Numerical study on the combustion process in a gas turbine combustor with different reference velocities

The mixing and combustion processes under different reference velocities in a gas turbine combustor were numerically investigated using the Flamelet Generated Manifold (FGM) model based on the Reynolds Averaged Navier-Stokes (RANS) method. The flow and combustion fields show strong self-similarity except on the slow auto-ignition in the mixing layer between fuel-rich product and fresh air upstream of the flame stabilization position. The time-scale analysis was carried out to understand the combustion modes inside the combustor. In general, the residence time of the fuel-mixture is much longer than both the chemical time scale and the mixing time scale. Thus, the combustion properties in each sub-zone were dominated by the mean flow structures. Furthermore, the combustion process exhibits a mixing-controlled feature in total. However, partially premixed combustion still appears on the flame base. Most of the fuel was found to be oxidized in the primary zone and the intermediate zone; however, the slow oxidization reactions also play a non-negligible role on the whole combustion process. Finally, a sketch map on the space of mixture fraction and combustion efficiency was proposed to understand the mixing and oxidization experiences of the fuel mixture.