Abstract
Hot streaks and rotor–stator interaction have a great influence on the aerothermal performance of turbine blades. Previous investigations have conducted limited study of the film-cooled blade. To investigate the combined effects of a hot streak and rotor–stator interaction on the coated blade, an unsteady numerical simulation has been conducted with an efficient unsteady Navier–Stokes solver in this paper. The numerical results at four different relative stator–rotor locations (t = 0/4 T, 1/4 T, 2/4 T, and 3/4 T) have been investigated in one stator period. Compared with the stator, rotor–stator interaction exerts a significant impact on the cooling performance of the rotor blade under hot streak inlet conditions. The overall cooling effectiveness distribution of the coated rotor blade is similar to that of the uncoated blades in one stator period. Relatively lower overall cooling performance of the rotor blade can be observed in the 1/4 stator period. Then, the cooling performance begins to increase and relatively larger cooling effectiveness can be observed in the 3/4 stator period. The addition of a TBC is generally beneficial to the improvement of blade surface cooling performance, especially for the areas with low overall cooling performance. However, a negative cooling effectiveness increment can be observed at the trailing edge. It shows that for an area with poor cooling performance, the addition of thermal barrier coating will have the opposite effect. Therefore, it is necessary to enhance the design of cooling arrangements at the trailing edge to maximize the insulation performance of TBCs for the coated rotor blade.
Highlights
Due to the continuing demand for higher thermal efficiency, the turbine inlet temperature has far exceeded the melting point of the metal material [1,2,3]
The results showed that unsteady film cooling effectiveness fluctuations at the leading edge (LE) region are the most significant, with the mean-to-peak fluctuation amplitude reaching over ±100%
Since both the internal heat conduction and the convection heat transfer have been considered in the unsteady calculation, the temperature distribution of the numerical results can directly reflect the flow and heat transfer effects in the turbine stage
Summary
Due to the continuing demand for higher thermal efficiency, the turbine inlet temperature has far exceeded the melting point of the metal material [1,2,3]. Wang et al [16] carried out the unsteady computational study of hot streaks at different turbulence intensities and different circumferential positions They found that the hot streak’s relative position affects the airfoil surface temperature variations and the vane and blade mid-span HTC. Wang et al [17] studied the combined effect of the hot streak and the swirling flow on the cooling performance of rotor blades They concluded that the heat transfer environment of rotor blades shows great differences with different inlet swirl directions. For the coated rotor blade, a wide variety of factors are known to contribute to the complexity of aerothermal and TBC insulation performance, which include the hot streak, the residual swirl, high levels of mainstream turbulence and unsteadiness, rotational effects, and rotor–stator interaction [22,23,24,25,26]. Coatings 2022, 12, 25 trying to provide a guideline for the design of the cooling arrangements to maximize the insulation performance of TBCs under the hot streak inlet condition
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