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)

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.