摘要
在给定通道雷诺数的条件下,实验研究了矩形内冷通道中截断肋片在6种不同排布方式下的换热特性,并结合三维数值模拟方法,基于流动特征深入分析了其中的对流换热机理。研究表明:6种不同排布方式下,结构2‑3‑5‑9通道的换热性能最好,结构2‑5‑3‑9通道的换热性能最差;结构2‑3‑5‑9通道的压力损失最大,结构2‑5‑9‑3通道的压力损失最小。就总体热性能而言,结构2‑9‑5‑3的最好,结构2‑3‑5‑9的次之,结构2‑5‑3‑9的最差。对流动特征的分析可知,肋片截断区域诱导的横向涡增强主流与边界层流体的掺混,强化了受热壁面与流体间的换热;截断肋片的不同方式排布使通道中流动特征不尽相同,但截断区域的涡结构基本相似。
内部对流冷却是燃气涡轮设计中最早应用的冷却技
相较于连续直肋,截断肋因能减小通道压力损失而被广泛研
本文在前期研究基础
实验系统如

图1 实验系统示意图
Fig.1 Illustration of experimental system
为表述方便,本文模型根据一个周期内4排截断肋片中每排截断肋片的个数为命名规则。如

图2 不同内冷结构示意图
Fig.2 Illustration of different internal cooling structures
对采集到的液晶图片进行处理,得到测试段通道壁面的温度和壁面换热系数,液晶的具体校准过程及校准结果参见文献[
实验过程中通道入口平均速度u0通过以下公式获得
(1) |
式中:umax和
通道雷诺数定义如下
(2) |
式中:ρ、μ和Dh分别为空气的密度、动力黏度以及通道的水力直径。
壁面对流换热系数定义为
(3) |
式中:qw和qloss分别为测试段壁面施加的热流密度以及测试段的热损失。壁面温度Tw通过对液晶图片进行处理得到,流体参考温度Tf由以下公式给出
(4) |
式中:Tin为通道入口流体温度,由温度计测得;Q、Lheated和cp分别为测试段的加热功率、测试段长度和空气的比热容;H和W分别为通道的高度和宽度。
壁面努塞尔数定义为
(5) |
式中λ为空气的导热系数。
范宁摩擦因数定义为
(6) |
式中:Δp为两测压孔间的压降,L为两测压孔的距离。本文将选取Dittus‑Boelter公式和Blasius公
实验误差由文献[

图3 计算模型及边界条件
Fig.3 Computational model and boundary conditions
采用商用软件ANSYS ICEM CFD 17.2对计算域进行结构化网格划分,且加密近壁面网格以确保

图4 结构2‑3‑5‑9的网格划分及独立性验证结果
Fig.4 Mesh adopted in simulations and mesh independent test for Case 2‑3‑5‑9
为验证本文的数值模型,以结构2‑3‑5‑9的实验数据为基础,比较不同湍流模型下计算得到的测试段表面无量纲努塞尔数及其展向平均值。由

图5 比较结构2‑3‑5‑9实验和数值模拟结果中通道底面的努塞尔数云图及展向平均分布图
Fig.5 Validation of numerical model by comparing the Nusselt number contours and laterally averaged Nusselt number on the bottom wall of the test section for experimental and numerical results for Case 2‑3‑5‑9

图6 实验得到的不同结构测试段表面努塞尔数分布云图
Fig.6 Nusselt number distribution contours for considered six cases by LCT experiment
为定量比较不同结构下肋片下游的换热特性,

图7 比较图6中不同结构的努塞尔数云图对应的努塞尔数展向平均分布
Fig.7 Comparisons of laterally‑averaged Nusselt number distributions corresponding to the contours shown in Fig.6 for different structures
为明晰截断肋片不同排布方式下的流动换热机理,

图8 测试段底面不同结构的流线图以及y = 0.003 mm的x‑z平面上流体的速度分布云图比较
Fig.8 Surface streamline on the bottom wall and velocity magnitude contours on a x‑z plane at y = 0.003 mm of test section for considered structures

