Stability Characteristics of Turbulent Hydrogen Dilute Diffusion Flames

Diffusion flame combustion of high-hydrogen fuels in land-based gas turbine combustors may include dilution of the fuel with inert gases and high velocity fuel injection to reduce NOx emissions. Stability regimes of such combustors are investigated in this study by examining turbulent dilute diffusion flames of hydrogen/nitrogen mixtures, issuing into a quiescent environment from a thin-lipped tube. This study has revealed two distinctly different types of lifted flames: lifted, laminar-base flames, for which liftoff heights vary from 1 to 3 jet diameters above the jet exit and are controlled by differential diffusion, and lifted, turbulent-base flames that stabilize much further downstream and are dominated by turbulent processes. In addition, stability limits governing the detachment or reattachment of the flame to the lip of the burner are examined, as well as the limits governing transitions between the two types of lifted flames and transition from these lifted flames to blowout.