Flame flashback is the uncontrolled upstream propagation of a premixed flame, and can lead to thermal damage of components in gas-turbine combustors. We are studying the type of flashback where the flame propagates within the wall boundary layer of a swirling flow. This work is relevant to gas-turbine combustors that operate with high-hydrogen-content syngas fuels derived from coal gasification. Sponsored by DOE UTSR.
The successful design of future premixed and fuel-flexible gas turbine combustors requires an improved fundamental understanding of flashback. During a flashback event the flame, nominally stabilized in the combustion chamber, propagates upstream into the premix section. The presence of the flame in the premix section constitutes a potentially catastrophic failure of the combustor as the parts upstream of the combustion chamber are not design to withstand high temperatures. Since virtually all gas turbine combustors feature a swirling flow for flame stabilization and mixing purposes, a detailed investigation of flashback in such complex flow fields is needed. Currently employed combustors designed to run on natural gas are challenged by the desire to use high-hydrogen content fuels. Combustors operated with such fuels are particularly susceptible to flashback owing to the fast kinetics, high diffusivity and low density of hydrogen. The upstream flame propagation frequently occurs in the low-momentum region of a boundary layer either along the center body or along the outer wall of the premix section (depending on the geometry of the combustor).