Investigation of Hydrogen Enriched Natural Gas Flames in a SGT-700/800 Burner Using OH PLIF and Chemiluminescence Imaging

Abstract

The effect o f hydrogen enrichment to natural gas flames was experimentally investigated at atmospheric pressure conditions using flame chemiluminescence imaging, planar laser-induced fluorescence of hydroxyl radicals (OH PLIF), and dynamic pressure moni toring. The experiments were petformed using a third generation dry low emission (DLE) burner used in both SGT-700 and SGT-800 industrial gas turbines from Siemens. The burner was mounted in an atmospheric combustion test rig at Siemens with optical access in the flame region. Four different hydrogen enriched natural gas flames were investi gated; 0 vol. %, 30 vol. %, 60 vol. %, and 80 vol. % of hydrogen. The results from flame chemiluminescence imaging and OH PLIF show that the size and shape of the flame was clearly affected by hydrogen addition. The flame becomes shorter and narrower when the amount of hydrogen is increased. For the 60 vol. % and 80 vol. % hydrogen flames the flame has moved upstream and the central recirculation zone that anchors the flame has moved upstream the burner exit. Furthermore, the position of the flame front fluctuated more for the full premixed flame with only natural gas as fuel than for the hydrogen enriched flames. Measurements of pressure drop over the burner show an increase with increased hydrogen in the natural gas despite same airflow thus confirming the observa tion that the flame front moves upstream toward the burner exit and thereby increasing the blockage of the exit. Dynamic pressure measurements in the combustion chamber wall confirms that small amounts of hydrogen in natural gas changes the amplitude of the dynamic pressure fluctuations and initially dampens the axial mode but at higher levels of hydrogen an enhancement of a transversal mode in the combustion chamber at higher frequencies could occur.

Thermoacoustic Instability Considerations for High Hydrogen Combustion in Lean Premixed Gas Turbine Combustors: A Review

“…Similar observations were reported by Park and Lee [70] and Kim et al [71] in later investigations using the same burner. The excitation of higher frequency instabilities due to hydrogen enrichment has also been reported in other studies [64,72,73].…”

“…On the contrary, the work of Lantz et al [72] revealed that transition to an M-shaped flame due to hydrogen enrichment in their combustor coincided with a suppression of self-excited combustion instabilities. The authors investigated natural gas flames enriched with up to 80% hydrogen by volume at atmospheric pressure using a third generation dry low emissions (DLE) burner employed by Siemens Energy in their SGT-700 and SGT-800 industrial gas turbines.…”

“…Many researchers have observed that the addition of hydrogen to natural gas leads to a transition in flame shape from a V-shape to an M-shape, although with different effects on dynamic instabilities [63,72,[75][76][77]. Referring back to Figure 4 from the work of Shanbhogue et al [75], it can be observed that the 100% CH 4 flame at φ = 0.58 exhibited a V-shape and was reported as being thermoacoustically stable.…”

“…The lower pressure amplitudes observed for the hydrogen-rich flame coincided with a reduction in the observed flame front fluctuations compared to the pure natural gas flame. Subash et al [76] extended the work of Lantz et al [72] by comparing the dynamics of pure natural gas and pure hydrogen flames using an optimised version of the same DLE burner. The pure hydrogen flame was shorter, more compact and stabilised closer to the burner exit compared to the pure methane flame.…”

Advanced Laser-Based Techniques for Gas-Phase Diagnostics in Combustion and Aerospace Engineering

“…26,27 Therefore, OH has been frequently used for tracing the position of the flame front by tracking steep gradients in the OH-planar laser-induced fluorescence (PLIF) image data. [28][29][30] Another approach to track the flame front region is to visualize CH or HCO, which are intermediate combustion species that form and be consumed in this thin layer. [31][32][33][34][35] The region where the preheating chemistry occurs, i.e., before the actual flame front, can be visualized by performing PLIF on formaldehyde, CH 2 O.…”