The interaction of flame and flow field in a lean premixed swirl-stabilized combustor operated on H2/CH4/air

The interaction of flame and flow field was studied in an enclosed lean premixed swirl-stabilized combustor operated on methane (CH4)- and hydrogen (H-2)- enriched CH4. This was accomplished by simultaneous measurements of the 2D velocity field using particle image velocimetry and planar laser induced fluorescence imaging of the hydroxyl (OH) radical. Experiments were conducted at an inlet Reynolds number of 13,500 and a theoretical swirl number of 1.5. The fuel was pure CH4 or a mixture of 60% CH4 and 40% H-2 by volume. The adiabatic flame temperature was 1350 +/- 20 degrees C for both fuels. Results show that the addition of H-2 changes the shape of the reaction zone, producing a shorter, and a more robust flame. Fuel composition also affected the location of the reaction zone, which in turn, influenced both instantaneous and time-averaged flow fields. Time-resolved measurements show vortical structures containing regions of high OH concentration around their edges. The combustion stabilized in regions of high compressive strain for the CH4 flame but not for the H-2-enriched CH4 flame. In the CH4 flame, reactions extinguished in the high velocity inlet jet region, where the H-2-enriched CH4 flame was able to sustain combustion. (c) 2004 The Combustion Institute. Published by Elsevier Inc. All rights reserved.