Shock tube measurements of iso-octane ignition times and OH concentration time histories

Ignition times and OH radical concentration time histories were measured behind reflected shock waves in iso-octane/O-2/Ar mixtures. Initial reflected shock conditions were in the ranges 1177 to 2009 K and 1.18 to 8.17 atm,,with fuel concentrations of 100 ppm, to 1% and equivalence ratios from 0.25 to 2. Ignition times were measured using endwall emission of CH and sidewall pressure. OH concentrations were measured using narrow-linewidth ring-dye laser absorption of the R-1(5) line of the OH A-X (0,0) band at 306.5 nm. The ignition time data and OH concentration time-history measurements were compared with model predictions of four current iso-octane oxidation mechanisms, and the implications of these comparisons are discussed. To our knowledge, these data provide the first extensive measurements of low-fuel-concentration ignition times and OH concentration time histories for iso-octane autoignition, and hence provide a critical contribution to the database needed for validation of a detailed mechanism for this primary reference fuel.