Effects of hydrogen enrichment in Methane/Air combustion with different inlet arrangements: A numerical approach

Abstract

Recently, H₂ enrichment for combustion and emission control in internal combustion engines, gas turbines, industrial boilers, and furnaces has been extensively studied. However, H₂ enrichment for various inlet designs to change combustion characteristics has not yet been studied. In this study, the effect of hydrogen enriched air and methane non premixed combustion on dynamic flow behavior, temperature, pollutant emission are investigated in geometries with two distinct inlet arrangements using ANSYS Fluent CFD software. A reduced version of GRI-Mech 3.0 methane chemistry reaction including 19 species was used in the study. Hydrogen was added to methane fuel (CH₄) at the inlet within the range 0∼50 % by mass while the mass flow rate of fuel is constant. The findings indicate that as the H₂ enrichment increases, there is a noticeable shift in the peak temperature towards the fuel inlet. Additionally, the overall temperature of the combustion chamber remains homogenous indicating flame stability and consistent combustion in both geometries. The addition of 50 % H₂ resulted in a reduction of approximately 37 % in the outlet temperature. Besides, H₂ enrichment led to lower CO and CO₂ emissions in both geometries, which is up to 99.99 % reduction in CO and 88.47 % reduction in CO₂ for 50 % H₂ addition. The lower emission of CO and CO₂ could be attributed to the facts that with H₂ enrichment the carbon content in the fuel stream decreases, mixture becomes leaner and subsequently results in more complete combustion. In both inlet configurations, the emission of NO exhibited a slight decrease upon the introduction of 15 % H₂ but beyond 30 % enrichment there was a notable increase in NO production, primarily attributed to the peak temperature zones. In comparison, the second inlet arrangement has produced lower CO and CO₂ emission than the first one, while the first inlet arrangement has resulted in overall lower NO emission.