Water injection and alcohol fuel 14

[patprimmer]

slim

While alcohol, or at least Methanol and to a lesser extent Ethanol have less energy per unit mass, they also require more fuel for stoichiometric reaction so that in theory all the fuel and oxygen are fully consumed.

The extra fuel required is more than the decrease in energy, so the net energy that can be released per unit of oxygen is about 10 to 15% greater or at least in that ballpark.

If you got a decrease in power from using alcohol, there was an increase in energy waste somewhere, from anything as simple as the mixture was to cold to light off properly at the lower compression. Methanol seems to keep improving at up to about 16:1 CR. With a bad designed chamber/piston dome it can require up to 60 deg ignition advance in an engine that might normally require 35 Deg for optimum.

Although you claim nothing else changed with your tests, you in fact went richer via the alcohol added to the intake manifold. The weaker alcohol made you less rich.

Regards
Pat
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[140Airpower]

Pat, Good Point, "Although you claim nothing else changed with your tests, you in fact went richer via the alcohol added to the intake manifold. The weaker alcohol made you less rich".
Anectdote: When Pratt and Whitney first deployed water injection for the R-2800 they instructed crews in the field to add alcohol as an anti-freeze. Using Methanol was fine, Ethanol was ok, but when Isopropanol was used, there was a loss of power.

 

[Lou Scannon]

Slim3, I agree with Pat and 140Air, the power increase you noted when you injected water/methanol in those 318 engines was probably due partly to a slight and beneficial enrichment due to the methanol, considering that the starting point for engines of that vintage was probably lean of optimal for power. And partly due to the evaporative cooling effect on charge density (as shown in NACA Report 756 Figure 6 above).
My remarks in this thread about the effects of internal cooling on power should be taken in a context that assumes that the engine is already running at an optimized fuel/air ratio for power, and the internal coolant is intended for cooling via heat of evaporation and charge dilution, not enrichment of the fuel/air mixture.

"Schiefgehen will, was schiefgehen kann" - das Murphygesetz

 

[maxc]

Slim3 What was the flow rate of the methanol/water injected in the 318? Did I miss that?

 

[Slim3]

Sorry maxc, I had no equipment to monitor flow rate and it was always ethanol that I had made with my still. All I did was done with standard mechanics tools. The flow rate was adjusted to a high rate while at a high throttle opening until the engine stumbled and then leaned out just enough to make the engine run cleanly (no stumble or misfire) and that was the method use on each proof of ethanol/water tested, all the way down to plain water. 100 proof did perform best as the company that gave me several injection systems claimed.

Thanks hemi, pat and airpower for all the info as it seems that what you say is that my increase in power on the 318's was the result a richer mixture with the additional fuel (alcohol) and a cooling of the air charge in the intake due to the evaporation of the alcohol and water. Did I correctly understand what you all said?

Slim3
"I'll be back" I am now playing with compressed air as a power source for an engine. Don't dispute that just yet as I already know that the Otto engine is not efficient enough to get any range with what compressed air can be carried on a vehicle.

 

[patprimmer]

Yep pretty much.

Regards
Pat
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[btrueblood]

"I am now playing with compressed air as a power source for an engine. "

Think about liquid nitrogen instead. U of Washington did this awhile back on a little Grumman mail jeep, and wrote a white paper that showed why/how it could be economically feasible.

 

[Slim3]

btrueblood, I ruled out "fuels" like that due to cost. Can you picture gas stations/markets with liquid Nitrogen in stock for customers and how much would that cost for a fill up? That would get a better range then just a compressed air tank but there is no system set up to refill. I went at it from a different direction and worked on the poor geometry of the Otto engine design in an attempt to make better use of the power applied to a crankshaft. What I came up with was the result of my studies while building a Olds 215 V-8 that starts on direct injected compressed air. Just entered the car in a local car show this last Saturday and won 3rd place in a class with finely detailed cars and mine was very poorly detailed but the uniqueness of the direct injected air start system drew a lot of interest in judges and spectators.

The car manufactures in my eyes are not serious about decreasing the value of oil stock with their electric cars. I can buy a used Hummer and tow a trailer for ten years and be ahead in dollars of someone who bought a new electric car today. The only compressed air cars I can find are for inside a warehouse use or the one TaTa is coming out with.

This subject probably needs a new thread started.
Slim3

 

[140Airpower]

slim3, The compressed air engine starter is something unique. Have you calculated the energy capacity of your compressed air tank and figured the cost per BTU?

 

[thruthefence]

The Soviet Bloc M14P radial aircraft engine uses a Compressed air starter. The reservoir tank charges up in flight after engine start, but if for some reason it fails to start, you can pump it back up by hand. Used to be a guy at the airport that has a Sukhoi with one of these things in it.

 

[140Airpower]

I've heard of compressed air starting, but never knew if it involved a compressed air motor or directly applying air pressure to the pistons.

 

[Slim3]

Many diesel truck engines on the over the road trucks use a compressed air powered starter motors but I directly inject compressed air into the combustion chamber to spin the engine over to start this engine.
I designed and built a air distributor keyed to the camshaft and an engage and disengage system so the distributor is not running all the time that the engine is running. The engine runs on gasoline.

I have an on-board air tank to supply air to start the engine. The tank is a 35lb freeon bottle and using 185 PSI, I get only about two tries to start the engine. Right now I just refill the tank from a shop compressor but have designed a two stage 12v compressor to build and put on-board. Barely got the car ready for the car show and no time to build my compressor so I just carried an old Oxy bottle to the show to demonstrate the start system. I have documented all this on my web site just as a hobby.

