A 3D multiphysics model and its experimental validation for predicting the mixing and combustion characteristics of an afterburner

For the design and development of solid oxide fuel cell (SOFC) systems, auxiliary components such as the combustor play a significant role. The waste products, leaving the fuel cell are processed by the combustor. Therefore, it is of paramount importance to understand and improve the knowledge of the detailed processes, occurring within the component. This will influence the overall performance of the SOFC system. Especially, the mixing and combustion characteristic requires attention. A 3D computational fluid dynamics (CFD) model has been developed to investigate the combustion chamber of the Jülich combustor design, in detail. The model is utilised in the simulation of the turbulent, chemically reacting species transport. Nominal data from a 20 kW SOFC system is used for a detailed analysis. The complex vortex shapes of the species at the orifice outlets, as well as the flow field within the chamber have been depicted. The flame shape and temperature field have been predicted. Experimental case data have been used to compare the numerically predicted exhaust gas temperatures and surface temperature distributions, which show good agreement. The simulation results indicate different species mixing behaviour and flame shapes at the combustor orifices. Recirculation due to swirl is determined to cause different flame temperatures. The created CFD model provides invaluable details of the mixing and combustion characteristic of the component that will be considered in design optimisation processes.