Fuels

Fuel is any substance that produces energy/heat/power either by itself or by combustion of other substances.
E.g. Wood, diesel and biogas.

Types of fuel

1. Solid fuel - wood, coal, charcoal.
2. Liquid fuel - Petroleums (petrol, diesel, kerosene), alcohols (methanol, ethanol, butanol).
3. Fuel gas - coal gas, water gas, syngas, biogas.
4. Bio fuel - ethanol made from sugar wastes.
5. Fossil fuel - formed from fossilised remains of plants and animals.

Calorific value is the total quantity of heat produced by complete combustion of unit mass in air. Expressed as kcal/m³ or British Thermal Unit/Cubic Foot.
1 kcal = 3.96567 BTU.
Water gas is produced by passing steam over red-hot coke using the endothermic reaction. It is flammable.
carbon monoxide (CO) + hydrogen (H₂).
Producer gas is produced by passing insufficient air over red-hot coke. It is both flammable and inflammable.
carbon monoxide (CO) + Nitrogen (N₂).
Coal gas is produced by destructive distillation (heating in absence of air). It is flammable.
Hydrogen + methane + ethylene + acetylene + CO + nitrogen.
Natural gas is produced from petroleum and composed mostly of methane (83%) with least amounts of ethane, propane, butane, and pentane.
Liquefied petroleum gas (LPG) is produced from petroleum and mixture of mostly propane (C₃H₈) and butane (C₄H₁₀), with least amounts of other hydrocarbons from C₂ to C₅.
Compressed natural gas (CNG) is produced from petroleum and composed mostly of methane (CH₄) with 85%.
Bio gas or Gobar gas is produced from organic wastes. Composition of Methane (CH₄) + Carbon dioxide (CO₂) + Hydrogen (H₂) + Nitrogen (N₂)

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Flame is the visible part of the combustion. It has 3 parts.

1. Inner part - least temperature and black due to pressure of unburnt particles.
2. Middle part - hot + biggest part, luminous (emits light), limited oxygen supply and yellow due to incomplete combustion.
3. Outer part - hottest part, non-luminous, full oxygen supply and blue due to complete combustion.