A numerical study of the characteristics of laminar lifted methane/hydrogen flames in heated coflow

The characteristics of laminar lifted methane/hydrogen jet flames in heated coflow are investigated using 2-D axisymmetric numerical simulations with OpenFOAM. It is found that a highly-diluted laminar methane jet flame with small amount of hydrogen addition exhibits a unique feature that its liftoff height decreases with increasing fuel jet velocity, similar to experimental observation. The Damköhler number and chemical explosive mode (CEM) analyses verify that the decrease of the liftoff height of the methane/hydrogen jet flame is primarily attributed to highly-diffusive hydrogen molecule, which is also confirmed by additional simulations in which the diffusivity of hydrogen molecule is artificially set to that of methane