Cetane Number

cetane number

a measure of the quality of a diesel fuel expressed as the percentage of cetane in a mixture of cetane and 1-methylnapthalene of the same quality as the given fuel

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cetane number [′sē‚tān ‚nəm·bər]

(chemical engineering)

The percentage by volume of cetane (cetane number 100) in a blend with α-methylnaphthalene (cetane number 0); indicates the ability of a fuel to ignite quickly after being injected into the cylinder of an engine.

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Cetane Number 

an arbitrary quantitative characteristic of the spontaneous combustion of diesel fuels in the cylinder of an engine. As is the case with the octane number of a gasoline, the cetane number of a diesel fuel is determined under strictly controlled conditions; cetane and α-methylnaphthalene, the cetane numbers of which are assumed to be 100 and 0, respectively, are used as the standard references. The ignition quality of a fuel being tested is characterized by determining the composition of a blend of cetane and α-methylnaphthalene that has an equivalent ignition quality. Quantitatively, the cetane number indicates the percentage by volume of cetane in the reference blend. The higher the cetane number of a diesel fuel, the quicker the ignition of the fuel in the engine, the smoother the pressure increase, and the quieter the operation of the engine. The cetane numbers of present-day diesel fuels range from 40 to 55. Additives, such as organic peroxides and nitroalkanes, are used to improve the cetane number.