Flow field energy analysis of dynamic impinging stream reactor based on modal decomposition
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摘要: 采用实验和理论分析相结合的方法，对动态撞击流反应器流场内的能量分布规律进行研究。借助TR–PIV(Time-Resolved Particle Image Velocimetry)技术对动态撞击流反应器内部流场进行测量，在不同喷嘴间距与喷嘴内径比值L/d、平均出口速率及出口速率差条件下，考察了反应器内部流场的流动结构和流场能量。将动态撞击流反应器内二维速度场进行本征正交分解，提取出流场不同尺度拟序结构及不同本征模态下的能量特征，流场大尺度相干结构分布于径向射流区和两侧喷嘴上下近壁面处。随着L/d增大，反应器内部流场低阶模态含能量先增大后减小，L/d = 4时，流场能量最高；反应器内部流场低阶模态含能量随平均出口速率和出口速率差增大而增大。在动态出口速度条件下，反应器内部流场能量更高，流场大尺度相干结构更为明显，显著强化了流场内的动量交换，有利于提高混合效果。Abstract: The study investigates the energy distribution patterns within the flow field of a dynamic impact stream reactor through a combination of experimental and theoretical analysis. The flow field inside the dynamic impact stream reactor is measured using TR–PIV (Time-Resolved Particle Image Velocimetry) technology. Various nozzle spacings, different outlet mean velocities, and different outlet velocity differences are examined to understand the flow structure and energy distribution within the reactor. By performing eigenvalue orthogonal decomposition on the two-dimensional velocity field within the dynamic impact stream reactor, different scale quasi-ordered structures within the flow field and energy characteristics under different eigenmodes are extracted. Large-scale coherent structures in the flow field are distributed in the radial jet region and near the wall surface below the two nozzles. The energy of low-order modes in the reactor's flow field initially increases and then decreases as the nozzle spacing increases, with the highest energy proportion observed at a nozzle spacing of L/d = 4. The energy also increases with increasing outlet mean velocity and outlet velocity difference. Under dynamic outlet conditions, the energy proportion in the flow field of the impact stream reactor is higher, and the large-scale coherent structures in the flow field are more pronounced. This significantly enhances momentum exchange within the flow field, contributing to improved mixing efficiency.
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图 4 动态撞击流反应器内xOy平面瞬时流场速度矢量图
Figure 4. Instantaneous velocity vector diagram of xOy plane in dynamic impinging stream reactor
图 6 不同出口速率差下流场前10阶模态含能量分布
Figure 6. The energy distribution of the first 10 modes in the flow field with different outlet velocity differences
图 7 不同L/d下动态流场前10阶模态累积能量
Figure 7. The first 10 modes of the dynamic flow field accumulate energy under different L/d
图 8 不同平均出口速率下动态流场前10阶模态含能量分布
Figure 8. The energy distribution of the first 10 modes of the dynamic flow field at different average outlet rates
图 9 xOy平面前4阶模态涡量场重构
Figure 9. The first 4 modes of the xOy plane are used to reconstruct the vorticity field
表 1 实验工况
Table 1. Experimental condition setting
Nozzle d/mm vd/(m·s−1) va/(m·s−1) L/d Left, Right 10 0.2, 0.4, 0.6, 0.8, 1.0 1.3, 1.4, 1.5, 1.6, 1.7 3, 4, 5 
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表 2 前6阶POD模态相对能量贡献率的衰减量
Table 2. The attenuation of the relative energy contribution rate of the first 6 POD modes
Decay of relative
contributionva/(m·s−1) 1.3 1.4 1.5 1.6 1.7 (n1 − n2)/n1 27.0% 33.0% 35.0% 39.0% 45.0% (n2 − n3)/n1 16.0% 9.7% 19.0% 17.0% 16.0% (n3 − n4)/n1 10.0% 14.0% 9.5% 11.0% 8.9% (n4 − n5)/n1 5.3% 5.4% 6.3% 6.7% 10.7% （n5 − n6）/n1 2.3% 5.3% 2.8% 5.0% 3.0%
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