Tran Manh Vu

Effects of Hydrocarbon Addition on Cellular Instabilities in Expanding Syngas-Air Spherical Premixed Flames

Experiments were conducted in a constant-pressure combustion chamber to investigate the effects of hydrocarbon addition on cellular instabilities of syngas-air flames. The measured laminar burning velocities were compared with the predicted results computed using reliable kinetic mechanisms with detailed transport and chemistry. The cellular instabilities that included hydrodynamic and diffusional-thermal instabilities of the hydrocarbon-added syngas-air flames were identified and evaluated. Further, experimentally measured critical Peclet numbers for fuel-lean flames were compared with the predicted results. Experimental results showed that the laminar burning velocities decreased significantly with an increase in the amount of hydrocarbon added in the reactant mixtures. With addition of propane and butane, the propensity for cell formation was significantly diminished whereas the cellular instabilities for methane-added syngas-air flames were not suppressed.

Experimental Study in H2/CO/CH4-Air and H2/CO/C3H8-Air Premixed Flames. Part 1: Laminar Burning Velocities and Markstein Lengths

Flame propagation characteristics of hydrogen/carbon monoxide/methane (or propane)–air premixed mixtures were studied in a constant pressure combustion chamber with a schlieren system at room temperature and elevated pressures. Unstretched laminar burning velocities and Markstein lengths of various mixtures were obtained by analyzing high-speed schlieren images. Also, the experimentally measured unstretched laminar burning velocities were compared with numerical predictions using the PREMIX code with a H2/CO/C1–C4 mechanism, USC Mech II, developed by Wang et al. [23]. The two data from experiments and predictions show good agreement. The results indicate a significant increase in the unstretched laminar burning velocities with hydrogen enrichment and a decrease with the addition of hydrocarbons, whereas the opposite effects for the Markstein lengths were observed.

Experimental Study in H2/CO/CH4–Air and H2/CO/C3H8–Air Premixed Flames. Part 2: Cellular Instabilities

Experiments in a constant pressure combustion chamber at room temperature and elevated pressures using schlieren system were conducted to investigate the cellular instabilities in hydrogen/carbon monoxide/methane (or propane)–air premixed flames. In the present study, hydrodynamic and diffusional-thermal instabilities were evaluated to elucidate their effects to flame instabilities. Effective Lewis numbers of premixed flames with methane addition decrease for all of the cases. Meanwhile, the effective Lewis numbers with propane addition increase for lean and stoichiometric conditions, but they increase for rich and stoichiometric cases for hydrogen-enriched flames. With propane addition, the propensity for cells formation is significantly diminished whereas the cellular instabilities for hydrogen enriched flames are promoted. With methane addition, the similar behavior of cellularity is obtained, indicating that methane is not a candidate for suppressing cells formation in hydrogen/carbon monoxide/methane–air premixed flames.