Investigation on combustion characteristics and thermal performance of a three rearward-step structure micro combustor fueled by premixed hydrogen/air

In order to achieve high and uniform wall temperature distribution in the micro combustor, a threedimensional mathematical model of the premixed hydrogen/air mixtures in the micro combustors with rearward-step structure is established in this work. The effects of rearward-step structure, inlet velocity on combustion characteristics and thermal performance in the micro combustor are investigated. The results indicate that the rearward-step structure enhances the combustion intensity and stabilizes the flame in micro combustor. When the inlet velocity is 7.0 m/s, with the increase in the rearward-steps from one to three, the maximum combustion efficiency difference is about 2.28% and the percentages of improvements in lower and upper flammability limits are 20% and 3.5%, respectively. The achieved results show that the rearward-step structure increases the mean outer wall temperature and deteriorates the outer wall temperature uniformity in the micro combustor. When the inlet velocity is 5.0 m/s, the mean outer wall temperature and the temperature difference of the combustor with 3-steps are 6.3 K and 39.6 K higher than that of the combustor with 1-step, respectively. The maximum synergy degree in the micro combustor with 3-steps is 2.99% when the inlet velocity and equivalence ratio are 7.0 m/s and 1.5, respectively.(c) 2022 Elsevier Ltd. All rights reserved.