Study on the film superposition method for dense multirow film Hole layouts

The film superposition method is an important tool in the design of film cooling structures. The method can quickly predict the temperature at the film cooling surface and reduce the number of iteration cycles required when designing the film cooling structure. The film superposition characteristics of different dense multirow hole layouts (different pitches of rows, pitches of holes and inclinations of holes) are investigated at different blowing ratios. This study investigates the limitations of the Sellers superposition method in predicting the cooling effectiveness of dense multirow holes. This further explores and explains the main reasons for the insufficient prediction accuracy of the superposition method. The approach does not consider the spanwise diffusion of coolant or the mutual interference of jets from different rows. To quantify these two influencing factors, this study proposes two correction parameters: the spanwise nonuniformity coefficient and the streamwise dissipation rate. Implementing the superposition method with these two correction parameters can predict the cooling effectiveness of dense multirow holes more accurately. The superposition method is validated based on different types and arrangements of film holes. This study utilizes the film cooling effectiveness of single-row holes obtained through the Goldstein formula and numerical calculations to make superposition predictions and compare them with experimental data. The superposition results of single-row holes based on Goldstein's formula are in good agreement with the experimental results at a small blowing ratio, and the superposition results of single-row holes based on numerical calculations show good agreement with the experimental results. •The study proposes a superposition method for dense multi-row hole layouts.•Spanwise diffusion is quantified by the spanwise nonuniformity coefficient(α).•Streamwise dissipation rate(β) quantifies the interference of film jets.•The superposition method can quickly predict η using empirical formulas.