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过程工程学报 ›› 2022, Vol. 22 ›› Issue (11): 1468-1478.DOI: 10.12034/j.issn.1009-606X.221440

• 研究论文 • 上一篇    下一篇

双层撞击流混合器浓度时间序列的多重分形分析

张建伟， 唐俊， 董鑫*， 冯颖   

  1. 1. 沈阳化工大学 能源与动力工程学院
    2. 沈阳化工大学机械与动力工程学院
  • 收稿日期:2021-12-27 修回日期:2022-01-29 出版日期:2022-11-28 发布日期:2022-11-28
  • 通讯作者: 董鑫 dongxin1106@syuct.edu.cn
  • 作者简介:张建伟(1964-)，男，辽宁省义县人，博士，教授，研究方向为新型高效节能过程装备的开发，E-mail: zhangjianwei@syuct.edu.cn；通讯联系人，董鑫，E-mail: dongxin1106@syuct.edu.cn.
  • 基金资助:
    国家自然科学基金项目;辽宁省兴辽英才计划项目;辽宁省自然科学基金

Multifractal analysis of concentration-time series in double-layer impinging stream mixer

Jianwei ZHANG,  Jun TANG,  Xin DONG*,  Ying FENG   

  1. School of Mechanical and Power Engineering, Shenyang University of Chemical Technology, Shenyang, Liaoning 110142, China
  • Received:2021-12-27 Revised:2022-01-29 Online:2022-11-28 Published:2022-11-28
  • Contact: xin -DONG dongxin1106@syuct.edu.cn

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摘要： 利用平面激光诱导荧光技术(PLIF)对双层撞击流混合器的浓度场进行了实验测量，获得了不同径向位置处的浓度时间序列，通过多重分形去趋势波动方法(MF-DFA)研究了浓度时间序列中的多重分形特性，得到不同喷嘴间距和射流雷诺数下的多重分形谱，实现了流场特性的定量表征。结果表明，随着喷嘴间距增大，浓度时间序列的奇异性减弱，随着射流雷诺数增大，浓度时间序列的奇异性增强，喷嘴间距对浓度时间序列奇异性的影响比射流雷诺数更为显著。浓度信号的奇异性越强，流体粒子脉动越剧烈，混合效果越强，喷嘴间距对混合的促进作用大于射流雷诺数。通过分析多重分形谱参数(Δα, αmin, α0)随径向位置的变化规律得出了流型的转变区域，并将双层撞击流混合器由撞击中心处向下分为二次撞击区、涡旋区、一次撞击区。浓度信号的奇异性二次撞击区>一次撞击区>涡旋区，对混合的促进作用二次撞击区>一次撞击区>涡旋区。研究结果为更深入地揭示撞击流混合器内部流动模式和撞击流复杂无序的流动机理提供了理论依据。

关键词: 撞击流, 流域, 多重分形谱, 非线性动力学, 分形

Abstract: The concentration field of a double-layer impinging stream mixer was measured by the planar laser-induced fluorescence (PLIF) technique. The multifractal characteristic of the concentration-time series was investigated by using the multifractal detrended fluctuation method (MF-DFA). The multifractal singular spectrum under different nozzle spacing and jet Reynolds number was analyzed to realize the quantitative characterization of flow field characteristics. The results showed that the singularity of the concentration-time series increased with the jet Reynolds number. With the increase of the nozzle spacing, the singularity of the concentration-time series became weakened, and the influence of nozzle spacing on the singularity of concentration-time series was more significant than that of Reynolds number. The stronger the singularity of concentration signal of the double-layer impinging stream mixer, the more intense the motion of fluid particles, and the stronger the mixing effect. The promoting effect of nozzle spacing on mixing effect was greater than jet Reynolds number. According to the variation of multifractal spectrum of concentration time series of double-layer stream mixer, the singular spectrum parameters of concentration time series were obtained. Based on the distribution of the multifractal spectrum parameters (Δα, αmin, α0) along the radial position in the multifractal singular spectrum, the flow field in the double-layer impinging stream mixer was divided into axial impingement zone, vortex zone, and radial impingement zone from the impact center downward. The singularity of concentration signal of double-layer impinging stream mixer was larger than the primary impact region and larger than the vortex region. The effect of secondary impact zone on mixing was stronger than that of primary impact area and stronger than that of vortex area. It can provide a theoretical basis for revealing the flow pattern of the impinging stream system and the complex and disordered flow mechanism of the impinging stream.

Key words: Impinging stream, flow regimes, Singularity spectrum, nonlinear dynamics, fractals