1. Date of download: 5/28/2016 Copyright © ASME. All rights reserved. Visualization of Different Flashback Mechanisms for H 2 /CH 4 Mixtures in a Variable-Swirl Burner J. Eng. Gas Turbines Power. 2014;137(3):031507-031507-9. doi:10.1115/1.4028436 Variable-swirl burner with optical access Figure Legend:

2. Date of download: 5/28/2016 Copyright © ASME. All rights reserved. Visualization of Different Flashback Mechanisms for H 2 /CH 4 Mixtures in a Variable-Swirl Burner J. Eng. Gas Turbines Power. 2014;137(3):031507-031507-9. doi:10.1115/1.4028436 Cross section of swirler, premixing tube, and combustor Figure Legend:

3. Date of download: 5/28/2016 Copyright © ASME. All rights reserved. Visualization of Different Flashback Mechanisms for H 2 /CH 4 Mixtures in a Variable-Swirl Burner J. Eng. Gas Turbines Power. 2014;137(3):031507-031507-9. doi:10.1115/1.4028436 Swirl number as a function of ratio of axial/tangential momentum Figure Legend:

4. Date of download: 5/28/2016 Copyright © ASME. All rights reserved. Visualization of Different Flashback Mechanisms for H 2 /CH 4 Mixtures in a Variable-Swirl Burner J. Eng. Gas Turbines Power. 2014;137(3):031507-031507-9. doi:10.1115/1.4028436 Normalized axial velocity profiles obtained from LDA measurements for different swirl numbers Figure Legend:

5. Date of download: 5/28/2016 Copyright © ASME. All rights reserved. Visualization of Different Flashback Mechanisms for H 2 /CH 4 Mixtures in a Variable-Swirl Burner J. Eng. Gas Turbines Power. 2014;137(3):031507-031507-9. doi:10.1115/1.4028436 Normalized tangential velocity profiles obtained from LDA measurements for different swirl numbers Figure Legend:

6. Date of download: 5/28/2016 Copyright © ASME. All rights reserved. Visualization of Different Flashback Mechanisms for H 2 /CH 4 Mixtures in a Variable-Swirl Burner J. Eng. Gas Turbines Power. 2014;137(3):031507-031507-9. doi:10.1115/1.4028436 Different flashback mechanisms observed under various test conditions Figure Legend:

7. Date of download: 5/28/2016 Copyright © ASME. All rights reserved. Visualization of Different Flashback Mechanisms for H 2 /CH 4 Mixtures in a Variable-Swirl Burner J. Eng. Gas Turbines Power. 2014;137(3):031507-031507-9. doi:10.1115/1.4028436 OH* chemiluminescence image sequence of upstream flame propagation caused by CIVB. Image interval = 0.444 ms, exposure time = 72 μs, swirl number = 0.66, fuel H 2 mole fraction = 0.9, Φ = Φ FB = 0.234. Figure Legend:

8. Date of download: 5/28/2016 Copyright © ASME. All rights reserved. Visualization of Different Flashback Mechanisms for H 2 /CH 4 Mixtures in a Variable-Swirl Burner J. Eng. Gas Turbines Power. 2014;137(3):031507-031507-9. doi:10.1115/1.4028436 OH* chemiluminescence image sequence of upstream flame propagation in the boundary layer. Image interval = 2.072 ms, exposure time = 72 μs, swirl number = 0.0, fuel H 2 mole fraction = 0.9, Φ = Φ FB = 0.671. Figure Legend:

9. Date of download: 5/28/2016 Copyright © ASME. All rights reserved. Visualization of Different Flashback Mechanisms for H 2 /CH 4 Mixtures in a Variable-Swirl Burner J. Eng. Gas Turbines Power. 2014;137(3):031507-031507-9. doi:10.1115/1.4028436 OH* chemiluminescence image sequence of flame propagation in the premixing tube caused by auto-ignition. Image interval = 0.074 ms, exposure time = 72 μs, swirl number = 0.24, fuel H 2 mole fraction = 0.15, Φ = Φ FB = 0.696. Figure Legend:

10. Date of download: 5/28/2016 Copyright © ASME. All rights reserved. Visualization of Different Flashback Mechanisms for H 2 /CH 4 Mixtures in a Variable-Swirl Burner J. Eng. Gas Turbines Power. 2014;137(3):031507-031507-9. doi:10.1115/1.4028436 OH* chemiluminescence image sequence of blowout of the flame due to auto-ignition. Image interval = 0.074 ms, exposure time = 72 μs, swirl number = 0.24, fuel H 2 mole fraction = 0.15, Φ = Φ FB = 0.696. Figure Legend:

11. Date of download: 5/28/2016 Copyright © ASME. All rights reserved. Visualization of Different Flashback Mechanisms for H 2 /CH 4 Mixtures in a Variable-Swirl Burner J. Eng. Gas Turbines Power. 2014;137(3):031507-031507-9. doi:10.1115/1.4028436 Adiabatic flame temperature at flashback as a function of H 2 mole fraction Figure Legend:

12. Date of download: 5/28/2016 Copyright © ASME. All rights reserved. Visualization of Different Flashback Mechanisms for H 2 /CH 4 Mixtures in a Variable-Swirl Burner J. Eng. Gas Turbines Power. 2014;137(3):031507-031507-9. doi:10.1115/1.4028436 Flame front displacement in the optical section of the premixing tube during the flashback events for various fuel H 2 mole fraction/flashback mechanisms Figure Legend:

13. Date of download: 5/28/2016 Copyright © ASME. All rights reserved. Visualization of Different Flashback Mechanisms for H 2 /CH 4 Mixtures in a Variable-Swirl Burner J. Eng. Gas Turbines Power. 2014;137(3):031507-031507-9. doi:10.1115/1.4028436 Linear approximation of the flame front displacement for various fuel H 2 mole fraction/flashback mechanisms Figure Legend:

14. Date of download: 5/28/2016 Copyright © ASME. All rights reserved. Visualization of Different Flashback Mechanisms for H 2 /CH 4 Mixtures in a Variable-Swirl Burner J. Eng. Gas Turbines Power. 2014;137(3):031507-031507-9. doi:10.1115/1.4028436 The displacement of the second flame front in the premixing tube obtained in four flashback events caused by auto-ignition under the same condition: swirl number = 0.24, fuel H 2 mole fraction = 0.15, Φ = Φ FB = 0.696 Figure Legend:

15. Date of download: 5/28/2016 Copyright © ASME. All rights reserved. Visualization of Different Flashback Mechanisms for H 2 /CH 4 Mixtures in a Variable-Swirl Burner J. Eng. Gas Turbines Power. 2014;137(3):031507-031507-9. doi:10.1115/1.4028436 Equivalence ratio at flashback as a function of total air mass-flow rate (the H 2 mole fraction of the mixtures are presented next to each data point) Figure Legend: