异型截面孔气膜冷却机理实验研究

High performance film cooling is essential for the design of high temperature turbine blade in heavy-duty gas turbine. The purpose of this project is to improve the film cooling performance greatly through investigating the flow and heat transfer mechanisms of the film hole with shaped cross section. The experimental investigations on the influences of geometrical and aerodynamic parameters will deeply reveal the flow and heat transfer phenomena of the shaped cross section holes, and obtain the optimal geometrical configurations and the applicable mainstream and coolant conditions. The experimental investigations on the influences of conjugated heat transfer and the cooling characteristics of combined structure will clarify the influencing mechanism of solid heat conduction on film cooling, and establish the matching criterion between shaped cross section hole and internal cooling structure. The experimental investigation on the influences of pressure gradient and endwall secondary flow will obtain the heat transfer characteristics of the shaped cross section hole on the different blade region and location, and establish the blade design method using shaped cross section hole. According to the experimental investigation on the integrated cooling effectiveness, the optimized arrangement of the shaped cross section holes on turbine blade will be performed. The innovation of this project is to put forward the concept of shaped cross section hole, which transfers the study focus of film hole from the hole exit structure to the cross-sectional shape. The technical route starts from the basically mechanism investigation, then expands to the matching with internal cooling structure, finally establishes the blade design method and verifies the integrated cooling effectiveness. The investigation of this project will lay the foundation for the high performance film cooling design of the heavy-duty gas turbine blade.

高效气膜冷却对重燃高温透平叶片设计至关重要。本项目以大幅提升气膜冷却性能为目标，系统研究异型截面气膜孔的流动与传热机理。实验研究几何与气动参数的影响，深入揭示异型截面孔的流动传热现象，获取气膜孔高效几何构型及适用的主流与冷气条件；实验研究耦合传热影响以及复合结构的冷却特性，阐明固体导热对异型截面孔气膜冷却的影响机制，建立异型截面孔与内部冷却结构的匹配准则；实验研究压力梯度和端壁二次流的影响，获得异型截面孔在叶片不同区域和位置的流动传热特性，建立异型截面孔的叶片设计方法；实验研究异型截面孔叶片的综合冷效，优化异型截面孔的叶片排布。本项目的创新之处是明确提出了异型截面孔的概念，将高效气膜孔的研究重点由出口结构转至横截面形状。基于提出的异型截面孔，技术路线从基本流动传热机理出发，继而扩展到与内部冷却结构的匹配，最终建立叶片设计方法并验证综合冷效。研究将为重燃透平叶片高效气膜冷却设计奠定基础。

重型燃气轮机的透平进口温度已提升至1600℃以上，对于这一温度等级以上的透平叶片冷却，除提升高温合金和隔热涂层材料的性能之外，先进冷却技术的支撑显得尤为重要。为突破气膜冷却性能瓶颈，打破传统圆形截面对气膜冷却孔型结构的限制，本项目以发展有别于常规圆形截面的异形截面气膜孔为目标，主要研究具有大截面长宽比、不同截面形状的槽型截面孔的气膜冷却流动与传热机理，建立针对此类孔型的透平叶片设计方法。单排孔平板实验发现，在不同的倾斜角、长径比和定位角下，半圆侧壁矩形扩散孔的绝热气膜冷却效果均大幅高于圆截面扇形孔；多排孔平板实验显示，由于出口宽度的增加，半圆侧壁矩形扩张孔具有不同于圆截面孔型的多排叠加规律；通过对半圆侧壁矩形扩散孔上下游壁的外凸处理，提出了梭型截面扩散孔结构，进一步提升了绝热气膜冷却效果；垂直带肋通道的数值研究证实，槽型截面孔的宽截面可以显著减弱垂直横流影响，在带肋通道中比常规圆截面孔具有显著优势；叶片端壁实验研究表明，半圆侧壁矩形扩散孔在强二次流影响下的气膜冷却效果明显高于圆截面扇形孔；气热耦合实验表明，采用槽型截面孔与典型内部冷却结构组合的综合冷效比采用扇形孔提高了近0.1。本项目研究初步揭示了槽型截面孔的气膜冷却流动与传热机理，多种模型的实验和数值研究均验证了气膜孔采用异形截面可以显著提升透平叶片不同区域的气膜冷却性能。