Auto-ignition of toluene-doped n-heptane and iso-octane/air mixtures:High-pressure shock-tube experiments and kinetics modeling

摘要

Toluene is often used as a fluorescent tracer for fuel concentration measurements, but without consider-ing whether it affects the auto-ignition properties of the base fuel. We investigate the auto-ignition of pure toluene and its influence on the auto-ignition of n-heptane and iso-octane/air mixtures under engine-relevant conditions at typical tracer concentrations. Ignition delay times τ_ (ign) were measured behind reflected shock waves in mixtures with air at φ = 1.0 and 0.5 at p = 40 bar, over a temperature range of T= 700-1200 K and compared to numerical results using two different mechanisms. Based on the models, information is derived about the relative influence of toluene on τ_ (ign) on the base fuels as function of temperature. For typical toluene tracer concentrations ≤10%, the ignition delay time τ_ (ign) changes by less than 10% in the relevant pressure and temperature range.