Role of Octane & Cetane numbers in fuel!

Octane numbers are associated with petrol and cetane number with diesel. the greater the numbers, the lesser is the chance of knocking and detonation.

Shameeran

Hello CEans, What are the roles of octane and Cetane numbers in Fuel and what would be effects in case if vary their contents in the fuels?

Octane number and Cetane number both measure the tendency of fuel to ignite spontaneously. Octane number is used for petrol and Cetane number for diesel.

In Cetane number scale, high value represents fuels(diesel) that ignites readily and therefore will have less chance of detonation in a diesel engine. Cetane number is actually a measure of a fuel's ignition delay. In a particular diesel engine, higher cetane fuels will have shorter ignition delay periods than lower cetane fuels.
In the octane number scale, high values represent fuels that resist spontaneous ignition and, therefore, have less tendency to knock in a gasoline engine. Octane number is actually a measure of a fuel's autoignition (prematurely) delay. In a particular internal combustion engine, higher octane fuels will have larger ignition delay periods than lower octane fuels.

High cetane number fuels have low octane numbers, and vice versa. This is one reason why we can't use petrol in diesel engine and vice versa.