轴流压气机转子叶顶流场对微喷气的响应机制研究

Response Mechanism of Tip Flow Field in an Axial Compressor Rotor with Micro Injection

关键词:  微喷气  轴流压气机  非定常响应  稳定性  瞬态攻角  叶顶

Key words:  Micro injection  Axial compressor  Unsteady response  Stability  Transient incidence angle  Tip

摘要:

为了揭示叶顶流场对微喷气的响应机制，深入探究微喷气扩稳机理，以高负荷轴流压气机转子为研究对象，通过求解三维雷诺时均N-S方程对其进行了5通道高精度非定常数值研究。借助时间精确的数值模拟，获得了实壁和喷气工况下压气机转子的基元级性能、总性能和叶顶流场非定常特征。研究发现，在相同流量水平下，较之实壁工况，微喷气可以显著改变叶顶流场非定常特征的时空分布，削弱叶顶流场的自激振荡幅值。微喷气通过改变叶顶瞬态攻角对流场施加影响，叶栅掠过喷嘴过程中，正对喷嘴部位的攻角会发生突降，流场扩压程度和阻塞水平关于攻角突变的响应呈现出强烈的时滞性和非线性，攻角突降所诱导出的低阻塞水平在时域内持续时间约为低攻角水平持续时间的3倍。微喷气能够提高叶栅的承载能力，增强其对时均攻角的耐受力，拓宽流量裕度，增大吸力面分离在诱发流动失稳过程中的贡献比例。

Abstract:

To reveal the response principle of tip flow field to micro injection and study the stability enhancement mechanism deeply， 5 passages high accuracy unsteady numerical prediction was conducted on a high load axial compressor rotor by solving three dimensional Reynolds averaged N-S equation. Through time-accurate numerical simulation， elementary stage performance， overall performance and unsteady characteristics of tip flow field are obtained with the rotor working at smooth casing and micro injection conditions. It concludes， compared with smooth casing condition， micro injection can fundamentally change the temporal and spatial distribution of tip unsteady characteristics and attenuate self-sustained oscillation amplitude of tip flow field with compressor operating at the same mass flow level. Micro injection imposes on tip flow field by changing the transient incidence angle， in the process of rotor sweeping through the nozzle， incidence angle which faces the nozzle directly will suffer a plummet. The response of flow field diffusion degree and obstruction level to the abrupt change of incidence angle show a strong hysteretic and nonlinear nature， and the duration of low obstruction level induced by incidence angle sudden reduction is about three times that of low incidence angle level in time domain. Micro injection can enhance load bearing capacity of cascade， increase limit time-averaged incidence angle， improve stall margin， and increase the weight of suction separation in the process of inducing flow instability.