combustion and flame

[madhur123456]

only gases burn with flame. but when you burn wood, it intially burns with a flame. later it only glows without a flame . what do you think is the reason

[gen2]

wood contains combustible materials that will vaporise when heated and produce a flame. When these are all gone, you are left with carbon which does not vaporise.

[ORAC60]

when wood burns it gives off a gas because of resin & rosin and also if its pine it has oils like turpentine in it to burn
these are all combustable gasses

[beso]

Prior to combustion the wood undergoes pyrolysis where the solid lignin fibres are broken doen to gasses.

The combustion you see in a flame is actually burning acetylene which you would recognise if you ever used acetylene welding equipment.

At first abundunt volatiles are released and the quantity of gas forces the flame front well away from the wood. The flame is oxygen starved and yellow.

Later when the wood is very hot and the most volatile pyrolysis products have been burnt the decomposition progresses more slowly. With the slower release there is plenty of oxygen available and the combustion happens where the gas is released at the surface of the wood with minimal flame.

[solera]

It is the old story you know PETROL does not burn, it is the vapour given off mixed with oxygen from the air in the correct proportion that ignites, when you look at a wooden matchstick it is the gas driven off that burns, the heat from the head being struck provides the initial heat to start the cycle, try to start a fire with apiece of 4x2 and you would need a blow lamp to initiate the heat necessary for the production of flammable gases to be driven off in sufficient quantities to continue the fire.

[dozeydo]

If you'd like to show that it's the gas that burns over a solid fuel, try lighting a candle and letting it burn for a minute or so. Then blow it out and quickly apply a flame to the trail of "smoke" that you see coming off the wick. If you're quick and do it before it spreads out, you will see the trail light and the flame go down it to relight the candle.