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ABSTRACT
The lifted flame with hot co-flow can represent typical combustion features in the practical systems with recirculation of the combustion product. In this study, the methane/air lifted flame was simulated by large eddy simulation. Regarding the special stabilization mechanism in the lifted flame, two different one-step methane oxidation mechanisms were used: (i) the conventional mechanism widely used in engineering simulations and (ii) a modified mechanism considering the effects of the equivalence ratio. By comparing the simulation results with the experimental data, both mechanisms could predict the liftoff phenomenon; however, the simulation using the modified mechanism provided more reasonable results.
Nomenclature
| A | = | the pre-exponential factor |
| E | = | the total energy |
| Ea | = | the activation energy |
| ksgs | = | the subgrid kinetic energy |
| Prt | = | the turbulent Prandtl number |
| = | the source term of the energy | |
| Sij | = | the rate-of-strain tensor |
| Sct | = | the turbulent Schmidt number |
| = | the turbulent velocity | |
| Ys | = | the mass fraction of the species s |
| = | the source term of the species s | |
| Δ | = | the mesh scale |
| φ | = | the equivalence ratio |
| μ | = | the molecular viscosity |
| μt | = | the subgrid viscosity |
| νt | = | the subgrid kinematic viscosity |
| τc | = | the chemical time scale |
| τij | = | the stress tensor |
| τm | = | the mixing time scale |
| τsgs | = | the subgrid shear stress tensor |
| = | the global reaction rate | |
| ωf | = | the resolved reaction rate |
| ωt | = | the subgrid reaction rate |
Nomenclature
| A | = | the pre-exponential factor |
| E | = | the total energy |
| Ea | = | the activation energy |
| ksgs | = | the subgrid kinetic energy |
| Prt | = | the turbulent Prandtl number |
| = | the source term of the energy | |
| Sij | = | the rate-of-strain tensor |
| Sct | = | the turbulent Schmidt number |
| = | the turbulent velocity | |
| Ys | = | the mass fraction of the species s |
| = | the source term of the species s | |
| Δ | = | the mesh scale |
| φ | = | the equivalence ratio |
| μ | = | the molecular viscosity |
| μt | = | the subgrid viscosity |
| νt | = | the subgrid kinematic viscosity |
| τc | = | the chemical time scale |
| τij | = | the stress tensor |
| τm | = | the mixing time scale |
| τsgs | = | the subgrid shear stress tensor |
| = | the global reaction rate | |
| ωf | = | the resolved reaction rate |
| ωt | = | the subgrid reaction rate |