Impact of distance on heat transfer at the leading edge of blades in a rotating state

To enhance the high-temperature capability of turbine blades and meet the requirements of advanced design, this research examines the intricate flow characteristics and the heat transfer occurring on the internal walls effects of leading-edge impingement cooling structures under different impingement distances. In this study, copper block method is employed for heat transfer testing, extending the testing range of rotating impingement cooling channels from Redj = 1 × 104, Ro = 0.2 to Redj = 5 × 104, Ro = 2.0. The findings reveal that the Nusselt number along the channel is significantly influenced by flow distribution and turbulence intensity. At lower Re (Re ≤ 2 × 104), the flow velocity increases along the channel due to the decrease in pressure drop, resulting in enhanced heat transfer. However, at higher Re (Re ＞ 2 × 104), increased flow rate leads to intensified turbulence and thickening of the boundary layer, consuming fluid energy and reducing the temperature difference, thereby adversely affecting heat exchange around the impingement holes. Moreover, Nu decreases with increasing rotation speed, with the highest average decrease of 15.3 % when Ro reaches 0.25. For cases where Redj ＜ 4.3 × 104, an impingement distance-to-diameter ratio (Z/D) = 2 exhibits optimal heat transfer performance. Conversely, when Redj＞4.3 × 104, the influence of impingement distance will diminish. Larger impingement distances increase the HTC but are accompanied by increased non-uniformity. Therefore, selecting an appropriate impingement distance can reduce boundary layer formation and flow separation, thereby forming an optimal flow structure, which contributes to promoting heat exchange and improving heat transfer uniformity. A correlation based on geometrical parameters has been proposed to predict the average Nusselt number for jet impingement arrays with varying geometrical configurations.