S.I. Yang

Bio: S.I. Yang is an academic researcher from National Formosa University. The author has contributed to research in topics: Combustion & Premixed flame. The author has an hindex of 13, co-authored 17 publications receiving 724 citations. Previous affiliations of S.I. Yang include National Central University & Princeton University.

High-pressure laminar flame speeds and kinetic modeling of carbon monoxide/hydrogen combustion

Abstract: Laminar flame speeds were accurately measured for CO/H 2 /air and CO/H 2 /O 2 /helium mixtures at different equivalence ratios and mixing ratios by the constant-pressure spherical flame technique for pressures up to 40 atmospheres. A kinetic mechanism based on recently published reaction rate constants is presented to model these measured laminar flame speeds as well as a limited set of other experimental data. The reaction rate constant of CO + HO 2 → CO 2 + OH was determined to be k = 1.15 × 10 5 T 2.278 exp(−17.55 kcal/ RT ) cm 3 mol −1 s −1 at 300–2500 K by ab initio calculations. The kinetic model accurately predicts our measured flame speeds and the non-premixed counterflow ignition temperatures determined in our previous study, as well as homogeneous system data from literature, such as concentration profiles from flow reactor and ignition delay time from shock tube experiments.

Correlations of high-pressure lean methane and syngas turbulent burning velocities: Effects of turbulent Reynolds, Damköhler, and Karlovitz numbers

Abstract: This paper investigates correlations of high-pressure turbulent burning velocities (ST) using our recent ST measurements of lean methane and syngas spherical flames at constant elevated pressures (p) and constant turbulent Reynolds numbers (ReT ≡ u′LI/ν), where u′, LI, and ν are the r.m.s. turbulent fluctuation velocity, the integral length scale of turbulence, and the kinematic viscosity of reactants, respectively. Such constant constraints are achieved by applying a very large high-pressure, dual-chamber explosion facility that is capable of controlling the product of u′LI in proportion to the decreasing ν due to the increase of p. We have found that, contrary to popular scenario for ST enhancement with increasing p at any fixed u′, ST actually decreases similarly as laminar burning velocities (SL) with increasing p in minus exponential manners when values of ReT are kept constant. Moreover, ST increases noticeably with increasing ReT varying from 6700 to 14,200 at any constant p ranging from 1 atm to 10 atm. It is found that a better correlation for the normalization of ST is a power-law relation of ST/u′ = aDab, where Da = (LI/u′)(SL/δF) is the turbulent Damkohler number, δF ≈ α/SL is the laminar flame thickness, and α is the thermal diffusivity of unburned mixture. Thus, the very scattering ST data for each of lean methane and syngas mixtures can be merged on their ST/u′ vs. Da curves with very small data fluctuations. For lean methane flames with the Lewis number (Le) ≈ 1, ST/u′ ≈ 0.12Da0.5 supporting a distributed reaction zone model anticipated by Ronney (1995), while for lean syngas flames with Le ≈ 0.76 ≪ 1, ST/u′ ≈ 0.52Da0.25 supporting a theory predicted by Zimont (1979). A simple physical mechanism is proposed in attempt to explain what causes the aforesaid discrepancy on the power-law constants.

Comprehensive H2/O2 kinetic model for high-pressure combustion

Abstract: An updated H2/O2 kinetic model based on that of Li et al. (Int J Chem Kinet 36, 2004, 566–575) is presented and tested against a wide range of combustion targets. The primary motivations of the model revision are to incorporate recent improvements in rate constant treatment and resolve discrepancies between experimental data and predictions using recently published kinetic models in dilute, high-pressure flames. Attempts are made to identify major remaining sources of uncertainties, in both the reaction rate parameters and the assumptions of the kinetic model, affecting predictions of relevant combustion behavior. With regard to model parameters, present uncertainties in the temperature and pressure dependence of rate constants for HO2 formation and consumption reactions are demonstrated to substantially affect predictive capabilities at high-pressure, low-temperature conditions. With regard to model assumptions, calculations are performed to investigate several reactions/processes that have not received much attention previously. Results from ab initio calculations and modeling studies imply that inclusion of H + HO2 = H2O + O in the kinetic model might be warranted, though further studies are necessary to ascertain its role in combustion modeling. In addition, it appears that characterization of nonlinear bath-gas mixture rule behavior for H + O2(+ M) = HO2(+ M) in multicomponent bath gases might be necessary to predict high-pressure flame speeds within ∼15%. The updated model is tested against all of the previous validation targets considered by Li et al. as well as new targets from a number of recent studies. Special attention is devoted to establishing a context for evaluating model performance against experimental data by careful consideration of uncertainties in measurements, initial conditions, and physical model assumptions. For example, ignition delay times in shock tubes are shown to be sensitive to potential impurity effects, which have been suggested to accelerate early radical pool growth in shock tube speciation studies. In addition, speciation predictions in burner-stabilized flames are found to be more sensitive to uncertainties in experimental boundary conditions than to uncertainties in kinetics and transport. Predictions using the present model adequately reproduce previous validation targets and show substantially improved agreement against recent high-pressure flame speed and shock tube speciation measurements. Comparisons of predictions of several other kinetic models with the experimental data for nearly the entire validation set used here are also provided in the Supporting Information. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 44: 444–474, 2012