Application of a Turbulent Jet Flame Flashback Propensity Model to a Commercial Gas Turbine Combustor

Abstract

Because flashback is a key operability issue associated with low emission combustion of high hydrogen content fuels, design tools to predict flashback propensity are of interest. Such a design tool has been developed by the authors to predict boundary layer flashback using nondimensional parameters. The tool accounts for the thermal coupling between the flame and burner rim and was derived using detailed studies carried out in a test rig at elevated temperature and pressure. The present work evaluates the applicability of the model to a commercial 65 kW microturbine generator (MTG). Two sets of data are evaluated. One set is obtained using the combustor, removed from the engine, which has been configured to operate like it does in the engine but at atmospheric pressure and various preheat temperatures. The second set of data is from a combustor operated as it normally would in the commercial engine. In both configurations, studies are carried out with various amounts of hydrogen added to either natural gas or carbon monoxide. The previously developed model is able to capture the measured flashback tendencies in both configurations. In addition, the model is used to interpret flashback phenomena at high pressures and temperatures in the context of the engine conditions. An increase in pressure for a given preheat temperature and velocity reduces the equivalence ratio at which flashback occurs and increases the tip temperature due to lower quenching distance. The dependency of the flashback propensity on the injector tip temperature is enhanced with an increase in pressure. The variation of critical velocity gradient with equivalence ratio for a constant preheat temperature is more pronounced at higher pressures. In summary, the model developed using the high-pressure test rig is able to predict flashback tendencies for a commercial gas turbine engine and can thus serve as an effective design tool for identifying when flashback is likely to occur for a given geometry and condition.