出口宽高比对S弯喷管流固耦合特性影响

Influence mechanism of aspect ratio on fluid-structure interaction characteristics of serpentine nozzle

针对涡扇发动机用双S弯喷管,通过串行双向松耦合方法研究了不同出口宽高比对双S弯喷管流固耦合特性的影响。研究结果表明,S弯喷管的结构变形特征主要位于S弯第一弯下游通道及喷管等值段出口上壁面,且随着出口宽高比增加,喷管第一弯下游区域变形量逐渐增大,出口的变形量先增大后减小,S弯喷管上、下壁面的最大变形均出现在S弯第一弯下游区域。由于喷管出口壁面向外膨胀,出口宽高比在耦合作用下相比设计值减小。流固耦合作用对不同宽高比S弯喷管的流场特征与气动性能产生影响,在小宽高比时喷管结构变形后产生的流动分离对喷管下游流动产生较大影响,此时喷管沿轴向向上弯曲角度减小,推力矢量角减小;在大宽高比时喷管沿轴向向上弯曲角度随着出口宽高比增加逐渐增大,推力矢量角增大。当宽高比为2时总压恢复系数降低了0.56%,流量系数降低了2.67%,推力系数降低了0.72%;当宽高比为10时,此时总压恢复系数降低了0.36%,流量系数降低了4.34%,推力系数降低了1.37%。

The influence of the aspect ratio on two-way fluid-structure interaction characteristics of double serpentine nozzles for turbofan engines was investigated by the serial two-way loosely coupled algorithm.The results show that the structural displacement characteristics of the serpentine nozzle are mainly located in the downstream channel of the first bend and the exit upper wall of the equivalent section of the nozzle,and that with the increase of the aspect ratio,the displacement of the downstream area of the first bend of the nozzle gradually increases,while that of the exit of the nozzle first increases and then decreases.The maximum displacements of the upper and lower walls of the serpentine nozzle both appear in the downstream wall of the first bend.Because of the outward expansion of the nozzle outlet wall,the outlet aspect ratio decreases compared with the design value under fluid-structure interaction.The fluid-structure interaction influences the flow field characteristics and flow losses of different aspect ratios.The flow vortex caused by the deformation of the nozzle structure has a large influence on the downstream flow of the nozzle with a small aspect ratio.In this case,the axial bending angle of the nozzle decreases and the thrust vector angle de-creases.In the case of large aspect ratios,the nozzle axial bending angle increases with the increase of the aspect ra-tio,and the thrust vector angle increases.At an aspect ratio of 2,the total pressure recovery coefficient is reduced by 0.56%,the flow coefficient 2.67%and the thrust coefficient 0.72%,while the three are reduced by 0.36%,4.34%and 1.37%,respectively,when the aspect ratio is 10.