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Effect of cavity depth on thermal performance of a cooled blade tip under rotation

Sakaoglu, Sergen
Kahveci, Harika Senem
In this paper, the effect of cavity geometry of a squealer blade tip on its thermal performance is investigated. Numerical analyses were performed for three depth-to-width ratios for a cooled squealer tip. Also investigated is the effect of cooling introduction into the flow tip and the effect of rotation via the comparison of stationary and rotational domains where the latter was simulated by rotating the blade. The rotational speed and boundary conditions used in the numerical study are chosen to represent the turbine operating environment. The blade tip used had a cooling configuration consisting of seven holes of the same size located on the tip near the blade pressure side. The study presents a discussion on the flow physics within the tip gap and heat transfer on the blade tip. Film-cooling performance of the considered blade tip geometries is demonstrated using distributions of film-cooling effectiveness. It is observed that both the rotation and the addition of cooling at the tip significantly alter the tip gap flow, which is found to have a strong effect on the blade tip heat transfer. The addition of cooling increased the heat transfer coefficient on the blade tip, while an increase in the rim height resulted in higher film effectiveness since the amount of leakage flow entering the cavity floor was reduced.