Flame propagation of mixtures of air with high molecular weight neat hydrocarbons and practical jet and diesel fuels

Laminar flame speeds of mixtures of air with n-C14H30, n-C16H34, a petroleum-derived JP-5 jet fuel, a camelina-derived hydrotreated renewable JP-5 jet fuel, a petroleum-derived F-76 diesel fuel, and an algae-derived hydrotreated renewable F-76 diesel fuel, were measured in the counterflow configuration at atmospheric pressure and elevated unburned mixture temperatures. Digital particle image velocimetry was used to measure the axial flow velocities along the stagnation streamline. The experiments for n-C14H30/air and n-C16H34/air mixtures were modeled using recently developed kinetic models, and the experimental data were predicted satisfactorily. Both experiments and simulations revealed that the laminar flame speeds of n-C14H30/air and n-C16H34/air mixtures are very close to each other, as expected. On the other hand, the laminar flame speeds for the four practical fuels were found to be lower than n-C14H30 and n-C16H34, due to the presence of aromatics and branched hydrocarbons. Similarly, the laminar flame speeds for the alternative fuels were found to be higher than the petroleum-derived ones, again due to the presence of aromatic compounds in the latter. Further insight into the effects of kinetics and molecular transport was obtained through sensitivity analysis.