arXiv subjects

Ronald K. Hanson

Publications and source records attributed to Ronald K. Hanson.

3 recordsLinked to original sources

arXiv2026

Carbon black and hydrogen production from methane pyrolysis: measured and modeled insights from integrated gas and particle diagnostics in shock tubes

Methane (CH4) pyrolysis is a promising route to co-produce hydrogen (H2) and carbon black (CB) while avoiding emissions associated with steam-methane reforming and furnace black processes. Model development of pyrolytic CB synthesis requires experimental observations of concurrent gas chemistry, particulate formation, and morphology. This work presents a combined experimental and modeling study of CH4 pyrolysis behind reflected shock waves in 5% CH4/Argon mixtures at post-reflected shock temperatures (T5) of 1850-2450 K and P5 around 4.5 atm. Laser absorption diagnostics quantified CH4, C2H4, and C2H2 mole fractions, while multiwavelength extinction (633 and 1064 nm) resolved time-dependent particle formation and the temperature-dependent evolution of optical maturity. Simulations reproduce small-molecule speciation well, but large variations in predicted polycyclic aromatic hydrocarbons (PAHs) persist among models. Coupled gas-particle simulations capture accurate volume fraction (fv) trends and the influence of gas dynamics but underpredict induction times at high T5. Samples collected at the shock tube endwall were analyzed by transmission electron microscopy (TEM) to quantify primary particle size distributions and nanostructure arrangement. Image segmentation and manual measurements showed reduced primary particle size growth (dp) with increasing T5, while graphitic nanostructure generally increased. This study provides an integrated benchmark for improving models of CB and H2 production from CH4 pyrolysis by constraining gas-phase kinetics, PAH-driven inception, particle dynamics, and particle maturity. The results highlight that accurate partitioning of mass between particle number and particle size is an important constraint for further model development.

physics.chem-ph↗

arXiv2020

Dual-comb spectroscopy for high-temperature reaction kinetics

In the current study, a quantum-cascade-laser-based dual-comb spectrometer (DCS) was used to paint a detailed picture of a 1.0 ms high-temperature reaction between propyne and oxygen. The DCS interfaced with a shock tube to provide pre-ignition conditions of 1225 K, 2.8 atm, and 2% p-C3H4/18% O2/Ar. The spectrometer consisted of two free-running, non-stabilized frequency combs each emitting at 179 wavelengths between 1174 and 1233 cm-1. A free spectral range, f_r, of 9.86 GHz and a difference in comb spacing, Δf_r, of 5 MHz, enabled a theoretical time resolution of 0.2 us but the data was time-integrated to 4 us to improve SNR. The accuracy of the spectrometer was monitored using a suite of independent laser diagnostics and good agreement observed.

physics.chem-ph↗

arXiv2019

Information-Driven Design for Shock Tube / Laser Absorption Studies of Fundamental Rate Constants in Combustion, with Application to Methanol Pyrolysis

Shock tube experiments, paired with precision laser diagnostics, are ideal venues to provide kinetics data critically needed for the development, validation and optimization of modern combustion kinetics models. However, to design sensitive, accurate, feasible and information-rich experiments that may yield such data often requires sophisticated planning. This study presents a mathematical framework and quantitative approach to guide such experimental design, namely a method to pin-point the optimal conditions for specific experimentation under realistic constraints of the shock tubes and diagnostic tools involved. For demonstration purpose, the current work is focused on a key type of shock tube kinetic experiments -- direct determination of fundamental reaction rate constants. Specifically, this study utilizes a Bayesian approach to maximize the prior-posterior gain in Shannon information of the rate constants to be inferred from the intended experiment. Example application of this method to the experimental determination of the CH$_3$OH + H (k$_1$) and CH$_2$O + H (k$_2$) rate constants is demonstrated in shock tube/laser absorption studies of the CH$_3$OH pyrolysis system, yielding new recommended rate constant expressions (over 1287 K - 1537 K) as: k$_1$ = $ 2.50 \times 10^6 (T/K)^{2.35} exp(-2975 K /T) \, cm^3mol^{-1}s^{-1} \pm 11.4\%$ and k$_2$ = $7.06 \times 10^7 (T/K)^{1.9} exp(-1380 K/T) \, cm^3mol^{-1}s^{-1} \pm 9.7 \%$. Potential extension to other types of kinetic studies, e.g. prediction of combustion benchmarks such as ignition delay times and species yields, and global uncertainty minimization of generic reaction models, are also briefly discussed.

physics.chem-ph↗