can be set to inject water up to some low value like 25% of fuel. However, I have not seen anything that says there is a limit to how much water can be injected under high boost up to 360%, 3.6 x the amount of fuel by weight direct injected. In WWII 60% of fuel was common and 150% of fuel was documented. The combined anti-knock effects run anywhere from 1.5 to 3 octane numbers, ON, per 10%. One test gave 20 ON for 60%.Later in the power stroke water returns the energy it has absorbed. In a turbo setup, I believe the return of energy should be greater compared to an open exhaust setup. However, water lowers the thermal efficiency of an engine overall (in terms of BSFC) even while increasing the maximum boost allowable and power output (the figures I've seen on efficiency do not account for the decrease in the required cooling power).Also, there is a great benefit in mixing 50% Methanol with the water in terms of much better evaporation, cooling and increased charge density in the manifold and therefore more power. The merits of Methanol were discussed before.
 140Airpower (Automotive) 3 May 12 19:49
 winfielblue, I think you are correct.
 140Airpower (Automotive) 3 May 12 20:16
 1gibson, I think that thermal efficiency is a tricky thing to measure accurately. BSFC is a standard yardstick since Ricardo's early days, but measurements of BSFC on a dyno can be skewed by such things as coolant temps and whether the engine runs its own water pump and provides its own power for the radiator fan. Heat rejection is a factor and ignition or injection timing, mixture, CR, back pressure, etc come into play. The use of an intercooler is part of the cooling budget. I am well aware of the undeniable advantages, but I wonder about the thermal accounting.
 winfieldblue (Automotive) 3 May 12 20:46
 Hemi, I have no diagrams for that, I'm trying to figure out why my N.A. idi diesel makes more power with a cooler intake charge while using the same fuel quantity (full throttle). This engine has no computer,so intake air temp doesn't change injection timing or the amount of fuel injected. Where does the extra power come from? 3 possible explanations spring to mind, one being a higher compression ratio from more air density, two being more heat transfer into the cooler combustion air rather than to the cylinder/head/piston,and three I'm wondering if the expansion rate of air is linear in regard to temperature. Any other offerings would be appreciated!
 azmios (Automotive) 9 Oct 12 12:46
 Slim, I think the SAE paper 2009-01-2808 and 2009-32-0047 will shed some light on why water injection makes more power. There are also many gas turbine that use water injection to make more power, lower fuel consumption and reduces NOx.
 Slim3 (Automotive) (OP) 10 Oct 12 2:02
 Thanks azmios, I will try to find those SAE papers and read them. I am about to finish up my direct injected compressed air starting system on my show car and plan to enter it in the Oct 13th British car show in Nashville.
 azmios (Automotive) 10 Oct 12 2:52
 Slim, if you go over the paper, water has a high specific heat capacity and latent heat of evaporation. This simply mean that it will absorb a lot of combustion heat thus minimizing the combustion heat from being wasted. Furthermore, the gas constant R for steam is much higher than nitrogen or CO2, at high temperature, the pressure increase is also much bigger than the CO2 or N2 gas expansion.
 Compositepro (Chemical) 10 Oct 12 12:48
 Er... the gas constant is just that, constant. You are probably referring to the molecular weight effect where one gram of water vapor has more volume than one gram of CO2. However, the effect of temperature and pressure change is the same on both gases.
 azmios (Automotive) 10 Oct 12 13:20
 Compositepro, Not really, you first have to read the SAE paper. The gas constant R is independent of the molecular weight. The constant R is relevant according to the P=mRT/V. With higher specific heat capacity of water, you will get higher T. Once you plug in that T, the higher R will give you higher P too.
