Fundamental Experiment and Numerical Analysis of a Modular Microcombustor with Silicon Carbide Porous Medium

The use of porous media in combustion processes has been widely researched and investigated. In this paper, the effect of employing porous media on microcombustion was studied using numerical simulation. Simulated results demonstrated good agreement with the experimental results, and thus validated the model. Analysis has been carried out with dimensional analysis and basic theorem which incorporates the Biot number in an attempt to fundamentally understand the effects brought about by equivalence ratio, thermal conductivity of the solid matrix and mass flow rate on microthermophotovoltaic (TPV) performance. One of the key results has demonstrated that the higher the equivalence ratio of the fuel/air mixture, the higher will be the mean wall temperature. A peak-shift phenomenon has been observed, where the position of maximum flame temperature shifts downstream away from the inlet at lower equivalence ratio. Results from the Biot number analysis has indicated that the higher the thermal conductivity of the wall is, the more uniform the wall temperature distribution will be. A lower mean wall temperature is obtained when the thermal conductivity of the solid matrix is installed at 50 W/mK, whereas higher mean wall temperatures can be achieved for either small (5 W/mK) or very large (500 W/mK) thermal conductivity. It is clearly evidenced that the performance of microcombustors can be markedly enhanced by incorporating a thermally effective porous medium. The theoretical understanding gained from the present research will facilitate the design of more energy efficient, stable and better controllable portable TPV on-field power systems.