This study concerned the modeling of combustion and radiative heat transfer in the generic gas turbine combustor of TU Darmstadt. The main air stream entered the combustion chamber via a swirler nozzle. The fuel entered the chamber separately via a pipe at the center of the nozzle. The swirl of the air caused a recirculation zone, which stabilized the flame. After the primary combustion zone, a secondary air stream was injected to rapidly dilute the fuel/oxidizer mixture and to lower the temperature in the combustor.
HEXPRESS™ was used to generate a full hexahedral unstructured mesh, containing about 1 million mesh cells, for the whole geometry. The mesh was refined behind the swirler nozzle, in order to capture the flow gradients in this region.
The combustion calculation was run in two steps, using the dedicated multiphysics capabilities of FINE™/Open software. First, an adiabatic non-premixed combustion calculation was performed (no radiative heat transfer). The thermo-chemical properties of the fluid were defined via the use of a flamelet library generated using TABGen/Chemistry. The post-processing included a reactive flow field inside the combustion chamber (contours of the species such as CO2, CH4, NOx). Then, the impact of taking into account the radiative heat transfer was computed. The radiative heat transfer was modelled using the P1 radiation model and the Weigted-Sum-of-Gray-Gases (WSGG) approach for the determination of the optical properties. A comparison with the temperature field of the adiabatic case shows that the radiative heat transfer slightly decreased the temperature in the system.
The picture above shows the static temperature contours in a cutting plane through the combustor.