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1,346 results on '"Hanson, Ronald K."'

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

Author

Wang, Shengkai, Ding, Yiming, and Hanson, Ronald K.

Subjects
Physics - Chemical Physics
Abstract

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.

Published
2019

20. Dual-comb spectroscopy for high-temperature reaction kinetics

Author

Pinkowski, Nicolas H., Ding, Yiming, Strand, Christopher L., Hanson, Ronald K., Horvath, Raphael, and Geiser, Markus

Subjects
Physics - Chemical Physics, Physics - Optics
Abstract

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, {\Delta}f_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.

Published
2019
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37. Logistic-Regression-Based Meta-Analysis of Factors Affecting Flame Stability in a Shock Tube.

Author

Susa, Adam J., Ferris, Alison M., Zheng, Lingzhi, and Hanson, Ronald K.

Subjects
FLAME stability, SHOCK tubes, MOLECULAR weights, CRITICAL temperature, HEAT capacity
Abstract

This work describes a meta-analysis performed in an effort to better understand the parameters controlling flame stability in shock-tube flame experiments. The data set used in the analysis was aggregated from multiple prior studies employing the shock-tube flame speed method, as well as previously unreported results. Flames are first qualitatively classified as being smooth, distorted, or wrinkled based on end-wall images. A subset of trials capturing the stability transition from stable to unstable flames are then selected from each set of experiments. Across all data sets, the transition between stable and unstable flames is analyzed as a binary classification problem using logistic regression. The resulting classification model, cast in terms of a multivariate power-law expression for the critical temperature ($${T_{{\rm{crit}}}}$$ T crit ) at which flames become unstable, is found to be highly predictive of the stability transition. Consideration of the trained model coefficients allows the effects of different experimental parameters on $${T_{{\rm{crit}}}}$$ T crit to be identified. Model parameters provide significant new insight into the selection of diluents in experiments; the use of a test gas with a high heat capacity ratio is found to have the most beneficial effect toward increasing $${T_{{\rm{crit}}}}$$ T crit , while the effects of Lewis number and molecular weight are determined to be negligible. Ignition-location and pressure effects are less well quantified due to limited available data and are identified as key areas of further study. [ABSTRACT FROM AUTHOR]

Published
2024
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