The Effect of Hydrogen Peroxide on NH3/O2 Counterflow Diffusion Flames

Abstract

The impact of adding H2O2 in the fuel stream on the structure of non-premixed opposed-flow NH3/O2 flames was investigated numerically using a verified computational tool and validated mechanism. The results illustrate the dual role of the added H2O2 within the fuel jet. A small amount of H2O2 within the NH3 stream acted as a fuel additive that enhanced the reaction rate via reducing the kinetic time scale. However, a novel flame structure appeared when the H2O2 mole fraction within the fuel stream increased to χH2O2 > 16%. Unlike the pure NH3/O2 flame, a premixed reaction zone was discerned on the fuel side, in which H2O2 reacts with NH3 and played the role of an oxidizer. Then, the remaining NH3 that survived premixed combustion continues reacting with O2 and forms a non-premixed flame. As a result of this structure, it was shown that the well-established conclusion of “near-equilibrium” non-premixed flame analysis in which the strain on the flame is determined by the momentum fluxes of the counter-flowing streams does not hold for the flames that were studied in this paper. It was also shown that when H2O2 acted as an oxidizer, it produced substantial amounts of HO2, which allowed for low-temperature formation of NO2 through the reaction of NO with HO2.

Computational investigation of ammonia-hydrogen peroxide blends in HCCI engine mode

“…It is noted that the two-stage ignition exhibited herein is a feature introduced due to the addition of hydrogen peroxide as ammonia as a sole fuel exhibits single stage ignition. 50,51 Consequently, the first stage ignition is instrumental to the control of the whole ignition process as it can lead to qualitatively different outcomes.…”

“…More importantly, they highlighted that the hydrogen peroxide addition can reverse the inherent effect of steam dilution in retarding the ignition delay time, by facilitating the increased production of OH radicals. Finally, Yang et al 51 investigated the effect of hydrogen peroxide addition on ammonia-based counter-flow diffusion flames. Their numerical work showcased the dual role hydrogen peroxide has: that of a fuel and that of an oxidiser.…”