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束腰结构扰流柱通道的传热和阻力特性 总被引:1,自引:0,他引:1
本文对涡轮叶片尾缘中具有束腰结构扰流柱的冷却通道的传热和流动阻力特性进行了实验研究,重点研究了雷诺数、扰流柱的束腰比以及不同组合的影响.结果表明:(1)通道平均努塞尔数随着Reynolds的增加而增大,而当Reynolds数较大时,与圆柱通道相比,束腰结构扰流柱通道的换热效果稍低;(2)通道内平均努塞尔数随着束腰比的增大先增大后降低,然后有所变缓,而其压力损失却曲折波动;(3)在三排扰流柱中,第Ⅱ排束腰结构扰流柱对换热效果影响最大,第Ⅰ排影响最小.当第Ⅰ排和第Ⅲ排为束腰结构扰流柱时,其换热减弱,而压力损失系数却增大. 相似文献
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有扰流柱的复合倾斜式气膜冷却导向叶片换热特性的研究 总被引:1,自引:0,他引:1
本文采用试验方法研究复合倾斜式涡轮导向叶片的内换热特性。针对有无扰流柱、有无气膜孔以及三种不同直径的节流孔的模型进行了试验研究,获得了扰流柱、气膜孔以及180°弯的节流板孔径的变化对其内换热特性的影响,并得到了一些换热准则方程,从而获得了加强叶片内部换热的方法。 相似文献
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为了评估复杂冷却涡轮内部冷却结构变化对涡轮气动及传热性能的影响,本文采用气热耦合计算方法对三种具有不同内部冲击结构的高压导叶进行了研究。分析了无冲击冷却结构、冲击挡板结构以及冲击套筒结构对涡轮气动及传热性能的影响规律。结果表明:在气动性能方面,无冲击冷却结构方案总流量最大,带有冲击套筒结构方案最小,同时涡轮气动效率也会随着内部结构的变化而变化;在传热方面,通过对比可以发现两种冲击方案都会对叶片表面最大温度进行降低,但冲击套筒结构方案同时还能够降低叶片表面平均温度。 相似文献
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为了研究网格缝结构的气膜冷却特性,开展了平板模型试验研究,使用瞬态液晶测温技术测量了缝下游表面的气膜冷却效率和换热系数分布,在相同压比下与圆柱孔进行了气膜冷效对比,同时研究了缝内扰流柱布局对网格缝结构气膜冷却特性的影响。网格缝结构的吹风比范围为0.26M1.25。实验结果表明:网格缝结构的气膜冷效展向分布均匀性比圆柱孔有显著提高,且吹风比增加后不会出现射流脱离壁面的现象;在扰流柱和缝后斜面的作用下,缝下游会形成对卷旋涡,使得最下游一排扰流柱下游的气膜冷效相对较高;扰流柱顺排时,缝下游气膜冷效分布更均匀,大吹风比时,顺排结构的展向平均气膜冷效比叉排结构高出23%~84%,换热系数比高出11%;吹风比M1时,顺排结构的流量系数更高,M1时,叉排结构的流量系数更高。 相似文献
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《工程热物理学报》2021,42(9):2269-2274
受端区二次流的影响,叶片前缘和压力面根部角区端壁难以实现有效冷却。为了实现该区域的冷气覆盖,本文研究了新型冷却结构离散台阶缝的端区气膜冷却特性。离散台阶缝在叶片周向主要覆盖叶片前缘区域,能够集中冷气冷却换热恶劣的区域。本文研究了两种不同离散台阶缝轴向位置(AP1,AP2)和三种不同冷气量(MFR=0.43%,0.88%,1.33%),通过红外热像仪测量端区气膜冷却效率分布。结果表明,增加离散台阶缝与叶片的轴向距离,能够有效提高叶片上游区域的冷却效果,但在通道内部,结果相反。增加冷气量能够提高端壁的气膜冷却效果。此外,应用五孔探针测量叶栅通道喉部附近截面二次流流场特征,解释了通道冷却分布的机理。 相似文献
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Comparisons of Heat Transfer Enhancement of an Internal Blade Tip with Metal or Insulating Pins 下载免费PDF全文
Cooling methods are needed for turbine blade tips to ensure a long
durability and safe operation. A common way to cool a tip is to use
serpentine passages with 180-deg turn under the blade tip-cap taking
advantage of the three-dimensional turning effect and impingement like
flow. Improved internal convective cooling is therefore required to
increase the blade tip lifetime. In the present study, augmented heat
transfer of an internal blade tip with pin-fin arrays has been investigated
numerically using a conjugate heat transfer method. The computational domain
includes the fluid region and the solid pins as well as the tip regions.
