A couple of outside questions...?
Has anyone really explored the effect of mixing a pretty large amount of oil with the burning liquid (atomized, of course, if not vaporized)?
Methanol, by itself, has about half the heat yield per unit weight as gasoline, per my veteran Marks' Manual. That might explain some of the "hotter" effect of gasoline fuels...
Kerosene, as used in our diesels, is also mixed with (non-burning, we hope) oil, and with low heat yield ether. Our diesels run cooler than glow or spark fired engines, but the whole engines heat more evenly top to bottom... Kerosene compares very well in heat yield with mid-Octane "white" gasolines, per an older Marks' Manual. Why the difference in engine heating?
Methanol, per an SAE paper I saw quite a while back, has a flame propagation rate too fast to measure reliably, but gasoline's can be measured. These are for clean fuel/air conditions, not messed about with oil droplets or vapors. Seems to suggest that methanol might actually burn quicker in our mixed fuel conditions?
Possible answers to some of these thoughts? Fuel/air ratio? Heat of vaporization?
Methanol, and slightly hotter burning ethanol by the way, are VERY broadly tolerant of fuel/air (by weight) ratios in which you get a good burn. Neither gasoline nor kerosene are as tolerant. I think I recall methanol would burn well in ratios of lower than 7(air) to 1(methanol), by weight, on up to as lean as you cared to go. Gasolines burn in a range of about 12:1 and up, with kerosene's range being similar, or even less tolerant.
That crazy word stoichiometric means, as I understand it, the ratio of liquid fuel to air (by weight) in which all the fuel burns in the available oxygen in the air, and all the oxygen is consumed in doing that. When too rich, there is excess fuel that does not burn. When too lean, all the fuel is consumed and there is excess oxygen left over.
Our engines are essentially air pumps, which pump the fuel/air mix to where we can burn it for power. (And convert the heat/expansion to shaft rotation. And pump out the burned gases.) Gasoline and kerosene are limited by the amount of air the engine can pump to the combustion chamber. Methanol is much less limited, burning well at ratios that would 'damp out' combustion of gasoline or kerosene.
The lower power we usually get from spark-fired gasoline fuel engines may be limited by the amount of fuel the engine, as air pump, can deliver for burning within the suitable fuel/air ratios. Similarly for kerosene, in an ether fired model "diesel."
The hotter engine temperatures we see in gasoline-burning sparkers is probably from the higher heat a gasoline burn can yield, and from the idea that gasoline does not 'chill' as well as methanol when it is vaporized. Gasoline sparkers run much longer on the same gasoline quantity as glows on glow fuel. Fuel mileage is more like glow engines when sparkers burn glow fuel.
For our 'diesels', ether chills well at vaporization; kerosene and oil don't. The higher heat yield of kerosene, in the proportions in typical diesel fuels, works well to turn sport diesels around their torque peak RPM, and helps their noted fuel economy. There's less ether, at around 30% of fuel volume in diesel fuels, than there is methanol in glow fuels. That reduces the cooling-by-evaporation benefit. The entire engine soaks to a more uniform temperature than we often see from glow engines, but the hottest parrts of the diesel usually aren't as hot as the uppers of a glow engine. (Ether is also 'lighter' than kerosene or gasoline, so consider the weight factor, too.)
BTW, I've heard that Nitromethane actually has a "poor" heat yield per unit of weight compared to gasoline or methanol. Well, it is heavier (denser) than water, and almost half-again as dense as methanol. It does 'bring its own oxygen' which takes some of the demand off the engine's ability to deliver oxygen to where the fire is. We do know that nitro DOES work!
Your thoughts? I like this kind of thread...!
Topic: nitro (2) (Read 1525 times)
