叶片表面粗糙度对压气机叶栅内三维角区分离及损失研究

Effectiveness of Blade Surface Roughness on 3D Corner Separation and Loss in Compressor Cascade

在实际使用过程中,压气机容易由于腐蚀磨损等原因导致叶片表面粗糙度增加,这将使得整级压气机的气动性能下降。与此同时,由轮毂横向流所诱发的角区分离也将造成巨大的流动损失。为了探究叶表粗糙度变化是否会促进角区分离的产生,以及粗糙度变化对压气机内损失类型的影响,借助CFX商用软件对低雷诺数扩压叶栅展开数值计算研究。同时,还引入Gamma模型来研究粗糙度变化对转捩的影响。研究发现,叶片表面粗糙度的增加将使得分离转捩和旁路转捩加强,但对逆转捩影响较小。此外,借助损失源分析方法,将叶栅内的损失分为前缘损失、叶型摩擦损失、二次流损失和尾迹损失。结果表明,在角区分离严重且表面等效砂砾粗糙度增加到50μm时,相比于光滑情况,其总损失增加了9.6%。借助拓扑分析,可以发现随粗糙度增加,前缘分离泡不断前移,扰乱前缘部分流动,由此导致的前缘损失随粗糙度变化最为明显。

The compressor blade surface roughness is easily deteriorated by deposits of ash and sand, as well as corrosion at wet environment, which results in the failure of aerodynamic behavior for compressor failed.Meanwhile, the three-dimensional(3D) separation near the hub causes large performance loss for compressor.Thus, a low-Reynolds compressor cascade was studied to investigate that whether the roughness on the blade can promote the 3D separation and make a difference on all type of the loss in the cascade or not by CFX. In this study, the Gamma transition model was introduced to investigate the influence of blade surface roughness to transition phenomenon. It can be concluded that the blade surface roughness has more effect on the separation transition and the bypass transition than the reverse transition. Furthermore, a detailed loss sources analysis model was used to study the loss influenced by the surface roughness, which divided the total loss in the cascade into the leading edge loss, the surface friction loss, the secondary flow loss and the wake flow loss. The results show that the total loss increases to 9.6% at large scale of corner separation condition when the equivalent sand grain roughness in the blades increases to 50μm. And the leading edge loss is most sensitive to the surface roughness. With the help of the topology analysis method, it can be found that the movement of the separation bubble is the most obvious phenomenon in the field as the roughness increasing.