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E85 is, by definition, a blend of 15% gasoline and 85% ethanol. E85 is so well liked because ethanol pollutes far less than gasoline when burned, and can be made naturally from vegetables such as corn (therefore making it renewable). But in the real world, E85 isn't the miracle it seems. It is much more
corrosive than gasoline (because of the high alcohol content), and it produces far worse fuel economy than gasoline alone (about 10-15% in most cases).
Biodiesel is vegetable oil. It is so well liked because it is used in diesel engines (which almost always achieve better fuel economy than a gasoline engine of the same size).
So it seems obvious that the two fuels, when combined, would make for a pretty good fuel (never mind gasoline). So obvious, in fact, that people are experimenting with compression-ignition alcohol-diesel engines (in fact, some tractors used in pulling contests already use alcho-diesel as a fuel, with spark plugs to ignite the alcohol and glow plugs for the diesel).
In my opinion, they have it wrong. I propose a 50-50 vegetable oil- ethanol mix for a fuel. Only the fuels aren't mixed before combustion (they are storred in different tanks). Combustion is where the magic happens. Let me point out that this idea isn't just for an alternative to gasoline or a more efficient engine. Its main focus is on making a diesel/alchohol engine in a spark-ignited gasoline type configuration. First off, since two stroke engines can successfully burn an amount of oil mixed in with gasoline (in fact newer 2-strokes are actually not bad pollution wise), I know it can be done. During the intake stroke, a small injector injects a variable amount of vegetable oil (normally 50% of the usual fuel-to-air ratio). This is then compressed (only about an 11:1 compression ratio, not near enough to make it combust like normal). Then when the piston starts to come up, a direct injector sprays the ethanol in a fine mist over the layer of vegetable oil and air mix. Even though the vege-air mixture would be homogenous, I'd still bet the ethanol stays at the top. Then near top-dead-center, bang! The ethanol (which is near the top) is ignited, which then ignites the vegetable oil (which normally wouldn't be ignited from a spark plug but uses the alcohol as kind of a pilot). The beauty of it is that the engine can be just as light internally as a normal gasoline engine. The idea is to not have to sacrifice revvs for efficiency and alternative fuels.
Ethanol Direct-Injection
http://www.ethanolboost.com/
mostly baked [discontinuuity, Aug 12 2007]
[link]
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One potential problem I can see would be the different temperatures needed by the two fuels. Diesel likes to run very hot; can we get alcohol in there without it flashing early? |
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I'm pretty sure. Since alcohol is used in many turbocharged gasoline engines to avoid preignition, it seems that it would be easy to keep it from preigniting. And the fact that it would be directly injected (in the cylinder for less time than if it was port injected) helps even more. |
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This is a good idea, but I think it might be already baked to some degree. I'll see if I can find a link. [RayfordSteele], I think that pre-ignition would be more of a problem with the biodiesel than with the ethanol. The key would be using the high-octane (about 100) of the ethanol to control the low octane (about 50 or 60) of the diesel. |
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A bun for the nutritious sounding "homogenous vege-air mixture". [+] |
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Interesting link, where they're located is only about a 20 minute drive from me. |
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It didn't say, but is the ethanol direct-injection for gasoline or diesel (or both) engines? Even if for diesel, I made this idea knowing that alcohol/diesel engines already exist to some degree. I just wanted a better design. Oh and I suppose, say, 25% of the ethanol could be injected with the vegetable oil (to make an overall octane rating of about 73, since it would be 2/3 vegetable oil and 1/3 ethanol) while the other 25% is directly injected as the pilot) |
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I bet this design would be better with a Crower Cycle, since the steam cycle would take away a lot of the vegetable oil's heat from combustion (and reduce the risk of preignition). |
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Oh, and this might work quite well in either small 4-stroke engines or 2-stroke (the diesel would lubricate the engine and be pumped in, while the alcohol would be direct injected). |
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I have an old friend who's a vegetarian alcoholic. He might like this. |
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