Impact of nitric oxide (NO) on n-heptane autoignition in a rapid compression machine

Abstract

This paper investigates the impact of nitric oxide (NO) on n-heptane ignition in a rapid compression machine (RCM). The ignition delays of stoichiometric mixtures of n-heptane and varying amounts of NO (0–400 ppm) are measured in an argon diluent at 9 bar and over 650–1000 K. In the low temperature oxidation regime (≤ 720 K), ignition of n-heptane was promoted by NO up to 100 ppm, whilst higher NO levels do not further promote ignition. Stronger promoting effects are observed in the negative temperature coefficient (NTC) regime and at higher temperatures where the ignition delays are monotonically reduced with up to 400 ppm NO addition. Such impacts significantly suppress the NTC behaviour o..