图9 测试段不同结构在y = 0.003 mm的x‑z平面上的湍流动能分布云图
Fig.9 Local turbulence kinetic energy distributions on a x‑z plane at y = 0.003 mm of test section for considered cases
为了更好地理解不同排布方式下的流动特性,
(7) |
式中:pref为通道入口压力,qref为通道入口动压。由图可见,通道中低压力系数区域位于截断肋后回流区,该区域流体湍流动能小、换热差;高压力系数区域位于截断肋前侧冲击区以及相邻两排肋片间流体的再附着区,由于肋片前后压力梯度的作用,流体绕过截断区域,在肋后形成横向涡。此外,由图可知,即使每排截断肋肋片个数相等,由于4排截断肋片排布方式的差异,肋后压力系数分布也有所差异,这与

图10 测试段底面不同结构的压力系数分布云图
Fig.10 Pressure coefficient distributions on the bottom wall of test section for considered cases

图11 不同内冷结构通道中4个y‑z截面上的流线图及湍流动能分布图,4个y‑z截面分别为X/P=1,2,3和4
Fig.11 Streamline and TKE distributions on four y‑z planes, i.e., X/P=1,2,3 and 4 for the considered cases
本文通过实验结合数值模拟的方法,在给定内冷通道雷诺数的条件下,研究了构形截断肋中4排截断肋片的6种不同排布方式下的换热特性和流动换热机理,得到以下结论:
(1)在6种排布方式中,结构2‑3‑5‑9的换热性能最好,结构2‑9‑5‑3的换热性能次之,结构2‑5‑3‑9的换热性能最差;结构2‑3‑5‑9通道的压力损失最大,结构2‑9‑5‑3通道的压力损失次之,结构2‑5‑9‑3通道的压力损失最小;结构2‑9‑5‑3的总体热性能最好,结构2‑3‑5‑9的次之,结构2‑5‑3‑9的总体热性能最差。
(2)截断区域的存在使得肋片后方产生负压梯度,肋后形成一对反向旋转的横向涡,对流体产生剧烈扰动,通道中主流流体与边界层内流体的掺混得到增强;截断肋的不同排布方式下流体的流动特征不同,但其在截断区域所诱导的涡结构相似。
参考文献
林宏镇,汪火光,蒋章焰.高性能航空发动机传热技术[M].北京:国防工业出版社,2005. [百度学术]
LIN Hongzhen, WANG Huoguang, JIANG Zhangyan. Heat transfer technology of high performance aero‑engine[M]. Beijing: National Defense Industry Press, 2005. [百度学术]
XIE Changtan, XUE Shulin, YANG Weihua. Experimental investigation on convective heat transfer characteristics in ribbed channel[J]. Transactions of Nanjing University of Aeronautics and Astronautics, 2018, 35(6): 962‑972. [百度学术]
席雷,徐亮,高建民,等.涡轮叶片厚壁带肋通道冷却性能的实验研究[J].西安交通大学学报,2021,55(3): 29‑36. [百度学术]
XI Lei, XU Liang, GAO Jianmin, et al. Experimental study on the cooling performance of thick‑wall ribbed channel in turbine blade[J]. Journal of Xi'an Jiaotong University, 2021, 55(3): 29‑36. [百度学术]
张勃,吉洪湖,张靖周,等.网格式肋化通道换热与总压损失特性研究[J].航空动力学报,2004,19(2):201‑205. [百度学术]
ZHANG Bo, JI Honghu, ZHANG Jingzhou, et al. Experiemnal study of heat transfer and total pressure drop of a grid‑ribbed rectangular channel[J]. Journal of Aerospace Power, 2004, 19(2): 201‑205. [百度学术]
罗马,贺宜红,孙瑞嘉,等.高阻塞比肋化通道对流换热特性实验研究[J].南京航空航天大学学报,2018,50(4): 471‑476. [百度学术]
LUO Ma, HE Yihong, SUN Ruijia, et al. Experimental study on heat transfer characteristics of high bolckage ribs channel[J]. Journal of Nanjing University of Aeronautics & Astronautics, 2018, 50(4): 471‑476. [百度学术]
LI Shian, XIE Gongnan, SUNDéN B, et al. Computational analysis of side‑wall heat transfer of a turbine blade internal cooling passage with truncated ribs on opposite walls: ASME Paper GT2012⁃68073[R].[S.l.]: ASME, 2012. [百度学术]
SINGH I, VARDHAN S, SINGH S, et al. Experimental and CFD analysis of solar air heater duct roughened with multiple broken transverse ribs: A comparative study[J]. Solar Energy, 2019, 188: 519‑532. [百度学术]
