Water injection and alcohol fuel 14

[Slim3]

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]

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

Regards
Pat
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[Slim3]

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?".

 

[MiketheEngineer]

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]

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.

Regards
Pat
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[Slim3]

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.

 

[jellydonut]

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]

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]

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.

 

[patprimmer]

Ummmm

jellydonuts 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.

Regards
Pat
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[Slim3]

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.

 

[thruthefence]

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.

http://www.kls2.com/cgi-bin/arcfetc...ers&id=<airliners.1996.265@ohare.chicago.com>

 

[Slim3]

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.

 

[140Airpower]

patprimmer, your comments are insightful as always, but I’d like to bring up some additional issues.

“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.”

It is actually quite relevant. An important benefit of the steam stroke in the Crower engine is that the energy comes from heat rejected into the engine metal, obviating the need for a cooling system. This energy normally lost to the atmosphere is partly saved. The example of the amount of water needed to internally cool the Crower engine tells you how much water is needed to similarly cool a 4-stroke with water injection. Studies during WWII investigated the possibility of total internal cooling of aero engines while enjoying the other advantages of water injection. It was found effective at medium and high power, but not practical to carry the necessary weight of water in an aircraft. It was also not possible to run at lean cruise while injecting enough water to completely cool the engine due to rough running (apparently extinguishing the burn). Finally, the added alcohol needed to avoid freezing would compromise the cooling ability of the water (they were not considering converting from AvGas to alcohol). More on internal cooling below.

“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.”

Are you discounting the work the turbocharger does in charging the engine, reducing induction losses to negative values (supercharging), thus compensating for exhaust pressure? The greater volume of exhaust flow means it is possible to have a turbo setup run with higher intake pressure than exhaust back-pressure in stationary or constant speed engines that do not have a demand for quick acceleration. Small scrolls and wastegates make auto installations inefficient.
Economy also comes with the smaller, lighter, lower capacity engine and, possibly, lower pumping losses at cruise.
And, of course density gained on the intake side is multiplied during the combustion process into additional power, making a turbo system worthwhile even when not so efficient and despite a lower static CR. But, auto turbo setups are indeed almost never for economy.

“Technology already exists to form water emulsion in petrol.”

As far as I know, water/gasoline emulsions are not stable, long-term. Methanol/water is stable, but Methanol/gasoline is unstable in the presence of moisture, even atmospheric humidity.

“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. “

Pat, this is true, but only part of the equation. It ignores the fact of greatly reduced heat rejection as mentioned above. The lower heat rejection shows up as energy of expansion. The saved energy is all converted to additional pressure. This does not translate completely to added power because the peak pressure is lower, as you observe, but the pressure at succeeding parts of the expansion stroke is greater. Overall, it CAN be a gain. Spark advance should be increased.

 

[Lou Scannon]

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]

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]

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.

 

[dgallup]

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.

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[1gibson]

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]

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.