In the combustion process, Air-Fuel Ratio refers to the mass of air to the mass of fuel. Fuel can be Solid, Liquid, Gas, or maybe a combination of these. The combustion process can be in an internal combustion engine or Industrial Furnace.
Types of AFR ratio or mixture:
• What is an “Ideal” AFR Ratio: Scientifically, an AFR ratio of 14.7:1 (Mass basis) is treated as a perfect AFR ratio for Normal Petrol.
• Lean Fuel Mixture: The air-fuel mixture contains more air than the required quantity required for complete combustion (i.e. more air content and less fuel content). Gives High efficiency at higher temperatures.
Produces hot gases like (NO2).
For Example AFR mixture containing 16.5:1 is to be considered a lean mixture.
• Rich Fuel Mixture: Air fuel mixture contains more fuel than the required quantity required for complete combustion (i.e. less air content and high fuel content). Gives low efficiency at lower temperatures.
Produces cool gases like (CO).
For Example AFR mixture containing 13:1 is to be considered a rich mixture.
Importance of AFR: Ratio of masses of air to fuel identifies whether the Combustion process is feasible or not. AFR directly impacts performance and pollution parameters (SOx, NOx, CO, etc.)
Please refer to the below image for a better understanding:
