On the Ignition Quality of Normal Paraffins

A hydrocarbon fuel has its inherent ignition property definitely related with its chemical structure, and, for the family of normal paraffins, the characteristic values may be supposed to increase with the carbon number. In this study, we investigated the nature of the inherent ignition property in such a way that the reductions in ignition lag in a CFR Diesel engine were measured when several kinds of normal paraffins higher than Cetane, liquid or solid, were mixed with or dissolved in a liquid paraffin base fuel to varied amount and the rate of ignition lag decrease was used for evaluation. Kogasin I (nearly Octane) was adopted as the base fuel, and two higher liquid paraffins (C16 and C17) and three solids (C19, C21·5, and C81) were examined. It was found that the inherent ignition property increases with the carbon number irrespective of whether liquid or solid paraffins. The characteristic values obtained for C17, C19, C21·5, and C31 were 104, 115, 136, and 202 in terms of cetane value, respectively.