Over the last few decades strict regulations are being implemented to reduce pollutant emissions, mainly CO, NOx and unburned hydrocarbons. Simultaneously, the share of renewable energies in the market is constantly growing, boosted by these regulations and by stronger social and political conscience on environmental issues. In response to these phenomena strong research efforts are oriented to the development of new staged combustion concepts and low emissions technologies with the ability to burn hydrogen enriched natural gas. In this paper we perform an experimental and numerical study, focusing our research on a premixed hydrogen-methane-air reactive jet in hot crossflow (RJICF), which is relevant for combustors with axially staged fuel injection.

Firstly, ignition dynamics and flame stabilization are studied experimentally for a hydrogen-methane-air premixed jet in crossflow. The composition of this crossflow is given by the hot combustion products from a first stage that features a lean methane-air flame (f~cf~ = 0.8). Three jet parameters are varied to study the effect of hydrogen on the flame morphology, stabilization mechanism and ignition, namely the fuel blend (B = 0-100 % of hydrogen), the equivalence ratio (f~j~ = 0.8-1.5) and the jet-to-crossflow momentum ratio (J = 5-25). High-speed hydroxyl (OH) chemiluminescence is used to characterize the self-ignition process from a non-reactive (air) to a reactive (fuel+air) jet and the subsequent flame dynamics. OH laser induced fluorescence (OH-LIF) and OH-LIF-based thermometry are used to study the stationary behavior of the jet in cross flow flame. Secondly, three-dimensional (3D) large eddy simulations (LES) are performed of the same experimental setup under similar test conditions of fuel blend, equivalence ratio and jet-to-crossflow momentum ratio. The aim of the numerical simulations is to complement the experimental data and give insight  in the combustion chemistry at play in the windward and leeward reactive shear layers.

The results show the dynamics of the jet ignition for the different test cases and the average behavior and jet morphology. A strong effect of hydrogen is observed even for low concentrations if compared to the pure methane fueled jet, promoting ignition notably and moving the anchoring location of the windward side flame towards the jet root. Strong asymmetry is observed between the robust anchoring of the flame at the root of the jet on the leeward side and a more dynamic flame at the windward side that is strongly affected by the test conditions (fuel blend, jet equivalence ratio and jet-to-crossflow momentum ratio). The windward flame tends to attach at the jet root when hydrogen is added to the fuel mixture, even for low concentrations, and also when the overall jet equivalence ratio becomes rich. Again, strong influence of hydrogen is observed, increasing temperatures in the near-flame region and stabilizing the windward side flame. The jet flame size and morphology are more compact under the presence of hydrogen and for leaner mixtures with lower momentum ratios.


Morphology and Dynamics of a Premixed Hydrogen-Methane-Air Jet Flame in Hot Vitiated Turbulent Crossflow

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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