叶根倒角对轴流压气机转子两端区流动结构的影响研究

为了揭示叶根倒角对跨音速转子的气动性能影响规律,以NASA的Rotor67转子为研究对象,采用数值方法研究了叶根倒角对跨音速轴流压气机角区分离和工作裕度的影响机制。结果表明：叶根倒角的引入改善了叶片倒角区前缘附近的来流攻角适应性及该区域的叶型几何曲率分布特征,进而提升叶根吸力面的抗分离能力。带有倒角结构的转子叶片在其叶根倒角未覆盖区的叶型中后段周向压力梯度大于原型叶片,有利于克服气流沿吸力面流动时产生的离心力,进而抑制了尾缘附近的分离现象,使得该区域效率提升了3.9%以上。倒角的存在借助于径向平衡约束,重塑了叶尖区域的沿程叶表静压分布,并减小了尖区的入口轴向速度,直接导致叶尖区域主流流体的通流能力明显削弱,并诱发相对更强的间隙泄漏流,从而使得跨音转子提前发生失速,压气机工作裕度降低了19%以上。

Study on the Effect of Blade-Root Fillet on the Flow Structure of the Rotor End Zone of Axial Compressor

The numerical investigation has been performed to analyze the influence of blade-root fillet on the performance of NASA Rotor67. The results show that the application of blade-root fillet improves both the adaptability of incidence angle of the leading edge of blade near hub and the distribution of the geometric curvature of blade profile. Therefore, the ability of flow in boundary layer to resist separation along suction surface near hub has increased accordingly. In comparison with the baseline rotor, the circumferential pressure gradient has increased near the latter part of new blade root where the root fillet is not covered. It is beneficial to suppress the centrifugal force of the mainflow passing through the passage along suction surface and reduce the separation near the trailing edge, as a result, an increase of 3.9% of local efficiency has been produced in this area. With the aid of new radial equilibrium induced by the root fillet, the distribution of static pressure along blade surface near tip has been reproduced and the axial velocity near entrance of blade tip has decreased as well. All the change of tip flow in new rotor induces relatively stronger leakage massflow and reduces the through-flow capability of mainflow near tip passage. Thus, the rotating stall of new rotor with fillet has occurred in advance and a decrease of 19% in stall margin of the new rotor is produced accordingly.