Local linear stability analysis of cyclone separators
Local linear stability analysis of cyclone separators
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DOI：
10.1017/jfm.2017.89
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发表时间：
2017-01
影响因子：
3.7
通讯作者：
T. A. Grimble;A. Agarwal;M. Juniper
中科院分区：
文献类型：
--
作者：
T. A. Grimble;A. Agarwal;M. Juniper
采用局部线性稳定性分析方法，研究了旋风分离器内涡核的非定常进动。的稳定性分析的结果进行了比较与实验测量的旋涡振荡，使用高速摄影与粒子播种和热线风速仪。实验揭示了旋风内振荡行为的明显空间变化。非定常运动集中在装置的两端，即狭窄的锥体尖端和锥体顶部的排气管下方，这被称为涡流探测器。局部稳定性分析表明，绝对不稳定性存在于整个流动的一些非零方位波数。观察到的非定常流驱动的剪切层和惯性波之间的耦合限制在涡核。稳定性分析与实验的比较表明，相同的频率和模式形状的行为，并建议本地分析准确地预测系统的不稳定模式。旋进涡核产生窄带噪声。还绘制了与声学测量旋风分离器中的系统是由关键的无量纲参数，如旋流数和出口直径比定义。研究结果表明，局部稳定性分析的适用性，一个复杂的旋流系统，并产生可靠的细节的不稳定的内部旋风分离器的基本机制。
Local linear stability analysis is applied to the flow inside a cyclone separator to investigate the unsteady precession of the vortex core. The results of the stability analysis are compared with experimental measurements of the vortex oscillations using high-speed photography with particle seeding and hot-wire anemometry. The experiments reveal distinct spatial variation in the oscillation behaviour within the cyclone. The unsteady motion is focused at each end of the device, at both the narrow cone tip and just below the exhaust duct at the top of the cone, which is known as a vortex finder. The local stability analysis shows that an absolute instability is present throughout the flow for some non-zero azimuthal wavenumbers. The unsteady flow is observed to be driven by coupling between the shear layer and inertial waves confined within the vortex core. Comparison of the stability analysis with experiments shows the same frequency and mode shape behaviour and suggests that the local analysis accurately predicts the unstable modes of the system. The precessing vortex core is responsible for a narrow-band acoustic noise. Comparisons are also drawn with acoustic measurements made on cyclones in which the system is defined by key non-dimensional parameters, such as the swirl number and outlet diameter ratio. The results in this study demonstrate the applicability of local stability analysis to a complex swirling system and yield credible details about the underlying mechanisms of the unstable flow inside the cyclone.