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68 comments on Khosla and I Finally See Eye to Eye

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Black_Dog on February 20, 2008 - 12:13pm Permalink | Subthread | Parent | Comments top

As I understand things, an internal combustion engine with an Otto cycle can run on 180 proof ethanol. That's 90% ethanol, 10% water. The reason that pure ethanol is needed to make E10 or E85 is that the water in low purity ethanol prevents mixing of the gasoline with the ethanol. There are problems with E85 when water absorbed from the air causes the ethanol to separate from the E85 mix and drop to the bottom of the tank. This might not be a big problem once the fuel is put into a car, but makes shipping and storing the mixture rather difficult and pure ethanol can not be shipped thru a pipeline.

The reason the 15% gasoline is needed in the E85 mixture is to be able to start the engine, especially when doing so under cold conditions. Another solution to this part of the problem would be to use two tanks, one for gasoline and the other for low purity ethanol. Start the engine on gasoline and run that way until warm, then switch to the ethanol tank. With today's computer controlled injection systems and oxygen sensor feedback, this approach should be relatively simple to accomplish. On shutdown, the engine could switch back to gasoline for a brief period to clear the ethanol from the injectors. With cars set to run this way, many small time producers could use local resources to produce low grade 180 to 190 proof fuel ethanol, using heat from local sources, such as wood or solar energy. Of course, the big time oil companies would not like this prospect one bit, as they could not control the marketing and distribution of the ethanol.

E. Swanson

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joule on February 20, 2008 - 5:27pm Permalink | Subthread | Parent | Comments top

Black_Dog -

Your idea of having a duel fuel system has some precedent with an interesting bit of trivia.

During the 1910s and 1920s mechanical tractors were just starting to make major inroads into US farming practice. At that time, in rural areas kerosene was quite readily available and reasonably inexpensive. Gasoline, however, was not so easy to get and was much more expensive, so some of the early tractors ran a crude Otto cycle engine on kerosene.

But the kerosene first had to be vaporized, and this was accomplished by means of a heat exchanger in contact with the exhaust manifold. These tractors had a single fuel tank separated into two compartments by an internal partition. One side held kerosene and the other gasoline. You started the engine on gasoline and ran it on gasoline until it warmed up and then turned a valve to switch it over to kerosene.

These kerosene-fueled tractors made a distinctive popping sound, and so the farmers nicknamed the early John Deere tractor "Johnny Popper."

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john15 on February 20, 2008 - 8:20pm Permalink | Subthread | Parent | Comments top

I think PHEV cars are the best because you have two fuel options. I think we'll be finding out that having diverse sources of power are a good thing.

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HvyOilGuy on February 21, 2008 - 12:09am Permalink | Subthread | Parent | Comments top

The problem with this "solution" (other than the fact that a lot of ethanol is burned) is that it doesn't take advantage of the octane boosting power of ethanol very well. If you're going to keep wet ethanol in a separate tank why not just inject it when you need the octane--according to this:

http://www.autobloggreen.com/2006/10/25/mit-researchers-developing-an-on...

Only about 5% ethanol is required, overall, which, IMO, is the limit we should impose on ourselves in this ridiculous "food-to-fuel" frenzy we are embarking upon. Driving up food costs for those least able to afford it to satisfy and SUV's does strike me as immoral. Feed a Hummer--starve 10 children to death.

But, I digress--a similar trick was used in aircraft during WWII using (smaller amounts of ) pure water when extra power/range was need. (Lugging the engine, gave you the extra range, but also needed a fuel mixture with high anti-knock characteristics).

The popping sound that's heard when kerosene is fed into a gasoline engine is knock or ping--very detrimental to an engine. (next post)

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Black_Dog on February 21, 2008 - 11:15am Permalink | Subthread | Parent | Comments top

Thanks for the link, HvyOilGuy, but you missed the point entirely. Were running out of oil, remember?

The proposed use of a separate fuel tank was to enable the use of "wet" ethanol during most of the operation of the engine. The octane boost for gasoline, which one would expect from E10, was not the reason. I was suggesting another approach to that presently being used, that is, a mixture of 85% ethanol with 15% gasoline, called E85.

As for water injection, I am well aware of its use as an octane booster and there have been various systems marketed which provide this for cars. The newer ones appear to be quite sophisticated. I bought one years ago, thinking to try it on a high compression (13:1) engine project I built back in the 1980's. The injector system is still sitting in the box in my attic. If I ever get around to fixing my Ford SHO's blown head gasket, I may install the device to the engine, since the Yamaha engine in the SHO was designed for high octane fuel, even though it will run on regular. The knock sensor probably cuts the spark advance to allow operation.

As I recall from my college IC engines course, the use of water injection on WW II aircraft piston engines was intended to allow higher supercharge boost, which gave higher effective compression ratios, thus more power and better efficiency.

E. Swanson

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HvyOilGuy on February 22, 2008 - 10:19pm Permalink | Subthread | Parent | Comments top

Actually, it's you who is missing the point, IMO. We shouldn't be trying to replace fuels we are consuming that are now (or soon will be) in decline on a Btu per Btu basis, especially with ethanol for which the external costs outweigh the benefits, which seem to accrue to the few. We need to move on to a new transportation paradigm that relies less and less on the private automobile.

That being said, if the "blending value" of ethanol to boost compression ratio and efficiency for the entire fuel system, is sufficienly high, it would justify the production of a certain amount to attain this benefit. I think the article states that it does, but only up to about 5% of the total.

When ethanol is used in excess of this amount, it no longer yields the benefit that the first incremet did--it basically behaves as E85 does now--which hasn't been received all that favorably by the motoring public.

Once you reach the point where more ethanol doesn't provide any special boost, you have reached the practical limit, IMO.

I apologize that the link I gave wasn't particularly informative, since part of the system also involves the use of a supercharger, in addition to the ethanol injection. Maybe this one is a little better, but still just a "news" story.

www.technologyreview.com/Energy/18304/

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Squalish on February 22, 2008 - 5:00am Permalink | Subthread | Parent | Comments top

The other day, Robert brought up another point - oxidizers simply aren't needed on all cars built for the US market after 1994, which adjust their combustion mixture automatically if they encounter different combustability rather than needing it normalized to certain proportions. Ethanol was a great replacement for other environmentally unsound oxidizers, but it's largely an anachronism in 2008.

edit: Remind me to click the links before responding.

Looks interesting. I'd seen it before, but never quite distinguished the technology from others. It looks like it heavily overlaps with hybrid technology, though. Nice for cheapish sportscars and motorcycles for a higher power:weight ratio than hybrids, but electric start:stop driving, wheelhub motor 4WD, and plug-in ability are more attractive in mainstream vehicles IMO.

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Squalish on February 22, 2008 - 4:46am Permalink | Subthread | Parent | Comments top

Sounds similar to the diesel / veggie oil duality. You can run a diesel engine on No. 1 etrodiesel (-40C), No. 2 petrodiesel(-10C), biodiesel(-10 to 10C), or veggie oil(20C to 45C) equally well, but the fuel all gels below a certain temperature(given) and clogs the fuel line. You need to heat it until the fuel temperature is above its cloud point, so everything remains fully dissolved & viscous. So people use No. 1 petrodiesel to start the engine (and use the coolant system to heat the tank), and then switch over. Analogous systems exist for extreme cold weather and fuel additive tanks.

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68 comments on Khosla and I Finally See Eye to Eye

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