Lower flammability limits of H2/NH3/CH3OH mixtures under elevated pressures, temperatures and different blending ratios

Abstract

The lower flammability limits (LFLs) of H2/NH3/CH3OH mixtures and related flame morphologies are experimentally investigated under elevated pressures, elevated temperatures, and blending ratios. The results show that the flame morphologies of LFLs are mushroom-like, darkening with an increase in initial pressures and remaining unchanged with an increase in initial temperatures. Except for the flame wrinkles at 10:0:0 and 5:5:0, there is little difference in the flame morphologies with blending ratios. When NH3:CH3OH = 1:1, the LFLs of 0 % H2 decrease with elevated pressures while the rest increase, and the LFLs steadily decrease as H2 increases. When H2:CH3OH = 1:1, the LFLs of 100 % NH3 decrease with elevated pressures while the rest increase, and the LFLs increase as the NH3 increases. The LFLs of 0–40 % CH3OH rise with the increasing pressure when H2:NH3 = 1:1, while the LFLs of 60 % CH3OH are almost unchanged and the LFLs of 80–100 % CH3OH decrease. Additionally, the LFLs increase at 50–100 kPa and decrease at 150–250 kPa as CH3OH increases. The LFLs of the mixtures decrease with elevated temperatures. The prediction formula of H2/NH3/CH3OH mixtures’ LFLs under elevated pressures, elevated temperatures, and blending ratios is established. The average absolute error (AAE) and average relative error (ARE) are 0.11 % and 1.54 %.