﻿ 面阵CCD空间滤波技术测量颗粒流速度场分布
 上海理工大学学报  2020, Vol. 42 Issue (4): 339-345 PDF

Spatial filtering method based on array CCD for granular flow velocity measurement
WANG Bide, CUI Yu, HE Guoqing, ZHAO Zhengbiao, LI Ran, YANG Hui
School of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China
Abstract: Spatial filtering method (SFM) based on linear CCD cannot directly measure the velocity distribution of granular flow in a rotating drum, meanwhile, it is difficult to measure accurately the velocity at the single-point region with complex velocity in the granular flow. In view of that, a new granular flow measurement method based on array CCD spatial filtering was proposed. Captured images were divided so as to form simulated sub-filters, SFM was performed separately at each sub-filter region, and then, the velocity distribution of granular flow in the rotating drum could be measured. For the end wall region with complex velocity variation in the rotating drum, an orthogonal vector algorithm was used for the velocity vector sum operation, which could avoid errors caused by the angle measurement, thereby improve the accuracy of single-point region velocity measurement. Finally, an experimental rig was set up to verify the method.Resolution and accuracy were analyzed, as well. The results show that array CCD-based SFM can measure the velocity distribution of granular flow in the rotating drum, and the measurement error is lower than 2%.
Key words: spatial filtering velocimetry     array CCD     granular flow     velocity distribution

1 空间滤波测速技术 1.1 基于面阵CCD的空间滤波测速原理

 图 1 空间滤波测速原理 Fig. 1 Principle of spatial filtering velocimetry

 $v=\frac{P}{M}f$ (1)

1.2 空间滤波效应

 ${G}_{P}\left(\mu , \gamma \right)={D}_{P}\left(\mu , \gamma \right){T}_{P}\left(\mu , \gamma \right)$ (2)

 ${G}_{P}\left(f\right)=\frac{1}{v}{\int }_{-\infty }^{\infty }{D}_{P}(f/v, \gamma ){T}_{P}(f/v, \gamma ){\rm d}\gamma$ (3)

1.3 实验系统搭建

 图 2 滚筒颗粒流动层测速系统 Fig. 2 Velocity measurement system of granular flow in the rotating drum

2 实验系统参数分析 2.1 系统标定

 图 3 面阵CCD采集传送带原始图像 Fig. 3 Original image collected by array CCD for the conveyor belt

2.2 系统分辨率

 图 4 不同帧速下输出信号频谱 Fig. 4 Output signal spectrum at different frame rates

 图 5 不同光栅个数下信号主峰频谱带宽 Fig. 5 Spectral bandwidth of output signals under different grating numbers
3 实验结果与讨论

3.1 滚筒中颗粒流速度场分布与边壁效应

 图 6 2.5 r/min转速、40%填充度下，滚筒颗粒流表面速度场分布 Fig. 6 Granular flow velocity distribution in the rotating drum at 2.5 r/min, 40% filling degree

 图 7 图6黑色方框区域滚筒颗粒流的速度分布 Fig. 7 Velocity distribution of granular flow in the black square area in fig. 6
3.2 不同填充度下的颗粒流边壁效应

 图 8 3.5 r/min、不同填充度条件下滚筒中轴区域颗粒流的速度分布 Fig. 8 Velocity distribution for different filling degrees at 3.5 r/min
4 结　论

a. 通过实验数据结合理论分析发现，本文所设计的面阵CCD空间滤波系统的最佳时间分辨率为0.001 s，最佳空间分辨率为1 mm。根据传送带速度测量对系统进行标定，发现误差小于2%，优于线阵CCD空间滤波法。

b. 面阵CCD良好的视场使得对滚筒颗粒流整个表面测量成为可能，所采用的正交算法避免了传统线阵CCD空间滤波法的角度测量带来的误差。

c. 根据所测的滚筒颗粒流表面速度场分布，结合归一化处理，发现由于边壁效应的存在，滚筒颗粒流表面横向区域根据速度不同分为边壁摩擦、峰值速度、平稳3种区域。当滚筒内填充度变大时，峰值速度位置相应地更加靠近滚筒中心位置。

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