I heard there was a Russian plane that used an air start system but didn't know if it was a air starter or direct injected air.

I know some WWII bombers used a type of shot gun shell to blow into one cylinder of an 18 cylinder radial engine to start it.

Slim3

 

[140Airpower]

slim3, I congratulate you on your cleverness. Neat.

 

[Lou Scannon]

Coffman starter

"Schiefgehen will, was schiefgehen kann" - das Murphygesetz

 

[msquared48]

This is a very interesting string, but you guys have really lost me here.

I have been thinking about adding additional alcohol.water injection to my 3/4 ton 1993 Suburban with a gas guzzling 454 to get better mileage for years. If I choose to do this, the test for me will be:

1. Documentable better mileage results in the field beyond the current 12 mpg I am getting.

2. The combination of fuels used to be cheaper than the straight gasoline price - I use 92 Octane.

2. No decrease in power delivered to the tranny and transfer case.

3. No damage to the engine or transmission while doing this.

Idealistic? Perhaps, but the intent is to save a little money and extend the life of the engine is possible. I am still thinking this one through. Thanks for the enlightening discussions here. Keep it up!

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[patprimmer]

Mike.

In my often not humble enough opinion, the only way to get better real mileage is to:-

1) Increase the compression ratio and use water injection to suppress detonation and use the extra compression to gain fuel economy. It might take some time to repay the investment in water injection equipment and a LOT longer to pay for new high compression pistons and their installation.

2) Use water/alcohol injection and cut fuel to correct mixture to previous levels, then forget to count the alcohol as fuel.

3) If you are building the engine anyway, the extra cost then, may not be all that great.

Water is by far the cheapest knock suppressant you can get.

I doubt the alcohol added to the water will be a cheap fuel.

I see the main advantage for water injection being in supercharged engines for knock suppression and therefore allowing more boost to get considerable power rather than economy gains.

Regards
Pat
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[Slim3]

Thanks Pat, that pretty much sums up my construction, operation of a still, building of an alcohol engine and the experiments afterwards on my DOE grant. I tried ethanol from wheat and from corn and both worked well in my engine. As for cost in operation of a still to make ethanol, I didn't decrease the cost of the batching process (first part of the operation) but I did lower the cost of the distillation part. (that is what I received the grant for) I found that the cost of the whole process was not as expensive as oil companies were claiming. (up to the 190's proof) They were trying to mislead the public by not mentioning what was expensive. The last process to get from the 190's proof (best a still can do) to 200 proof necessary to mix in gasoline to prevent separation.

While it is true that using corn does raise the value of corn thus a cost increase to the public of a food source. When using corn that is slated for livestock the cost was not raised much, because the nutritional value of the mash after distillation is the same as it was before. Admittedly you need to get all of the alcohol out of the mash before feeding it to livestock as I had some wobble legged chickens wondering around my property after feeding them my mash after distillation.

The use of sugarcane instead of a grain would dramatically lower the cost further as much more ethanol can be had from an acre of cane then from any grain as Brazil knows. Secondly, two expensive procedures during the batching process can be eliminated that turn the starch into sugar that yeast can eat. Plus my tests proved that a very high compression engine runs as well or better on as low as 170 proof over the same engine running on 200 proof.

So I contend that we should burn our alcohol and tell OPEC to drink their oil. Also tell our own government to only trade grain for oil and put some clamps on our own oil companies. Maybe then we would not be financially raped every time we went to fill up our cars. Also send a message to the auto manufactures to get serious about fuel mileage instead of what they are presently doing.

Slim3

 

[msquared48]

Slim3:

Thanks Pat. If I have to rebuld the engine at 218,000 miles to get better mileage, it will not be worth it in the long run, hands down. Maybe if it was a new engine and I was 20 years younger...

Did you ever investigate using cat-tails instead of corn?

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[patprimmer]

Mike

I think your post is out of sequence a bit. I am sure the first response was to me and the last comment was for slim.

slim

I agree that using a simple still that still leaves a bit of water in the alcohol is the best method so long as you don't try to mix the alcohol with hydrocarbon fuel in the tank.

To get the best gains, you should correct for total fuel to air by counting only the actual alcohol content of water/alcohol from the injection system. You should reduce the hydrocarbon fuel to compensate for the alcohol. This would be near on impossible with a normal reasonably modern automotive carby. I can't remember ever seeing one with an on the fly lean out or adjustable main jet.

I guess if you blocked the power valve circuit and did not increase the main jet to compensate then injected alcohol via a separate system at the point where the power valve normally opens to give power a:f rather than cruise a:f, however I don't think the change would be enough.

A solar still might change the economics of making your own alcohol, or burning waste vegetable matter from the crop supplying the starch/sugar. I doubt the waste vegetable matter is enough heat to run the still.

There are a lot of variables to study to optimise this due to the higher cooling from the evaporation of the water content of the 170 proof alcohol and the higher displacement of air in the manifold from the alcohol portion as it evaporates and the changes to cooling/displacement of air balance as the alcohol:water ratio changes. Engine speed, manifold runner and plenum and port and valve size, cam timing, compression ratio, quality and timing of spark, load at cruise and power required at WOT are all going to impact on the optimisation.

At low speed high vacuum, a higher portion of the evaporation is going to occur in the manifold, but at lower vacuum and higher speed a higher portion of the evaporation is going to happen during compression and even after ignition.

Regards
Pat
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[msquared48]

Pat... you're right.

Mike McCann
MMC Engineering

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