What is the cetane number


What is the cetane number ?

Cetane Number are nothing but the indicator of performance of engine and combustion process.


It is an index of the Ignition Quality (Ignition delay characteristics ) of diesel fuel which defines the way combustion proceeds in the engine .

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It is used for compression engines. (C.I engine ).

It is Shortly written as CN.

Cetane number

It is determined by comparing the Ignition quality of standard solution (cetane +Alpha -methyl Naphthalene ) with Ignition quality being tested.

It is the percentage of cetane contained in the standard solution which has an Ignition delay equalling the Ignition delay of fuel tested.

Good Ignition quality CN =100

Higher the CN ,Better is the fuel ,shorter is the Ignition delay, and easier id the starting of combustion.

CN varies from 35 to 55.

If density increase , CN decrease.

Cetane Rating (Cetane Number)

It is an indicator of combustion speed of Diesel Engine.

It is the measure of ignition quality of fuel.

If CN increases = (shorter the time between fuel injection and rapid combustion or pressure rise), better ignition quality.

Considered as poor fuel (if Cetane number < 37), usual range is 30-35.

It is an inverse function of a fuel’s ignition delay.

Only use for light distillate diesel oils, for heavy (residual) fuel oil two other scales are used : CCAI and CII.

Alkyl nitrates and Di-tert-butyal peroxide are used as additives to raise the Cetane number.

It is generally denoted by (CN).

It is used for CI Engine