Numerical and Experimental Investigation on an Effusion-Cooled Lean Burn Aeronautical Combustor: Aerothermal Field and Emissions

Lean burn combustion is increasing its popularity in the aeronautical framework due to its potential in reducing drastically pollutant emissions (NO_x and soot in particular). Its implementation, however, involves significant issues related to the increased amount of air dedicated to the combustion process, demanding the redesign of injection and cooling systems. Also, the conditions at the combustor exit are a concern, as high turbulence, residual swirl, and the impossibility to adjust the temperature profile with dilution holes determine a harsher environment for nozzle guide vanes. This work describes the final stages of the design of an aeronautical effusion-cooled lean burn combustor. Full annular tests were carried out to measure temperature profiles and emissions (CO and NO_x) at the combustor exit. Different operating conditions of the ICAO cycle were tested, considering Idle, Cruise, Approach, and Take-off. Scale-adaptive simulations with the flamelet generated manifold (FGM) combustion model were performed to extend the validation of the employed computational fluid dynamics (CFD) methodology and to reproduce the experimental data in terms of radial temperature distribution factor (RTDF)/overall temperature distribution factor (OTDF) profiles as well as emission indexes (EIs). The satisfactory agreement paved the way to an exploitation of the methodology to provide a deeper understanding of the flow physics within the combustion chamber, highlighting the impact of the different operating conditions on flame, spray evolution, and pollutant formation.