Abstract
The present work has been performed to evaluate the effect of three shaped holes (cylindrical hole, expansion-shaped hole and fan-shaped hole) with forward injection and backward injection on film cooling effectiveness on the adiabatic wall flat plate. All the cases are computed under eight blowing ratios (M) = [0.25, 0.5, 0.75, 1.0, 1.25, 1.5, 1.75 and 2.0]. The results show that for film cooling hole structure with backward injection, a pair of rotating vortex is formed at the outlet of film cooling hole. Differing from the classical counter rotating vortex pair (CRVP) found in each hole with forward injection, the vortexes are expanded away from the test wall under the function of transverse main flow and are broken quickly. It indicates that the rotating vortex pair does not promote the mixing of main flow and jet flow. The uniformity of local film cooling effectiveness of the hole with backward injection is higher than that of the hole with forward injection. In terms of the spatially averaged film cooling effectiveness with a certain hole shape, the value under backward injection exceeds that under forward injection at a certain point: (1) M=0.5 for cylindrical hole, (2) M=0.75 for expansion-shaped hole and (3) M=1.25 for fan-shaped hole. The comparison of the calculation results of different holes with backward injection shows that in the case of high blowing ratio, a uniform distribution with higher film cooling effectiveness is easier to achieve with fan-shaped hole.
Highlights
Increasing the turbine inlet temperature is one of the important technical approaches to improve the engine’s integrated performance
Based on three kinds of shaped holes, the impact of jet flow on film cooling effectiveness along the forward injection and backward injection are analyzed in the present paper
The conclusions are summarized as follows: (1) For film cooling hole structure with backward injection, a pair of rotating vortex is formed at the outlet of film cooling hole
Summary
Increasing the turbine inlet temperature is one of the important technical approaches to improve the engine’s integrated performance. Gritsch et al. demonstrated that the spanwise averaged film cooling effectiveness of laid-back fan shaped hole improved with blowing ratio from 0.5 to 1.5, which is contrary to the cylindrical hole. This is mainly attributed to the decreased jet momentum and lateral spreading of the jet flow. It is obviously that there would be a higher momentum loss in jet flow with backward injection, the jet flow spreads in the spanwise direction, resulting a higher spanwise averaged film cooling effectiveness. This work mainly focuses on the effect of jet flow injecting way on fluid flow, heat transfer and film cooling performance under each shape hole with backward and forward injection. The variation tendencies for film cooling effectiveness in blowing ratios are discussed
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