Modeling of Hydrogen Jet Diffusion Flames : On the Direct Influence of Molecular Viscosity

Abstract

First, it was predicted that the increase of molecular viscosity due to high temperature raises the dissipation rate of turbulence in low turbulent regions in a combustion field. The objective of the present study is to verify this prediction in experimental and theoretical ways. Experiments were carried out on jet diffusion flames of hydrogen, and then, a numerical simulation was conducted for the experimental results. In the simulation, the k-ε two-equation model was used as a turbulence model and a new source term was added to the k-equation to represent the dissipation of turbulence energy due to molecular viscosity. The calculated results agreed well with the experimental ones. It was found that the new source term suppresses turbulence in low turbulent regions situated around the nozzle exit and the periphery of jets, and changes the condition in the whole combustion field greatly, The present work suggested that the consideration of the viscous effect is important in the modeling of turbulent combustion fields.