Experiments suggest that space station fire extinguishers that squirt gases at a flame are less effective than on terra firma, since they direct air and oxygen to the fire, providing additional fuel. Moreover, the data obtained aboard the space station—through experiments such as comparing how fire spreads on flat objects versus spherical ones—will help engineers better understand the behavior of fuel and flames on Earth, where approximately 75 percent of our power comes from some form of combustion.
NASA scientists are especially excited about the potential applications for a bizarre, unprecedented type of combustion they observed in space this past spring: When certain types of liquid fuel catch fire, they continue to burn even when the flames appear to have been extinguished.
The fuel combustion occurs in two stages. The first fire burns with a visible flame that eventually goes out. The flame may flicker or smoke a bit at first, but once the process is stabilized, the flame will burn cleanly and steadily in a quiet teardrop shape, giving off carbon dioxide and water vapor. A quietly burning candle flame is a very efficient combustion machine. But if the flame gets too little or too much air or fuel, it can flicker or flare and unburned carbon particles soot will escape from the flame before they can fully combust.
The wisp of smoke you sometimes see when a candle flickers is actually caused by unburned soot particles that have escaped from the flame due to incomplete combustion. Click Here for Candle Research Studies. Above that is a small dark orange-brown section, and above that is the large yellow region that we associate with candle flames.
The oxygen-rich blue zone is where the hydrocarbon molecules vaporize and start to break apart into hydrogen and carbon atoms. The hydrogen is the first to separate here and reacts with the oxygen to form water vapor.
Some of the carbon burns here to form carbon dioxide. Charcoal is wood that has been heated to remove nearly all of the volatile gases and leave behind the carbon. That is why a charcoal fire burns with no smoke. A side effect of these chemical reactions is a lot of heat. The fact that the chemical reactions in a fire generate a lot of new heat is what sustains the fire. Many fuels burn in one step.
Gasoline is a good example. Heat vaporizes gasoline and it all burns as a volatile gas. There is no char. Humans have also learned how to meter out the fuel and control a fire. A candle is a tool for slowly vaporizing and burning wax.
As they heat up, the rising carbon atoms as well as atoms of other material emit light. This "heat produces light" effect is called incandescence, and it is the same kind of thing that creates light in a light bulb. It is what causes the visible flame. However, as most lanterns are made of paper and we all know that paper burns quite easily, why is it that the paper lanterns do not get consumed by the flames from the candle within?
Of course if the paper comes in contact with the flame, it will burn but generally, the flame of the candle only point upwards and do not move too far to the side therefore keeping the paper lanterns safe from being burned up.
Do you know why the flame point only upwards? When a candle burns, the flame heats the nearby air and starts to rise. As this warm air moves up, cooler air and oxygen rush in at the bottom of the flame to replace it.
When that cooler air is heated, it too rises up and is replaced by cooler air again. This creates a continual cycle of upward moving air around the flame, which gives the flame a teardrop shape.
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