Probing the low temperature oxidation chemistry of RP-3 kerosene: Experimental and kinetic modeling investigation

Abstract

Elucidating the formation of intermediates, especially active species like peroxy radicals and hydroperoxides, is crucial to explore the low temperature reaction network and validate the kinetic model. While low temperature oxidation kinetics of single hydrocarbon has been widely studied, the comprehensive speciation study on the transportation fuels is still lacking and challenging due to the complex compositions of real fuels. This work aims to investigate the speciation pool and develop predictable kinetic model for the low temperature oxidation of RP-3 kerosene. An atmospheric jet stirred reactor combined with synchrotron vacuum ultraviolet photoionization mass spectrometry was used to investigate the RP-3 kerosene oxidation in the temperature range of 480–770 K and equivalence ratios of 0.5, 1.0 and 2.0. Major products and key intermediates were quantified and categorized into several groups, including peroxy radicals, hydroperoxides, alkenes, alcohols, aldehydes, acids and aromatics. Furthermore, a three-component surrogate fuel consisting of 60.0% n-dodecane, 31.5% ethylcyclohexane, and 8.5% n-butylbenzene (by mole) was formulated to represent the RP-3 kerosene. A kinetic model for the three-component surrogate fuel was developed based on the comprehensively validated kinetic model of single components. This model was validated against the low temperature oxidation speciation data, ignition delay times and laminar flame speeds of RP-3 over wide range of conditions. Rate of production and sensitivity analysis were performed to explore the low temperature oxidation reaction network. The results indicate that the negative temperature coefficient behavior of RP-3 is dominated by the reactions of n-alkane, which is easier to proceed low temperature chain-propagation reactions leading to the production active OH radicals. The reaction network of each fuel component is effectively coupled from the view of OH regeneration and consumption, and finally affects the distribution of speciation pool during RP-3 low temperature oxidation. Regarding the characteristic speciation pool, it is found that the formation and consumption of peroxy radicals, hydroperoxides, alkene, aldehyde, and alcohol intermediates are controlled by the reaction network of alkane. While the formation and depletion of aromatic intermediates are affected by the interaction kinetics of fuel components with different chemical functionalities. These results improve the current understanding of the speciation pool and interaction kinetics during RP-3 low temperature oxidation. The kinetic model of RP-3 kerosene developed and validated in this work could be applied for numerical simulation of aero-engine.