Numerical Analysis of Combustion and Thermal Performance of a Bluff-Body and Swirl-Stabilized Micro-Combustor with Premixed NH3/H2/Air Flames

This research presents a novel bluff-body and swirl-stabilized micro-combustor fueled by an ammonia/hydrogen mixture, aimed at enhancing flame stabilization for zero-carbon micro-combustion-based power generators. Employing numerical simulations, the study examines the effects of bluff-body geometry, inlet mass flow rate, vane angle, and combustor material on combustion and thermal efficiencies. Key findings demonstrate that the shape of the bluff-body significantly influences the combustion outcomes, with cone-shaped designs showing the lowest radiation efficiency among the tested geometries. The study identifies an optimal inlet mass flow rate of 9×10−6 kg/s, which achieves a combustion efficiency of 99% and superior uniformity in the mean outer wall temperature. While variations in flow rate primarily affect NO emissions and outer wall temperatures, they have minimal impact on combustion efficiency. Further analysis reveals that adjusting the vane angle from 15 to 60 degrees significantly improves mean outer wall temperatures, temperature uniformity, and combustion and radiation efficiencies, while also reducing NO emissions. The 60-degree angle is particularly effective, achieving approximately 44% radiation efficiency. Additionally, material selection plays a pivotal role, with silicon carbide outperforming others by delivering an optimized mean outer wall temperature (approximately 910 K), radiation efficiency (38.5%), and achieving the most uniform outer wall temperature. Conversely, quartz exhibits significantly lower thermal performance metrics.