Multi-Coupled Numerical Analysis of Advanced Lean Burn Injection Systems

Lean burn aero-engine combustors usually exploit advanced prefilming airblast injection systems in order to promote the formation of highly homogeneous air-fuel mixtures with the main aim of reducing NOx emissions. The combustion process is strongly influenced by the liquid fuel preparation and a reliable prediction of pollutant emissions requires proper tools able to consider the most important aspects characterizing liquid film evolution and primary breakup. This paper presents the numerical analysis of an advanced lean burn injection system using a multi-coupled two-phase flow three-dimensional solver developed on the basis of OpenFOAM modelling and numerics. The solver allows the coupled solution of gas-phase, droplets and liquid film exploiting correlation-based and theoretical models for liquid film primary atomization. A detailed analysis of the liquid film evolution is presented together with an investigation of the influence of film modelling and primary breakup on the combustion process at different operating conditions. The combustion field is strongly influenced by the characteristics of droplet population generated by the liquid film and this study proposes a computational setup, suitable for industrial calculations, able to account for all the main physical processes that characterize advanced prefilming airblast injection systems.