58770 - A Computationally Efficient Method That Predicts Light-Around for Both Gas- and Liquid-Fueled Combustion 

Controlling light-around and re-light presents design challenges for gas-turbine manufacturers. Researchers have studied the detailed phenomena in laboratory experiments to elucidate controlling factors and modes of behavior. Several groups have reported high-fidelity simulations of the fluid dynamics, turbulent mixing and light-around phenomena using large eddy simulations (LES) on highly refined computational meshes. While such simulations can reproduce experimental observations, they are computationally expensive and tend to be impractical for routine design analyses. In this work, we present a less computationally intensive CFD approach, which has been tested against laboratory experiments using both gaseous-fuel injections and liquid-fuel injections.

Results demonstrate that a CFD model using a RANS representation of the turbulent flow can provide consistent predictions of ignition time and light-around sequence in linear, multi-burner configurations. These simulations depend on solution-adaptive mesh refinement and well validated chemical kinetics, as well as established ignition-kernel and spray models. With this approach, results compare well to data in all cases studied, using the same model settings and mesh strategy throughout. The simulations generate light-around sequences and total-ignition times that agree well with experimental measurements. Observed trends are predicted when varying burner spacing as well as the fuel and injection method. The wall-clock times for these simulations were about one day for the full light-around sequence from spark timing, which is expected to be fast enough for use in practical design exploration.