Abstract
In this study, the effect of mainstream velocity on the optimization of a fan-shaped hole on a flat plate was experimentally investigated. The experiment was conducted by changing the forward expansion angle (βfwd), lateral expansion angle (βlat), and metering length ratio (Lm/D) of the film-cooling hole. A total of 13 cases extracted using the Box–Behnken method were considered to examine the effect of the shape parameters of the film-cooling hole under a 90 m/s mainstream velocity condition, and the results were compared with the results derived under a mainstream velocity of 20 m/s. One density ratio (DR = 2.0) and a blowing ratio (M) ranging from 1.0 to 2.5 were considered, and the pressure-sensitive paint (PSP) technique was applied for the film-cooling effectiveness (FCE). As a result of the experiment, the optimized hole showed a 49.3% improvement in the overall averaged FCE compared to the reference hole with DR = 2.0 and M = 2.0. As the blowing ratio increased, the hole exit area tended to increase, and this tendency was the same as that in the 20 m/s mainstream condition.
Highlights
Modern gas turbine engines have a tendency to incorporate continuously increasing turbine inlet temperatures to improve efficiency, which causes the gas turbine blades to be exposed to high thermal loads
Film cooling protects the blade surface by injecting coolant with relatively low temperatures compared to the high temperature combustion gas through a small hole on the blade surface [3]
When the compressed air stored in the air tank entered the test secsection, target velocity could be maintained by adjusting the control valve opening tion, thethe target velocity could be maintained by adjusting the control valve opening degree tion, the target velocity could be maintained by adjusting the control valve opening degree degree
Summary
Modern gas turbine engines have a tendency to incorporate continuously increasing turbine inlet temperatures to improve efficiency, which causes the gas turbine blades to be exposed to high thermal loads. Park et al [14] derived an optimized fan-shaped hole by analyzing the effects of the βfwd , βlat , and Lm /D on the FCE with an injection angle (α) of 30◦. They showed that the optimized hole resulted in a 52.4% improvement in the overall averaged FCE compared to the reference hole. Of the fan-shaped hole with βlat = 10 They applied the response surface methodology and the Kriging method to derive the optimized hole shapes, and they showed that the FCE of the optimized holes had improved by 4.5% and 7.5%, respectively, compared to the reference hole. The obtained results were compared with those from the low-speed conditions of Park et al [14]
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