Session chaired By Pr. Aimee Morgans
The growing interest in hydrogen as a fuel for energy production and transportation demands specific scientific investigations. Hydrogen combustion is well known as the simplest possible fuel in terms of chemical kinetics and it has been used for decades by the space industry to fuel rocket engines. It is however much complex in terms of transport and mixing properties, and its very light weight raises issues for storage. Recently, interest has grown around the idea of adding hydrogen to hydrocarbons that are more commonly used in industry, with two objectives: 1) lower the carbon content of the exhaust gases and 2) sustain stable combustion in lean conditions. In ground-based gas turbines for example, hydrogen may be added to natural gas. The properties of this dual fuel then need to be studied. In this work a confined turbulent Methane/Hydrogen/Air swirling premixed flame stabilized over a bluff-body  is studied with numerical simulation. Two levels of enrichment are considered: 1) 90% of hydrogen in mole (very high level) and 2) 60% of hydrogen in mole (high level). For both levels, Large Eddy Simulations (LES) are performed with either adiabatic or non-adiabatic boundary conditions to assess the impact of heat losses on the flame structure. The DTFLES approach is used for turbulent combustion modelling. Chemical kinetics are described with Analytically Reduced Chemistry (ARC) enabling an accurate insight on the chemical phenomena. It allows in particular to capture and explain the transition from V to M shape when increasing the hydrogen proportion. The specific species and reactions that are sensitive to the thermal boundary condition can also be identified with ARC. The simulation results are compared with measurements and with a previous numerical investigation using tabulated chemistry (F-TACLES)  that was deemed to not well predict the combined effect of local strain rate and heat losses. Direct comparison with experiment is also done using detailed OH* chemistry, calculated with two strategies: either OH* is calculated as a transported species, or it is calculated in a post-processing step from the other computed species. Finally, the prediction of NOx and its sensitivity to the various above-mentioned conditions is presented.  R. Mercier et al., « Experimental and Numerical Investigation of the Influence of Thermal Boundary Conditions on Premixed Swirling Flame Stabilization », Combustion and Flame 171 (september 2016): 42‑58, https://doi.org/10.1016/j.combustflame.2016.05.006.