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.