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ABSTRACT
The present study was conducted to evaluate the total cooling effectiveness in combined full-coverage film cooling and impingement jet using an infrared thermographic technique. The effect of film cooling hole angle, blowing ratio, and height to diameter ratio between the film cooling and impingement jet plates was discussed. The total cooling effectiveness increased as impingement jet cooling was added. The angled film cooling holes had approximately 4.6% higher total cooling effectiveness than the normal film cooling holes. The total cooling effectiveness was almost constant regardless of height to diameter ratio, but enhanced as the blowing ratio was increased.
Nomenclature
| d | = | Diameter of injection and film cooling hole |
| p | = | Hole spacing of film cooling plate |
| p’ | = | Hole spacing of injection plate |
| H | = | Gap distance between injection and film cooling plate |
| t | = | Thickness of film cooling plate |
| t’ | = | Thickness of injection plate |
| he | = | External heat transfer coefficient |
| hi | = | Internal heat transfer coefficient |
| k | = | Thermal conductivity of film cooled plate |
| M | = | Blowing ratio |
| Th | = | Temperature of main flow |
| Tc | = | Temperature of coolant (= T2) |
| T21 | = | Temperature of ejected coolant |
| Taw | = | Adiabatic wall temperature |
| Tw | = | Temperature of film cooled plate surface |
| Vh | = | Main flow velocity |
| Vc | = | Secondary flow velocity at the film cooling hole |
| x | = | Streamwise distance from the first row of hole |
| y | = | Spanwise distance from the center of hole |
| Rejet | = | Reynolds number of jet flow |
Greek letters
| ρh | = | Density of main flow |
| ρc | = | Density of secondary flow |
| = | Local total cooling effectiveness | |
| η ad | = | Adiabatic film cooling effectiveness |
Funding
This work was supported by the human resources development program (No.20144030200560) of the Korean Institute of Energy Technology Evaluation and Planning (KETEP). The program is funded by the Korean government Ministry of Trade, Industry, and Energy.