The effect of methane addition on reacting hydrogen jets in crossflow

Abstract

The combustion characteristics in a jet in crossflow configuration are numerically investigated using Large Eddy Simulation (LES) with subgrid scale modelling for partially premixed combustion. The time-averaged statistics are compared with the experimental measurements. Both the temperature and velocity comparisons show good agreement with measurements. The distribution of reaction regions of nitrogen-diluted hydrogen fuel jet is then examined in both physical and mixture fraction space. The results demonstrate that the fuel consumption in potential core, near-field and far-field regions occurs at various mixture fraction ranges. In the potential core region, reactions predominantly occur between the lean and stoichiometric mixture fraction range. This range broadens to include fuel-rich conditions in the near-field region and narrows again to fuel-lean combustion in the far-field region. With these changes in the mixture fraction range, the fractional contribution from different combustion modes also changes. A closer study of these changes reveals that the fractional contribution from the non-premixed mode is highest at the end of the potential core region. The dependency of these combustion modes on the fuel composition is studied by increasing the volume fraction of methane in the jet. This resulted in altered chemical kinetics and thereby increased the fractional contribution of the non-premixed mode, particularly in the potential core region.