Laminar Burning Velocity of Alcohol Reforming Products and Effects of Cellularity on Flame Propagation 2015-01-0775

Utilizing heat of exhaust gases for on-board alcohol reforming process (thermo-chemical recuperation - TCR) is a promising way of increasing the internal combustion engine (ICE) efficiency and emissions mitigation. Knowledge of the laminar burning velocity of alcohol reforming products is necessary for simulating performance of internal combustion engines with TCR and for in-depth studies of the combustion process.

Laminar burning velocities of H₂, CO, CO₂ and CH₄ mixtures that simulate methanol and ethanol steam reforming products for various water-alcohol ratios are investigated in this work. The influence of flame cellularity on burning velocity is studied as well. The burning velocity is measured experimentally using a spherical closed combustion vessel. Measurements are taken by a pressure measurement method during the pressure-rise period and prior to it by a high-speed Schlieren photography.

The burning velocity is mapped as a function of CO and CH₄ selectivity's of the reforming process as well as for various air-excess factors (λ=1, 1.3, 1.6, 1.9). Maximal burning velocities up to 140cm/sec are observed for mixtures produced from reforming processes with zero CH₄ selectivity. For stoichiometric mixtures the burning velocity is found to be not affected by change in CO selectivity. In contrast, for lean mixtures, an increase in CO selectivity is shown to yield lower burning velocities. Higher CH₄ selectivity results in strong decrease in burning velocities for both stoichiometric and lean mixtures. Flame cellularity that increases burning velocity is found to occur earlier in mixtures with higher hydrogen content and at higher air-excess factors.