ZHANG Guohua, SUNDéN B, XIE Gongnan. Combined experimental and numerical investigations on heat transfer augmentation in truncated ribbed channels designed by adopting fractal theory[J]. International Communications in Heat and Mass Transfer, 2021, 121: 105080. [百度学术]
BEJAN A, LORENT S. The constructal law and the thermodynamics of flow system with configuration[J]. International Journal of Heat and Mass Transfer, 2004, 47: 3203‑3214. [百度学术]
BEJAN A, LORENR S. Design with constructal theory[M]. Hoboken, New Jersey: John Wiley & Sons Inc., 2008. [百度学术]
LI Xin, XIE Gongnan, LIU Jian, et al. Parametric study on flow characteristics and heat transfer in rectangular channels with strip slits in ribs on one wall[J]. International Journal of Heat and Mass Transfer, 2020, 149: 118396. [百度学术]
LIU Jian, HUSSAIN S, WANG Wei, et al. Heat transfer enhancement and turbulent flow in a rectangular channel using perforated ribs with inclined holes[J]. ASME Journal of Heat Transfer, 2019, 114: 041702. [百度学术]
邓贺方,姜玉廷,张建,等.狭缝斜肋内冷通道流动和换热特性的数值研究[J].推进技术,2020,41(9):2070‑2076. [百度学术]
DENG Hefang, JIANG Yuting, ZHANG Jian, et al. Numerical study on flow and heat transfer characteristics of internal cooling channel with slit inclined ribs[J]. Journal of Propulsion Technology, 2020, 41(9): 2070‑2076. [百度学术]
CHOMPOOKHAM T, THANPONG C, KWANKAOMENT S, et al. Heat transfer augmentation in a wedge‑ribbed channel using winglet vortex generators[J]. International Communications in Heat and Mass Transfer, 2010(37): 163‑169. [百度学术]
ZHENG Lu, XIE Yonghui, ZHANG Di, et al. Flow and heat transfer characteristics in channels with groove‑protrusions and combination effect with ribs[J]. ASME Journal of Heat Transfer, 2016, 138: 014501. [百度学术]
张峰,王新军,李军,等.肋片‑凹槽通道内的流动与换热特性数值研究[J].工程热物理学报,2017,38(7): 1512‑1518. [百度学术]
ZHANG Feng, WANG Xinjun, LI Jun, et al. Numerical investigation on the flow and heat transfer characteristics of the rib‑grooved channel[J]. Journal of Engineering Thermophysics, 2017, 38(7): 1512‑1518. [百度学术]
WHITE F M. Fluid mechanics[M]. 5th ed. Boston: McGraw‑Hill Book Company, 2003. [百度学术]
WEBB L R, KIM N H. Principle of enhanced heat transfer[M]. New York, NY, USA: Taylor Francis, 1994. [百度学术]
NATTANAPRATES N, JUNTASARO E, JUNTASARO V. Numerical investigation on the modified bend geometry of a rotating multipass internal cooling passage in a gas turbine blade[J]. ASME Journal of Thermal Science and Engineering Applications, 2018, 10: 061003. [百度学术]
MOFFAT R J. Describing the uncertainties in experimental results[J]. Experimental Thermal Fluid Science, 1988, 1(1): 3‑17. [百度学术]