Species Time-histories Research Articles

Experimental study of the methane/hydrogen/ammonia and ethylene/ammonia oxidation: Multi-parameter measurements using a shock tube combined with laser absorption spectroscopy

Ammonia (NH3) is a promising hydrogen carrier and carbon-free fuel, which can be synthesized using renewable energy and has attracted increasing attention from both academic and industrial communities. This study selected six absorption lines and developed a laser absorption diagnostics system that can simultaneously measure the temperature, CO, CO2, H2O, NH3, and NO time-histories during the oxidation of CH4/H2/NH3 and C2H4/NH3 mixtures (equivalence ratio ϕ ≈ 1.2) behind reflected shock waves. Since the fuels were highly diluted to reduce the nonideal effects and heat release behind reflected shock waves, the maximum NO mole fraction was only ∼0.2% and led to a small absorption (< 2.0%). Therefore. the wavelength modulation spectroscopy (WMS-2f/1f) was used for the NO time-history measurements while the other species were measured using fixed-wavelength absorption spectroscopy. A total of thirteen kinetics models were used to interpret the measurements. The main differences between the model predictions and measured data lie in two aspects: the mixture reactivities and the NO production. Generally speaking, for both CH4/H2/NH3 and C2H4/NH3 mixtures, the Glarborg model performs the best in predicting the temperature and species time-histories but the differences still exist. The high-quality experimental data support further analyses and improvements. Detailed kinetics analyses based on the Glarborg 2018 model were performed. It indicates that H + O2 = O + OH is the most sensitive and promoting reaction for both mixtures, followed by the H-abstraction reactions of H2 and C2H4. Conversely, the H-abstraction reactions of CH4 and NH3 impede oxidation due to competition with promoting reactions for reactants (H, OH, or O). Moreover, subsequent reactions involving the produced CH3 or C2H3 radicals also have significant effects on oxidation. The reactions affecting the NO plateau were also selected as the basis to optimize the predicted NO plateau. Although updating the rate constants of some key reactions improved model performance for both mixtures, discrepancies still exist, particularly for the C2H4/NH3 mixture.

Low-temperature oxidation of n-octane and n-decane in shock tubes: Differences in time histories of key intermediates

The impact of chain length on the time histories of key intermediate species that form upon first-stage ignition was studied experimentally in a shock tube using multi-color laser absorption diagnostics. CO, CH2O, OH, and composite time histories of heavier carbonyls were measured simultaneously during the low temperature oxidation of n-octane & n-decane in the temperature range of 720–860 K, and pressure range of 4.1–5.8 atm. The test mixtures were 0.64% & 0.6% fuel in oxygen, respectively. A two-color diagnostic was also developed and used in tandem with other diagnostics to quantify the evolution of temperature during oxidation. To our knowledge, this work reports the first measurement of CH2O, OH, and temperature during oxidation of C8 or heavier hydrocarbon fuels at low temperatures. The measured time histories were also compared against the predictions of two recent detailed kinetic models. Significant differences in the measured and predicted first-stage ignition delay times, absolute concentration of species post-ignition and the maximum rate of formation of species were observed. Our measurements will serve as targets for further refinement of these detailed kinetic models and in the development of rate rules for similar classes of fuels. The measurements also revealed significant differences in the relative reactivity of n-octane and n-decane. Taken together with previous speciation studies conducted in n-heptane, we observe a strong correlation between the species time histories, reactivity, and chain length of straight chain alkanes. This observation lends further support to the selection of CO and CH2O as target species for development of Low-Temperature Hybrid Chemistry (HyChem) models for real transportation and aviation fuels in future.

Multiwavelength Speciation in Pyrolysis of n-Pentane and Experimental Determination of the Rate Coefficient of nC5H12 = nC3H7 + C2H5 in a Shock Tube.

