Diisopropyl ketone (DIPK) is a promising biofuel candidate, which is produced using endophytic fungal conversion. In this work, a high temperature detailed combustion kinetic model for DIPK was developed using the reaction class approach. DIPK ignition and pyrolysis experiments were performed using UCF shock tube. The shock tube oxidation experiments were conducted between 1093 K and 1630 K for different reactant compositions, equivalence ratios (φ =0.5-2.0), and pressures (1-6 atm). In addition, methane concentration time-histories were measured during 2% DIPK pyrolysis in argon using cw laser absorption near 3400 nm at temperatures between 1300 and 1400 K near 1atm. To the best of our knowledge, current ignition delay times (above 1050 K) and methane time histories are the first such experiments performed in DIPK at high temperatures. Present data were used as validation targets for the new kinetic model and simulation results showed fair agreement compared to the experiments. The reaction rates corresponding to the main consumption pathways of DIPK were found to have high sensitivity in controlling the reactivity, so these were adjusted to attain better agreement between the simulation and experimental data. A correlation was developed based on the experimental data to predict the ignition delay times using the temperature, pressure, fuel concentration and oxygen concentration.
Aldehydes are major intermediates in oxidation and pyrolysis of hydrocarbons and particularly biofuels. While the high temperature oxidation chemistry of C3–C5 aldehydes have been studied in the literature, a comprehensive low temperature kinetics remains unaddressed. In this work, acetaldehyde, propanal, and 2-propenal (acrolein) oxidation was investigated at low-temperature combustion condition (500–700 K). The isomer-specific product concentrations as well as the time-resolved profiles were studied using Sandia's multiplexed photoionization mass spectroscopy (MPIMS) with synchrotron radiation from the advanced light source (ALS). The laser-pulsed photolysis generates chlorine atoms which react with aldehydes to form the parent radicals. In the presence of excess oxygen, these radicals react with O2 and form RO2 radicals. The temperature-dependent product yields are determined for 500 K to 700 K and the competition between the channels contributing to the formation of each product is discussed. In acetaldehyde oxidation, the formation of the main products is associated with HO2 elimination channel from QOOH or direct H atom elimination from the parent radicals. In propanal oxidation, the most intensive signal peak was associated with acetaldehyde (m/z = 44) which was formed through the reaction of α′-R with O2.The α′-RO2 intermediate decomposes to acetaldehyde+OH+CO via Waddington mechanism and formation of five-member ring transition state. In 2-propenal oxidation, the unsaturated radical produced from α-R reacts with O2 to form the primary products.
Ignition and flame propagation in methane/O2 mixtures diluted with CO2 are studied. A laser ignition system and dynamic pressure transducer are utilized to ignite the mixture and to record the combustion pressure, respectively. The laminar burning velocities (LBVs) are obtained at room temperature and atmospheric pressure in a spherical combustion chamber. Flame initiation and propagation are recorded by using a high-speed camera in select experiments to visualize the effect of CO2 proportionality on the combustion behavior. The LBV is studied for a range of equivalence ratios (ϕ = 0.8–1.3, in steps of 0.1) and oxygen ratios, D = O2/(O2 + CO2) (26–38% by volume). It was found that the LBV decreases by increasing the CO2 proportionality. It was observed that the flame propagates toward the laser at a faster rate as the CO2 proportionality increases, where it was not possible to obtain LBV due to the deviation from spherical flame shape. Current LBV data are in very good agreement with existing literature data. The premixed flame model from chemkin pro (Reaction Design, 2011, CHEMKIN-PRO 15112, Reaction Design, San Diego, CA) software and two mechanisms (GRI-Mech 3.0 (Smith et al., 1999, “The GRI 3.0 Chemical Kinetic Mechanism,” http://www.me.berkeley.edu/gri_mech/) and ARAMCO Mech 1.3 (Metcalfe et al., 2013, “A Hierarchical and Comparative Kinetic Modeling Study of C1–C2 Hydrocarbon and Oxygenated Fuels,” Int. J. Chem. Kinetics, 45(10), pp. 638–675)) are used to simulate the current data. In general, simulations are in reasonable agreement with current data. Additionally, sensitivity analysis is carried out to understand the important reactions that influence the predicted flame speeds. Improvements to the GRI predictions are suggested after incorporating latest reaction rates from literature for key reactions.
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