Study of hydrogen impact on lean flammability limit and burning characteristics of a kerosene surrogate

Abstract

Hydrogen impacts on lean flammability limits and the burning characteristics of n-decane, a kerosene surrogate, were studied using a spherical combustion chamber and Chemkin software at 460 K and 100 kPa. Laminar flame propagated spherically at λ = 0.8–1.3 by using 50 mJ IE, whereas further leaner mixture (λ ≥ 1.4) could be ignited at 1000 mJ. However, the wrinkles appeared on flame morphology thanks to higher IE. The effect of IE on flame morphology reduced with increasing the value of λ. In contrast, the flame distortion enhanced as lifting IE, 1000–3000 mJ. Near lean limit, the spherical flame appeared initially from 0 ms to 20 ms. When time increased from 20 ms, it buoyed due to slow flame speed and rapid radiation losses. Eventually, it disappeared at t ≈ 200 ms, and the mixture could not burn completely. Lean limits of n-decane were found λ = 1.6, λ = 1.7, and λ = 1.8 at 1000 mJ, 2000 mJ, and 3000 mJ, respectively. It linearly extended by 0.5 λ with 70% H2 addition (0–70%) and enormously enlarged by 1.3 λ with 20% H2 addition (70–90%). IE, 1000–3000 mJ, extended the lean limit by 0.2 λ. H radical produced greatly from H2 and CO by consuming OH, whereas it consumed by translating formaldehyde and oxygen into aldehyde, O and OH. OH produced significantly from the consumption of H and hydroperoxyl radicals. By lifting hydrogen, H and OH increased rapidly, which enhanced the reaction rates of dominant intermediates. Consequently, the lean limit improved.