Spray Autoignition Study of Bio-Oxygenated Additives Blended With Aviation Kerosene Under Engine-Like Cold-Start Conditions

Abstract

Bio-oxygenated fuels are expected to be used as a clean alternative energy source to improve the ignition behavior and pollutant emissions of RP-3 kerosene in compression ignition engines. In this study, the spray autoignition of PR-3 blended with different types of oxygenated fuels (including n-pentanol (PeOH), methyl propionate (MP), methyl ethyl ketone (MEK), 1,2-dimethoxyethane (1,2-DME), and 2-ethylhexyl nitrate (EHN)) was measured using a constant volume combustion chamber. Experiments were performed on three sets of blended fuels with different oxygen contents (2.5 wt%, 5 wt%, and 10 wt%) in the temperature range of 723–863 K and at ambient pressures of 2.2 and 4 MPa. A kinetic analysis utilized a merged RP-3 low-temperature kinetic model containing various oxygenated components. The ignition delay of blended fuels increases with the addition of PeOH, MP, and MEK, particularly PeOH, which demands more energy absorption at low temperatures due to its higher specific heat and latent heat of vaporization. As ambient pressure increased, the ignition delay period shortened for all blended fuels; however, PeOH and MEK demonstrated more significant low-temperature suppression. The combined kinetic model can reasonably predict the trend of the effect of oxygenated additives. 1,2-DME showed significantly more low-temperature reactivity versus PeOH, MP, and MEK. The variability is because the products of secondary O2 addition and isomerization of 1,2-DME undergo low-temperature branched chain reactions, but other oxygenated fuels produce more inert components.