Abstract
The influence of the HS (hot streak) and unsteady wake on the overall cooling performance of a rotor blade was studied in this paper. The results show that: (1) Both the magnitude and temperature of the HS gradually drops down as it passes downstream of the vane passage. (2) Within one stator period, the highest cooling performance of the blade can be observed at the initial time points, when the LE (leading edge) of the blade turns towards the trailing edge of the vane. (3) The lowest cooling performance of the blade can be observed at the time point 0.5 T, when the LE of the blade turns towards the center of the vane passage. (4) Surface temperatures in areas with unfavorable local heat flow are usually higher than the temperature of the coolant. The additional TBCs may exert adverse effects on heat dissipation from the substrate metal to the mainstream, which has a negative effect on the improvement of the overall cooling effectiveness of the coated blade. (5) Within a stator period, a relatively higher overall cooling effectiveness increment due to the coating can be observed at the relative location with lower cooling performance. Consequently, the additional TBCs are beneficial for decreasing the surface temperature difference and thus controlling the thermal stress under the HS inlet condition.
Highlights
To achieve higher performance and efficiency, the gas temperature of the turbine stage inlet far exceeds the melting point of the metal material [1,2]
The highest cooling performance of the blade could be observed at the initial time points of each stator period, when the LE of the blade turned towards the trailing edge of the vane
The lowest cooling performance of the blade could be observed at the time point 0.5 T, when the LE of the blade turned towards the center of the vane passage
Summary
To achieve higher performance and efficiency, the gas temperature of the turbine stage inlet far exceeds the melting point of the metal material [1,2]. Shi [7] researched the comprehensive effects of multi-layer TBCs on the cooling performances of C3X vane with film cooling; they concluded that the additional thermal barrier coatings can both reduce the surface temperature of the blade and have the opposite effect. Griffini [10] studied the cooling performance of turbine blades with film cooling under the HS effect They concluded that the HS exerted the greatest influence on the LE of the vane heat load distribution when the HS directly faces the LE of the vane. Most of the current literature only focuses on the influence of the HS on the cooling performance of the uncoated vane or blade, and few studies have focused on the coated blade [17,18] Based on these viewpoints, unsteady numerical simulation has been applied to the gas turbine stage with rows of the NASA C3X guide vane and a VKI rotor blade in this study. The influence of the HS and unsteady wake on the overall cooling performance of four different time points within one stator period have been studied to reveal the influence of the HS on TBC insulation and overall cooling performance of the coated blade
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