The differences between cetane number and octane number are as follows :
|Cetane number of a given diesel under test is defined as the percentage by volume of cetane in mixture of cetane and ∝-methyl naphthalene which exactly the knocking characteristics of the diesel under test.
||Octane number of given petrol under petrol under test is defined as the percentage by volume of is octane in mixture of is – octane and n-heptagon which exactly matches the knocking characteristics of the petrol under test .
|Cetane number indicates knocking characteristics of diesel in diesel engine .
||Cetane number indicates knocking characteristics of diesel in diesel engine .
|Higher the cetane number of diesel lesser is the knocking in diesel engine.
||Higher the octane number of petrol lesser is the knocking in petrol engine.
|Higher cetane number is due to less compactness, double bonds, cyclic structure and branches in straight chain hydrocarbon .
||Higher octane number is due to more compactness, double bonds, cyclic hydrocarbon .
|Fuel having higher cetane number has lower octane number and cannot be used in petrol engines.
||Fuel having octane number has lower cetane number and cannot be used in diesel engines.
|The antiknock agents have high oxygen content.
||The antiknock agents do not contain oxygen.
|Doping agents provide nascent oxygen at higher temperature to increase combustion rate and cetane number
||Doping agents undergo thermal degradation to form free radicals which reduce combustion rate increase octane number.