Prediction of flame speed and exergy analysis of premixed flame in a heat recirculating cylindrical micro combustor

Abstract

An interaction between wall heat recirculation, flame speed and thermodynamic irreversibility has been established from an analytical model based on flame sheet assumption pertaining to a premixed flame in a cylindrical micro combustor. The total rate of heat recirculation through the combustor wall and the flame speed depict global maxima depending on the wall to gas thermal conductivity ratio. The optimum value of wall to gas thermal conductivity ratio for maximum flame speed bears an inverse relation with the ratio of wall thickness to combustor radius and the outer wall Nusselt number. The proportional change in heat recirculation is more than that in heat generation with wall to gas thermal conductivity ratio, wall thickness to combustor radius ratio and outer wall Nusselt number. The exergy loss at outer wall is around 5–7% of inflow exergy while the exergy destruction in the process of heat recirculation and combustion is around 40–45% of inflow exergy. The second law efficiency is found to be almost constant around a value of 58%.