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基于频闪拍照和稳态液晶测温技术,实验研究了不同气膜孔出流角对旋转态整级涡轮叶片前缘外壁面的气膜冷却特性的影响。实验中,叶片前缘处的主流雷诺数为6.3378×104。实验转速为574 r/min,对应的旋转数为0.0018。平均吹风比从0.5变化到1.25。射流采用N2,其对应的密度比为1.04。结果表明:展向平均气膜冷效是随吹风比的增加而单调增加的,其中最佳吹风比为M=1.25。对于所有吹风比,在-4.3相似文献
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本文通过数值模拟的方法同时考虑了耦合传热和冷却流通道流动对气膜冷却的影响.计算结果表明,在考虑耦合传热的情况下,冷却流通道流动的影响仍然存在,但随着壁面导热系数的增大,这种影响减弱;同时在考虑耦合传热的情况下,受保护壁面温度场分布更加均匀,冷却效果更好.计算结果还表明吹风比为0.5时的冷却效果优于吹风比为1.0的情况. 相似文献
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V. Yu. Petelchyts A. A. Khalatov D. N. Pysmennyi Yu. Ya. Dashevskyy 《Thermophysics and Aeromechanics》2016,23(5):713-720
The paper presents results of computer simulation of the film cooling on the turbine blade leading edge model where the air coolant is supplied through radial holes and row of cylindrical inclined holes placed inside hemispherical dimples or trench. The blowing factor was varied from 0.5 to 2.0. The model size and key initial parameters for simulation were taken as for a real blade of a high-pressure high-performance gas turbine. Simulation was performed using commercial software code ANSYS CFX. The simulation results were compared with reference variant (no dimples or trench) both for the leading edge area and for the flat plate downstream of the leading edge. 相似文献
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In this work, the complexity of the flow field arising from the impact of the interaction of coolant jets with a hot cross-flow under rotation conditions was numerically simulated using large eddy simulation with artificial inflow boundary condition. The finite-volume method and the unsteady PISO (Pressure Implicit with Splitting of Operators) algorithm were applied on a non-uniform staggered grid. The simulations were performed for four different values of rotation number (Ro) of 0.0, 0.03021, 0.06042, and 0.12084, a jet Reynolds number of 4700, based on the hole width and the jet exit velocity. The air jet was injected at 30° and 90° in the streamwise direction with a density ratio of 1.04 and a velocity ratio of 0.5. The flow fields of the present study were compared with experimental data in order to validate the reliability of the LES technique. It was shown that the rotation has a strong impact on the jet trajectory behaviour and the film cooling effectiveness. The film trajectory always inclines centrifugally. Under rotating conditions, the film trajectory departs from the centreline to the left boundary. The deflection becomes greater as Ro increases. Furthermore, it was also found that the injection angle has a strong impact on separation and reattachment behaviour as well as the strength of the penetration into the cross-flow. As it increases, the distribution of the film cooling downstream the jet exit is more non-uniform and the film cooling effectiveness level slightly decreases. 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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The present study was conducted to evaluate the total cooling effectiveness in combined full-coverage film cooling and impingement jet using an infrared thermographic technique. The effect of film cooling hole angle, blowing ratio, and height to diameter ratio between the film cooling and impingement jet plates was discussed. The total cooling effectiveness increased as impingement jet cooling was added. The angled film cooling holes had approximately 4.6% higher total cooling effectiveness than the normal film cooling holes. The total cooling effectiveness was almost constant regardless of height to diameter ratio, but enhanced as the blowing ratio was increased. 相似文献
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The interaction between the film-cooling jet and vortex structures in the turbine passage plays an important role in the endwall cooling design. In this study, a simplified topology of a blunt body with a half-cylinder is introduced to simulate the formation of the leading-edge horseshoe vortex, where similarity compared with that in the turbine cascade is satisfied. The shaped cooling hole is located in the passage. With this specially designed model, the interaction mechanism between the cooling jet and the passage vortex can therefore be separated from the crossflow and the pressure gradient, which also affect the cooling jet. The loss-analysis method based on the entropy generation rate is introduced, which locates where losses of the cooling capacity occur and reveals the underlying mechanism during the mixing process. Results show that the cooling performance is sensitive to the hole location. The injection/passage vortex interaction can help enhance the coolant lateral coverage, thus improving the cooling performance when the hole is located at the downwash region. The coolant is able to conserve its structure in that, during the interaction process, the kidney vortex with the positive rotating direction can survive with the negative-rotating passage vortex, and the mixture is suppressed. However, the larger-scale passage vortex eats the negative leg of the kidney vortices when the cooling hole is at the upwash region. As a result, the coolant is fully entrained into the main flow. Changes in the blowing ratio alter the overall cooling effectiveness but have a negligible effect on the interaction mechanism. The optimum blowing ratio increases when the hole is located at the downwash region. 相似文献