We report the application of a multiwavelength speciation strategy to the study of n-pentane (nC5H12) pyrolysis behind reflected shock waves in a shock tube. Experiments were conducted with 2% nC5H12/0.8%CO2/Ar (by mole) between 1150 and 1520 K in the pressure range of 1-2 atm. Utilization of laser absorption spectroscopy at eight wavelengths allowed time-resolved measurements of n-pentane, ethylene, methane, heavy alkenes, and temperature. The measured time histories were compared against the predictions of four recently developed chemical kinetic models for heavy hydrocarbons. It was found that none of the models reconciled the measured species time histories simultaneously. Sensitivity analysis was conducted to identify key reactions influencing the evolution of ethylene and other major pyrolysis products. The analysis revealed that the unimolecular decomposition of n-pentane into n-propyl and ethyl radicals has a dominating influence over the evolution of ethylene in the temperature range of 1150-1450 K. The rate coefficient of this reaction was then adjusted to match the measured ethylene time histories for each experiment. The rate coefficients thus determined, were fit against temperature using an Arrhenius expression given by k1(T) = 3.5 × 1014 exp(-67.2 kcal/RT) s-1. The average overall 2σ uncertainty of the measured rate coefficient was found to be ±35%, resulting primarily from uncertainties in the rate coefficients of secondary reactions. The measured rate coefficient, when used with the models, leads to a significant improvement in the prediction of species time histories. Further improvements in the model are possible if the rate coefficients of relevant reactions pertaining to small hydrocarbon chemistry are determined with an improved accuracy, and less uncertainty. To the best knowledge of the authors, this is the first experimental determination of the rate coefficient of C5H12 → nC3H7 + C2H5.

Using shock tube species time-histories in Bayesian parameter estimation: Effective independent-data number and target selection

Species time-histories in shock tube experiments provide rich kinetic information for parameter estimation, but there are two problems in using these data in Bayesian approaches. First, the effective independent-data number is not equal to the number of data points in a curve, so brute multiplication of all data points in likelihood function can weaken the constraints from prior information. Second, taking all points of a curve as targets can lead to results different from that of taking several representative points in the curve. In this paper, we employed maximum a posteriori estimation combined with a neural network response surface to optimize a propane mechanism against multispecies time-histories of propane pyrolysis in a shock tube. Three methods of calculating the likelihood function are used: multiplying all points in a curve (C-160), taking the averaged likelihood in each point (C-1), and taking the likelihood of last points (LastP). The influence of effective independent-data number was studied by comparing C-1 and C-160. It was found that C-160 performed slightly better in fitting experimental data, but brute multiplication overtuned the rate constants beyond a reasonable range. The larger the effective independent-data number, the more severe the overtuning, leading to only a slight improvement of model predictions. The influence of target selection is investigated by comparing LastP and C-1. LastP outperformed C-1 slightly, which can be attributed to the fact that larger discrepancies observed between experimental data and model predictions of the last point can increase the weights of likelihood functions. This further implies that several critical points can represent the entire line for point estimation. This paper can provide a reference both for modelers about reasonable utilization of species time-histories, and for experimentalists about the importance of a detailed probability distribution of measurement error, as well as experiment design with emphasis on critical points.

Shock Tube/Laser Absorption Measurements of Cyclopentadiene Pyrolysis.

High-temperature cyclopentadiene pyrolysis was examined behind reflected shock waves in a heated shock tube using several laser absorption diagnostic schemes. A two-color, online-offline sensor near 3335 cm-1 was used to measure time histories of acetylene, while a three-color scheme of diagnostics at 10.532, 10.675, and 11.345 μm yielded measurements of cyclopentadiene and ethylene. Species time histories of cyclopentadiene decomposition and acetylene formation as well as ethylene yields are reported from 1319 to 1678 K at 1.2-1.5 atm. In addition, the overall decomposition rate of cyclopentadiene is reported, and comparisons are made to a number of kinetic models.

Thermometry and speciation for high-temperature and -pressure methane pyrolysis using shock tubes and dual-comb spectroscopy

Quantum-cascade-laser dual-comb spectroscopy (QCL-DCS) is a promising technology with ultra-fast time resolution capabilities for chemical kinetics, atmospheric gas sensing, and combustion applications. A pair of quantum-cascade frequency combs were used to measure absorbance from methane’s band between 1270 and 1315 cm−1 at high-temperature and -pressure conditions that were generated using a high-pressure shock tube. Results here mark a major improvement over previous QCL-DCS measurements in shock tubes. Improvements came from a unique spectral-filtering strategy to correct for a bimodal power-spectral density of QCL frequency combs and careful optimization of the laser setup and experimental conditions. Our modified QCL-DCS was ultimately used to measure temperature within 2% and methane mole fraction within 5% by fitting HITEMP spectral simulations to spectra recorded at 4 μs temporal resolution. We measure temperature and species time-histories during methane pyrolysis at conditions between 1212–1980 K, and 12–17 atm, all at 4 μs resolution. Good agreement is observed with kinetic models, illustrating the potential of future applications of DCS in kinetics and combustion research.

