文氏管出口张角对旋流杯流动不稳定性的影响

Effects of Venturi Divergence Angle on Flow Instability of Swirl Cup

关键词:  文氏管  流动不稳定性  大涡模拟  旋进涡核  本征正交分解

Key words:  Venturi  Flow instability  Large eddy simulation  PVC  POD

摘要:

为探究旋流杯内流动不稳定现象，针对带不同出口张角文氏管的旋流杯冷态流场进行了大涡模拟，并结合PIV试验结果进行了验证。研究结果表明，文氏管出口张角对时均流场的影响主要在旋流杯内部区域，对下游恢复区域基本无影响；旋流杯瞬态流场中存在旋进涡核（PVC）和小涡旋结构，出口张角对PVC的运动频率和形态基本无影响，对小涡旋结构影响较大，相同Q值下，56°张角旋流杯方案的小涡旋结构更丰富；经本征正交分解方法（POD）分析，旋流杯的强脉动结构为PVC和小涡旋结构。56°张角旋流杯方案的小涡旋结构能量更强，脉动幅度较大，能更好地对燃油进行剪切破碎，有利于强化雾化效果。

Abstract:

In order to explore the flow instabilities in the swirl cup， the large eddy simulation （LES） was carried out for the non-reacting flow of swirl cup with different venturi divergence angles. The LES simulation results are verified by Particle Image Velocimetry （PIV） experiment. The results indicate that the effects of venture divergence angle on the time-averaged flow field are mainly in the inner region of the swirl cup， and venture divergence angle has no significant effect on the downstream recovery region. There are precessing vortex core （PVC） and small vortex structures in the transient flow field of swirl cup. The venturi divergence angle has no significant effect on the shape and frequency of PVC， while has a great impact on the small vortex structures. Under the same Q value， the small vortex structure of 56° swirl cup scheme is more abundant. According to Proper Orthogonal Decomposition （POD） analysis， the strong pulsating structures of the swirl cup are PVC and small vortex. The small vortex structure of 56° swirl cup scheme has stronger energy and larger pulsating amplitude， which is better for the fuel to shear and break up， further enhancing the atomization effect.