Large-Eddy Simulations of Dilution Jet Effects on a Lab-Scale Rich-Quench-Lean Spray Flame

The Rich–Quench–Lean (RQL) concept remains a leading strategy for low-emission aero-engine combustors. Recent experiments at the University of Cambridge have investigated the effects of primary and dilution air on the aerodynamics and soot formation tendencies in an RQL spray flame. Building on this work, the present study uses large-eddy simulations (LES) to examine the effects of airflow distribution on combustion behavior in a bluff-body, swirl-stabilized RQL configuration operating at a fixed global equivalence ratio of 0.4. Three cases with varying primary/dilution air splits are simulated using a compressible multiblock LES solver with Lagrangian spray tracking, reduced finite-rate kerosene chemistry, and a partially stirred reactor (PaSR) model for subgrid turbulence–chemistry interaction. Non-reacting results show that the LES captures the influence of dilution jets on recirculation structure and turbulence levels. The reacting simulations are then compared with a focus on overall spray and flame behavior, and the competition between chemistry and mixing time scales is analyzed across the three conditions. The observed trends demonstrate a consistency with experimental measurements and provide a verified framework for future LES-based soot modeling in this system.