Time-Resolved Measurements of Intermediate Concentrations in Fuel-Rich n-Heptane Oxidation Behind Reflected Shock Waves

Abstract

The chemical kinetics of the oxidation of n-heptane (C7H16) — an important reference compound for real fuels — are well studied at stoichiometric and lean conditions. However, there is only limited information on the chemical kinetics of fuel-rich combustion. In order to improve the accuracy of chemical kinetic models at these conditions, the oxidation of rich n-heptane mixtures has been investigated. Combustion of n-C7H16/O2/Ar mixtures at equivalence ratios, ϕ, of 2.0 behind reflected shock waves has been studied at temperatures ranging from 1075 to 1418K and at pressures ranging from 1.6 to 1.9atm. Reaction progress was monitored by recording ethylene (C2H4) concentration time-histories and initial n-heptane decay rates at a location 2cm from the endwall of a 13.4m long, 14cm inner diameter shock tube. Ethylene and n-heptane concentration time-histories were measured using absorption spectroscopy at 10.532μm from a tunable CO2 laser and at around 3.4μm from a continuous wave distributed feedback interband cascade laser (ICL), respectively. The measured concentration time-histories were compared with modeled predictions from the Lawrence Livermore National Lab (LLNL) detailed n-heptane reaction mechanism. To the best of our knowledge, the current data are the first time-resolved n-heptane and ethylene concentration measurements conducted in a shock tube at these conditions.