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ABSTRACT
Detailed flow field and heat transfer characteristics of an array of three corotating dual swirling impinging flames arranged in a triangular configuration have been investigated experimentally as well as numerically. Effect of varying separation distance and inter-jet spacing on interactions and impingement heat transfer has been studied at fixed Reynolds numbers under stoichiometric conditions. Adjacent co-swirling flames developed strong interactions resulting in high heat transfer due to increased mixing and turbulence. Bending of inner non-swirling flames takes place toward geometric center of the array due to asymmetric interactions. Numerical simulation also predicted asymmetric interactions resulting in the formation of large distorted recirculation bubble in each dual-swirling flame. Interacting co-swirling flames resulted in the formation of circulating patterns of flow at the geometric center of array. The effect of inter-jet spacing on average heat flux is observed to be more significant than separation distance.
Nomenclature
| A | = | Area of impingement plate |
| d | = | Diameter of inner pipe (mm) |
| Di | = | Inner diameter of outermost pipe of the burner (mm) |
| Do | = | Outer diameter of the burner (mm) |
| Dh | = | Hydraulic diameter (mm) |
| H | = | Separation distance (mm) |
| H/Dh | = | Nondimensional separation distance |
| k | = | Turbulent kinetic energy (m2/s2) |
| M | = | Molecular mass (kg/kmol) |
| n | = | Data point in thermal image |
| p | = | Pressure (Pa) |
| q″ | = | Heat flux (kW/m2) |
| q″avg | = | Averaged heat flux (kW/m2) |
| Re | = | Reynolds number |
| S | = | Inter-jet spacing (mm) |
| S/Dh | = | Nondimensional inter-jet spacing |
| t | = | Time (s) |
| T | = | Temperature (K) |
| um | = | Mean velocity at burner exit (m/s) |
| u, v, w | = | Velocity components in x, y, and z direction |
| X | = | Mole fraction |
| x, y | = | Coordinate axis on impingement plate |
| x/Dh,y/Dh | = | Nondimensional distances |
| z | = | Thickness (mm) |
| Z | = | Downstream distance from burner exit (mm) |
| IHCP | = | Inverse heat conduction procedure |
| MCIJ | = | Multiple conventional impinging jets |
| MFC | = | Mass flow controllers |
| MSIJ | = | Multiple swirling impinging jets |
| RANS | = | Reynolds averaged Navier–Stokes |
| RCZ | = | Recirculation zone |
| RJRC | = | Radial jet reattachment combustion |
| RNG | = | Renormalization group theory |
| RSM | = | Reynolds stress model |
| SST | = | Shear stress transport |
Greek Symbols
| α | = | Thermal diffusivity (m2/s) |
| ε | = | Dissipation rate (m2/s3) |
| λ | = | Thermal conductivity (W/mK) |
| μ | = | Dynamic viscosity(kg/m s) |
| ρ | = | Density (kg/m3) |
| ϕ | = | Equivalence ratio |
Subscripts
| atm | = | Atmospheric |
| avg | = | Average |
| dev | = | Deviation from averaged value |
| dev, rms | = | Root mean square deviation |
| f | = | Front side of impingement plate |
| i | = | Loop index, inner flame |
| j | = | Index for chemical species |
| o | = | Outer flame |
| r | = | Rear side of impingement plate |
| w | = | Wall |