Experimental and modeling study on the oxidation of Jet A and the n-dodecane/iso-octane/n-propylbenzene/1,3,5-trimethylbenzene surrogate fuel

Jet A POSF 4658 and n-dodecane/iso-octane/n-propylbenzene/1,3,5-trimethylbenzene (2nd generation surrogate) oxidation experiments were conducted in a shock tube at high pressures and at fuel lean and rich conditions to verify if the formulated surrogate fuel emulates the combustion characteristics of the jet fuel. A model was developed for the 2nd generation surrogate using an existing 1st generation surrogate model (consisting of n-decane/iso-octane/toluene) as the base model and sub-models for n-propylbenzene and 1,3,5-trimethylbenzene were included from the literature. The experimental work on both the Jet A and 2nd generation surrogate was performed in a heated high-pressure single pulse shock tube at equivalence ratios of 0.46, 1.86 and 0.47, 1.85, respectively. Experimental data were obtained over the temperature range of 879-1733 K, a pressure range of 16-27 atm, and reaction times from 1.34 to 3.36 ms. The mole fractions of the stable species were determined using gas chromatography and mass spectroscopy. Comparing the Jet A and the 2nd generation surrogate experiments showed that the surrogate fuel emulates the decay of O-2, and the formation of CO, CO2, and C-1-C-3 intermediate species within experimental errors. The modeling results of the 2nd generation surrogate model compared against the experimental data showed good agreement with the mole fractions of CO, CO2, C-1-C-3 intermediate species and the decay of the surrogate fuel and oxygen. Comparison of the modeling results for O-2 decay to the 2nd generation surrogate experiments and pure 1,3,5-trimethylbenzene oxidation experiments revealed that the surrogate fuel model is capable of predicting O-2 decay with a greater degree of accuracy in the 2nd generation surrogate experiments than in that of pure 1,3,5-trimethylbenzene experiments. This suggests that the radical pool formed due to the non-aromatics species during the consumption of 2nd generation surrogate fuel components prior to the formation of CO and CO2 could contribute to the initial decay of O-2 at lower temperatures and thereby results in better prediction by the model, which includes both non-aromatics and aromatics chemistry, of O-2 decay and formation of CO and CO2. Flow reactor simulations of the 2nd generation surrogate fuel experiments showed the surrogate model captures the overall trends of the decay of O-2 and the formation of CO, CO2, and H2O. Additionally, simulated shock tube ignition delay times above 750 K were within a factor of two when compared to experimental ignition delay times. (C) 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.