Effects of number of air holes on flame and heat transfer characteristics in a multihole baffled combustor combined with micro-thermophotovoltaic and micro-thermoelectric systems

Currently, micro power generators have been widely drawing attention for various applications. In this study, the H₂–air micro combustor (MC) with a multihole baffle plate was combined with two power generators based on micro-thermophotovoltaic and micro-thermoelectric systems. The reacting flow and conjugate heat transfer including the MC wall were analyzed by the detailed reaction mechanism and the outer wall condition of convection and radiation. From the resulting thermal fields, the characteristics of heat emission and electrical potential were examined. Eight baffles with different numbers of air holes (N_a) and three global equivalence ratios were selected, and a baffle with N_a = ∞ was adopted to compare the multihole and annular air flows. The combustion characteristics depending on N_a were explored by analyzing the changes in the reaction zone, the flammable range, reaction rate, and wall heat transfer rate. The N_a effect on wall and center recirculation zones was comparable to the variation due to other geometrical variables of the baffle plate. As N_a increased, the combustion efficiency increased to 20% of the N_a = ∞ case. The combustion efficiency equivalent to the swirl MC was obtained for N_a = 5–8, having enhanced preheating effects and large center recirculation zones. Compared to N_a = ∞, the mean temperature of the multihole baffled MC increased by 6.4%–19.2% depending on N_a. The emitter efficiency related a TPV system was comparable to the swirling flow MC. For a thermoelectric generator, the conversion efficiency of N_a = ∞ was similar to that of a Swiss-roll MC, and the multihole baffled MC showed a high conversion efficiency of 1.55%–3.58% depending on N_a and the global equivalence ratio.