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The focus of this numerical study is to conceive a new basic film cooling configuration in order to increase film cooling effectiveness, especially at the leading edge zone between the injection holes where cooling is mostly needed. The new configuration, resulting from the tangential slot configuration and especially adapted to the leading edge of an asymmetrical blade, is compared to the uniform slot configuration. Three alternatives geometries were proposed and numerically tested to find the configuration that provides the best film cooling effectiveness. The simulation is conducted at a fixed density ratio of 1.0 and a blowing ratio of 0.7. A new parameter, Rc, is defined to measure the rate of blade coverage by the film cooling. The outcomes of the numerical results indicate that the three proposed configurations allow better thermal protection because of their higher film cooling coverage. At suction side, the new configurations provide a better film cooling coverage than the baseline case. The minimal improvement is at approximately 34%, with a light superiority of case 1. At pressure side, the use of the tangential slot is especially interesting for the allowed minimum adiabatic effectiveness values between 0.3 and 0.5. 相似文献
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涡轮动叶吸力侧单排气膜孔冷却性能研究 总被引:2,自引:0,他引:2
本文通过数值模拟的方法,针对涡轮叶片吸力侧的单排气膜孔,研究了无量纲气膜孔出流位置、气膜孔复合角度和冷却空气质量流量占比对其气膜冷却效率与气动掺混损失的影响。结果表明,对于近前缘气膜孔,0.5%的冷却空气质量流量可以在保证较好的气动效率的同时在下游附近提供较高的绝热气膜冷却效率;对于中后部气膜孔,90°的气膜孔导致的掺混损失比相同冷气量的近前缘气膜孔高出一倍,此时复合角为60°的气膜孔有更好的气膜冷却效果。对比不同的孔排位置,位于流向位置0.3的气膜孔可以在下游较大区域取得良好的冷却效果,而且不引起过大的掺混损失。 相似文献
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Experimental and numerical study of the effect of conjugate heat transfer on film cooling 总被引:1,自引:0,他引:1
Combined convection heat transfer and thermal conduction for film cooling of a flat plate with 45° ribs on one wall was investigated experimentally and numerically. The flat plate surface temperature was measured using thermochromic liquid crystals. The results show that the film cooling is the main mechanism for the local cooling with a very low thermal conductivity while the convection heat transfer of the coolant in the coolant channel is the dominant heat transfer mechanism for the high thermal conductivity plate, with both film cooling and convection heat transfer by the coolant being important with medium thermal conductivity walls. 相似文献
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超音速气膜冷却及其受斜激波的影响 总被引:2,自引:0,他引:2
选取了一组接近超燃发动机内部实际工况的边界条件,对二维平行缝槽形式的超音速气膜冷却进行了数值计算,比较了吹风比、缝槽高度和隔板厚度等因素对壁面冷却效率的影响,并考虑了不同强度的斜激波入射气膜冷却边界层对壁面冷却效果和压力分布的影响.通过回归分析,不受激波影响的超音速气膜冷却的壁面冷却效率可以整理成统一的关联式.计算结果表明,斜激波入射将使入射点及其下游的壁面冷却效率降低,但是这个影响没有向上游传播. 相似文献
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本文对水平槽道内发汗冷却建立了包括主流区、多孔壁面区和致密壁面区在内的完整的物理模型和数学描述, 对耦合传热过程开展了数值模拟,对平板发汗冷却的机理进行了深入的研究。研究表明:发汗冷却减小了壁面处的速度梯度,使下壁面边界层明显增厚;随着冷却流体的注入,壁面处的湍流应力明显增大;湍流应力的最大值向没有发汗冷却的壁面一侧偏移,并且增加了最大湍流应力;边界层的增厚使得发汗冷却区域壁面摩擦阻力系数降低。随着冷却剂流量的增大,壁面温度也随之下降;数值模拟结果与实验结果较好地吻合。 相似文献
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基于BP神经网络的多参数气膜冷却效率研究 总被引:1,自引:0,他引:1
气膜冷却作为当代燃机高温透平中必需的冷却手段,其冷却性能在多种参数的影响下表现复杂。采用BP神经网络模型对多种几何、流动参数变化下的气膜冷却系统的绝热气膜冷却效率进行预测。选择气膜冷却系统的吹风比、密度比、主流湍流度、面积比和长径比作为神经网络的输入参数,以燃气轮机透平叶片气膜冷却的实际运行工况为范围建立数据库。计算结果表明,采用贝叶斯归一化法训练后建立的气膜冷却神经网络模型在预测精度上要优于经验公式法,而且参数适用范围更广,具有良好的发展应用前景。 相似文献
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A. A. Khalatov I. I. Borisov Yu. Ya. Dashevskiy A. S. Kovalenko S. V. Shevtsov 《Thermophysics and Aeromechanics》2014,20(6):713-719
Results of an experimental study of a flat plate film cooling efficiency from a single row of inclined holes embedded in a “shallow” trench are presented. It is shown the cooling efficiency of such a configuration is much greater than that of the traditional configuration of inclined round holes. This provides more uniform surface coverage by the coolant film. The flow external turbulence increases the film cooling efficiency by 5–8%, while the freestream flow acceleration reduces it by 10–15%. 相似文献