What is diffusion fire?
Table of Contents
What is diffusion fire?
Diffusion flames are a phenomenon in which fuel and oxidizer come together in a reaction zone through molecular and turbulent diffusion. The fuel may be in the form of a gaseous fuel jet or a condensed medium (either liquid or solid), and the oxidizer may be a flowing gas stream or the quiescent atmosphere.
What are the four elements in the diffusion flame process?
The four elements are oxygen to sustain combustion, sufficient heat to raise the material to its ignition temperature, fuel or combustible material and subsequently an exothermic chemical chain reaction in the material.
What is an example of a diffusion flame?
The candle flame is a classical example of a diffusion flame. The flame reaches a steady state almost immediately after a match is brought up close to the wick, and if the air in the room is sufficiently still, it does little flickering. The flame basically remains constant in shape and size.
What is the color of diffusion flame?
orange-yellow color
The soot typically produced in a diffusion flame becomes incandescent from the heat of the flame and lends the flame its readily identifiable orange-yellow color. Diffusion flames tend to have a less-localized flame front than premixed flames.
Why diffusion flame is yellow?
The common flame of a candle is a classic example of a diffusion flame. The yellow color of the flame is due to the large number of incandescent soot particles in the incomplete combustion reaction of the flame.
What is the difference between diffusion flame and premixed flame?
Diffusion flames occur at the interface where fuel vapour and air meet. Unlike premixed flames, the fuel vapour and the oxidant are separate prior to burning. The dominant process in the diffusion flame is the mixing process.
What are the 4 elements that must be present for a fire to exist?
Oxygen, heat, and fuel are frequently referred to as the “fire triangle.” Add in the fourth element, the chemical reaction, and you actually have a fire “tetrahedron.” The important thing to remember is: take any of these four things away, and you will not have a fire or the fire will be extinguished.
Why is diffusion flame yellow?
What are the properties of flame?
Flame is a mixture of gases (vaporised fuel, oxygen, carbon dioxide, carbon monoxide, water vapour, and many volatile materials). The flame produces energy (i.e., heat and light). The flame is not a matter, but fire is a matter. Flame is a chemical reaction.
What is the difference between premixed flame and diffusion flame?
The flame zone of a premixed flame may be less than 1 mm thick. As the volume of the hot burnt gas is greater than that of the same mass of cold unburnt gas, the flame front is pushed outwards from the ignition point, like the skin of an inflating balloon….Premixed and diffusion flames.
| Gas | Lower limit | Upper limit |
|---|---|---|
| Propane | 2.4 | 9.5 |
Are diffusion flames usually subsonic or supersonic?
Categorization of Flames: Most fires are subsonic, turbulent diffusion flames when particularly hazardous.
What are the properties of fire?
What are the types of flames?
There are three types of flames natural flame, carburizing flame and oxidizing flame.
What are the two types of flame?
There are two types of flames:
- Non-luminous flame and.
- Luminous flame.
Why is a diffusion flame more hazardous than a premixed flame?
The flame speed and HRR depends on the fuel oxidizer mixture. Typically premixed flames have greater HRR and flame speeds. This is largely due to the physics of a diffusion flame. Both buoyancy and momentum driven diffusion flames have a core of fuel which mixes with oxygen at a surrounding layer via diffusion.
How do you measure the speed of a flame?
The flame speed is derived from the cone angle and the velocity of the unburned gas based on the nozzle diameter and volumetric flow rate, Su = Vu sin α, as illustrated in Fig.
How does water affect the burning process of a solid?
Water cools and smothers the fire at the same time. It cools it so much that it can’t burn anymore, and it smothers it so that it can’t make any more of the oxygen in the air explode. You can also put out a fire by smothering it with dirt, sand, or any other covering that cuts the fire off from its oxygen source.
What are the 8 physical properties of fire?
The properties include: thermal inertia, ignition temperature, heat of combustion, heat of gasification, total energy and opposed flow flame spread properties. An illustration of the importance of the properties in predicting fire growth is presented in a correlation of flashover time for the ISO 9705 room-corner test.
