Insights into the flow and scalar structures when shifting from methane to hydrogen turbulent flames using simultaneous PIV – OH PLIF and spontaneous Raman scattering

This study discusses fundamental turbulence-chemistry interactions in a canonical non-premixed bluff body burner fueled with 100% methane or hydrogen. Simultaneous time-resolved PIV&OH-PLIF and 1D Spontaneous Raman Scattering (SRS) have been employed to provide deeper insights into the difference in combustion regimes between CH and H operations. The analysis of the instantaneous time-resolved PIV and OH-PLIF datasets reveals the presence and absence of local extinctions in methane and hydrogen flames despite the mean flow topology being similar across the test cases. The instantaneous scatter plots of 1D Raman data in the mixture fraction space further quantified the spatial evolution of temperature and major species. Finally, the regime identification scheme is implemented over instantaneous 1D SRS data to identify the different flame/mixture regimes. The change in combustion regime is observed even very close to the burner exit while switching between CH and H, which is attributed to the probability of localized flame extinctions. Overall, this study provides detailed interlinks between flow field aerodynamics and scalar structures in the two different flames whose thermo physical properties are entirely different and form a comprehensive database for cornerstone computational model validation.