旋风分离器旋涡尾端测量及压力特性分析

Analysis on location and pressure of vortex end in gas cyclone

采用多点压力传感器对旋风分离器轴向、径向不同位置的压力时间序列信号进行了测量分析,同时用液体示踪法对旋风分离器内流动进行了显示。结果表明,壁面压力在筒体段及锥体段的周向分布轴对称;锥体下口及料腿顶部区域,壁面压力出现陡降突变,周向分布不再对称,在相对分离器入口约270°方位处出现凹陷,压力降至最低;再往下壁面压力很快回升,又复现轴对称。这些特征可作为旋涡尾端的识别标志,由此识别的旋涡尾端位置与液体示踪显示的旋转的封闭液环位置几乎一致。试验还发现,当入口气速大于5m.s-1时,旋风分离器内外旋流区压力波动的频率不同,内旋流压力波动频率高于外旋流且随入口气速增减而增减,外旋流区的压力信号频率则不随入口气速改变;内旋流涡核碰到器壁处的壁面压力信号会同时具有内、外旋流两个主频率。采用壁面压力信号可以很好地研究旋风分离器旋涡尾端的位置及其动态特性。

The pressure signals at different axial and radial positions of a cylinder-on-cone cyclone were measured and analyzed by the fast Fourier transform（FFT）.The vortex end of the cyclone was also visualized with red ink tracer.The results show that the wall pressure keeps stable in the cylinder and decreases gradually in the cone.The pressure values are almost same at different azimuths,indicating an axisymmetrical wall pressure profile in the cyclone.However,in the upper part of dipleg,the wall pressure suddenly falls,becomes non-axisymmetrical,and comes to the minimum at about 270° azimuth.In the lower part,the wall pressure rises rapidly and returns to axisymmetry.The vortex end is bended to the wall and turns around in this region.It is considered as the evidence of the vortex end.The position determined by the pressure measurement is close to the position of rotating ring observed in the tracing experiment.It is also found that the frequency of inner vortex is different from that of outer vortex when the inlet gas velocity is larger than 5 m·s-1.The inner vortex flow fluctuates stronger and faster than its outer partner and the frequency increases with the inlet velocity resulting from the increase in turbulence intensity,while the frequency of outer vortex keeps invariant.In the vortex tail zone,the vortex breaks and the inner vortex fluctuation is involved in the wall pressure signal.Therefore,the position and dynamic characteristics of the vortex end can be well identified from the pressure measurement.The measurement can provide some experimental basis for assessing the relation of natural vortex length.