Shock tube study of ethanol pyrolysis I: Multi-species time-history measurements

Time-histories of the concentration of major products of ethanol pyrolysis at 1 atm and 10 atm in the temperature range of 1200–1600 K were measured behind reflected shock waves using fixed-wavelength laser absorption spectroscopy. Measurement of absorbance at nine wavelengths enabled the determination of the evolution of CH4, C2H4, C2H5OH, CO, CH2O and CH3CHO during the pyrolysis of 2% C2H5OH/Argon mixtures. These measurements enabled almost complete tracking of oxygen and carbon during pyrolysis. The performance of five recently developed kinetic models was evaluated against the measurements. It was found that none of these models could reconcile all the measured time-histories simultaneously. Sensitivity and Rate-of-production analysis revealed that the thermal decomposition and H-abstraction reactions of ethanol are the key reactions that have a controlling influence on the species time-histories. Additional experiments were designed and conducted to infer the rate constants of these reactions. The details of these experiments, the rate constant determination methodology, and the implications of the updated rate constants on the model performance are discussed in the companion paper [1]. To the best of our knowledge, this work represents the first detailed study of ethanol pyrolysis involving simultaneous measurement of multiple species in a shock tube using laser absorption spectroscopy.

Competitive oxidation of methane and C2 hydrocarbons discerned by isotopic labeling and laser absorption spectroscopy of CO isotopologues in shock-heated mixtures

The competitive oxidation of methane with C 2 hydrocarbons of differing functional groups (alkane, alkene , and alkyne) was examined experimentally via combustion of isotopically-labeled fuel mixtures and laser absorption spectroscopy of carbon monoxide isotopologues. Quantitative species time-histories of the 12 CO and 13 CO isotopologues were measured simultaneously and in situ using laser absorption spectroscopy behind reflected shock waves, used for near-instantaneous heating and auto-ignition of binary mixtures containing equal carbon fractions of the different fuels. A driver extension and gas tailoring were employed on the shock tube facility to extend test times up to 30 milliseconds, enabling dilute ignition of the fuel blends over a range of temperatures from 1100–1800 K. Tested fuel mixtures were primarily fuel-rich to force the competition of carbon oxidation between the fuel components. The novel dataset of multi-isotopologue species time-histories were compared to available chemical mechanisms, revealing insights on the influence of each C 2 fuel on methane ignition. The GRI-MECH 3.0 and Foundational Fuel Chemistry Model (FFCM-1) reaction models were modified to incorporate 13 C reactions and species. Detailed comparison of the measurement data with FFCM-1 simulations revealed generally good agreement at elevated temperatures ( > 1500 K), with increasing divergence at lower temperatures, particularly for mixtures involving ethane and acetylene . Reaction pathway and sensitivity analysis of the variance between data and the modified mechanisms reveal key reactions likely responsible for the disagreements.

Speciation measurements in shock tubes for validation of complex chemical kinetics mechanisms: Application to 2-Methyl-2-Butene oxidation

Abstract Shock-tube species time histories can be used to generate multiple validation targets to develop and validate detailed chemical kinetics mechanisms. In this study, new shock-tube species time-history data are provided to further validate the detailed mechanisms for 2-methyl-2-butene (2M2B). Experiments were conducted in mixtures of 2M2B/O2 diluted in 99.5% inert gas at three equivalence ratios of ϕ = 0.5, 1.0, and 2.0 over a temperature range of 1396 to 1752 K near atmospheric pressure. Time histories of CO and H2O were measured using laser absorption diagnostics near 4.6 and 1.4 µm, respectively. Chemiluminescence from OH* was also collected near 307 nm to allow ignition delay time determination. Detailed procedures and considerations for the data processing of the laser absorption experiments are provided. The results from the OH* profiles showed two distinct peaks: one near time-zero and the other later in the experiment corresponding to the main ignition. The predictions from three 2M2B kinetics mechanisms were compared with the experimental results. A quantitative comparison is also presented using the multiple characteristic times extracted from the species time history profiles to quantify the performance of the mechanisms. A reaction pathway analysis was performed on the decomposition of 2M2B, revealing clear discrepancies in the major reaction pathways of these mechanisms. A sensitivity analysis was also performed, leading to similar conclusions regarding the differences among the mechanisms. The sensitivity analysis also showed that the OH* peak near time-zero is mainly due to the rapid 2M2B fuel decomposition reactions, indicating that these reactions can be independently validated using the OH* peak near time-zero as a target. This paper provides not only the first detailed species time-history measurements for 2M2B in a shock tube, but it also documents the proper collection and interpretation of such data, which is useful for future studies.

