气动掠对高负荷轴流压气机叶片载荷匹配机制的影响研究

The overall performances and operation ranges are both restricted greatly by the large losses and complicated flow phenomenon in flowfields when the stage loading increases in axial compressors. Fortunately, it appears that aerodynamic sweep benefits the high loading axial compressors for its large advantages in improving stable operation range, reducing flow losses and attenuating corner separation in blades. So the sweep has become one of the hot research topics in the areas of flow controlling and a large number of investigations on it have been carried out for decades. It's concluded that large theoretical and practical significances exist in exploring the mechanisms of aerodynamic sweep on complicated flow phenomenon in high loading compressors and establishing the optimization rules as well. In this condition, the influence of sweep on the spanwise and streamwise loading matches of highly loaded axial compressors will be investigated in this project and the main researching work includes: the effect of sweep on loading match and transportation in compressors, coupling relationships among the blade loading change, 3-D shock structures, boundary layer development and stable operation range in swept blades. The numerical simulation and experimental analysis are both used in this project to improve the understanding of mechanisms in which the aerodynamic sweep affects internal flow in high loading compressors and to clarify the relationships of blade loading change due to sweep and the complicated flow phenomenon in compressors. In this way, the connections of sweep and key aerodynamic parameters of compressors will be revealed in detail and the optimization rules of aerodynamic sweep will also be established in the compressors with different loading. All the researches in this project will benefit for the widely application of sweep greatly in the design and optimization of highly loaded compressors.

压气机载荷的增加以及内部流动复杂性的加剧，会严重制约其效率和稳定工作裕度的提高。而气动掠在改善高负荷压气机失速裕度、减少气动损失和控制角区分离等方面效果明显，已经成为国内外学者研究的焦点之一。因此深入揭示高载荷条件下气动掠对轴流压气机内部流动及总体性能的影响，并建立相应的优化准则具有重要的理论和现实意义。本申请项目拟从气动载荷的角度进一步揭示掠对高负荷轴流压气机内部流动的影响机理，主要研究内容包括：气动掠对高负荷压气机内部载荷匹配及输运机制的影响、掠型叶片内部载荷变化与三维激波特性、附面层发展和压气机稳定工作裕度之间的本质联系。通过上述研究，详细阐述气动掠引起的载荷变化与高负荷压气机内部复杂流动现象之间的内在联系，揭示气动掠与压气机关键气动参数之间的耦合关系，并建立针对不同载荷压气机的气动掠优化设计准则，为掠技术在高负荷压气机中的成熟应用提供便捷途径。

跨音速轴流压气机载荷的增加以及内部流动复杂性的加剧，会严重制约其效率和稳定工作范围，而气动掠在改善高负荷压气机失速裕度、减少气动损失和控制角区分离等方面效果明显，已经成为国内外学者研究的焦点之一。本项目通过深入揭示气动掠与压气机内部径向载荷匹配、通道激波特性、边界层内低能流体径向迁移之间的耦合关系，阐明了气动掠对高负荷轴流压气机总体性能和工作裕度的影响机理，并建立了基于气动、结构强度和振动特性约束下的复合掠优化设计方法。首先，本项目结合扩压叶栅通道内激波结构和波后边界层随背压变化规律，详细分析了高负荷轴流压气机不同叶高基元级的增压特点，并揭示超音速扩压叶栅内激波增压和叶型偏折扩张增压在叶片流道内的匹配关系。其次，针对前掠和后掠转子的叶表静压分布和三维流场结构，阐明了气动掠影响压气机径向载荷匹配的物理本质：气动掠引起压气机不同叶高基元级相对位置的变化（尤其是掠叶片前、尾缘线的展向分布），并在新的径向平衡约束下重新构建三维转子叶片的进/出口气流展向分布特征，进而改变掠型叶片不同叶高基元级的实际工作状态以及基元级载荷的径向平衡关系。当掠型叶片不同叶高基元级的实际工作状态发生变化时，其叶片通道内的激波强度及位置也会随之发生改变，并影响波后边界层内低能流体的径向输运，而叶表吸力面边界层内低能流体在不同叶高的集聚效应与当地的激波结构又存在相互制约关系，最终反映在压气机总体特性的变化上。最后，本项目通过整合气动前掠和后掠分别对三维转子叶尖和中径流场的改善作用，建立了复合掠叶片优化改型方案，并兼顾基元级扩散因子、叶片应力安全系数化以及叶尖与叶根弦长比三方面因素的约束，以确定不同叶高基元级最佳的掠型位移量，充分挖掘掠叶片的气动收益。采用该方法设计的复合掠叶型，不仅使跨音转子的工作裕度提升18%以上，还使其在设计工况相同增压比下的效率提升1%左右，且新的复合掠叶片的强度和振动特性均满足设计要求。