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Detailed heat transfer measurements were conducted on the endwall surface of a large‐scale low‐speed turbine cascade with single and double row injection on the endwall upstream of leading edge. Local film cooling effectiveness and the heat transfer coefficient with coolant injection were determined at blowing ratios 1.0, 2.0, and 3.0. In conjunction with the previously measured flow field data, the behaviors of endwall film cooling and heat transfer were studied. The results show that endwall film cooling is influenced to a great extent by the secondary flow and the coverage of coolant on the endwall is mainly determined by the blowing ratio. An uncovered triangle‐shaped area with low effectiveness close to pressure side could be observed at a low blowing ratio injection. The averaged effectiveness increases significantly when injecting at medium and high blowing ratios, and uniform coverage of coolant on the endwall could be achieved. The averaged effectiveness could be doubled in the case of double row injection. It was also observed that coolant injection made the overall averaged heat transfer coefficient increase remarkably with blowing ratio. It was proven that film cooling could reduce endwall heat flux markedly. The results illustrate the need to take such facts into account in the design process as the three‐dimensional flow patterns in the vicinity of the endwall, the interactions between the secondary flow and coolant, and the augmentation of heat transfer rate in the case of endwall injection. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(3): 141–152, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20007 相似文献
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对有限长中等半径比同心旋转圆柱间Taylor-Couette流进行了数值计算,以研究侧墙对Taylor-Couette流的影响。圆柱的半径比为0.83,形状比为6,泰勒数在0~357之间。内圆柱旋转,外圆柱静止。数值计算结果表明,在无滑移侧墙边界条件下,在泰勒数低于临界泰勒数时,在侧墙边界层的作用下侧墙附近出现侧墙涡,而在滑移侧墙边界条件下,直到泰勒数大于临界泰勒数,轴间才出现明显的涡流。当泰勒数处在89~112之间,侧墙静止和侧墙旋转时产生的最大径向速度分别约为内筒表面线速度的3%~4%和7%~10%。侧墙静止时,随着泰勒数的增加,边界层的厚度也随之递增。侧墙旋转时,边界层厚度基本不变。在泰勒数大于临界泰勒数时,随着泰勒数的增加,侧墙静止和侧墙旋转时侧墙涡的轴向长度分别增加和减少,在滑移边界条件下,侧墙涡的轴向长度约等于轴间距。在3种侧墙边界条件下,层流涡向波动涡转捩的临界泰勒数变大。 相似文献
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Z. G. Liu N. Guan C. W. Zhang G. L. Jiang 《Nanoscale and Microscale Thermophysical Engineering》2015,19(3):221-243
The flow resistance and heat transfer characteristics of deionized water flowing through a rectangular channel (60 mm × 5.2 mm × 0.5 mm) with staggered array micro pin-fin circular, diamond, and elliptical groups are experimentally investigated over Reynolds numbers ranging from 8 to 1,000, and the investigation shows that the flow resistance increases due to the endwall effect and large pin-fins density at low Re. With the increase in Re, the endwall effect is weakened, but the flow resistance still increases due to the appearance of vortex resistance, and the heat transfer is enhanced due to the flow disturbance or transition from laminar flow to turbulent flow. The experimental results are also compared with predictions of the theoretical correlations for the staggered array micro pin-fin groups, and the comparisons indicate that only the correlation related to the diamond shaped micro pin-fin groups approximately agrees with experimental data, and the other correlations do not describe well the flow and heat transfer characteristics covering laminar, transitional, and turbulent states in circular and elliptical test sections. 相似文献
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在涡轮叶栅端壁21%、51%、81%轴向弦长处和距前缘9%轴向弦长端壁处布置4排圆柱形气膜冷却孔,运用CFD方法模拟吹风比、轴向倾角α和展向倾角β3个影响因素共同作用下的端壁平均气膜冷却效率,通过正交方案选出最优孔排布置方式.结果表明:吹风比对端壁平均气膜冷却效率的影响最大,展向倾角β影响次之,轴向倾角α影响最小;吹风比为2.0,轴向倾角α为30°,展向倾角β为45°(第1、第3排冷却孔与y轴负方向成45°,第2、第4排冷却孔与y轴正方向成45°)布置时,端壁表面平均气膜冷却效率最高,为3个因素影响下的最优方案. 相似文献
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IntroductionA ttirbomachinery rotor must have a slhall hilt finite clearance relative to its surrounding casing. Theflow, which leaks thlough this fililte gap, has a surprisingly large effect on the aerodynamics of the flow.The loss produced due to the tip clearance is an.unavoidable loss. The presence of tip clearance ajtersthe endwall flow siglilflcaotly. The normal secondaryflow interacts with the leakage fluid ajs it easts fromthe suction surface. The leakage fluid rolls into whatis known… 相似文献
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应用热线测量和颗粒图像测速(PIV)技术,测量平端壁叶栅(FEW)和非轴对称端壁叶栅(CEW)的二次流动。基于叶栅内的涡结构和剪切应力,分析非轴对称端壁降低二次流损失的流动机理。实验结果表明:二次流在叶片吸力面的边界层分离导致壁面涡与主流流体的剪切掺混,这是叶栅二次流损失的主要来源;非轴对称端壁通过降低端壁横向压力梯度推迟二次流分离的发生,使壁面涡与主流区产生剪切掺混的范围缩小,并使端壁二次流的流向速度提高、壁面涡的强度降低,在上述两方面作用下叶栅内的剪切应力减小,叶栅二次流损失降低。 相似文献