Combustion and emission performance evaluation in ammonia/hydrogen-powered system with baffle and secondary injection applied

Abstract

Ammonia has recently gained significant attention due to its potential for zero carbon emissions during combustion, coupled with ease of storage and transportation. However, challenges related to poor combustion stability and high NOx emissions have limited the widespread use of NH3. To address these issues, this paper introduces a baffle structure and a secondary fuel injection strategy, and their optimal positions, widths, and injection ratios are determined through three-dimensional numerical calculations. The results demonstrate that the baffle effectively anchors the flame, enhancing both flame stability and wall temperature. Additionally, the disturbed flow near the baffle enhances the reaction between NO and NH3, resulting in reduced NO emission. The baffle structure with l = 1/10 and w = 4/5 achieves the optimal overall thermal characteristics, with approximately a 5.2 % increase in average wall temperature compared to the conventional straight-channel micro-planar combustor. Moreover, while increasing the secondary combustion injection ratio (R) significantly reduces NO emission, it also exacerbates ammonia leakage. The minimum achievable NO emission of 531 ppm is achieved at R = 0.1, where NH3 leakage is minimal. This study validates the feasibility of introducing a baffle and a secondary fuel injection strategy to enhance flame stability, improve thermal characteristics, and reduce NOx emissions in ammonia-hydrogen combustion.