59226 - Numerical Study on Effect of Rib Shape on Thermal Performance and Nox Emission in Premixed Ammonia-Fueled Micro-Combustors 

As a renewable energy source, ammonia is regarded as one of the ideal gases that can replace fossil fuels and has been extensively studied in large-scale combustion. However, studies on energy conversion efficiency and NOx emission at microscale are still inadequate. In this work, ammonia/oxygen premixed cylindrical micro-combustor with double ribs are numerically investigated. The key geometrical parameters of the ribs and the ammonia/oxygen equivalent ratio are evaluated based on thermal performance and NOx emission performance. Finally, the sensitivity analysis of NO, the main component of NOx, was carried out under different equivalent ratios. The results show that increasing the height of the rib and decreasing the distance between the first rib and the inlet can effectively inhibit the formation of NO. Among all cases, the combustor with Ս-shaped ribs is observed the minimum mole fraction at the outlet under the same working condition, which is 16% less comparing to the rectangular-shaped one. Besides, the average temperature of the outer surface shows a weak correlation with NO emission. Increasing the equivalent ratio can help gain higher mean wall temperature, but at the same time promotes NOx production. This study is helpful to the design and improvement of micro-combustor fueled by ammonia.