An Experimental and Kinetic Modeling Study of NO 2 Sensitization on the Autoignition of Ammonia

High Resolution Image Download MS PowerPoint Slide An experimental and kinetic modeling study was performed to investigate the influence of NO 2 addition on the autoignition characteristics of NH 3 /O 2 /Ar mixtures. Ignition delay times were measured using a shock tube at temperatures of 1450–2200 K, pressures of 0.14 and 1 MPa, equivalence ratios of 0.5, 1.0, and 1.5, and NO 2 concentrations from 0 to 2000 ppm. The results show that NO 2 addition significantly promotes NH 3 autoignition, with the enhancement strongly dependent on temperature, pressure, equivalence ratio, and NO 2 concentration. The effect is particularly pronounced at intermediate temperatures (1450–1700 K) and higher pressure, and exhibits a nonlinear relationship with NO 2 concentration. The updated Shrestha and Glarborg mechanisms accurately reproduced the experimental IDT data. The evolution of key species indicates that NO 2 addition significantly promotes NH 3 consumption, along with the formation of NO and the radicals OH and NH 2 . Flux analysis reveals that NO 2 addition introduces a novel ammonia consumption pathway via NH 3 + NO 2 = NH 2 + HONO, facilitating rapid NH 2 radical production. HONO decomposition further accelerates OH radical formation. Reaction rate analysis confirms that NO 2 promotes OH generation through NO 2 + H = NO + OH, especially in the early stages of NH 3 oxidation. Moreover, NO 2 addition significantly alters NH 2 consumption pathways, with both NO 2 and NO participating in reactions with NH 2, not only accelerating its consumption but also suppressing NH 2 self-recombination and other radical-consuming channels.