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首页> 外文期刊>Chemical Engineering Science >Multi-scale analysis on particle fluctuation velocity near the minimum pressure drop in a horizontal pneumatic conveying
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Multi-scale analysis on particle fluctuation velocity near the minimum pressure drop in a horizontal pneumatic conveying

机译：水平气力输送中最小压降附近颗粒波动速度的多尺度分析

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摘要

Multi-scale characteristics of particle fluctuation velocity at the MPD (minimum pressure drop) air velocity in the acceleration and fully-developed regimes are experimentally investigated. The high-speed particle image velocimetry (PIV) is first used to measure the fluctuating particle velocities at the MPD air velocity in a horizontal pneumatic conveying. Then the fluctuating particle velocities in the acceleration and fully-developed regimes are analyzed by the continuous wavelet transform and orthogonal wavelet multi-resolution technique. It is found that the wavelet components of low frequency dominate the fluctuating energy of axial particle velocity in the bottom part of the pipe, and contribute about 70% and 84% to the acceleration and fully-developed regimes, respectively. The more contribution to the fluctuating energy of vertical particle velocity, however, comes from the wavelet components of high frequency, accounting for about 82%. The low frequency component of auto-correlation suggests a large-scale particle flow in both acceleration regime and fully-developed regime. The low frequency wavelet component also makes a large contribution to spatial correlation of axial particle velocity, which increases from the acceleration regime to fully-developed regime. The PDF of low frequency components are asymmetrical near the bottom of the pipe, but the PDF of the relatively high frequency exhibits symmetry and the spread of the PDF evidently shrinks for increasing frequencies, implying a reducing fluctuation of high frequency component.
机译：实验研究了加速和完全发展状态下MPD（最小压降）空气速度下的颗粒波动速度的多尺度特性。高速粒子图像测速（PIV）首先用于在水平气动输送中以MPD空气速度测量波动的粒子速度。然后，通过连续小波变换和正交小波多分辨率技术，分析了在加速状态和充分发展状态下的起伏粒子速度。发现低频小波分量支配了管道底部轴向颗粒速度的波动能量，分别对加速和充分发展机制贡献了约70％和84％。然而，垂直粒子速度波动能量的更大贡献来自于高频的小波分量，约占82％。自相关的低频成分表明，在加速状态和充分发展状态下都存在大规模的粒子流。低频小波分量还对轴向粒子速度的空间相关性做出了很大的贡献，轴向相关性从加速状态到完全发展状态逐渐增加。低频分量的PDF在管道底部附近是不对称的，但是相对高频的PDF表现出对称性，并且PDF的扩展明显随频率的增加而缩小，这意味着高频分量的波动减小了。

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