Reflected shock-initiated ignition probed via simultaneous lateral and endwall high-speed imaging with a transparent, cylindrical test-section

A TRAnsparent cylindrical (TRAC) shock tube test section has been developed to explore the ignition structure behind reflected shockwaves via simultaneous lateral and endwall high-speed imaging using three fuel/oxidizer mixtures: 0.1% n-C7H16/1.10% O2/4.14% N2/94.66% Ar, 0.1% iC8H18/1.25% O2/4.69% N2/93.96% Ar, and 5% CH4/10% O2/85% CO2. During mild ignition, the first exothermic centers were located outside of the observable test section. It is shown that with increasing temperature the far-wall ignition events move closer to the endwall, until a strong ignition is achieved. The temperature gradients that promote mild ignition were quantified and were found to have a slight dependence on fuel with the RMS temperature gradients being 0.80% for n-heptane and 1.07% for isooctane. The impact of temperature gradients on metrics used to improve kinetic models, such as species time histories, is noteworthy. From this temperature gradient, an experimental correlation is provided to estimate the transition temperature from mild to strong ignition for a mixture. The effect of diagnostic location in non-homogeneous reactions is quantified in reference to ignition delay. The unique and insightful perspective on the ignition process under heavy shock bifurcation is also discussed.

Dual-camera high-speed imaging of the ignition modes of ethanol, methanol and n-hexane in a shock tube

Shock tubes are used as homogeneous batch reactors to measure ignition delay times, reaction rate coefficients and species time-histories of a variety of chemical systems. Any non-ideality or inhomogeneity in the shock tube experiment would affect the quality and usefulness of measured data. Experimental and computational efforts have previously been carried out to characterize the regimes of ideal operation of shock tubes. High-speed imaging has proven to be a highly useful tool to assess ignition homogeneity. In this work, a dual-camera setup has been used with an optical end-section in a circular shock tube to obtain simultaneous high-speed images from the shock tube endwall and sidewall, thus providing visualization of the ignition phenomenon in three dimensions. Two case studies are presented herein to demonstrate the quality of data and insights that are obtained using this diagnostic technique to study the ignition modes of different fuels. The first is a comparison of the ignition of two alternative fuels, methanol and ethanol, and the second is a study of the ignition dependence on the fuel concentration of a representative paraffinic fuel, n-hexane. The unique dual-camera imaging diagnostic enabled deeper insights into the ignition homogeneity, with all fuels exhibiting localized ignition at low temperatures. Methanol showed a higher propensity than ethanol to ignite far from the endwall, and the high concentration of n-hexane led to inhomogeneous ignition.

Shock tube/laser absorption measurements of the pyrolysis of JP-10 fuel

This work presents a novel application of multi-wavelength, multi-species laser absorption methods in the pyrolysis of JP-10 fuel. Two different multi wavelength approaches are used to measure the species from JP-10 pyrolysis in a shock tube at pressures of 2.5–3 atm and temperatures of 1166–1522 K. A five wavelength (5λ) analysis combination produces species time histories for ethylene, cyclopentadiene, and methane formation, as well as estimates of fuel decay. These results are extended further using a seven wavelength (7λ) combination of methods to measure ethylene, cyclopentadiene, propene, methane, allene, 1,3 butadiene, benzene, toluene, and fuel. Supplementary material includes details on the cyclopentadiene cross sections for 10.532 µm, 10.958 µm, and 11.345 µm. Simulations using two recent models are compared to the experimental data and the discrepancies are examined.

