叶型近前缘区域一体化设计降低前缘敏感性的机制探索

It is well known that a blade leading edge spike flow can usually be found due to the effects of the connecting of separate curves of blade leading edge and blade surface during blade design procedure, the blade manufacturing errors and also the natural erosion effect during the engine service. The spike flow usually has to significant effects on blade surface boundary layer development, one is a flow disturb effect and the other one is a disturb magnification effect, which can cause the deviation of blade performance from the idealized design condition. This effect is much more serious for the blade with controlled diffusion airfoil. In this project, we suggest a novel method to deal with this problem, i.e. using an integral curve to design the blade leading edge and the adjacent section of blade suction surface which makes a strong flow acceleration downstream blade leading edge. During the design procedure, the transition of the curvature of blade leading edge and blade surface can be carefully controlled to weaken the spike flow; meanwhile, the strong flow acceleration can damp the upstream flow disturbance. By using this method, the sensitivity of blade leading edge might be reduced significant, which can make the blade maintain a high performance during a wide operating range. Some numerical research will conducted at first to clarify the effects of different blade leading edge and suction side acceleration section geometrics on the performance of blade surface boundary layer. Then, a series of large eddy simulations and planar cascade experiments will be carried out for analyzing the flow mechanisms of different geometric-response of typical boundary layer parameters and coherent structures. Based on the above studies, the design principles of the integral curve will be suggested and design function of the curve will be developed. Finally, the design function will be validated by large eddy simulations, planar cascade experiments and compressor test experiments.

在叶型设计过程中，传统的叶片前缘和叶身分开造型，以及加工误差和使用过程中的自然侵蚀，都容易造成在前缘处出现一个突然膨胀扩压过程，即Spike流动。这种流动具有扰动源和扰动放大器双重效应，会改变理想的叶表附面层发展状态，使叶型性能偏离设计状态。该问题在可控扩散叶型中尤为突出。本项目提出了利用叶片前缘和吸力面加速段一体化造型的新思路来解决该问题。通过前缘与叶身曲率的合理过渡减弱Spike扰动，同时通过控制前缘后的强加速抑制扰动增长，起到降低叶型对前缘的气动和几何敏感性，使之在更宽广的工作范围内都保持高性能的作用。研究将首先通过数值模拟系统分析前缘和吸力面加速段对叶表边界层的作用机制，并利用大涡模拟和平面叶栅实验从边界层典型参数的变化和拟序结构的发展层面对该机制深入分析。然后将凝炼出叶型近前缘区域一体化造型的基本原则，并发展相应的造型函数。最后将通过大涡模拟、平面叶栅和压气机实验台实验进行验证。

为了解决传统叶片造型方法中前缘和叶身分开造型易导致前缘和叶身曲率不连续，进而导致叶型设计鲁棒性低的问题，本项目提出了叶片前缘和吸力面加速段一体化造型的方法。在项目研究过程中，通过系统分析研究前缘对叶型气动性能和叶表附面层发展影响的机制和影响因素，首先发展了曲率连续前缘造型方法；然后通过从工程实际中提炼出的加工偏差形式，系统分析了不同前缘形式对叶型气动鲁棒性的影响；最后，为了在提高叶型性能的同时也提高叶型的气动鲁棒性，发展了前缘和叶身一体化造型的新叶型设计方法。经过9套高低速平面叶栅和一套低速大尺寸单级压气机实验，从不同层面验证了采用理论和数值方法研究成果的可靠性，证明了叶片前缘和叶身一体化造型方法设计得到的叶型在性能上的优势及其潜在的工程应用价值。在研究过程中为了实施精细化测量，还发展了高精度叶表附面层IPIV数据处理方法、5孔气动探针分区标定/测量方法和叶片前缘高空间分辨率压力测量方法。