 (2)  hemi (Automotive) 10 Oct 12 18:21
 Azmios, water injection, along with other substances and methods of internal cooling, does not inherently increase power. In fact, with no other changes, it does the opposite. The benefit of internal cooling is that it permits more power to be made, due to its various direct effects on physical limitations on maximum power, which are application dependent. The most obvious effect is it reduces local peak temperatures in the combustion chamber and exhaust system. Taking advantage of this effect, the performance engineer can increase the maximum charge flow, gaining net power while not exceeding material temperature limits. A secondary effect of the cooling is that combustion rates are reduced, which tends to reduce peak pressure. Taking advantage of this, the performance engineer can take steps to move the combustion phasing closer to TDC, or increase the charge flow, gaining net power while not exceeding power cylinder and cranktrain stress limits. In Otto-cycle applications, maximum power is typically knock-limited. Internal cooling typically has a very strong effect on suppressing knock. Taking advantage of this, the performance engineer can re-optimize compression ratio, charge flow, air/fuel ratio, and combustion phasing for substantial gains in net power. "Schiefgehen will, was schiefgehen kann" - das Murphygesetz
 patprimmer (Publican) 10 Oct 12 19:30
 Hemi. An excellent explanation. Regards Pat See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers & http://eng-tips.com/market.cfm for site rules
 hemi (Automotive) 10 Oct 12 22:13
 Thanks Pat. Every once in a while, a blind squirrel finds a nut. "Schiefgehen will, was schiefgehen kann" - das Murphygesetz
 patprimmer (Publican) 10 Oct 12 22:37
 Even if only by bumping into it and hitting his head hard. Regards Pat See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers & http://eng-tips.com/market.cfm for site rules
 azmios (Automotive) 11 Oct 12 6:26
 hemi, i think you should rear paper below "High output supercharging without intercooling: theory and results" by J W G Turner and R J Pearson. There is also an explanation that Slim is looking for on why the mixture of methanol and water returns better power in Charles Taylor's engine text book. As for your explanation about water in the combustion chamber not producing any power. I beg to differ because of the paper below: - 1) Lestz, S.J., Melton, R.B. Jr., Rambie, E.J.,“Feasibility of Cooling Diesel Engines by Introducing Water Into the Combustion Chamber,” SAE paper no. 750129, 1975 The paper above is done by the US Army researchers decades ago,the paper will tell you why you're wrong. The power went up a lot when water is present in the combustion chamber. In case you are not aware, Nasa also published several papers on the use of water injection to achieve extreme thrust in the jet engine. These papers will also tell you that you are really wrong. I wish that I can tell you a whole lot of other wonderful things that can come with water in combustion chamber of piston and turbine engines, unfortunately for me most of them are classified. There are so many things that people outside of the organizations that do skunkwork under the government funded research projects will never understand. Even if others fail to understand, we dont simply insult them, instead we simply say "ignore him he's not one of us, dont bother to explain". Anyhow, I bet you wont bother to read all these papers right that I quoted right, so I wont bother to explain any further.
 Slim3 (Automotive) (OP) 11 Oct 12 10:42
 Thanks again azmios, for the clear explanation. I didn't know why it worked, I just know for sure that it does work and works well from my experiments and practical application. Those in doubt need to actually try it. Slim3
 azmios (Automotive) 11 Oct 12 11:25
 Slim3, here is another proof to support your claim http://www.lotuscars.com/gb/engineering/lotus-exig...
 140Airpower (Automotive) 11 Oct 12 15:32
 The effects of water introduced in piston engines has been studied since the very early days of the 20th century and comprehensive, complete and definitive answers are not all in hand. Studies are being done to this day. However, of everything I have found, nobody says that water releases energy and produces power and in fact water CANNOT produce power in these types of engines. That is not to say that the ENGINE cannot produce more power with the introduction of water for several reasons. The most obvious reasons have already been mentioned by other posters. From what I've read, a normally aspirated engine that is performing correctly will suffer a loss of power if water is injected into the manifold. For a supercharged engine there are a variety of results that you can get depending on circumstances and especially if the engine is designed for water injection. Gas turbines are different.
 patprimmer (Publican) 11 Oct 12 21:57
 azmios. Unless I really missed something somewhere, if the power from the steam pressure is more than the power absorbed to convert the water to steam, you have an over unity device. ie you just destroyed the classic laws of thermodynamics and can now build a perpetual motion machine that will contribute work to the outside as well as sustaining itself. Now if we can also turn lead to gold we can control the worlds power and wealth. Regards Pat See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers & http://eng-tips.com/market.cfm for site rules
 Slim3 (Automotive) (OP) 12 Oct 12 1:10
 Pat, you mean that you can heat air and get just as much power as heating water and turning it into steam? I didn't know that. Why didn't steam engines just heat the air and not bother with the water? Does heating air give you the same expansion power as turning water to steam? That still don't explain to this uneducated mind why in my test runs that an injection of 50/50 water/alcohol out performed any other mixture ratio in either direction. And did it in a good 318 Dodge and a worn out 318 Dodge. The company that gave me the injection systems made that claim and I had to test it because I couldn't understand why and I still don't understand it. Slim3
 azmios (Automotive) 12 Oct 12 3:51
 140, let's make it simple. Once fuel is ignited, there will be lots of heat released. Heat alone will not move piston or turbine, but expansion of gas will. If I ask my 9 years old son to put down a burning campfire or cool off hot metal quickly, he will not use gas or fan, instead he will use water. Similarly, if I dont absorb the combustion heat in a turbine or piston engine quickly, lots of heat will be absorbed by the metal, coolant and the combustion gases. Once the combustion gases absorb the heat, it will expand and pushes the piston down. The combustion gases consists mostly of N2 and CO2. Both have low specific heat capacity meaning that it will absorb some heat but it is not the best medium. Let's assume if we can somehow introduce water in the combustion chamber preferably when ignition event is about to end, the water in liquid state will absorb heat, until it reaches the boiling point. Once it boils, it will absorb a lot more heat in order to change its state to gas. Even in gaseous state, the specific heat capacity is still higher than N2 or CO2 thus it will continue to absorb heat until equilibrium is reached. Once the water turns into steam, you can use the gas constant R to calculate the pressure increase (to move the piston downward) using ideal gas law. This is what those SAE and Nasa technical papers are trying to tell us. I do agree with your opinion that water does not make power, nothing wrong with this as water is not a fuel. However, water is really helpful in absorbing the combustion heat and to expand to make work. Also, if you read the SAE papers, water can function as an energy carrier in which you can heat up water before it is injected into the combustion chamber. This will speed up the change from liquid state to gaseous state. Check out the work done by Transonic, they use fuel as an energy carrier by heating up the fuel before it is injected into the combustion chamber.
