光学仪器  2019, Vol. 41 Issue (5): 1-9 PDF

1. 上海理工大学 能源与动力工程学院，上海 200093;
2. 上海理工大学 动力工程多相流动与传热重点实验室，上海 200093

Experiment on particle size measurement and verification using light-blockage method
QI Yongjie1, SU Mingxu1,2
1. School of Energy and Power Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China;
2. Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China
Abstract: In order to detect and analyze the number and size of particulate matter in liquid media, the characterization of standard spherical particles were investigated by the method of light-blockage related to geometric optics and Mie scattering theory, while the method of angle scattering and the image method were used to verify the consistency of the measurement. A system was established that could be available simultaneously for the three methods. To perform a calibration, the amplitudes of obtained light-blockage signal for standard particles with six different sizes were statistically averaged and fitted, which consequently provided a fitting formula to determine the measurement results of other particles. The results for two standard particles and a mixed particle system showed that the median diameters for particles with nominal value of both 15.0 μm and 63.6 μm yielded a deviation less than 2%, and the mixed particles were also well identified in size.
Key words: Mie scattering theory    light-blockage    angle scattering    signal calibration

1 基本原理 1.1 光阻法原理

 图 1 光阻法检测颗粒原理示意图 Figure 1 Schematic diagram of particle detection by light-blockage method

 $\Delta E{\rm{ = }}\frac{a}{A}{E_0}$ (1)

 $\Delta E = \left[ {1 - {{\rm e}^{(\frac{{ - a}}{A}{K_{\rm ext}})}}} \right]{E_0}$ (2)

1.2 角散射原理

 图 2 同轴采光系统和异轴采光系统示意图 Figure 2 Coaxial lighting system and cross-axis lighting system
2 实验装置

 图 3 实验装置简图 Figure 3 A brief diagram of the experimental apparatus

3 实验结果与分析 3.1 光阻和散射信号处理

 图 4 透射信号滤波前后效果对比图 Figure 4 A comparison of transmission signal before and after filtering

 图 5 散射信号滤波前后效果对比图 Figure 5 A comparison of scattered signal before and after filtering
3.2 光阻法与角散射法同步采集颗粒信号分析

 图 6 同步采集光阻和光散射信号 Figure 6 Simultaneous acquisition of signal by light-blockage and angle scattering

 图 7 CCD相机拍摄单个颗粒通过光束的过程 Figure 7 The CCD camera captures the passing of a single particle by using a beam of light
3.3 颗粒的信号标定

 图 8 不同粒径标准颗粒的透射信号示意图 Figure 8 Transmission of standard particles with different particle sizes

 图 9 标准颗粒信号标定的拟合曲线 Figure 9 Fitting curve for calibration of standard particle signals
 $y = {y_0}{\rm{ + }}\frac{{A} }{{w\sqrt {{\text{π} / 2}} }}\exp \left[\frac{{{\rm{ - 2(}}d - {d_c})}}{{{w^2}}}\right]$ (3)

 $\frac{{\Delta E}}{{{E_0}}} = 0.19 + \frac{{ - 37.65}}{{164.41 \times \sqrt {\displaystyle\frac{\text{π} }{2}} }} \times \exp \left[ { - 2\frac{{{{(d - 1.47)}^{\rm{2}}}}}{{{{164.41}^2}}}} \right]$ (4)

3.4 标准颗粒测量结果的验证

 图 10 标准颗粒图像和光阻法测量结果 Figure 10 Images and particle-size distributions by light-blockage measurements

 图 11 标准颗粒信号测量值与拟合值对比 Figure 11 Comparison of measurement and fitting values of standard particle signals

 图 12 混合标准颗粒信号值与粒径分布 Figure 12 Measured signal and size distribution of mixed particles
4 结　论

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