Effect of hydrogen addition on the dynamics of premixed C1–C4 alkane-air flames in a microchannel with a wall temperature gradient

• Published in: International journal of hydrogen energy 2022-08, Vol.47 (71), p.30660-30670
• Main Authors: Edacheri Veetil, Jithin, Kumbhakarna, Neeraj, Singh, Satender, Velamati, Ratna Kishore, Kumar, Sudarshan
• Format: Article
• Language: English
• Subjects: Flame repetitive extinction and ignition; Hydrogen addition; Microscale combustion
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2022.07.030

The effect of hydrogen (H2) addition on the flame dynamics of premixed C1–C4 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)/H2 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. CH4/air mixture shows a higher HRR than C3–C4 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 CH4/air mixture, whereas it decreases monotonically for C3H8/air and C4H10/air mixtures with H2 addition. The amount of HRR and flame propagation velocity decreases with increase in H2 addition for lower-alkanes/air mixtures. The flame bifurcation effect is observed for CH4/air mixture, which disappears due to H2 addition in the mixture. The bifurcation effect is not present for other hydrocarbon/air mixtures investigated in the present study. The addition of H2 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.•CH4/air mixture shows a higher HRR than C3–C4 alkane/air mixtures.•FREI frequency shows a non-monotonic behavior for CH4/air mixture with H2 addition.•FREI frequency decreases monotonically for C3H8/air and C4H10/air mixtures with H2 addition.•The flame bifurcation effect is observed only for CH4/air mixture.