Experimental study of instability of gas-phase swirling flow in cyclone

doi:10.11949/0438-1157.20220486

Abstract

Abstract:

The gas-phase swirling flow in the cyclone has strong instability, which is manifested in the eccentric swing of the rotational center of the swirling center around the geometric center, which causes the instantaneous velocity of the flow field to fluctuate with time. It is not accurate to describe the instability characteristics of this swirling flow with time averaged flow field parameters, which need to be described with dynamic flow field parameters. Therefore, the instantaneous tangential velocity in ?300 mm cyclone was measured by hot wire/film anemometer. The results show that the instantaneous tangential velocity is the superposition of high-frequency pulsation formed by gas turbulence and low-frequency pulsation formed by eccentric swing of swirling flow. Based on this, the formation mechanism of swing of swirling flow was discussed. The low-frequency fluctuation of instantaneous tangential velocity comes from the eccentric swing of forced vortex, and the fluctuation amplitude is proportional to the eccentricity. According to the frequency domain of instantaneous tangential velocity, the calculation model of swing frequency related to the inlet velocity, cylinder diameter and vortex finder diameter of swirling flow was established.

Key words: cyclone, swirling flow, instantaneous tangential velocity, instability characteristics, swing frequency

摘要：

旋风分离器内气相旋转流具有较强的不稳定性，其表现形式是旋转流的旋转中心围绕几何中心的偏心摆动，导致流场的瞬时速度随时间发生脉动变化。这种旋流的不稳定特性难以用时均流场参数进行描述，需要用动态流场参数描述，为此采用热线风速仪测量了?300 mm旋风分离器内瞬时切向速度随时间的变化。实验结果表明瞬时切向速度是由气体湍流形成的高频脉动和旋转流偏心摆动形成的低频脉动两部分叠加构成，据此探讨了旋转流摆动形成的机制。瞬时切向速度的低频脉动来源于刚性涡的偏心摆动，脉动幅值与偏心距成正比。通过瞬时切向速度频域建立了旋转流的摆动频率与入口速度、筒体直径和排气管直径的计算模型。

关键词: 旋风分离器, 旋转流, 瞬时切向速度, 不稳定性, 摆动频率

CLC Number:

TQ 051.8

Jianfei SONG, Liqiang SUN, Ming XIE, Yaodong WEI. Experimental study of instability of gas-phase swirling flow in cyclone[J]. CIESC Journal, 2022, 73(7): 2858-2864.

宋健斐, 孙立强, 解明, 魏耀东. 旋风分离器内气相旋转流不稳定性的实验研究[J]. 化工学报, 2022, 73(7): 2858-2864.

Figures/Tables 9

Fig.1 Experiment setup for cyclone flow field measuring device

Fig.2 Instantaneous tangential velocity in cyclone (dr=110 mm)

Fig.3 Instantaneous tangential velocity in cyclone (z=370 mm)

Fig.4 Time-averaged tangential velocity profiles in cyclone

Fig.5 Effect of swing of swirling flow on tangential velocity fluctuation

Fig.6 Spectrum analysis of instantaneous tangential velocity in cyclone （dr=110 mm）

Fig.7 Spectrum analysis of instantaneous tangential velocity at r/R=0.12 in cyclone

Fig.8 Eccentric rotation of swirling flow in cyclone

Fig.9 Dominant frequency of experiment and model calculations

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