Numerical Study of Flow and Heat Transfer on a Blade Tip With Different Leakage Reduction Strategies

Abstract

Numerical calculations are performed to explore different strategies for reducing tip leakage flow and heat transfer on the GE-E3 High-Pressure-Turbine (HPT) rotor blade. The calculations are performed for a single blade with periodic conditions imposed along the two boundaries in the circumferential-pitch direction. Several leakage reduction strategies are considered, all for a tip-clearance of 1.5% of the blade span, a pressure ratio (ratio of inlet total pressure to exit static pressure) of 1.2, and an inlet turbulence level of 6.1%. The first set of leakage reduction strategies explored include different squealer tip configurations: pressure-side squealer, suction-side squealer, mean-camber line squealer, and pressure plus suction side squealers located either along the edges of the blade or moved inwards. The suction-side squealer is shown to have the lowest heat transfer coefficient distribution and the lowest leakage flow rates. Two tip-desensitization strategies are explored. The first strategy involves a pressure-side winglet shaped to be thickest at the location with the largest pressure difference across the blade. The second strategy involves adding inclined ribs on the blade tip with the ribs normal to the local flow direction. While both strategies lead to reduction in the leakage flow and tip heat transfer rates, the ribbed tip exhibits considerably lower heat transfer coefficients. In comparing the two desensitization schemes with the various squealer tip configurations, the suction side squealer still exhibits the lowest heat transfer coefficient and leakage flow rates.