Numerical investigation of H2/Air fueled micro combustion characteristics with trapezoidal ribs for micro thermophotovoltaic applications: Effect of rib height

Abstract

In this numerical study, the impact of equidistant trapezoidal ribs on the characteristics of premixed H2-air micro-combustion was investigated, with a specific focus on the rib height. The study comprehensively examined flame structure, flame front position, flame speed, and combustion efficiency. A comparative analysis was performed between a backward-facing step micro combustor (MCSD) and micro combustors with varying rib heights: MCRD1 (0.5 mm), MCRD2 (0.6 mm), and MCRD3 (0.7 mm). The incorporation of trapezoidal ribs resulted in the creation of elongated and evenly distributed recirculation zones, significantly enhancing mixing and promoting flame stability, particularly at higher rib heights. The recirculation zones played a critical role in influencing the chemical reaction rate and the species distribution, leading to higher flame speed and greater combustion intensity. The findings highlight the outcomes of incorporating ribs in terms of combustion efficiency. The combustion efficiency values for MCRD1, MCRD2, and MCRD3 were recorded as 96.95%, 96.75%, and 96.61%, respectively, while the MCSD had a combustion efficiency of 97.14%. Hence, the recommended range of rib height is considered advantageous in ensuring an optimal balance between improved flame stabilization and maintaining a satisfactory level of combustion efficiency. The findings provide valuable insights for optimizing micro-thermophotovoltaic systems.