Experimental and numerical study on heat transfer in trailing edge cooling passages with dimples/protrusions under the effect of side wall slot ejection

Combined experimental and numerical studies were conducted on the heat transfer and pressure performance in gas turbine trailing edge rectangular and trapezoidal cooling passages with ejection slots. Considering the space restrictions inside narrow cooling channel near trailing edge and pressure drop considerations, dimple and protrusion structures are adopted as heat transfer enhancement devices inside cooling channel. Experimental study is based on transient infrared thermography technique and numerical study is based on RANS method using commercial software CFX. In this study, rectangular channel and trapezoidal channel are both investigated with and without ejection slots. The effects of channel cross-section, roughened structures and slot ejection are considered. From the results, the flow characteristics near roughened structures and ejection slots are obtained. Mechanisms of heat transfer enhancement are explained according to specific flow patterns. Meanwhile, the Nusselt number distributions on channel surface are presented by both methods. The heat transfer enhancement capability of each channel configuration is evaluated and comparisons of infrared results and numerical predictions are made. Finally, the channel overall heat transfer coefficient and friction ratio are evaluated on each configuration. Summarizing the results, it can be estimated that, the cooling performance inside trailing edge internal cooling passages can be elevated by arranging dimples and protrusions, or the combination with other typical devices such as ribs or pin-fins.