Publicado 18 números por año
ISSN Imprimir: 1064-2285
ISSN En Línea: 2162-6561
Indexed in
NUMERICAL INVESTIGATION OF FILM COOLING SUBJECT TO BULK FLOW PULSATIONS
SINOPSIS
One of the important parameters that affects the gas turbine blades film cooling is the behavior of the main flow. Due to the blade rotation, a periodical frequency is moving through the main flow. In this study, a numerical simulation is used to investigate the effect of the bulk flow pulsations on film cooling. The study is carried out on a flat plate surface with a simple cylindrical hole inclined by 30° with the direction of the main flow stream. The study is carried out at blowing ratios of 0.5, 1.0, and 2.0. The free stream Strouhal number ranged from 0 to about 0.49, and the coolant Strouhal number ranged from 0 to 4.1 compared to 0.2-6.0 for the operating turbine range. The free stream is represented by a sinusoidal profile with pulsation velocity amplitude in the free stream of ± 20% of the time-averaged free stream velocity. The realizable k-ε model is used to solve the momentum equation. A comparison with previous experimental studies is presented to verify the numerical model. The results show that the pulsating flow has a significant effect on the film cooling performance for pulsating frequency higher than 35 Hz. For pulsating frequency higher than 35 Hz, at blowing ratio 0.5, as the pulsating frequency increases, the film cooling effectiveness decreases while at blowing ratio 2.0, the film cooling effectiveness increases with increasing pulsating frequency. The reduction in the overall-time averaged film cooling effectiveness at pulsating frequency 75 Hz with blowing ratio equal to 0.5 is about 49.7% of the film cooling at zero pulsating frequency, while the increase in it at the pulsating frequency 75 Hz with blowing ratio equal to 2 is about 108%.
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