A streamlined approach to hybrid-chemistry modeling for a low cetane-number alternative jet fuel

Abstract

The development of renewable, alternative jet fuels presents an exigent challenge to the aviation community. In this work, a streamlined methodology for building computationally efficient kinetic models of real fuels from shock tube experiments is developed and applied to a low cetane-number, broad-boiling alternative jet fuel (termed C-4). A multi-wavelength laser absorption spectroscopy technique was used to determine species time-histories during the high-temperature pyrolysis of C-4, and a batch gradient descent optimization routine built a hybrid-chemistry (HyChem) kinetic model from the measured data. The model was evaluated using combustor-relevant, high-pressure ignition delay time measurements with satisfactory agreement. The present model enables predictive simulations of C-4 in practical environments, while the underlying methodology described here can be readily extended to build kinetic models for a broad range of real fuels of interest.

Skeletal and Compact Validated Mechanisms for Iso-dodecane Using a Decoupling Methodology

“…Among the candidate components for iso-alkanes in jet fuels composition, iso-dodecane is the most appropriate compound to be used as a surrogate for ATJ fuel − and as a major component in the surrogate formulation of JET A, , JP8, and HRJ fuels , because of its physicochemical characteristics being similar to the average of the real fuel such as molecular weight, H/C ratio, density, and flash point. Table shows various physicochemical properties of iso-dodecane in comparison with jet fuels.…”

Quantum-cascade-laser-based dual-comb thermometry and speciation at high temperatures

“…On the other hand, single-wavelength LAS diagnostics, such as those employed in [3], are temporally limited only by the detection electronics (order MHz), but lack the spectral resolution necessary to quantitatively interrogate complex chemical environments such as fuel pyrolysis. Recent efforts to study pyrolysis chemistry have employed large arrays of lasers tuned to unique frequencies to achieve sufficient spectral resolution [4][5][6][7], an approach that has been successful in moderately complex environments but remains costly and cumbersome for broader applications.…”

“…This work presents a methodology for fitting DCS measurements to fundamental spectral databases in high-temperature shock-tube studies, using methane as the target species. Methane's discrete high-temperature spectrum has recently been incorporated into the HITEMP database [25], and it represents an important target species in pyrolysis studies, hybridchemistry kinetic model development, and natural-gas kinetics research [4,[26][27][28][29]. To achieve spectral fitting of DCS measurements, the DCS system was first validated against the HITEMP methane model in a static cell at atmospheric temperature, where it demonstrated accurate resolution of methane's absorption features at up to 4 µs resolution.…”

The pyrolysis of propane

“…To obtain absorbance data at every wavelength at a common condition of 1300 K, the authors ran a large number of experiments near the target condition and linearly interpolated between traces to generate temperature‐appropriate absorbance signals 24 . The same process was used to speciate a series of jet fuels 25,26 …”

“…However, pyrolysis chemistry has inherently been challenging to study optically, as larger hydrocarbons break into smaller ones with similar, overlapping absorption spectra. The introduction of new diagnostic wavelengths with unique sensitivities to individual species, 17‐22 coupled with their use in multiwavelength schemes, 23 has enabled species measurements in highly blended spectral environments 24‐27 . Notably, six wavelengths were recently used to provide effectively complete speciation during the pyrolysis of ethane, the second most abundant species in natural gas 28 .…”