The effects of hydrogen addition on flame extinction in a lean-premixed swirl-stabilized combustor operating on natural gas and air were studied. Measurements of equivalence ratio at flame blowout have been made at pressures ranging from 1 to 8 atmospheres, hydrogen concentration in the fuel of 0-80% and inlet velocities of 40 and 80 m/s. Increasing the hydrogen concentration in the fuel from 0% to 80% reduced the equivalence ratio at blowout from Φ ～ 0.46 to Φ ～ 0.30. Combustor pressure was found to have little effect, while increasing the nozzle velocity from 40 to 80 m/s increased Φ at blowout by roughly 0.05. Modeling of the experimental data using a zero-dimensional perfectly stirred reactor model worked well for predicting hydrogen concentration effects, the insensitivity to pressure and the effect of inlet velocity. The reactor model was found, however, to be sensitive to the choice of chemical kinetic mechanism. Other methods of correlating the data using a dimensionless timescale approach were limited by the relatively low Dam-koehler number in the flame anchoring regions.
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