Heat recirculation and heat losses in porous micro-combustors: Effects of wall and porous media properties and combustor dimensions

The micro-combustor is a key component of most combustion-based micro power generation devices. Porous micro-combustors stand as a potential promising solution able to sustain reactions under a wider range of conditions. Multiple heat transfer modes co-exist and are closely coupled in porous micro combustors, and therefore the primary objective of the present study is to analyze various heat fluxes occurring in porous micro-combustors in a quantitative manner in order to reveal their relative importance and provide clues for better design and operation of such devices. Numerical simulations of premixed combustion of H-2/air in porous combustors with the combustor heights from 1.0 mm to 2.0 mm are carried out. By quantifying heat recirculation and heat losses in the preheat zone and the reaction zone, respectively, the effects of the wall thermal conductivity and the porous media properties (thermal conductivity and porosity) on the flame temperature are discussed. Comparing the results of different combustor heights shows that the smaller porous micro-combustor has a higher proportion of heat recirculation relative to heat losses. The flame temperature is found to be inversely related to the ratio of total heat losses to total heat recirculation. The methodology developed in this study could be easily applied to other micro-combustor configurations with or without the porous media with necessary adaptions. (c) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The study aims to analyze heat fluxes in porous micro-combustors and discuss the effects of wall thermal conductivity and porous media properties on flame temperature. Results show that smaller porous micro-combustors have a higher proportion of heat recirculation relative to heat losses, and flame temperature is inversely related to the ratio of total heat losses to total heat recirculation.