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Enhancing film cooling effectiveness in a gas turbine end-wall with a passive semi cylindrical trench

Computational studies were carried out in the end-wall of a linear cascade, of chosen blade profile, which is provided with one row of cylindrical film cooling holes inclined at 30o to the end wall. CO2 gas was used as the coolant supplied through the film holes, maintaining a blowing ratio of 0.6. The film cooling hole row was positioned at the leading edge of the cascade. The mainstream fluid was air and based on its properties at the cascade inlet, the flow was found turbulent. A semi cylindrical trench was placed at two positions upstream of the cascade leading edge and three positions downstream of it. Ansys Fluent 15.0 was used to compute the film cooling effectiveness of the cascade end-wall. Trench positioned at a distance of twice that of film hole diameter, was found to show a highest increase of area averaged effectiveness value by 30.4% over the baseline. Further to this, the influence of the trench diameter was carried out where the trench with diameter twice that of film hole diameter was found to show a 31.3% increase of cooling effectiveness over the baseline. Studies on the influence of blowing ratio showed a highest increment of cooling effectiveness value by 43.5% over the baseline a blowing ratio of 1.2.
PAPER REVISED: 2017-09-13
PAPER ACCEPTED: 2017-12-28
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