Slide 1

Slide 2

Combustion and flame

Slide 3

Introduction - combustion Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame.

Slide 4

FLAME A flame is the visible (light- emitting), gaseous part of a fire. It is caused by a highly exothermic reaction taking place in a thin zone. If a fire is hot enough to ionize the gaseous components, it can become a plasma.

Slide 5

Types Smoldering Rapid Turbulent Microgravity

Slide 6

Smoldering combustion SSSSmoldering is the slow, low- temperature, flameless form of combustion, sustained by the heat evolved when oxygen directly attacks the surface of a condensed-phase fuel. Solid materials that can sustain a smoldering reaction include coal, cellulose, wood.

Slide 7

Rapid combustion Rapid combustion is a form of combustion, otherwise known as a fire, in which large amounts of heat and light energy are released, which often results in a flame. This is used in a form of machinery such as internal combustion engines.

Slide 8

Turbulent combustion Combustion resulting in a turbulent flame is the most used for industrial application (e.g. gas turbines, gasoline engines, etc.) because the turbulence helps the mixing process between the fuel and oxidizer.

Slide 9

COMBUSTIBLE SUBSTANCES PAPER MATCHSTICK

Slide 10

NON-COMBUSTIBLE SUBSTANCES SANDSTONES

Slide 11

During extreme heat of summer, at some places dry grasses catch fire. From grasses, it spreads to trees, and very soon the whole forest is on fire.It is very difficult to control such fires.

Slide 12

IGNITION TEMPERATURE The lowest temperature at which a substance catches fire is called its ignition temperature. WHITE PHOSPOROUS

Slide 13

Microgravity Combustion processes behave differently in a microgravity environment than in Earth- gravity conditions due to the lack of buoyancy. For example, a candle's flame takes the shape of a sphere.

Slide 14

Fuels Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. Most fuels used by humans undergo combustion, a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air.

Slide 15

Types

Slide 16

LIQUID FUELS Combustion of a liquid fuel in an oxidizing atmosphere actually happens in the gas phase. It is the vapour that burns, not the liquid. Therefore, a liquid will normally catch fire only above a certain temperature: its flash point.

Slide 17

SOLID FUELS Solid fuel refers to various types of solid material that are used as fuel to produce energy and provide heating, oih sually released through combustion.Solid fuels include wood, charcoal, peat, coal, Hexamine fuel tablets, and pellets made from wood, corn,wheat, rye and other grains.

Slide 18

HOW CAN WE CONTROL FIRE?? FIRE EXTINGUISHER The most common fire extinguisher is water. But water works only when things like wood and paper are on fire. If electrical equipment is on fire, water may conduct electricity and harm those trying to douse the fire. Water is also not suitable for fires involving oil and petrol. For fires involving electrical equipment and inflammable materials like petrol, carbon dioxide is the best extinguisher. CO2, being heavier than oxygen, covers the fire like a blanket. Since the contact between the fuel and oxygen is cut off, the fire is controlled. The added advantage of CO2 is that in most cases it does not harm the electrical equipment.

Slide 19

Different Zones of Candle flame

Slide 20

The amount of heat energy produced on complete combustion of 1 kg of a fuel is called its calorific value. The calorific value of a fuel is expressed in a unit called kilojoule per kg (kJ/kg). Calorific Values of Different Fuels

Slide 21

Burning of Fuels Leads to Harmful Products 1. Incomplete combustion of these fuels gives carbon monoxide gas. It is a very poisonous gas. It is dangerous to burn coal in a closed room. The carbon monoxide gas produced can kill persons sleeping in that room. 2. Combustion of most fuels releases carbon dioxide in the environment. Increased concentration of carbon dioxide in the air is believed to cause global warming. 3. Burning of coal and diesel releases sulphur dioxide gas. It is an extremely suffocating and corrosive gas. Moreover, petrol engines give off gaseous oxides of nitrogen. Oxides of sulphur and nitrogen dissolve in rain water and form acids. Such rain is called acid rain. It is very harmful for crops, buildings and soil.

Slide 22

Director Bharath