Measurements of Heat Transfer Coefficients in Rib-Roughened Trailing-Edge Cavities With Crossover Jets

Abstract

Liquid crystals were used in this experimental investigation to measure the local and average heat transfer coefficients on the walls of six test sections simulating the trailing edge cooling cavity of a modern turbine blade. All test sections had trapezoidal cross sectional areas with two rows of racetrack-shaped slots on two opposite bases. Crossover jets, issued from the slots on one base, impinged on the test section rib-roughened walls and exited from the slots on the opposite wall. The first test section had all smooth walls and served as a baseline. The remaining five test sections were rib-roughened on either one wall or two opposite walls simulating the pressure and suction sides of the blade trailing-edge cooling cavity. In the first four tests, the jets issued into the test section along the test section plane of symmetry. Therefore, the two opposite walls, simulating pressure and suction sides of the blade, saw the same jet effects. This symmetric pattern was altered in test sections 5 and 6 in which the jets were tilted towards one or the other wall at an angle of 6°. The ribs in the roughened test sections, covering only 62% of the wall span, were mounted to the surface with an angle of attack to the jet axis, α, of 30°. The objective of this study was to investigate the effects that crossover jets have on the heat transfer coefficient and pressure recovery in a cooling cavity of a modern gas turbine blade. Major conclusions of this study were that combining the crossover jets with rib-roughened surfaces can be an effective method of cooling the trailing edge cavities and by proper arrangement of the jets and ribs, heat transfer coefficients on the two opposite walls can be tailored.