High-resolution molecular fingerprinting in the 11.6-15 µm range by a quasi-CW difference-frequency-generation laser source

: We report an approach for high-resolution spectroscopy using a widely tunable laser emitting in the molecular fingerprint region. The laser is based on difference-frequency generation (DFG) in a nonlinear orientation-patterned GaAs crystal. The signal laser, a CO2 gas laser, is operated in a kHz-pulsed mode while the pump laser, an external-cavity quantum cascade laser, is finely mode-hop-free tuned. The idler radiation covers a spectral range of ∼11.6-15 µm with a laser linewidth of ∼ 2.3 MHz. We showcase the versatility and the potential for molecular fingerprinting of the developed DFG laser source by resolving the absorption features of a mixture of several species in the long-wavelength mid-infrared. Furthermore, exploiting the wide tunability and resolution of the spectrometer, we resolve the broadband absorption spectrum of ethylene (C2H4) over ∼13-14.2 µm and quantify the self-broadening coefficients of some selected spectral lines

Ignition studies of n-heptane/iso-octane/toluene blends

Journal articleIgnition delay times of four ternary blends of n-heptane/iso-octane/toluene, referred to as Toluene Primary Reference Fuels (TPRFs), have been measured in a high-pressure shock tube and in a rapid compression machine. The TPRFs were formulated to match the research octane number (RON) and motor octane number (MON) of two high-octane gasolines and two prospective low-octane naphtha fuels. The experiments were carried out over a wide range of temperatures (650-1250 K), at pressures of 10, 20 and 40 bar, and at equivalence ratios of 0.5 and 1.0. It was observed that the ignition delay times of these TPRFs exhibit negligible octane dependence at high temperatures (T > 1000 K), weak octane dependence at low temperatures (TSaudi Aramco (FUELCOM); King Abdullah University of Science and Technology (KAUST)2018-07-0

The combustion kinetics of the lignocellulosic biofuel, ethyl levulinate

Ethyl levulinate (Ethyl 4-oxopentanoate) is a liquid molecule at ambient temperature, comprising of ketone and ethyl ester functionalities and is one of the prominent liquid fuel candidates that may be easily obtained from lignocellulosic biomass. The combustion kinetics of ethyl levulinate have been investigated. Shock tube and rapid compression machine apparatuses are utilised to acquire gas phase ignition delay measurements of 0.5% ethyl levulinate/O-2 mixtures at phi = 1.0 and phi = 0.5 at similar to 10 atm over the temperature range 1000-1400K. Ethyl levulinate is observed not to ignite at temperatures lower than similar to 1040 K in the rapid compression machine. The shock tube and rapid compression machine data are closely consistent and show ethyl levulinate ignition delay to exhibit an Arrhenius dependence to temperature. These measurements are explained by the construction and analysis of a detailed chemical kinetic model. The kinetic model is completed by establishing thermochemical-kinetic analogies to 2-butanone, for the ethyl levulinate ketone functionality, and to ethyl propanoate for the ethyl ester functionality. The so constructed model is observed to describe the shock tube data very accurately, but computes the rapid compression machine data set to a lesser but still applicable fidelity. Analysis of the model suggests the autooxidation mechanism of ethyl levulinate to be entirely dominated by the propensity for the ethyl ester functionality to unimolecularly decompose to form levulinic acid and ethylene. The subsequent reaction kinetics of these species is shown to dictate the overall rate of the global combustion reaction. This model is then use to estimate the Research and Motored Octane Numbers of ethyl levulinate to be >= 97.7 and >= 93, respectively. With this analysis ethyl levulinate would be best suited as a gasoline fuel component, rather than as a diesel fuel as suggested in the literature. Indeed it may be considered to be useful as an octane booster. The ethyl levulinate kinetic model is constructed within a state-of-the-art gasoline surrogate combustion kinetic model and is thus available as a tool with which to investigate the use of ethyl levulinate as a gasoline additive. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.Research (University of Limerick, Trinity College Dublin & KAUST) reported in this publication was carried out under the Future Fuels project supported by the Competitive Center Funding (CCF) program at King Abdullah University of Science and Technology (KAUST). Research conducted at National University of Ireland, Galway and Trinity College Dublin was supported by Science Foundation Ireland. Computational resources were provided by the Irish Centre for High-End Computing, ICHEC.2020-04-0

The combustion kinetics of the lignocellulosic biofuel, ethyl levulinate

Ethyl levulinate (Ethyl 4-oxopentanoate) is a liquid molecule at ambient temperature, comprising of ketone and ethyl ester functionalities and is one of the prominent liquid fuel candidates that may be easily obtained from lignocellulosic biomass. The combustion kinetics of ethyl levulinate have been investigated. Shock tube and rapid compression machine apparatuses are utilised to acquire gas phase ignition delay measurements of 0.5% ethyl levulinate/O-2 mixtures at phi = 1.0 and phi = 0.5 at similar to 10 atm over the temperature range 1000-1400K. Ethyl levulinate is observed not to ignite at temperatures lower than similar to 1040 K in the rapid compression machine. The shock tube and rapid compression machine data are closely consistent and show ethyl levulinate ignition delay to exhibit an Arrhenius dependence to temperature. These measurements are explained by the construction and analysis of a detailed chemical kinetic model. The kinetic model is completed by establishing thermochemical-kinetic analogies to 2-butanone, for the ethyl levulinate ketone functionality, and to ethyl propanoate for the ethyl ester functionality. The so constructed model is observed to describe the shock tube data very accurately, but computes the rapid compression machine data set to a lesser but still applicable fidelity. Analysis of the model suggests the autooxidation mechanism of ethyl levulinate to be entirely dominated by the propensity for the ethyl ester functionality to unimolecularly decompose to form levulinic acid and ethylene. The subsequent reaction kinetics of these species is shown to dictate the overall rate of the global combustion reaction. This model is then use to estimate the Research and Motored Octane Numbers of ethyl levulinate to be >= 97.7 and >= 93, respectively. With this analysis ethyl levulinate would be best suited as a gasoline fuel component, rather than as a diesel fuel as suggested in the literature. Indeed it may be considered to be useful as an octane booster. The ethyl levulinate kinetic model is constructed within a state-of-the-art gasoline surrogate combustion kinetic model and is thus available as a tool with which to investigate the use of ethyl levulinate as a gasoline additive. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.Research (University of Limerick, Trinity College Dublin & KAUST) reported in this publication was carried out under the Future Fuels project supported by the Competitive Center Funding (CCF) program at King Abdullah University of Science and Technology (KAUST). Research conducted at National University of Ireland, Galway and Trinity College Dublin was supported by Science Foundation Ireland. Computational resources were provided by the Irish Centre for High-End Computing, ICHEC.peer-reviewed2020-04-0