基于近场散射的颗粒粒径分布测量

针对传统的前向小角散射粒径测量系统中心光过强、杂散光干扰、散射角过小等缺点,本文采用一种新型的近场散射(NFS)方法测量前向小角散射光,研究并搭建了基于近场散射的颗粒粒径测量系统,将最大散射角提高到40.5°;在无需空白测量的情况下采用差分方法对透射光和散射光干涉成的散斑图像进行处理,有效去除中心光和杂散光的影响;对差分散斑图像进行快速傅里叶变换(FFT)频谱处理得到散射光强分布,利用Chahine算法对颗粒粒径进行了反演。最后,利用已知粒径(39.2μm和67.3μm)的标准颗粒对测量系统的准确性进行了单峰分布的验证,测量误差在5%之内;对于粒径为39.2μm和67.3μm的混合颗粒进行了双峰分布验证,在43.3μm和74.1μm处出现峰值,测量误差在10%左右。

Particle size distribution measurement based on near field scattering

To solve the problems such as high intensity of transmitted light, stray light interference and small scattering angle in the traditional low-angle light scattering techniques, a novel near field scattering (NFS) was adopted to derive the traditional low-angle scattering intensity. A particle size measurement system based on near filed scattering was proposed and built with the scattering angle up to 40.5°. Heterodyne method was applied to process the near field speckle images generated by interference between the transmitted and scattered fields, which is capable of completely removing the stray light. The angular intensity distribution was determined by fast Fourier transform (FFT) frequency spectral analysis of the heterodyne signal. The particle size distributions were inversed by Chahine algorithm. Experimental results on measurement of both monodisperse and bimodal samples with known diameters which are 39.2 μm and 67.3 μm, was presented. For monodisperse samples, the measurement error was less than 5%, for bimodal samples, there was two apparent peaks in 43.3 μm and 74.1 μm, the error was about 10%.