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ABSTRACT
Ignition and combustion of an infinite linear array of gaseous fuel pockets in a stagnant oxidizing environment under the microgravity condition is studied by a numerical approach. The combustion process is considered isobaric and the fluid motion is induced by density gradients due to the heat and mass transfer processes. A simple finite chemical reaction mechanism and the ideal gas equation of state are considered. The thermophysical properties, except density, are assumed constant. The Finite Volume Method is used with a hybrid non-staggered grid in a generalized system of coordinates. The SIMPLEC algorithm solves the modified pressure–velocity coupling. The Damköhler number effects on flame dynamics and on the fuel consumption are analyzed. Three stages in the burning processes: the induction time, the flame propagation and the diffusive burning are identified. The merging processes of the fuel pockets and of the flames are depicted.
Nomenclature
| b | = | half distance between two gas pockets |
| B | = | pre-exponential factor |
| c | = | truncation distance of the domain |
| cp | = | specific heat at constant pressure |
| D | = | mass diffusivity |
| Da | = | Damköhler number |
| e | = | initial temperature inside the gas pockets |
| k | = | thermal conductivity |
| Le | = | Lewis number |
| m | = | mass |
| p | = | modified pressure |
| pt | = | thermodynamic pressure |
| Pe | = | Peclet number |
| q | = | heat of reaction |
| r | = | cylindrical radial coordinate |
| R | = | spherical radial coordinate |
| Re | = | Reynolds number |
| s | = | stoichiometric coefficient in mass basis |
| t | = | time |
| T | = | temperature |
| u | = | velocity vector |
| V | = | volume |
| Y | = | mass fraction |
| z | = | axial cylindrical coordinate |
| Z | = | mixture fraction |
| β | = | Zel’dovich number |
| λ | = | second viscosity |
| μ | = | dynamic viscosity |
| θ | = | angular spherical coordinate |
| ρ | = | density |
| Ω | = | fuel consumption rate |
| Subscripts | = | |
| a | = | adiabatic |
| c | = | characteristic |
| f | = | fuel |
| o | = | oxidant |
| t | = | thermodynamic |
| 0 | = | initial value |
| ∞ | = | ambient conditions |
| Superscripts | = | |
| + | = | dimensional quantity |
Nomenclature
| b | = | half distance between two gas pockets |
| B | = | pre-exponential factor |
| c | = | truncation distance of the domain |
| cp | = | specific heat at constant pressure |
| D | = | mass diffusivity |
| Da | = | Damköhler number |
| e | = | initial temperature inside the gas pockets |
| k | = | thermal conductivity |
| Le | = | Lewis number |
| m | = | mass |
| p | = | modified pressure |
| pt | = | thermodynamic pressure |
| Pe | = | Peclet number |
| q | = | heat of reaction |
| r | = | cylindrical radial coordinate |
| R | = | spherical radial coordinate |
| Re | = | Reynolds number |
| s | = | stoichiometric coefficient in mass basis |
| t | = | time |
| T | = | temperature |
| u | = | velocity vector |
| V | = | volume |
| Y | = | mass fraction |
| z | = | axial cylindrical coordinate |
| Z | = | mixture fraction |
| β | = | Zel’dovich number |
| λ | = | second viscosity |
| μ | = | dynamic viscosity |
| θ | = | angular spherical coordinate |
| ρ | = | density |
| Ω | = | fuel consumption rate |
| Subscripts | = | |
| a | = | adiabatic |
| c | = | characteristic |
| f | = | fuel |
| o | = | oxidant |
| t | = | thermodynamic |
| 0 | = | initial value |
| ∞ | = | ambient conditions |
| Superscripts | = | |
| + | = | dimensional quantity |