Flow structure and heat transfer characteristics of sweeping and steady impingement jets with/without chevrons on a semi-circular concave surface

Abstract

Striving for improved gas turbine performance requires operating at higher gas flow temperatures, posing challenges in preserving the structural integrity of the gas turbine. To respond to these challenges, gas turbine manufacturers have turned to internal cooling and jet impingement to provide an effective solution for cooling the leading edge of the gas turbine blades. Fluidic oscillator is known for its sweeping behavior and expansive coverage of targeted surface and, thus, it can efficiently remove heat. In this study, the author numerically simulated the cooling performance of the leading edge of the gas turbine blades under constant heat flux while using four different configurations of jet impingement: a sweeping jet, a sweeping jet with chevrons, a steady jet, and a steady jet with chevrons. The results showed that the sweeping jet configuration with chevrons outperformed the steady jet configurations owing to oscillating jet impingement and a higher intensity of turbulence that increased the entrainment of jet flow. Under the configuration of a sweeping jet with chevrons, the targeted surface recorded an average Nusselt number that is 19.2% higher than the one with a steady jet without chevrons, along with a more uniform distribution of the surface temperature. The outstanding behavior of the sweeping jet with chevrons is due to the its internal flow behavior, i.e., oscillating flow nature of the sweeping jet with augmented turbulence at the exit of the chevron's nozzle.