Numerical Investigation of Effusion Cooling Air Influence on the CO Emissions for a Single-Sector Aero-Engine Model Combustor

Abstract

Stricter aviation emissions regulations have led to the desire for lean-premixed-vaporized (LPP) combustors over rich–quench–lean (RQL) burners. While this operation mode is beneficial for reducing NOx and particulate emissions, the interaction of the flame and hot exhaust gases with the cooling flow results in increased CO emissions. Predicting CO in computational fluid dynamics (CFD) simulations remains challenging. To assess current model performance under practically relevant conditions, large-eddy simulation (LES) of a lab-scale effusion cooling test-rig is performed. Flamelet-based manifolds, in combination with the artificial thickened flame (ATF) approach, are utilized to model the turbulence–chemistry interaction (TCI) in the test-rig with detailed chemical kinetics at reduced computational costs. Heat losses are considered via exhaust gas recirculation (EGR). Local transport effects in CO emissions are included through an additional transport equation. Additionally, a conjugate heat transfer (CHT) simulation is performed for good estimations of the thermal boundary conditions. Extensive validation of this comprehensive model is conducted using the available experimental dataset for the studied configuration. Subsequently, model sensitivities for predicting CO are assessed, including the progress variable definition and the formulation of the CO source term in the corresponding transport equation. To investigate the flame thickening influence in the calculated CO, an ATF post-processing correction is further developed. Integrating multiple sophisticated pollutant submodels and evaluating their sensitivity offers insights for future investigations into modeling CO emissions in aero-engines and stationary gas turbines.