Combustion and Flame

Carburized flames and oxidised flames are the forms of natural flames. Carburizing flames have more fuel, whereas oxidising flames have more oxygen. Various materials utilised different flames depending on the weld condition.

Combustion is a chemical process in which a substance interacts swiftly with oxygen to produce heat. The starting element is known as gasoline, and the oxidizer is known as an oxygen source. The fuel can be solid, liquid, or gas, but for aeroplane propulsion, the fuel is usually a liquid.

When a substance reacts with oxygen then it gives heat, this process of giving heat is called combustion. The substance undergoing the process of combustion is said to be combustible. During this process of combustion, light is given as a flame or as a glow.

•       Oxygen is necessary for combustion
•       Ignition temperature- It is the temperature at which substance catches fire at the lowest temperature
•       Petrol, and alcohol are inflammable substances as they have very low ignition temperature

Fire:

Fire is a state, or process of combustion. There are three essential requirements to produce fire: fuel, air (supplies oxygen) and heat (increase temperature of the fuel beyond the ignition temperature). By removing any one or more requirements, fire can be easily controlled.

Fire Extinguisher:

A fire extinguisher is a fire protective device used to extinguish fires.

•       Common fire extinguisher is water – Water brings down the ignition temperature of the material and water vapours cut off the supply of air
•       Carbon dioxide (CO₂) acts as the best fire extinguisher, as it forms a blanket around the fire that brings down the fuel temperature, for fires involving electrical equipment and inflammable materials like petrol

Types of Combustion:

Types of combustions are as follows: rapid combustion, spontaneous combustion, and explosion.

•       Rapid Combustion: Material burns rapidly as a result heat and light is produced
• Spontaneous Combustion: Material suddenly bursts into flames, without any apparent cause. For example, burning of phosphorus in air at room temperature

⮚  Disastrous fires in coal mines occurred due to spontaneous combustion of coal dust

⮚  Due to lightning strikes or the heat of the sun has caused spontaneous forest fires

•       Explosion: Evolution of heat, light, and sound occurs when a material is ignited that liberates a large amount of gas formed during the reaction

Flame:

Visible and gaseous part of a fire is called flame. Substances like kerosene oil and molten wax on burning vaporises and give flames. Three different zones of a flame are – dark zone, luminous zone, and non-luminous zone.

Fuel:

It is the source of heat that is used in domestic and industrial purposes. A fuel is any substance that can be made to react with other substances and release energy in the form of thermal energy. These substances are called fuels.

 Characteristics of a Good fuel:

•       It is cheap
•       Readily available
•     Easy to transport
•       A large amount of heat is produced
•       It burns easily in the air
•       No undesirable substances are left

Fuel efficiency: It is expressed in terms of its calorific value that is expressed in units of kilojoule per kg. The amount of heat energy produced on complete combustion of 1 kg of a fuel is called its calorific value.

Harmful effects of Fuel Burning:

With the increase in the consumption fuel, it has affected the environment in following ways:

•       Pollutants like carbon particles in air cause respiratory problems
•       Incomplete combustion of a fuel produces poisonous carbon monoxide gas
•       Combustion of most fuels’ releases carbon dioxide in the environment                                                                                              Global warming is the result of increased carbon dioxide in the air. Global warming is the rise in temperature of the atmosphere of the Earth and results in:

⮚  Melting of polar glaciers

⮚  Rise in the sea level

⮚  Floods in the coastal areas

⮚  Submergence of Low-lying coastal areas.

CNG (Compressed Natural Gas) is being used in place of diesel and petrol as fuels in automobiles, because CNG is cheaper and produces less harmful products in small amounts, and thus called a cleaner fuel.

Conclusion

Combustion is described as a quick exothermic event that releases a significant amount of energy in the form of heat, and flames are combustion reactions that may propagate across a suitable medium.

In reality, combustion is the outcome of dynamic or time-dependent activities that take place at the molecular level between atoms, molecules, radicals, and solid barriers. This chapter discusses how combustion causes pollution, the dynamics of pollutant production and oxidation, and methods for reducing pollution.