Turbulent convective heat transfer between the fluid and pins, and heat
conduction within pins and tip are simultaneously computed. The main
objective of the present study is to observe the effect of the pin
material on heat transfer enhancement of the pin-finned tips. It is
found that due to the combination of turning, impingement and pin-fin
crossflow, the heat transfer coefficient of a pin-finned tip is a factor
of 2.9 higher than that of a smooth tip at the cost of an increased pressure
drop by less than 10%. The usage of metal pins can reduce the tip temperature
effectively and thereby remove the heat load from the tip. Also, it is found
that the tip heat transfer is enhanced even by using insulating pins having
low thermal conductivity at low Reynolds numbers. The comparisons of overall
performances are also included. 相似文献
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涡轮叶顶冷却布置对叶顶传热冷却性能的影响 总被引:2,自引:0,他引:2
本文采用数值模拟的方法,对比分析了1+1/2对转涡轮四种不同的叶顶冷却布置方案对叶顶传热、冷却性能以及气动特性的影响。四种布置方案分别是:靠近压力面垂直叶顶方向、靠近压力面且与叶顶有30°出射角、中弧线位置垂直叶顶方向、中弧线位置有30°出射角。研究表明,气膜孔沿压力面布置与气膜孔沿中弧线布置相比可以降低叶顶传热系数;由于气膜孔倾斜布置气膜射流动量降低,且削弱了肾形涡的影响,气膜的侧向覆盖范围增大。因此气膜孔靠近压力面布置可以提高气膜冷却效率;气膜孔靠近压力面且有30°出射角比垂直布置叶顶热负荷减少2.7%。另外,气膜孔靠近压力面布置可以降低主流的泄漏流量,有利于减小泄漏损失和提高涡轮效率。 相似文献
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本文针对GE-E3第一级动叶前缘的冲击/气膜复合冷却结构进行了热流耦合数值研究。采用标准k-ω湍流模型,分析了前缘气膜孔对称布置时,其角度对透平动叶前缘冲击/气膜复合冷却特性的影响;在五种冷气质量流量比(MFR=0.005,0.010,0.016,0.020,0.025)下,研究了气膜孔在不同角度(β=20°,25°,30°,40°,50°,60°)时的透平动叶前缘冷却换热效果。研究结果表明:在本文研究范围内,气膜孔角度越小,透平动叶前缘的平均综合冷却效率越高;随着冷气质量流量比增大,透平动叶前缘的平均综合冷却效率逐渐提高。 相似文献
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在国产六面顶压机上,采用温度梯度法,在5.6 GPa,1200—1400?C的高压高温条件下,裂晶问题频繁出现的合成周期内,围绕裂晶现象开展了Ib型宝石级金刚石单晶的生长研究,系统考察了降温工艺对宝石级金刚石单晶品质的影响.针对宝石级金刚石单晶常见的裂纹缺陷,借助于扫描电子显微镜,分别对优质金刚石单晶和存在裂纹金刚石单晶的表面形貌进行了表征;利用微区傅里叶转换红外光谱测试手段,对上述两类晶体的N杂质含量分别进行了测试,依据测试结果,对裂晶出现的原因进行了分析;分别采用传统断电降温和缓慢降温工艺,考察了晶体生长结束后的降温工艺对宝石级金刚石单晶品质的影响.结果表明,缓慢降温工艺在很大程度上可以有效抑制裂晶问题出现.另外,从宝石级金刚石单晶品质和单晶受到的外应力两个方面着手,分别对裂晶出现的机理和采用缓慢降温工艺有效解决裂晶问题的机理进行了讨论. 相似文献
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Spray cooling is an effective tool to dissipate high heat fluxes from hot surfaces. This article thoroughly investigates the effect of thickness of a hot stainless steel plate on the cooling time, cooling rate, heat flux, and heat transfer coefficient under constant mass flow rate maintained at 1 MPa using water as the coolant. Cylindrical samples of stainless steel with constant diameter (D = 25 mm) and thickness (δ = 7.5, 12, 16.5, and 21 mm) were used in the present study. Critical droplet diameter to achieve an ultra-fast cooling rate of 300°C/s was estimated by using an analytical model for samples of varying thicknesses. The analytical model (one side spray cooling) showed good agreement with experimental results with a relative error of 3.2% in the plate thickness range of 1–12 mm. An increasing trend in maximum heat flux was found with increasing thickness of the plate. Maximum heat flux as high as 1,800 kW/m2 was achieved for a 21-mm-thick sample. Heat transfer coefficients in the range 0.092–96.24 kW/m2K, 0.111–98.9 kW/m2K, 0.074–63.4 kW/m2K, and 0.127–55.63 kW/m2K were reported for sample of varying thicknesses in the present study. Limited published work is available with reference to water spray cooling dynamics and thickness of stainless steel plate. Therefore, the present study focuses on the correlation between the thickness of the plate and spray dynamics of water spray cooling. 相似文献