Study on Aerodynamic and Cooling Performance of Turbine Blade Squealer Tip with Film Cooling Pulsation Characteristics Considered

To study how the pulsating coolant extracted from the compressor affect the flow and cooling characteristics of the squealer tip of a gas turbine blade, the aerodynamic and cooling performance of the turbine blade squealer tip with film cooling pulsation characteristics is studied by numerically solving three-dimensional unsteady Reynolds-averaged Navier-Stokes (URANS) equations and using the standard k-ω turbulence model. Nine film holes are arranged along the middle camber line of the squealer tip at equal intervals, and sinusoidal function is used to describe the discipline of the coolant pulsation. The tip film cooling effectiveness and total pressure loss coefficient are compared and studied at three pulsating amplitudes and five pulsating frequencies. The results show that there are obvious differences in the coolant penetration and adhesion at different instants in a pulsating cycle. When the coolant blowing ratio fluctuates slightly, the increase of the pulsating frequency changes the phase of the tip film cooling effectiveness curve, but has no effect on the overall cooling performance. However, when the coolant blowing ratio fluctuates greatly, the increase of the pulsating frequency will slightly improve the tip cooling efficiency, and affected by the delayed feedback effect, as the pulsating frequency increases to the maximum value of 2 000 Hz, the lowest value of film cooling effectiveness is increased by about 50% compared to 250 Hz during the pulsation period. The high-temperature mainstream periodically invades the coolant pipeline with the large amplitude pulsation, causing damage to the original structure of the film holes at the tip middle chord and trailing edge. The averaged total pressure loss coefficient follows the law of sinusoidal function when the coolant blowing ratio pulsates with a low frequency, the total pressure loss difference increases at varied instants with the pulsating amplitude enlargement. Meantime, the difference gradually decreases when the pulsating frequency increases. This study can provide the reference for the aerothermal performance analysis of the turbine blade squealer tip with consideration of the film cooling pulsation characteristics. © 2022, Editorial Office of Journal of Xi'an Jiaotong University. All right reserved.