利用红外热像仪测试了冠齿喷嘴射流冲击平直靶面的对流换热特性，在射流雷诺数为5 000~20 000、冲击间距比为1~8范围内，与普通圆管射流进行了对比，并对冠齿数和冠齿长度的影响进行了初步分析。研究结果表明，冠齿射流冲击对流换热显著高于圆形射流，在小冲击间距下，冠齿射流冲击的局部对流换热系数分布在冲击驻点附近呈现明显的梅花瓣状特征，当射流冲击间距比达到4以后，冠齿射流的局部对流换热系数分布则呈现出常规圆形射流冲击的特征；以2倍或4倍射流直径作为区域平均范围，冠齿射流的区域平均努塞尔数相对圆形射流的增加幅度在15%~30%之间，相对增加幅度与射流雷诺数和射流冲击间距比相关；在本文的冠齿结构参数范围内，冠齿伸出长径比为0.6的6-冠齿结构取得的射流冲击强化传热效果较优。
An experimental investigation of chevron nozzle jet impingement heat transfer on a flat surface was performed by using the infrared camera. The tests were conducted with typical Reynolds numbers ranging from 5 000 to 20 000 and dimensionless nozzle-to-surface distances ranging from 1 to 8. A comparison with the round nozzle jet was made, and the geometric effects of the chevron nozzle were analyzed. The results show that the chevron nozzle plays a significant role in improving jet impingement heat transfer. At small impinging distances, the distribution of local convective heat transfer produced by the chevron-jet shows an obvious lobe-shaped feature in the vicinity of the impinging stagnation point. When the dimensionless nozzle-to-surface distance is beyond 4, distribution of local convective heat transfer produced by the chevron-jet is similar to that by the round jet. The averaged Nusselt number of the chevron nozzle jet area of either 2 or 4 times of the nozzle diameter for average achieves 15%-30% increase compared to that of the round nozzle jet, and the increase depends on the jet Reynolds number and dimensionless nozzle-to-surface distance. For the current geometric parameters of the chevron nozzle, it is found that the 6-chevron nozzle with a chevron length-to-nozzle diameter of 0.6 can produce more favorable heat transfer enhancement.
[1] VISKANTA R. Heat transfer to impinging isothermal gas and flame jets[J]. Experimental Thermal and Fluid Science, 1993, 6(2):111-134.
[2] BUNKER R S. Gas turbine heat transfer:Ten remaining hot gas path challenges[J]. ASME Journal of Turbomachinery, 2007, 129:193-210.
[3] FREGEAU M, GABR M, PARASCHIVOIU I, et al. Simulation of heat transfer from hot-air jets impinging a three-dimensional concave surface[J]. Journal of Aircraft, 2009, 46:721-725.
[4] WEIGAND B, SPRING S. Multiple jet impingement-A review[J]. Heat Transfer Research, 2011, 42:101-142.
[5] CARLOMAGNO G M, IANIRO A. Thermo-fluid-dynamics of submerged jets impinging at short nozzle-to-plate distance:A review[J]. Experimental Thermal and Fluid Science, 2014, 58:15-35.
[6] COLUCCI D W, VISKANTA R. Effect of nozzle geometry on local convective heat transfer to a confined impinging air jet[J]. Experimental Thermal and Fluid Science, 1996, 13:71-80.
[7] BRIGNONI L A, GARIMELLA S V. Effects of nozzle-inlet chamfering on pressure drop and heat transfer in confined air jet impingement[J]. International Journal of Heat and Mass Transfer, 2000, 43:1133-1139.
[8] LEE J H, LEE S J. The effect of nozzle configuration on stagnation region heat transfer enhancement of axisymmetric jet impingement[J]. International Journal of Heat and Mass Transfer, 2000, 43:3497-3509.
[9] GAO N, SUN H, EWING D. Heat transfer to impinging round jets with triangular tabs[J]. International Journal of Heat and Mass Transfer, 2003, 46:2557-2569.
[10] YU Y Z, ZHANG J Z, XU H S. Convective heat transfer by a row of confined air jets from round holes equipped with triangular tabs[J]. International Journal of Heat and Mass Transfer, 2014, 72:222-233.
[11] YU Y Z, ZHANG J Z, SHAN Y. Convective heat transfer of a row of air jets impingement excited by triangular tabs in a confined crossflow channel[J]. International Journal of Heat and Mass Transfer, 2015, 80:126-138.
[12] ZAMAN K B M Q, BRIDGES J E, HUFF D L. Evolution from ‘tabs’ to ‘chevron technology’-A review[J]. International Journal of Aeroacoustics, 2011, 10:685-710.
[13] KONG F S, JIN Y Z, SETOGUCHI T. Numerical analysis of chevron nozzle effects on performance of the supersonic ejector-diffuser system[J]. Journal of Thermal Science, 2013, 22:459-466.
[14] 单勇, 张靖周, 邵万仁, 等. 冠状喷口抑制涡扇发动机喷流噪声试验和数值研究[J]. 航空学报, 2013, 34(5):1046-1056. SHAN Y, ZHANG J Z, SHAO W R. Experimental and numerical research on jet noise suppression with chevron nozzle for turbine engines[J]. Acta Aeronautica et Astronautica Sinica, 2013, 34(5):1046-1056(in Chinese).
[15] VIOLATO D, SCARANO F. Three-dimensional evolution of flow structures in transitional circular and chevron jets[J]. Physics of Fluids, 2011, 23(12):124104.
[16] VIOLATO D, IANIRO A, CARDONE G, et al. Three-dimensional vortex dynamics and convective heat transfer in circular and chevron impinging jets[J]. International Journal of Heat and Fluid Flow, 2012, 37:22-36.
[17] GUAN T, ZHANG J, SHAN Y, et al. Conjugate heat transfer on leading edge of a conical wall subjected to external cold flow and internal hot jet impingement from chevron nozzle-Part 1:Experimental analysis[J]. International Journal of Heat and Mass Transfer, 2017, 106:329-338.
[18] GUAN T, ZHANG J, SHAN Y. Conjugate heat transfer on leading edge of a conical wall subjected to external cold flow and internal hot jet impingement from chevron nozzle-Part 2:Numerical analysis[J]. International Journal of Heat and Mass Transfer, 2017, 106:339-355.
[19] VINZE R, CHANDEL S, LIMAYE M D, et al. Local heat transfer distribution between smooth flat surface and impinging incompressible air jet from a chevron nozzle[J]. Experimental Thermal and Fluid Science, 2016, 78:124-136.
[20] 李鑫郡, 张靖周, 谭晓茗. 单个压电风扇传热特性研究[J]. 航空学报, 2017, 38(7):205-214. LI X J, ZHANG J Z, TAN X M. Characteristics of heat transfer with a single piezoelectric fan[J]. Acta Aeronautica et Astronautica Sinica, 2017, 38(7):205-214(in Chinese).
CJA