The thermal decomposition of ethane

Ethane pyrolysis chemistry plays a critical role in the combustion behavior of natural gas and gives insight into the decomposition patterns of larger alkanes. In this work, ethane pyrolysis was studied behind reflected shock waves with a convex optimization-based laser absorption speciation technique. Species time-histories of ethane, ethylene, methane, and acetylene were quantified in the decomposition of 1% and 2% ethane in argon at conditions between 1178 and 1527 K and 3.1–4.2 atm. Six laser wavelengths, simultaneously probing sensitive regions of each species’ spectra, enabled the sensitive detection of all major pyrolysis products and confirmed the negligible formation of other species. The time-history data presented in this work paint a coherent picture of ethane decomposition that motivates specific refinements to state-of-the-art detailed kinetic models.

Shock Tube Measurement of the CH3 + C2H6 → CH4 + C2H5 Rate Constant.

The rate constant for the CH3 + C2H6 → CH4 + C2H5 reaction was studied behind reflected shock waves at temperatures between 1369 and 1626 K and pressures from 8.6 to 47.4 atm in mixtures of methane, ethane, and argon. Ethylene time histories were measured using laser absorption of radiation from a carbon dioxide gas laser near 10.532 μm. The resulting rate constant data can be represented by the Arrhenius equation k (T) = 3.90 × 1013 exp(-16670 cal/mol/RT) cm3 mol-1 s-1. We believe this is the first study to extend experimental data for this rate constant to temperatures above 1400 K. The overall 2σ uncertainty of the current data is +18%/-21% resulting primarily from uncertainties associated with the influence of secondary reactions and the fitting of rapidly changing species time histories at the higher temperatures.

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

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.

Multi-wavelength speciation of high-temperature 1-butene pyrolysis

Species time-history measurements provide important kinetics targets for the development and validation of detailed reaction models. Here, a multi-wavelength, multi-species laser absorption strategy is demonstrated that provides high-bandwidth species time-histories during 1-butene pyrolysis behind reflected shock waves. Measured shock tube absorbance traces at nine wavelengths were used to resolve nine species mole fractions in the pyrolysis of 5% 1-butene in argon at 1300 K, 1.8 atm. In addition to existing sensors for 1-butene, methane, ethylene, 1,3-butadiene, propene, allene, benzene, and cyclopentadiene, a new laser absorption sensor for ethane at 3.3519 µm was developed by measuring cross-sections of ethane and of expected major interferers. Additional measurements to complete a square absorption cross-section matrix were also performed that enabled the simultaneous solution of species mole fractions from absorbance time-histories under appropriate physical system constraints. Measured time-histories of the nine product species were also compared with existing flow-reactor-based kinetic mechanisms. The demonstrated method has further application potential in the speciation of larger, more complex fuels.

Shock tube study of normal heptane first-stage ignition near 3.5 atm

Shock tube ignition delay times and species time history measurements for Primary Reference Fuels (PRFs) such as normal heptane provide targets for the validation of combustion models, which in turn are used to develop more fuel-efficient engines that have smaller environmental footprints. However, a review of the literature has revealed that most of the shock tube ignition delay time and species measurement data for normal heptane have been obtained at elevated pressures, rather than at relatively low pressures where many other important experimental techniques such as jet-stirred reactors and flow reactors can provide corroborating results. One central problem preventing previous shock tube studies from examining first-stage ignition at these lower pressures was that ignition times were too long under these conditions to be measured within the available shock tube test times. To address this issue, recent advances in shock tube techniques for achieving long uniform test times have been applied in order to measure low-pressure first-stage ignition times of normal heptane together with normal heptane fuel time-history records at times up to about 30 ms. These measurements were performed in the Negative Temperature Coefficient (NTC) region (T=664−792 K) in lean mixtures (21%O2/Ar, equivalence ratio ϕ=0.5) at pressures of roughly P=3.5 atm using both the conventional and Constrained Reaction Volume (CRV) shock tube filling strategies. The data have been used to evaluate the performance of several combustion models, have been compared with other higher-pressure shock tube first-stage ignition times in n-heptane/20–21%O2 mixtures found in the literature, and have been fit using a two-zone Arrhenius model for first-stage ignition delay times. The results showed that some combustion models yield ignition delay time predictions that differ from the experimental results by as much as an order of magnitude, that under these conditions n-heptane first-stage ignition times scale by roughly P−0.71 but are insensitive to ϕ, and that the fraction of fuel remaining after first-stage ignition increases with increasing initial experimental temperature.

