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Abstract
<jats:p>The object of this study is the film cooling process on a flat plate. The subject of this study is the effect of film-cooling hole design in gas turbine blades with a thermal barrier coating on cooling efficiency. Four variants of the hole-thermal barrier coating pair are considered, along with their impact on cooling efficiency. The first option is an advanced technology for drilling holes through the existing TBC, which is geometrically equivalent to a hole in a blade without TBC. The second option is the traditional method of applying the TBC after the holes have been drilled, which results in partial blockage of the holes and deflection of the air jet away from the surface being cooled. Other options include applying the TBC after drilling the holes, creating a shallow trench with a depth of 0.4D. The study examines two types of trenches: ideal and wide. The above-mentioned hole-TBC pair configurations are considered for four types of holes: a standard cylindrical hole, a backward (upstream) cylindrical hole, and shaped holes of the laidback fan-shaped type with expansion angles of 7° (7-7-7 hole) and 15°. The objective of this study is to determine the extent to which different designs of the hole-TBC pair affect cooling efficiency. To achieve this goal, a numerical simulation method was chosen, and a series of numerical experiments was conducted using the commercial 3D CFD solver Ansys Fluent 2024 R2 in a steady-state configuration, employing the k−ε realizable turbulence model with enhanced wall function. Based on the results of the analysis, it can be concluded that for both forward and backward cylindrical holes a trench in the TBC layer improves cooling efficiency. A trench in the TBC layer for hole 7-7-7 is only beneficial at high blowing ratio (m > 1.5). For a wide fan-shaped hole with expansion angles of 15° and blowing ratio of m > 1.0, a very significant negative effect from hole blockage is observed; at the same time, the use of a trench demonstrates a substantial increase in the cooling efficiency of this type of hole. The practical value of this study lies in the ability to incorporate the data obtained into the film-cooling calculation methodology to more accurately predict efficiency for the specific hole-drilling technology used. </jats:p>