弯扭管道引起的旋涡畸变对离心压气机气动性能的影响

Effects of Swirl Distortion Induced by Bent-Torsion Ducts on Aerodynamic Performance of a Centrifugal Compressor

关键词:  弯扭管道  离心压气机  旋涡畸变  相对气流角

Key words:  Bent-torsion duct  Centrifugal compressor  Swirl distortion  Relative flow angle

摘要:

为了研究弯扭管道进气产生的旋涡畸变对离心压气机气动性能产生的影响，采用数值模拟及实验的方法进行研究。首先明确了管道出口截面二次流场结构随扭转角度的演化过程，发现随管道扭转角度增大，旋涡结构在孪生涡和偏置涡之间变化；当扭转角度等于90°时，管道出口近似呈现团涡结构。研究表明，与孪生涡相比，近似团涡的旋涡形式对压气机性能的影响更显著。在设计转速下，当近似团涡的旋涡方向与叶轮转动方向相同时，压气机压比和效率的下降量约达25%，并减小了喘振流量；而旋涡方向与叶轮转动方向相反时，压气机性能无明显变化，喘振流量同时增大。通过阐述不同叶高气流旋涡角度、旋涡强度与相对气流角之间的关联关系，发现叶轮进口气流旋涡在不同叶高位置上的旋涡角度和强度改变了叶片前缘相对气流角，进而对进气攻角产生明显作用。

Abstract:

In order to investigate the effects of the swirl distortion induced by the bent-torsion intake duct on the aerodynamic performance of a centrifugal compressor，the numerical and experimental methods were carried out. The evolution processe of the outlet secondary flow structure with the torsional angle is clarified firstly. It is found that the swril form changes between the twin swirl and the offset swirl as the torsion angle increases. The bulk swirl appears approximately at the duct outlet when the torsion angle equals to 90°. Compared with the twin swirl，the shape of bulk swirl produces more obvious effects on the compressor performance. When the bulk swirl has the same rotational direction with the impeller at the design speed，both the pressure ratio and the efficiency decreases about 25%，and the surge flow also decreases. But when the bulk swirl has the opposite rotational direction with the impeller，the compressor performance has no obvious change and the compressor surge flow increases. The relationship among the swril angle，the swirl intensity and the relative flow angle of the blade at different span are investigated in details. The results indicate that both the angle and intensity of the swirl at the impeller inlet in different spans vary the relative flow angle of the blade leading edge and have significant effects on the intake attack angle.