"The last thing you would expect is that a burning droplet of alcohol would produce enough water to put itself out. Or that a fireball the size of a pinhead would linger for eight minutes."
"One of the early surprises is the way that alcohol burns," Williams said. Alcohol is a family of chemicals, the two most common being ethanol - more familiar as grain alcohol - and methanol - the deadly wood alcohol.
"These two alcohols burn completely different," Williams said. The ethanol drops burned to extinction, or until no fuel was left. But the methanol droplets extinguished themselves, which has implications for anyone designing engines that burn alcohol. Alcohol is strongly hygroscopic, meaning it absorbs water ("pure" alcohol is impossible to produce)."
"Both alcohols produce water vapor as a byproduct, but it appears that methanol reabsorbed more of the vapor from its own exhaust. Then, when the water was heated it boiled away from the drop, taking enough heat energy with it to cool the flame and stop combustion. In an engine, that means you have to burn more fuel to do the same work."
"Williams said that the results could not be fully duplicated on the ground simply by tinkering with all possible running conditions on an engine. With data from FSDC, scientists will be able to tell better how to fine tune alcohol engine design."
"And there's the paradox. Common sense tells us that the flame should leap across the chamber, burning everything in an instant. Instead, it produces the tiny glowing dots - 1 to 10 mm (1/25 to 1/4 inch) across) that float for up to 500 seconds before they are extinguished by fans in the chamber."
Micro-fireballs Lighting the Way to Better Engine Designshttp://science.nasa.gov/science-news/sc ... 12jul97_1/