Abstract
The effect of hydrogen (H 2 ) addition on the flame dynamics of premixed C 1 –C 4 alkane/air mixtures in a microchannel is investigated using a detailed-chemistry model through two-dimensional numerical computations. A detailed computational study have been performed in a 2 mm diameter tube with 120 mm length and a wall temperature gradient along the axial direction of the channel. The numerical simulations are carried out for various stoichiometric hydrocarbon (HC)/H 2 mixtures at 0.15 m/s mixture inlet velocity. Flame repetitive extinction and ignition (FREI) flame pattern has been identified for all the fuel mixtures at these channel wall and mixture flow conditions. CH 4 /air mixture shows a higher HRR than C 3 –C 4 alkane/air mixtures. Flame residence time in microchannel increases with increase in hydrogen addition percentage for all the three hydrocarbon/air mixtures considered in the present study. A non-monotonic behavior of FREI frequency is identified for CH 4 /air mixture, whereas it decreases monotonically for C 3 H 8 /air and C 4 H 10 /air mixtures with H 2 addition. The amount of HRR and flame propagation velocity decreases with increase in H 2 addition for lower-alkanes/air mixtures. The flame bifurcation effect is observed for CH 4 /air mixture, which disappears due to H 2 addition in the mixture. The bifurcation effect is not present for other hydrocarbon/air mixtures investigated in the present study. The addition of H 2 in the mixture enhances the flame stability of hydrocarbon/air mixtures in the microchannel. • FREI flame pattern is observed for all the HC-H2 mixtures studied. • CH 4 /air mixture shows a higher HRR than C 3 –C 4 alkane/air mixtures. • FREI frequency shows a non-monotonic behavior for CH 4 /air mixture with H 2 addition. • FREI frequency decreases monotonically for C 3 H 8 /air and C 4 H 10 /air mixtures with H 2 addition. • The flame bifurcation effect is observed only for CH 4 /air mixture.
Published Version
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