Impact of thermal radiation on turbine blades with film cooling structures

Abstract

With increasing temperature in front of turbine blades, the impact of thermal radiation on the cooling of turbine blades continues to increase. Therefore, to ensure the long-term reliable operation of blades, the impact must be accurately evaluated. In this study, a method for separating the contribution of radiative heat flow from the total heat flow is proposed for turbine blades with different complex film-cooling structures. Here, the effect of the film hole angle on the proportion of the radiative heat flow was studied using parallel experiments and nonlinear regression methods, which allowed the radiative heat flow to be estimated with a high degree of accuracy. The method was verified by computational fluid dynamics (CFD) simulation data results showing that after considering the change in the physical properties of the boundary layer, the convective heat flow curve inclines upward along the wall temperature, and is no longer a linear function of the wall temperature. The radiative heat flow is driven by the 4th power of temperature, and the curve instead inclines downward. When the mainstream gas temperature was 1600 K, the radiant heat flow of the film cooling plate with a 30° hole angle accounted for up to 40 % of the total heat flow, with the 45° and 60° hole angles both accounting for more than 20 %. Future research must focus on the effect of thermal radiation in the heat transfer design of the blade.