![Sample our Engineering & Technology journals, sign in here to start your access, latest two full volumes FREE to you for 14 days]({"type":"image" , "src" : "/sda/5933/TOC-Subject-Sample-2021-Engineering-Tech.jpg"})
Abstract
The film cooling effectiveness and the jet exit conditions and the associated vortex structure downstream of the injection hole for both a circular exit shaped hole and an elliptical exit shaped holes were numerically investigated for the blowing ratios of 0.25, 0.5, 1, and 1.5. Four turbulence models, including the standard, RNG, realizable k − ϵ, and Reynolds-stress model, in combination with three near-wall approaches, were used for the present simulations. It was found that the predicted results using the realizable k − ϵ model combined with the standard wall function were in better agreement with the available experimental data from the literature. Further, the results indicate that the circular exit shaped hole improved the centerline and laterally averaged adiabatic effectiveness, particularly at high blowing ratios. Finally, adding the sister holes provided a notable decrease in the strength of the counterrotating vortex pairs, where the highest effectiveness was achieved for the circular exit shaped hole case with sister holes.
NOMENCLATURE
| a | = | semi-major axis of an ellipse |
| b | = | semi-minor axis of an ellipse |
| cp | = | specific heat capacity, J/kg-K |
| CESH | = | circular exit shaped hole |
| CRVP | = | counterrotating vortex pairs |
| D | = | diameter, m |
| DJFC | = | double-jet film cooling |
| DNS | = | direct numerical simulation |
| DR | = | density ratio |
| EESH | = | elliptical exit shaped hole |
| k | = | turbulent kinetic energy, m2/s2 |
| k′ | = | thermal conductivity, W/m-K |
| L | = | length, m |
| LE | = | leading edge |
| M | = | blowing ratio |
| p | = | pressure, N/m2 |
| Pr | = | Prandtl number |
| RNG | = | renormalization group |
| RSM | = | Reynolds-stress model |
| SST | = | shear-stress transport |
| T | = | temperature, K |
| TE | = | trailing edge |
| U | = | mean velocity, m/s |
| U+ | = | dimensionless velocity = U/uτ |
| u | = | fluctuating velocity, m/s |
| uτ | = | friction velocity |
| V | = | velocity, m/s |
| x, y, z | = | Cartesian coordinate |
| y+ | = | normalized distance = ypuτ/ν |
Greek Symbols
| α | = | thermal diffusivity = k′/ρcp, m2/s |
| β | = | injection angle, degrees |
| δ | = | Kronecker delta |
| Δx, Δy, Δz | = | mesh spacing in the x, y, z directions |
| ϵ | = | dissipation rate of turbulent kinetic energy, m2/s3 |
| η | = | adiabatic effectiveness |
| θ | = | fluctuating temperature, K |
| Θ | = | mean temperature, K |
| κ | = | Von Karman constant (= 0.4187) |
| μ | = | dynamic viscosity, N-s/m2 |
| ρ | = | density, kg/m3 |
| σk | = | Prandtl number for k |
| σϵ | = | Prandtl number for ϵ |
| τw | = | wall shear stress, N/m2 |
| ν | = | kinematic viscosity = μ/ρ, m2/s |
| ω | = | specific dissipation rate, s−1 |
| Ω | = | rotation rate, s−1 |
Subscripts
| aw | = | adiabatic wall |
| c | = | coolant |
| eff | = | effective |
| t | = | turbulent |
| ∞ | = | freestream (mainstream) |
| p | = | near-wall node of p |
Additional information
Notes on contributors
Siavash Khajehhasani
Siavash Khajehhasani received his B.Sc. degree in mechanical engineering from Shahid Bahonar University of Kerman, Iran, in 2007. He graduated in mechanical engineering with an M.Sc. degree from Iran University of Science and Technology (IUST) in 2010. His master's thesis was on modeling of turbulent heat flux terms in turbulent flows related to hot sections of gas turbine engines. He joined the Aero-Thermal Management Laboratory at Ryerson University in September 2011. The focus of his research was on CFD analysis of the flow and thermal characteristics of film cooling through designing and developing novel film cooling hole geometries to increase film cooling effectiveness and reduce aerodynamics losses. He completed his Ph.D. titled “Numerical Modeling of Innovative Film Cooling Hole Schemes” in June 2014 under the supervision of Prof. Bassam Jubran. His research interests are in gas turbine thermal management, film cooling, impinging jets, and aerodynamics.
Bassam Ali Jubran
Bassam Ali Jubran was educated at Cardiff University (formally University of Wales), Britain, graduating in 1980 with a B.Sc. honours degree in mechanical engineering. He obtained a Ph.D., also from the University of Wales, in 1984. He has more than 30 years of experience in leadership, research, and teaching positions. He is currently a professor of thermo-fluid engineering at Ryerson University, a member of the Professional Engineers of Ontario, and a member of the American Institute of Aeronautics and Astronautics (AIAA). He served as editor-in-chief of the Journal of Engineering Research, and was on the editorial board of the International Journal of Low Carbon Technologies. He is currently on the editorial board of the International Journal of Mathematics in Engineering, Science and Aerospace. He received the Hisham Hijjawi Award in the field of Energy and Informatics, 1997, and the Shoman Award for Young Arab Scientists (Engineering Sciences), 1994. He has published more than 100 refereed journal papers and more than 50 conference proceedings papers.