 azmios (Automotive) 12 Oct 12 3:58
 Pat, I beg to differ. The heat released from fuel is always more than the kinetic energy created after that. How can you have over unity unless someone is blinder than a blind squirrel??? Water in both liquid and gaseous states naturally have very high specific heat capacity meaning that it wont stop absorbing the heat until equilibrium is reached. The hotter the steam becomes, the bigger the gas expansion is. That's I quoted the use of specific heat capacity and gas constant R.
 azmios (Automotive) 12 Oct 12 4:23
 hemi, where are you? we need to debate further about this water injection as I have all the time to do so.
 hydroman247 (Mechanical) 12 Oct 12 4:24
 This is extremely interesting. Do you have any articles or research papers you can link us to azmios? Thanks
 azmios (Automotive) 12 Oct 12 4:48
 hydroman, scroll through my earlier replies. many of them are available for free, i have included the links
 patprimmer (Publican) 12 Oct 12 5:57
 There seems to be some misuse of some very technical sounding words here. I detect an attempt at BS baffles brains type sell job. Nothing, if it's colder than it's surroundings, no matter what it's specific heat, will stop absorbing heat until equilibrium is reached. That is kinda what equilibrium means and it has nothing to do with specific heat. This is simple high school physics. Regards Pat See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers & http://eng-tips.com/market.cfm for site rules
 azmios (Automotive) 12 Oct 12 10:49
 "Nothing, if it's colder than it's surroundings, no matter what it's specific heat, will stop absorbing heat until equilibrium is reached. That is kinda what equilibrium means and it has nothing to do with specific heat." Heat absorption has a lot to do with specific heat capacity. That's why some rankine cycle uses liquid that has greater specific heat capacity. Also, if you compress water, the specific heat capacity tend to go up and therefore becomes better heat absorber. You can read all of these in the papers that I listed above. Since these papers are peer reviewed and written by specialists in those areas, I would rather trust these authors than someone who makes a living as a textile engineer and never publish anything in engine journals.
 hemi (Automotive) 12 Oct 12 11:20
 azmios, The title and abstract of the SAE 2009-01-2808 paper are as follows: Feasibility Study of a Novel Combustion Cycle Involving Oxygen and Water Abstract: A novel combustion cycle which operates in 2-stroke operation and utilizes a novel exhaust valve timing and lift strategy is proposed to potentially replace the existing Otto and Diesel cycles. Air is replaced with oxygen to maximize the combustion efficiency and to enable broader range of fuels to be used. Water is injected into the combustion chamber to enhance the combustion heat absorption, gas expansion and to function as an energy carrier. Engine secondary heat that will otherwise be wasted to the environment is recovered and reused by the engine. Engine theoretical efficiency and out emissions are predicted to be improved. I don't need to read the whole paper to recognize that the process described is quite unrelated to water injected conventional cycles. Furthermore, it is a feasibility study only with theoretical results, not proven science; I haven't heard of any practical developents along these lines, have you? The same comments apply to the other paper you referenced, SAE 2009-32-0047 which is by the same author, I might add. I could not locate the Turner and Pearson paper on the web. Would you care to quote the passages from the US Army and NASA papers that state adding water increases power? "Schiefgehen will, was schiefgehen kann" - das Murphygesetz
 azmios (Automotive) 12 Oct 12 12:01
 Hemi, good to hear from you again. For the US army, read the first section of the conclusion and also the additional expansion in Figure 8 PV diagram. For the nasa paper, try this one "Analysis of Gas Turbine Engines Using Water and Oxygen Injection to Achieve High Mach Numbers and High Thrust" by Hennebery and Snyder. I have with me the paper from Turner and Pearson, not sure whether you can get the softcopy for free. As for the 2009-01-2808, the proposed concept is too complex and if you attend the previous SAE congress, many of what proposed in the paper are broken down into sub areas, like oxygen combustion, heat recovery, 2 stroke with poppet valve, etc. If you combine all these smaller researches, we may get something closer to what proposed in the paper.
 hemi (Automotive) 12 Oct 12 14:50

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