Classification of fuels | Fuel and its classification

The fuel can be classified mainly into three types one is a liquid fuel, the second one is gaseous fuel and another one is a solid fuel. Based on the type of fuel used by engines are classified as follows. Let us check out the detailed information on the classification of fuels here in this article. 

Classification of fuels: 

  • Engine using volatile liquid fuels for example - gasoline, alcohol, kerosene, benzene etc. The fuel is generally mixed with air to form a homogeneous charge in a carburettor outside the cylinder and drawn into the cylinder in its suction stroke. By an externally applied spark, the charge is ignited near the end of the compression stroke. These engines are called spark-ignition engines. 
  • Engine using gaseous fuels like CNG full form Compressed Natural Gas, LPG full form Liquefied Petroleum Gas, blast furnace gas and biogas. Gaseous fuels are comparatively better compared to liquid fuels because of reduced ignition delay. The gas is mixed with air and the mixture is introduced into the cylinder during the suction process. The working of this type of engine is similar to that of the engines using liquid fuels called SI gas engines.
  • Engine using solid fuels like charcoal, powdered coal etc. Solid fuels are generally converted into gaseous fuels outside the engine in a separate gas producer and the engine works as a gas engine. 
  • Engine using viscous liquid fuels like heavy and light diesel oils. The fuel is generally introduced into the cylinder in the form of minute droplets by a fuel injection system near the end of the compression process. Combustion takes place because of the fuels coming into contact with the high temperature compressed air in the cylinder. Therefore, these engines are called compression-ignition engines. 
  • Engines using two fuels. A gaseous fuel or a highly volatile liquid fuel is supplied along with air during the suction stroke or during the initial part of compression through a gas valve in the cylinder head and the other fuel is injected into the combustion space near the end of the compression stroke. These are called dual-fuel engines.