Aerothermal performance of cavity tip with flow structure effects in a transonic high-pressure turbine blade

Abstract

Understanding the mechanisms of leakage flow control and heat load distribution is important in optimizing the structure of cavity tips in gas turbines. This paper investigates the aerothermal performance of cavity tip in a transonic high-pressure turbine stage. By analyzing flow structure, the effects of squealer height, squealer width and gap height on aerothermal performance are explained. It has been found that both the leakage flow and heat load distribution are influenced by the structure of vortices in the cavity. The leakage flow is controlled by the suction-side cavity vortex and the scraping vortex. The heat load distribution relates to the “M-shaped” leakage flow induced by the scraping vortex. The geometric parameters can affect the structure of vortices, which then impacts the aerothermal performance of cavity tip. As the squealer height is 2.5τ0, both the leakage flow rate and average heat transfer coefficient decrease by 0.64 % and 6.6 %, respectively. A multi-objective optimization with a feedforward neural network prediction is conducted to determine the distribution characteristics of optimal design parameters. The optimal values are approximately 2.34 for the expansion ratio, 0.5τ0 for the squealer width and 0.5τ0 for the gap height. The optimal squealer height ranges from 1.5τ0 to 2.5τ0.