Flashback Propensity of Turbulent Hydrogen-Air Jet Flames at Gas Turbine Premixer Conditions

The flashback propensity of a premixed jet flame has been studied experimentally. Boundary layer flashback has been investigated under turbulent flow conditions at elevated pressures and temperatures (i.e., 3-8 atm and 300-500 K). The data presented in this study are for hydrogen fuel at various Reynolds numbers, which are representative of practical gas turbine premixer conditions, and are significantly higher than results currently available in the literature. Three burner heads constructed of different materials (stainless steel, copper, and zirconia ceramic) were used to evaluate the effect of tip temperature, a parameter found previously to be an important factor in triggering flashback. This study characterizes flashback systematically by developing a comprehensive non-dimensional model which takes into account all effective parameters in boundary layer flashback propensity. The model was optimized for new data and captures the behavior of the new results well. Further, comparison of the model with the single existing study of high-pressure jet flame flashback also indicates good agreement. For a given equivalence ratio, the critical velocity gradient and bulk velocity at flashback vary exponentially with pressure. The pressure exponent of the critical velocity gradient was found to be close to 1.1 at fuel-lean conditions and becomes higher as equivalence ratio is increased. The developed dimensionless correlation is Da = Const.Le(1.68) . Pe(f)(1.91) . (T-u/T-0)(2.57) . (T-tip/T-o)(-0.49) . (P-u/P-0)(-2.1), which can be used to predict the boundary layer flashback propensity for given parameters.