叶片加工偏差对叶栅临界攻角定性影响

Qualitative influence of blade machining deviation on cascade critical angle of attack

为了研究叶片加工偏差与压气机稳定性的关系,建立常用加工精度与压气机工作范围的量化关联,本文初步以多级高负荷轴流压气机级二级静子叶中截面为研究对象,构造了一种叶片表面几何不确定性降阶模型,并在3种常用加工精度下生成偏差叶型数据库。结合神经网络预测不确定性输入变量与叶栅临界攻角范围的关系,最终使用伪蒙特卡洛方法生成大量样本并开展统计学分析。结果表明:相比于原型,引入加工偏差使叶栅正临界攻角下降,负临界攻角上升,因此叶栅临界攻角范围下降,气动性能比原型更加恶化;以正临界攻角为例,当加工精度由2级提升到1级时,正临界攻角的均值由7.485 8°上降至7.557 1°,且叶片敏感部位由整个叶片区域变为前缘以及前半弦长,其轮廓度增减对临界攻角的影响趋势亦发生改变。由于上述分析所得均为统计学量化结果,因此本文研究结论将为今后设计优化三维叶栅或压气机转子提供理论依据,进一步节约加工成本。

In order to study the relationship between blade machining deviation and compressor stability,and establish the quantitative correlation between common machining accuracy and compressor working range,the middle section of two-stage stator blades of multi-stage high-load axial compressor was taken initially as the research object,a reduced order model of blade surface geometric uncertainty was constructed,and the deviation blade profile database under three kinds of common machining accuracy was generated.Combined with the relationship between the neural network prediction uncertainty input variables and the range of critical cascade angle of attack,pseudo-Monte Carlo method was used to generate a large number of samples and carry out statistical analysis.The results showed that,compared with the prototype,the introduction of machining deviation decreased the cascade positive critical angle of attack,and increased the negative critical angle of attack.Therefore,the range of critical angle of attack decreased,and the aerodynamic performance deteriorated more than the prototype.Taking the positive critical angle of attack as an example,when the machining accuracy increased from level 2 to level 1,the mean value of the positive critical angle of attack decreased from 7.485 8° to 7.557 1°,and the sensitive part of the blade changed from the whole blade area to the leading edge and the front half chord length,and the influence trend of the increase or decrease of the profile on the critical angle of attack also changed.Given the statistical quantification from above analysis results,the research conclusions could provide a theoretical basis for the design and optimization of 3D cascades or compressor rotors in the future,thus further saving the machining cost.