Effects of Hydrogen Addition, Oxygen Level, and Strain Rate on Combustion Characteristics of CH₄/H₂ in Staged MILD Combustion

Abstract

In this article, the effects of hydrogenation amount (0–80%), oxygen content (14–18%), and strain rate (10–1000 s−1) on the emission characteristics of NO and CO in moderate or intense low‐oxygen dilution (MILD) fractional combustion are studied under the actual working conditions of gas turbine (T = 723 K, P = 16.5 atm). The pathway of NO and CO production and the reaction with the greatest influence on their emissions are analyzed. In the findings, it is indicated that NO emissions are suppressed at lower hydrogen levels, while the addition of hydrogen leads to a decrease in CO emissions. Specifically, the key reaction for NO formation is H + NO + M = HNO + M, whereas CO emissions are primarily controlled by the direct reaction OH + CO = H + CO2. Furthermore, the reduction of oxygen levels effectively suppresses NO and CO emissions during MILD combustion. The variation in oxygen level exerts the greatest influence on the reaction rate of the NNH pathway. High concentrations of O2 are identified as the primary cause of elevated CO levels in MILD combustion. Finally, elevating the strain rate in MILD combustion demonstrates a mitigating effect on NO and CO emissions.