Ignition delay measurements for n-dodecane/N2/air mixtures at high pressures

Abstract

Ignition delay time measurements have been made in reflected shock experiments for n-dodecane at conditions relevant to diesel engines and those specifically found in the Engine Combustion Network Spray A experiments. The present shock tube studies were carried out for n-dodecane/air mixtures at equivalence ratios of 1.0 and 2.0 for nominal pressures of 40, 60, and 80 atm and also at 60 atm for stoichiometric n-dodecane/O2/N2 mixtures containing 13% and 15% O2, to emulate reduced-O2 mixtures containing exhaust gas recirculation. The parameter space spans the low-temperature, negative-temperature-coefficient, and high-temperature regimes (774 to 1163 K), providing characterization of the complex temperature dependence of ignition important in low-temperature combustion processes and the pressure and oxygen concentration dependencies across the three kinetic regimes. The measurements are compared a priori to several recent reduced kinetic models with experiment-modeling deviations near the experimental uncertainties in several cases. To our knowledge, the present experiments represent the first gas-phase homogenous autoignition measurements made for n-dodecane at the extremely high-pressure conditions found in Spray A.