Burning flame!?

Question

How does a flame form, don't say it's energy, I need something more. In ideal conditions, a piece of wood, why do the flames differ and how does it form?

Answer 1

okay you need to look at various sides to understand fire or any given flame, for example: the chemistry and combustion.


Chemistry - Combustion
A hydrocarbon is any organic compound composed soley of the elements hydrogen and carbon. Hydrocarbons can be found naturally in petroleum, which can be converted into useful products through a series of refinements. Useful hydrocarbon mixtures include cooking gas, gasoline, benzine, kerosene, and lubricating oils. The combustion of these hydrocarbons is a common source of energy. This combustion often occurs in atmospheric air.

Atmospheric air is mainly composed of Nitrogen and Oxygen. Combustion occurs when these hydrocarbons, along with air, are heated above their kindling temperature. Common byproducts of the combustion procces are water, carbon dioxide, and nitrogen.

Types of Flame

Laminar and Turbulent Flames :
Just like regular fluid flows, flame propagation can be grouped into laminar and turbulent categories. The character of a flame can even be quantified using Reynolds numbers. The exact science of assigning a flame a Reynolds number is not really within the scope of this report, so the discussion here will center on qualitatively defining the character of the flames. Laminar flames are steady and tend not to move much. Candles tend to have laminar flames. A Bunsen burner flame is another common laminar flame.

Unpredictability is one of the main characteristics of turbulent fluid flow. This trait carries over to turbulent flame propagation as well. Turbulent flames are unsteady and random. A common example of a turbulent flame is a campfire.


Premixed:
When the oxidizer and fuel are already mixed before combustion, the resultant flame is premixed. These flames are basically constant pressure and move at a velocity a little less than a few meters per second. The speed a premixed flame propagates at is dependent on the curvature of the flame and the local flow condition. (http://epswww.epfl.ch/aps/meet/DFD99/baps/abs/S470.html)

Whenever an combustion needs to occur within a small confined area, premixed flames are the flame used. For this reason, Gas fired furnaces & stoves, as well spark ignition car engines utilize premixed flames are used. Premixed flames can be both laminar and turbulent


Diffusion Flames:
Diffusion flames occur when the fuel and air streams enter the area where combustion occurs separately and mix during combustion. The outer boundary of a diffusion flame is defined by the interface between the fuel and oxidizer. This boundary area is called the reaction zone. The temperature of the flame is at its maximum within the reaction zone and the flame’s color is a light shade of blue. The inner area of the diffusion flame is the place where there is fuel but no oxidizer. No actual production of heat occurs in this inner area, but this area is warmed up as heat from the reaction zone transfers into it. This region is a yellowish color. This color is a result of the blackbody radiation emitted by soot particles. Soot is produced when the heat from the reaction zone transfers to the inner area of the flame, and heats up the fuel.
(http://www.tfd.chalmers.se/~svan/fmt_gk01/lectures/lecture_9.htm)
The combustion in diesel automobile engines happens because of diffusion flames. Like premixed flames, diffusion flames can be laminar and turbulent.

You can check the types of flame here:

http://www.eng.fsu.edu/~shih/eml4421/students'%20web%20pages/flame%20theory/index.html

Answer 2

"None y" and "slifer!" are providing good answers.
I want to underline the color of the flame.

If pure hydrogen is burned in oxygen, you can feel the heat but you can not see the flame. The flame is colorless.
If you burn fuel oil in air you get black smokes. The smoke is the unburned carbon particles.
If you burn liqified petrol gas (L.P.G.) in air , the flame color is bluish because of the very hot particles.
The flame of the LPG gets green if you add a very little amount of copper dust in it.

So, the color of the flame changes according to the substances being in the flame region.
The flame color is used to analyse the material using a spectroscope .

The flame can be obtained with electricity. A plasma torch uses electric arc to heat the inert gas which passes through the nozzle of the torch. The hot inert gas makes a flame but nothing is burnt !.

About your question: The flames of a piece of the burning wood differs because of the chemical structure of the wood. The wood includes oils, water and various (many) chemical matters. Each of these chemicals will affect the color of the flames.
Example: the wood of some kind of pines include turpentine oil, balsam (resin) etc. and burns with black smoke. The flames are long because of the oil.
Some other woods are burning with very little flames because of the little quantity of oils.

Answer 3

really all you need is carbon dioxide and oxygen and then a flamable substance to start a fire...the flames differ depending on what chemicals/materials are in what your burning

Answer 4

It is as random to you as it is to any scientist.