收敛缝形孔气膜冷却特性研究.pdf

南京航空航天大学 博士学位论文 收敛缝形孔气膜冷却特性研究 姓名：姚玉 申请学位级别：博士 专业：航空宇航推进理论与工程 指导教师：张靖周 2010-06 南京航空航天大学博士学位论文 I 摘 要 气膜冷却在现代航空涡轮发动机热端部件的冷却结构中具有十分重要的作用尽管国内外 针对气膜冷却已经开展了大量的研究，但进一步提高气膜冷却的性能仍然是一个富于挑战和创 新的研究课题，其核心问题在于如何降低气膜出流向主流的穿透率以及增强气膜出流向下游的 延伸能力本文以此为研究背景，对一种新型收敛缝形气膜孔冷却结构的流动和换热特性开展 了数值和实验研究研究内容主要包含两个方面：其一，针对平板收敛缝形气膜孔的冷却结构， 分析和探讨收敛缝形气膜孔的流动传热特性，揭示其强化冷却的物理特征，系统研究气膜孔结 构参数对于冷却特性的影响规律，获取较为优化的结构参数；其二，在平板气膜冷却的基础上， 开展涡轮叶片收敛缝形孔气膜冷却特性的研究，归纳主流雷诺数、吹风比及气膜孔弦向位置等 因素对叶栅气动及叶片换热特性的影响规律 对平板收敛缝形气膜孔影响气膜出流流动和冷却效果的机制进行了研究研究结果表明， 由于收敛缝形气膜孔所固有的流道型面，即在圆转矩形的过渡过程中，气膜孔沿出流方向呈逐 渐收敛状，在展向则呈两侧对称扩张状，使得气膜出流的状况以及气膜出流与主流的相互作用 均具有其独特的物理特征。

主要体现在： （1）二次流在两侧扩展流动并在两侧向上抬升形成与 常规圆形气膜孔卵形涡对旋向相反的涡对，涡对旋向的改变，避免了常规圆形气膜孔卵形涡对 诱导主流向气膜孔两侧区域的侵入现象，使得气膜出流在展向上的覆盖更为均匀； （2）二次流 在收敛孔内的加速流动提升了气膜出流向下游的延伸能力，同时气膜出流在侧向的扩张又使得 气膜出流向主流的穿透得到了有效抑制，气膜出流的速度剖面具有沿流向峰值速度增加且峰值 速度对应的壁面法向距离减小的特征因此，与常规圆形气膜孔相比，收敛缝形气膜孔能够有 效改善气膜冷却效率 在较宽的吹风比范围内，对平板收敛缝形气膜孔的冷却特性进行了研究，较为系统地分析 了收敛缝形气膜孔的结构参数对冷却特性的影响研究结果表明，随着吹风比的增加，收敛缝 形孔的流量系数和冷却效率均随着增大；无论在何种吹风比条件下，收敛缝形孔的冷却效率均 高于圆形孔，且在大吹风比下更为显著；缝宽 0.2d、高度为 1.2d 及倾角 35左右的气膜孔具有 较高的冷却效率及流量系数，是收敛缝形孔的较优结构参数 针对某型导向叶片的曲面结构，研究了吸力面收敛缝形孔气膜冷却对涡轮叶栅气动损失的 影响 研究结果表明， 收敛缝形气膜孔的能量损失和总压损失系数均随着吹风比的增加而增加； 随着主流雷诺数的增加， 不同位置处气膜孔的能量损失系数随之降低， 总压损失系数随之增加； 叶栅通道喉部上游气膜孔的能量损失及总压损失系数最低，而喉部下游的气膜孔在大部分工况 下的损失系数最高；与圆形孔相比，位于叶栅通道喉部上游收敛缝形气膜孔的损失系数较低， 收敛缝形孔气膜冷却特性研究 II 位于叶栅通道喉部及下游则存在气动损失较高的工况。

叶片吸力面 3 个典型位置处收敛缝形孔的气膜冷却效率随着吹风比及主流雷诺数的增加而 提高，显示出冷却效率随冷气流量增加而提高的特点；相对来说，叶栅喉部前气膜孔排的冷却 效果较好；与圆形孔相比，收敛缝形孔的冷气能更好地覆盖下游叶片，在展向形成相对连续的 气膜，冷却效率的均匀性较好，且沿程的冷却效率较高收敛缝形气膜孔的对流换热增强比随 着吹风比及主流雷诺数的增加而提高， 在不同工况下， 收敛缝形孔的换热增强能力高于圆形孔 相对于常规圆柱形气膜孔，位于叶栅通道喉部上游的收敛缝形气膜孔既具有较低的气动损 失系数又具有较高的气膜冷却效率，说明在叶栅流动的加速区域开设收敛缝形气膜孔可得到理 想的气动和冷却效果 关键词：关键词：收敛缝形孔，气膜冷却，涡轮叶片，涡轮叶栅，气动和换热特性 南京航空航天大学博士学位论文 III Abstract Film cooling plays a very important role in the cooling configuration of the modern gas turbine engines. A great deal of investigations focusing on the film cooling has been made, but the innovative technique enhancing the film cooling efficiency is also regarded as a challenging problem, of which the key is how to reduce the penetration of film outflow to primary flow and enhance the extensibility of film outflow along primary flow direction. Based on this research background, an innovation converging slot hole (console) film cooling configuration was studied in the present paper to further understand its flow and heat transfer characteristics. The content of the present investigation contains two main aspects. Firstly, for the plate console film cooling scheme, the flow and heat transfer performances of this innovative film cooling configuration is researched to reveal its physical mechanism for enhancing cooling characteristic, and the effects of film hole constructural parameters on the performance of film cooling are also studied to optimize the cooling film hole. Secondly, for the blade film cooling scheme, the study is made on the effects of primary flow Reynolds number, coolant blowing ratio and holes location on aerodynamic loss and heat transfer characteristics with converging slot film hole. The physical mechanism on film cooling enhancement of converging slot hole film cooling is investigated. The results show that the film outflow from converging slot hole is of inherent feature owing to its special internal flow passage, converging in streamwise direction and expanding in lateral direction, which behaives mainly that: (1) the secondary flow expands in the lateral direction and forms a pair of vortices originating from the converging slot hole sides, which is opposite to that from the cylindrical hole center. The alteration of vortice rotation direction makes the film coverage more uniform in lateral direction and prevents the primary flow from invading to the local area between film holes. (2) the secondary flow accelation insides the converging slot hole is benefit to promoting the film outflow spread along streamwise direction, and the secondary flow expanding in the lateral direction is capable of suppressing the film outflow penetration to the primary flow simultaneously, which makes the film outflow velocity distribution more reasonable, that is the film outflow peak velocity is promoted and the wall normal distance corresponding to film outflow peak velocity is reduced. Thus the adiabatic wall film cooling effectiveness for the converging slot hole is higher than that of the cylindrical film hole. The film cooling characteristics for the converging slot hole in a range of blowing ratios are studied, and the effects of converging slot hole parameters on the film cooling characteristics are 收敛缝形孔气膜冷却特性研究 IV analysed. Results show that the discharge coefficient and cooling effectiveness for converging slot hole increase with the increment of the blowing ratio. Under the same blowing ratio, the discharge coefficient and cooling effectiveness of the converging slot hole is higher than cylindrical hole, the advantage in improving film cooling effectiveness is more significant in the bigger blowi。