Advanced CRN Emission Prediction Model for Aircraft Engine Design

This work outlines a workflow for developing a reduced-order combustion-chamber model that enables rapid computation of performance and pollutant emissions for aircraft gas-turbine engine design processes, including configurations operating with Sustainable Aviation Fuels (SAF). The method is based on a zero-dimensional Chemical Reaction Network (CRN), selected for its computational efficiency and calibrated using data from high-fidelity, time-averaged unsteady 3D Computational Fluid Dynamics (CFD) simulations of an academic Rich-Burn/Quick-Mix/Lean-Burn (RQL) combustor. The CRN employs parallel Perfectly Stirred Reactors (PSRs) to represent flow and mixture inhomogeneities in the primary zone (PZ), and Plug Flow Reactors (PFRs) to model the secondary (SZ) and dilution (DZ) zones A comparison with CFD results across four operating points (take-off, climb-out, approach, and idle) demonstrates showed very good agreement for CO2 emissions (relative deviation <1.3 %), acceptable agreement for NOx (mean relative deviation = 15.7 %), and a mean relative deviation of 70 % for CO. In contrast, predictions of unburned hydrocarbons (UHC) show neither quantitative nor qualitative agreement, with the CRN model generally underpredicting UHC emissions. Analysis of UHC evolution along the flame tube axis reveals a rapid decrease in UHC concentrations at the beginning of the PFRs in the secondary and dilution zones, driven by oxidation caused by the freshly introduced mixing and dilution air, respectively.