obanion
Automotive
- Jan 1, 2004
- 101
Finally found some pertinent research papers on the subject, to confirm my suspicion. Diesel fuel, although having a near ideal autoignition for my test motor (10.5:1 compression) to achieve HCCI, the very poor evaporative, boiling, and mixing ability of diesel makes it impractical. I'm likely to wash down the cylinders with fuel. A gaseous (ideal IMO) or volatile liquid (gasoline) fuel is needed.
Dimethyl ether (DME) is a perfect fuel. Has just about the right autoignition, and being similar to propane in terms of storage (liquid at moderate pressure, gas at lower pressures). However, it's just too expensive to use. The whole point is COST efficiency. What good would 50% efficiency be when your fuel is 500% the BTU/$ cost? I need a fuel at least based on commonly available fuel.
So, I'm back to gasoline. The lowest octane to start, 87. Wish I could find places that pump 60 octane, then I wouldn't have a problem. So I need to add something that lowers the octane, so the lower the autoignition temperature on the additive the less of it I should need to get any desired level of octane reduction. I also want to preserve, and if possible improve the volatility (lower boiling point) of the gasoline. So the more volatile the additive, the better. Of course, it must mix and stay mixed with gasoline. I came up with diethyl ether, or just plain ether. I wouldn't think it would take much ether mixed in with the gas to bring down the octane significantly, and into the region of autoignition on 10.5:1 compression.
I know ether is scary stuff. Which is why I want to premix it, no on board storage of pure ether. I'm hoping it won't take more than say 5-10% mixed in. Then there is the whole issue of legality. Because you can get high on it directly, and it's used in the manufacture of some illicit drugs, I imagine some hoops will need to be jumped through before I can have a few gallons for this experiment.
There is always low octane petrols, hexane and heptane, and a few others. But they aren't nearly as low as ether, and I'm sure I'd need to a much higher % to get the desired results. Cost again goes up.
The engine will also run methanol in spark ignition mode for full power, and since those injectors are right there, and methanol sucks heat out and puts octane in, the methanol injectors can be used to give the little bit of adjustment of autoignition timing, once the gasoline fuel mix is optimized. The point is to make the HCCI fuel just about right, and use the lowest amount possible of methanol as a ignition retardant for hotter temps and high load conditions.
Dimethyl ether (DME) is a perfect fuel. Has just about the right autoignition, and being similar to propane in terms of storage (liquid at moderate pressure, gas at lower pressures). However, it's just too expensive to use. The whole point is COST efficiency. What good would 50% efficiency be when your fuel is 500% the BTU/$ cost? I need a fuel at least based on commonly available fuel.
So, I'm back to gasoline. The lowest octane to start, 87. Wish I could find places that pump 60 octane, then I wouldn't have a problem. So I need to add something that lowers the octane, so the lower the autoignition temperature on the additive the less of it I should need to get any desired level of octane reduction. I also want to preserve, and if possible improve the volatility (lower boiling point) of the gasoline. So the more volatile the additive, the better. Of course, it must mix and stay mixed with gasoline. I came up with diethyl ether, or just plain ether. I wouldn't think it would take much ether mixed in with the gas to bring down the octane significantly, and into the region of autoignition on 10.5:1 compression.
I know ether is scary stuff. Which is why I want to premix it, no on board storage of pure ether. I'm hoping it won't take more than say 5-10% mixed in. Then there is the whole issue of legality. Because you can get high on it directly, and it's used in the manufacture of some illicit drugs, I imagine some hoops will need to be jumped through before I can have a few gallons for this experiment.
There is always low octane petrols, hexane and heptane, and a few others. But they aren't nearly as low as ether, and I'm sure I'd need to a much higher % to get the desired results. Cost again goes up.
The engine will also run methanol in spark ignition mode for full power, and since those injectors are right there, and methanol sucks heat out and puts octane in, the methanol injectors can be used to give the little bit of adjustment of autoignition timing, once the gasoline fuel mix is optimized. The point is to make the HCCI fuel just about right, and use the lowest amount possible of methanol as a ignition retardant for hotter temps and high load conditions.
