Octane and Cetane Analyzers

The octane number of gasoline is based on two pure compounds. One, normal heptane, with a straight chain of seven carbon atoms, is designated as zero octane. The second, isooctane, with a chain of five carbon atoms and three methyl branches, is designated as 100 octane. Cetane is a saturated hydrocarbon with 16 carbon atoms in a straight chain. In the laboratory, cetane numbers are measured in a one-cylinder diesel engine, which is manufactured by the Waukesha Motor Company The performance of the test fuel is compared to mixtures of reference fuels that bracket the expected cetane number of the test fuel. The procedure is detailed in ASTM Standard Test Method D-613. The most extensive use of on-line octane analyzers is in the blending of finished gasolines. The components are mixed and delivered to product pipelines with little or no intermediate storage in tanks.