Impact of Spray Droplet Distribution on the Performances of a Kerosene Lean/Premixed Injector

Large-Eddy Simulation (LES) of a novel lean-premixed (LP) injection system for aeronautical burners is performed at elevated pressure / temperature operating conditions. This LP injector was designed to operate at high-pressure and high-temperature and it was experimentally investigated at DLR Cologne and at CORIA laboratory in Rouen. At DLR Cologne, the purpose was to measure droplets sizes and velocities thanks to the Phase Doppler Anemometry (PDA) technique. At CORIA, combustion under realistic pressure conditions was investigated on the HERON test rig with advanced and combined optical diagnostics, such as OH and Kerosene Planar Laser-Induced Fluorescence (PLIF). It was observed that the flame topology strongly depends on the pressure. This configuration is therefore an interesting validation database for LES. In this LP injector, liquid kerosene is injected far upstream of the injector in order to provide a gaseous fuel distribution as homogeneous as possible. In the LES, the full geometry of the injector is taken into account. One reference operating point at 8.33bar and 669.3K is simulated. A Lagrangian point-particle approach is chosen for the spray modeling with a prescribed Rosin-Rammler diameter distribution at injection. The two-phase combustion model relies on a tabulated chemistry approach. The flame/turbulence interactions are included via a presumed-PDF closure (PCM-FPI model). The impact of spray characteristics on the flame is analyzed through a dedicated parametric study. Four sets of parameters each with a different Sauter Mean Diameter are used to describe the spray droplet size distribution. An analysis of the characteristic evaporation time and its influence on the flame has been carried out. Numerical results are then compared with experimental data in order to bring detailed insights into the flame topology. This parametric study shows that the quality of the atomization strongly influences the flame topology and the fuel distribution inside the combustion chamber.