This is the second in a two part series investigating heat transfer and film cooling on a gas turbine shroud with a blade rotation speed of 1200 RPM. In this paper, the effect of coolant injection on a shroud using forward, backward and laterally oriented holes embedded in trenches is studied. Four injection configurations (θ = 45° and ϕ = 0°, 90°, 180°, 270°), each with cooling holes arranged in four rows in a staggered pattern are tested. Each row of cooling holes is embedded in a trench with a trench width of 3 hole diameters and a trench depth of 0.75 hole diameter. For each configuration, detailed heat transfer coefficient and film cooling effectiveness measurements are reported for nominal blowing ratios of 0.5, 1.0, 1.5 and 2.0. The results show that trenching increases the local film cooling effectiveness in and immediately around the trenches in all configurations studied. Trenching the coolant holes also does have varying effects on the heat transfer coefficients based on the direction of coolant injection. Generally, trenching does increase the heat transfer coefficient when compared to both the no-coolant and baseline injection cases especially in the entrenched region. Trenching does provide the best results for forward injection where the reduced jet momentum results in a more two dimensional and better lateral coolant spread when compared to the baseline case. With the increased lateral coolant spread does come an increase in the overall film cooling effectiveness but also a corresponding increase in the heat transfer coefficients in the near-trench region as it acts as a turbulence promoter. Embedding backward facing holes in trenches does result in higher local film cooling effectiveness in and around the trenches. However, trenching does decreases the persistence and penetration of the coolant coverage in the streamwise direction. Trenching also results in higher than baseline heat transfer values for backward injection. Trenching also does improve the cooling effectiveness in the trenches for both lateral injection methods.
Turbine Shroud Heat Transfer and Cooling With Blade Rotation: Part II — Effect of Trenched Holes With Forward, Backward and Lateral Injection
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Tamunobere, O, & Acharya, S. "Turbine Shroud Heat Transfer and Cooling With Blade Rotation: Part II — Effect of Trenched Holes With Forward, Backward and Lateral Injection." Proceedings of the ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. Volume 5A: Heat Transfer. Charlotte, North Carolina, USA. June 26–30, 2017. V05AT13A013. ASME. https://doi.org/10.1115/GT2017-65107
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