573 / 2019-01-18 14:23:40

Film-Cooling Effects Evaluation for Different Shaped-holes Under Real Gas Turbine Vane Working Conditions

Shaped-hole; Cooling efficiency; Film cooling; Numerical simulation

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In the cooling design of modern gas turbine vanes, film cooling plays an important role by protecting vane surface through isolating vane surface from hot gas. The shape of the cooling hole affects film-cooling efficiency directly. To find an optimized film cooling geometry candidate, a series of numerical investigations of different shaped-holes were carried out in this research. Firstly, Numerical simulation results of cooling performance for 4 different shaped-holes on a simplified plate model under 3 different blowing ratios (Br=1.5~2.5) were analyzed. Trapezoid hole with 10︒ outlet angle, trapezoid hole with 20︒ outlet angle, rectangle section inlet hole with 14︒expansion angle, tapered slot cooling hole were investigated. It was found that trapezoid hole with 10︒ outlet angle had a steady performance over a wide range of blowing ratios yet cooling coverage downstream was relatively narrow. Tapered slot cooling hole showed an outstanding cooling efficiency for its broad coverage and steady jet flow under wide blowing ratio working ranges. Based on those simplified plate model results, 3 kinds of different cooling hole geometries were applied on a real sized gas turbine vane model under real working conditions. Shaped-hole geometries include trapezoid hole with 10︒ outlet angle, trapezoid hole with 15︒ outlet angle and tapered slot cooling hole. In the same blowing ratio, the tapered slot cooling holes still showed the best cooling efficiency of all hole candidates been studied. But if we considered both the characteristics of coolant air consumption and heat shield effects, the tapered slot holes cooling design was found to have too large coolant air consumption. With the same cooling air consumption, the taped slot cooling holes distribution was very hard to satisfy the cooling efficiency requirement. It seemed that tapered slot hole was not practical for real gas turbine vane cooling design under real working conditions. On the contrary, Multi-row trapezoid hole with 10︒-15︒ outlet angle seemed to be better for its uniform cooling effect. Considering both coolant air consumption and film-cooling efficiency, an optimized shaped film cooling hole was recommended.