Evaluation of motor fuel flammability in accordance with engine requirements

Analysis shows that poor fuel combustion is the main source of damage in low-speed diesels operating on heavy fuels (containing residual products obtained in petroleum refining). However, no information is available on parameters characterizing the flammability of heavy fuels, and hence we have no basis for imposing standards on fuel flammability. An index recommended by the Shell Oil Company for evaluating flammability is called the CCAJ, in accordance with which the content of aromatic hydrocarbons in the fuel is determined on the basis of its density and viscosity. However, this index is sometimes inadequate in terms of correlating with flammability. Thus, out of 134 fuel samples that were investigated, for 12 of the samples, instead of the expected decrease of cetane number (CN) with increasing content of aromatic hydrocarbons, the CN actually increased; for 18 of the samples, the CN varied substantially (from 36 to 52 units) with exactly the same content of aromatic hydrocarbons; for 14 of the samples, no relationships whatever were found. From these data it was concluded that there is no correlation between the CCAJ index and the CN of the fuel. The large variation of CN among fuels with identical content of aromatic hydrocarbons cannotmore » be explained by experimental error in the CN determination by engine testing, which is {plus_minus}4 units. This report describes a mathematical method for the the interrelation between the average boiling point and viscosity for fuels.« less