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 |