Combustion in wavy micro-channels for thermo-photovoltaic applications - Part I: Effects of wavy wall geometry, wall temperature profile and reaction mechanism

The output power of a Micro-Thermo-Photovoltaic (MTPV) system strongly depends on the micro-combustor geometry and the micro-flame stability. In this context, numerous numerical and experimental works have been conducted and focused on geometries limited to circular and planar micro-channels (MCs) with and without sudden expansion. Therefore, the present work proposes a novel MC configuration with wavy walls. The use of wavy walls increases the MC surface and consequently the heat transfer characteristics of this system could be improved. In this study, two-dimensional numerical simulations on CH4-air premixed flames in the novel configuration have been carried out. The wavy MCs are heated with a wall temperature gradient in the streamwise direction. The investigations have been carried out with a MC height H = 600 mu m, a mixture velocity U = 1 m/s and the equivalence ratio Phi = 1. Moreover, the effects of various parameters on the flame behavior are reported: the wavy wall geometries, the maximum values of the temperature profile and the kinetic mechanisms of CH4 combustion. The results are original, since the effect of the wavy wall geometries are not available in the literature. In addition, the effects of the other parameters are not well documented in the literature, especially the CH4 combustion mechanisms. It is found that the flame location is sensible to the wavy wall geometry. As the number of waves increases, the flame moves towards the MC exit. The maximum value of the temperature gradient has an opposite effect. As the maximum temperature increases, the flame moves towards the MC inlet. The results show also that the flame location, shape and temperature are strongly affected by the different reaction mechanisms.