Combustion and Flame, Vol.225, 20-30, 2021
Effects of ozone on n-heptane low temperature chemistry and premixed cool flames
Ozone (O-3) has been shown to accelerate low and high temperature chemistry and is a promising strategy to effectively enhance and control combustion and ignition processes, such as for engines. There has, however, been a lack of experimental investigation of O-3 enhancement effects on low temperature chemistry and premixed cool flames. This study undertook a detailed experimental and numerical assessment of O-3 enhancement effects on ignition behavior, propagation speeds, flame temperatures, and CH2O production of n-heptane cool flames as functions of O-3 addition. Zero-dimensional simulations were used to gain insights into the effects of O-3 on two-stage ignition behavior and gradual suppression of NTC phenomena. Propagation speeds of O-3-enhanced cool flames were experimentally determined using a flame lift-offtechnique, and one-dimensional simulations utilizing several full and reduced mechanisms were performed for comparison. Enhancement by O-3 versus enhancement by preheating were experimentally compared and analyzed to evaluate relative effectiveness of these enhancement strategies. Finally, downstream temperature measurements and formaldehyde planar laser-induced fluorescence imaging (CH2O PLIF) were performed at different O-3 enhancement levels to further elucidate O-3 impacts, and numerical simulations were performed to support experimental insights. Results of this study reveal O-3 impacts on low temperature kinetics and resulting impacts on low temperature ignition and cool flames. (C) 2020 The Combustion Institute. Published by Elsevier Inc. All rights reserved.