Numerical Studies of the Combustion of Methane-Air Mixture in a Meso-Scale TPV Combustor with a Heat-Regeneration Reverse Tube and a Porous-Medium Injector

Abstract

The major objective of this paper is to develop a miniature combustor applied in a portable thermophotovoltaic (TPV) power generation system. The proposed miniature TPV system consists of a swirling combustor with the infrared thermal tube (ZrO2) acting as the emitter, a heat-regeneration reverse tube, and mixing-enhancing porous-medium fuel injection, which improves the low non-uniform illumination or incomplete combustion problems associated with conventional miniature TPV systems. A two-step global reaction mechanism was used to compute the chemical reactions of the reacting flows. Numerical simulations are performed to analyze the details of the flame structure and flame stabilization mechanism inside the meso-scale combustor with and without a reverse tube. In addition, these thermal conditions have strong effects on the combustion especially when the chamber dimension goes small and the ratio of surface area to volume becomes larger. Such as larger heat loss through the chamber wall to the ambient, may lead to the thermal quenching of meso-scale combustion. Therefore, the effect of various heat transfer conditions at chamber wall, e.g. with different wall heat conductivity on the combustion is delineated and discussed by numerical simulation. Results indicate that the proposed swirling combustor with a heat-regeneration reverse tube and porous medium can improve the intensity and uniformity of the combustion chamber (emitter) illumination, and can increase the surface temperature of the chamber wall. Correspondingly, the simulation results also indicated that the stable combustion in a meso-scale TPV combustor may be sustained through to control mass flow rate, heat loss conditions and maintaining proper thermal condition. Consequently, through such systematic numerical analysis, proper operational parameters for the meso-scale TPV combustor are suggested, which may be used as the guideline for meso-scale TPV combustor design.