Turbulence–Combustion Interactions in Premixed and Non-premixed Flames Generated by Hot Active Turbulent Jets

Direct numerical simulations of turbulent jet ignition (TJI)-assisted combustion of lean hydrogen–air mixtures are performed in a three-dimensional planar jet configuration for various thermo-chemical conditions. TJI is a novel ignition enhancement method which facilitates the combustion of lean and ultra-lean fuel–air mixtures by rapidly and continuously exposing them to high temperature combustion products. Fully compressible gas dynamics and species equations are solved with high order finite difference methods. The hydrogen–air reaction is simulated by a detailed chemical kinetics mechanism. Turbulence–combustion interactions in TJI systems are studied here for different conditions using the flame heat release, temperature, species concentrations, and a newly defined progress variable. Important phenomena such as localized flame extinction/re-ignition and simultaneous existence of premixed/non-premixed flames in TJI-assisted combustion are also investigated.