Shock-Tube Laser Absorption Measurements of CO and H₂O during Iso-Octane Combustion

Abstract

The oxidation of iso-octane was studied in two different shock tubes by recording mole fraction time histories of CO and H2O at various equivalence ratios (0.5, 1.0, and 2.0) at around 1.5 atm, between 1320 and 1815 K. Mixtures were diluted in 99% inert gases. Results show that the induction delay time for both CO and H2O are particularly sensitive to the temperature and the equivalence ratio. The CO profiles for the fuel-lean and stoichiometric mixtures present a peak in CO formation, due to the oxidation of CO to CO2. This peak was not observed for the fuel rich mixture, where the CO profile reaches a plateau within the time frame investigated. For the water profiles, they all present a plateau after the main water formation process, although this plateau is still ascending for the fuel-lean and stoichiometric mixtures during the test time. Experimental results were compared with detailed kinetics mechanisms from the literature, the most recent one (Atef et al. Comb. Flame 2017, 178, 111–134) being in overall good agreement with the data except for the maximum CO mole fraction at the lowest temperatures investigated. A numerical analysis was conducted with this model to explain the results and to identify ways to improve the model.

Experimental Kinetics Study on Diethyl Carbonate Oxidation

“…On the other hand, for the fuel-rich case, the peak was not as well defined, and the CO reached a plateau level. This plateau was to be expected and is typically observed for mixtures when the oxygen concentration is insufficient to fully oxidize the fuel [19,34,45].…”

An Experimental Kinetics Study of Isopropanol Pyrolysis and Oxidation behind Reflected Shock Waves

“…Two laser absorption diagnostics were utilized to simultaneously measure water and CO production during the same experiment via multiple window ports allowing access to the sidewall location, 1.6 cm downstream from the endwall of the AST. Only a brief discussion on these diagnostics is provided here, but more detailed information on the water and CO diagnostics has been described in previous studies [40][41][42][43].…”

“…Temperature predictions made by the Li et al model were used to account for temperature change during combustion and pyrolysis for both laser diagnostics. The mixtures were chosen to keep the temperature change below 150 K. Finally, previous studies estimated the uncertainties of the water and CO measurements at around 5.6% and 3.8%, respectively [43].…”

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“…A number of excellent and extensive research articles on NH 3 as a fuel have been written in recent years, and readers are directed to those to learn more. These include landmark publications by Valera-Medina et al, − Kobayashi et al, and Mathieu and Petersen which describe various challenges associated with production, transport, and utilization of NH 3 as a fuel.…”