低雷诺数下高亚声速压气机叶型流动损失机理研究

Flow and Loss Mechanism of High Subsonic Compressor Airfoil under Low Reynolds Number Conditions

关键词:  压气机  叶片  气动性能  边界层  层流  载荷分布  流动损失

Key words:  Compressor  Blade  Aerodynamic performance  Boundary layer  Laminar flow  Loading distribution  Flow loss

摘要:

以高亚声速压气机叶型为研究对象，利用数值模拟手段研究了不同雷诺数Re条件下叶片近壁面分离泡结构和边界层发展的内在关联，基于Denton损失模型，揭示了低Re下压气机叶型性能退化内因；在此基础上，通过叶型改型设计，获得两种不同载荷分布的新叶型，对比分析了载荷分布对分离泡结构和叶型流动损失的影响。结果表明，Re从1.2×10⁶ 降低到1.5×10⁵时，吸力面分离泡长度增加11.2%轴向弦长，此时叶型边界层损失略有增加，而叶型尾迹损失增加接近150%，分离泡强烈的“位移效应”导致尾迹损失急剧增加是低Re下压气机叶型性能退化的主要原因；采用前加载叶型能够促使转捩提前发生，同时降低流向逆压梯度，有效抑制分离泡的形成和发展，改善低Re条件下高亚声速压气机叶型的气动性能。

Abstract:

The aerodynamic performance of compressor operating at high altitude is significantly affected by the process of boundary layer separation and transition on the blade. It is of great importance to clarify the loss mechanism of compressor airfoil under low Reynolds number (Re) conditions. In the present study, numerical simulations were conducted to investigate the structure of laminar separation bubble (LSB) and its effects on the boundary layer development. The underlying physics of performance deterioration for compressor airfoil was also analyzed based on Denton’s loss model. In addition, the airfoil was redesigned to obtain two new airfoils with different loading distributions, then the structure of LSB and flow loss were compared. According to the simulation results, the length of LSB on the suction surface increased approximately by 11.2% of the axial chord when Re decreased from 1.2×10⁶ to 1.5×10⁵. As such, the boundary layer loss changed slightly but the wake loss increased by 150%. Consequently, the larger wake loss caused by the strong“displacement effect”of LSB was supposed to be the main reason for performance deterioration of compressor airfoil at low Re conditions. Further more, the effects of loading distribution on the development of LSB and flow loss were also studied in detail. For the front-loaded airfoil, the LSB was suppressed due to the early onset of transition and the weaker adverse pressure gradient on the suction surface, which has the potential to improve the performance of high subsonic compressor airfoil under low Re conditions.