Numerical evidence on deflagration fronts in a methane/n-dodecane dual-fuel shear layer under engine relevant conditions

To date, high resolution spray-assisted dual-fuel (DF) studies have focused on capturing the ignition process while the subsequent post-ignition events have been largely neglected due to modeling requirements and high computational cost. Here, we use a simplified approach for studying ignition front evolution after ignition. Three-dimensional scale-resolved simulations of igniting shear layers (0 <= Re <= 1500) are studied to better understand reaction fronts in engine-relevant conditions. We carry out quasi-DNS in a DF combustion setup consisting of premixed n-dodecane/methane/air/EGR at 700K as a fuel stream and premixed methane/air as the oxidizer at a pressure of 60 atmospheres and an ambient temperature of 900 K. The flow solution resolution is delta/10, where delta =laminar flame thickness. The present study primarily focuses on the hypothesized flame formation and its characterization. Under these conditions, the simulations indicate two-stage ignition further leading to reaction front initiation and dual-fuel flame establishment. For Re < 1500, a reaction front resembling DF deflagration is demonstrated close to the auto-ignition timescales. At Re = 1500, mixing effects promote more rapid dilution and the DF deflagration front formation is slightly delayed although still observed. For the first time, at rather short timescales of 0.2 - 0.4 IDT (ignition delay time) after the ignition, we provide numerical evidence on DF deflagration front emergence in shear-driven DF combustion processes via 3D numerical simulations for 0 < Re <= 1500.