Flame flashback in wall boundary layers of premixed combustion systems

The utilization of hydrogen-rich fuels in premixed and undiluted combustion systems faces a particular type of operational instability, which is flame propagation against the mean flow direction inside the wall boundary layer. This process, also known as wall flashback, has been investigated in a generic combustion experiment for laminar and turbulent flow conditions and different fuels using optical measurement techniques. The results have revealed that the existing physical model of wall flashback is inadequate. A static pressure rise upstream of the flame causes the boundary layer to separate and the flame to propagate upstream inside the associated backflow region. Based on these experimental findings and numerical simulation with a reduced kinetic mechanism, a new physical model for wall flashback and an according correlation method is presented.