An investigation of the effects of wall materials on flame dynamics inside a H2-air micro-combustor

Abstract

Micro-combustors, which are emerging as portable power sources, have serious flame stabilization issues due to enhanced heat losses. Hydrogen, an eco-friendly alternative to conventional fossil fuels, can be a potential fuel for micro-combustors because of its high calorific value, leading to high energy density. In the present work, numerical simulations of premixed lean (equivalence ratio = 0.5) hydrogen-air flames in a 2 mm wide channel with three different wall materials (glass, steel, and aluminum) were performed. The effects of the wall material on the dynamics of the flames were extensively studied. The walls of the combustor play an important role by conducting heat upstream and facilitating ignition and stabilization of the flame. For different values of wall thermal diffusivity, periodically oscillating flames of varying frequencies ( ∼ 400 − 1200 Hz) and intermittent bursting flames were observed. Time series analysis and modal decomposition of temperature fields were utilized to quantify the flame dynamics and to identify the dominant structures of the flames. A recurrence analysis using the temperature time series data revealed significant differences in flame dynamics, including period-2 oscillations and intermittency, for different wall materials. The underlying physics behind the periodic oscillations and intermittent bursting has been explained.