Assessment of modern detailed kinetics mechanisms to predict CO formation from methane combustion using shock-tube laser-absorption measurements

The formation of CO from stoichiometric and fuel-rich (ϕ = 2.0) methane mixtures highly diluted in Ar and He (99% dilution) was followed by laser absorption in a shock tube at pressures around 1 and 4 atm. Results showed that the CO formation begins after an induction time that varies with temperature and pressure for each mixture. For the stoichiometric mixture, after the induction period, the CO rapidly reached a maximum before quickly decreasing with a shallow, descending slope. For the fuel-rich case, a flat plateau was reached directly after the initial period of growth in the CO mole fraction. The maximum mole fraction of CO was found to increase with temperature for each mixture, and the data suggest that this increase in the CO mole fraction is relatively independent of the pressure, over the range of conditions investigated. These results were compared with several modern detailed kinetics mechanisms from the literature as well as the GRI 3.0 mechanism. This study demonstrates the need for detailed species time history data to further refine the kinetics mechanisms, which were largely validated with ignition delay times, laminar flame speeds, and limited speciation data. Most mechanisms adequately predicted the induction time for CO formation. However, the maximum mole fraction of CO at the peak was generally largely over-predicted by all models for the stoichiometric conditions, although the amount of CO was accurately predicted past this peak. The amount of CO at the plateau was also over-predicted for the fuel rich case at lower temperatures and for the high-pressure condition. Two modern models were overall better than the others at predicting the data, and a chemical analysis was conducted to investigate the differences between these two models as well as with the GRI 3.0 mechanism. This analysis showed that the CO formation pathway is essentially the same for these three models, the differences in the absolute predictions being due to the different reaction rates used for important reactions with regard to CO formation. The effects of specific reaction rates on the predicted CO profiles were investigated, and it can be concluded from this study that the data presented herein will be useful for modelers to further refine methane combustion chemistry.

Methane and Methyl Propanoate High-Temperature Kinetics

The biodiesel surrogate, methyl propanoate (MP), is more reactive than methane. Mixtures of the two can be used to control combustion initiation in various combustion systems. Reported here is a shock tube study of the influence of chemical interactions resulting from mixing the two fuels on observable combustion properties, such as global chemical time scales and species time histories. Experiments are carried out at pressures of about 4, 7.4, and 10 atm covering a temperature window of 1000 to 1500 K. Using direct laser absorption, CO time histories during MP pyrolysis are obtained. The CO absorbance is further used to determine pyrolysis times by means of which the effect of temperature on MP pyrolysis is probed. Reactivity differences are first examined with the fuel concentration maintained at 3% and then with the oxygen concentration fixed at 10%. The evidence of chemical interactions during ignition is observed through a reduction of methane ignition delay times caused by MP addition. The influence...

Ignition delay times, laminar flame speeds, and species time-histories in the H2S/CH4 system at atmospheric pressure

Hydrogen sulfide (H2S) composes up to 30% of certain natural-gas resources (“sour gas”) and can considerably alter combustion properties of methane (CH4), but few data on H2S/CH4 are available in the literature. In this work, new shock-tube and laminar flame speed data were obtained to facilitate future model validation. For the shock-tube experiments, a fuel-lean (φ = 0.5) 30/70 H2S/CH4 blend in 99% argon by volume was shock-heated to temperatures between 1538 and 2144 K and pressures near 1 atm. Laser absorption diagnostics at 4.5 and 1.4 µm were employed to measure CO and H2O time-histories, respectively. OH* chemiluminescence profiles were measured using an emission diagnostic at 307 nm. For the laminar flame speed experiments, measurements were carried out in a constant-volume vessel at 295 K and 1 atm for CH4/argon and H2S/CH4/argon (8.25% H2S) mixtures from φ = 0.7 to φ = 1.4. The predictions of several recent chemical kinetics mechanisms were compared to the data, leading to the conclusion that species containing both carbon and sulfur are unimportant for shock-tube conditions but can be quite influential for laminar flames. By combining the modeling efforts of two recent works, a tentative new model is proposed that shows marked improvement over the older models in terms of shock-tube ignition delay times. Flame speed predictions show a discrepancy with the new model but follow general experimental trends. To the best of the authors’ knowledge, this study provides the first shock-tube data and laminar flame speeds measured in the H2S/CH4 system.