Experimental and Numerical Investigations on a Combustor Model for Syngas Swirl Flames

An atmospheric combustor model with optical access for non-premixed swirl-stabilized flames was developed in order to investigate the combustion behavior of gas turbine fired with low caloric syngases and to create a data-base for the validation of numerical combustion models. In the present work, newly developed fully 3-D PIV measurements of the combustor aerodynamics at cold conditions are presented together with detailed wall temperature measurements in hot conditions. These data are respectively used to validate the combustor numerical model from an aerodynamic point of view and as boundary conditions when combustion simulations with different approaches are carried out. Thermocouple traverses data and global emissions analyzers results are then used as reference data for combustion models validation. Propane, as reference fuel, and a synthetic mixture of CH4, CO, CO2, and H2 are considered. The reactive flow was solved with two modeling approaches, namely the ED-FR and the flamelet combustion models. With the EDFR approach the propane-air combustion simulation was performed with a simple two-step reaction mechanism, while the syngas-air combustion case was simulated with a four-step one. Because flamelet model can treat multi-step chemical mechanisms with limited computational effort, a GRI 3.0 comprehensive mechanism and a reduced mechanism developed by Smooke have been used in this study to reproduce the syngas combustion process. As a whole, ED-FR model provide good agreement with the experimental thermal field while flamelet models correctly predicts the temperature trend, but with some local overestimation. As far as emissions are concerned, the Smooke flamelet approach proved to be the most reliable.