Jet Impingement Heat Transfer Enhancement With Different Crossflow Diverter Shapes

Abstract

Abstract Impingement cooling is an effective cooling structure in gas turbine blades, but the downstream heat transfer will be reduced seriously by crossflow. It has been proven that equipping a crossflow diverter in impingement channel can make jet free from crossflow and enhance the downstream heat transfer. In this paper, in order to obtain a kind of crossflow diverter with advantageous heat transfer performance, the flow and heat transfer characteristics of four crossflow diverters (Semi-Circular (SC), Semi-Rectangular (SR), Semi-Diamond (SD) and Semi-Four-pointed Star (SFS)) are compared in detail. To this end, a Baseline impingement cooling configuration is considered, in which the pitches on the streamwise and spanwise directions of impingement jets are all 6D and the distance from jet to target surface is 2D. Through detailed numerical verification, SST k-ω turbulence model is finally selected, and all simulations are performed under Reynolds number ranging from 3,500 to 14,000. It is found that the crossflow diverter can change the local jet Reynolds number distribution and effectively reduce the local mass velocity ratio of crossflow to jet. Results reveal that the crossflow diverter increases the heat transfer and inevitably increases the friction loss, but all of them can improve the comprehensive heat transfer performance over the simulated flow range. When the Reynolds number is 14,000, the best heat transfer performance can be achieved, and the comprehensive heat transfer performance parameters of SC, SR, SD and SFS cases can increase by up to 11.0%, 14.3%, 12.2% and 14.7% respectively. After determining SFS-shaped crossflow diverter with the best comprehensive heat transfer performance, the influence of its streamwise position on heat transfer and friction loss is also studied. The SFS-shaped diverter is placed at 2D, 2.5D, 3D, 3.5D and 4D from the center of adjacent upstream jet, respectively. Results show that the heat transfer and friction loss change a little when the distance increases from 2D to 3D, but the heat transfer decreases sharply and friction loss increases seriously when the distance increases from 3D to 4D.