【摘要】 利用氦氖激光器为光源,在自行设计的光散射实验装置上,对类似于湿蒸汽透平中出现的低浓度水汽所形成的球状微粒群进行了粒径平均尺寸及尺寸分布的理论研究和测量。分析了常用的几种粒径分布函数与实际微粒分布可能出现的偏差;选用了上限分布函数(ULDF),用优化计算和测量方法,求得最佳的分布函数值,由此确定一个优化的ULDF。在实验装置设计中,采用反高斯滤波器以消除光强的高斯分布效应,应用高精度傅里叶透镜降低象差引入的误差。设计制作32环光电探测器作为接收散射光功率谱元件。把悬浮在水中的玻璃微珠对本实验装置做定性测量,数据结果与用显微镜摄影统计方法所得结果和用Malvern仪测得的数据作了比较。结果表明,本实验装置具有测量精度高(相对误差<10%)、适用范围广(适用于水滴、油滴、煤粉颗粒等)、测量粒径的范固宽(5～200μm)等特点。更多还原

【Abstract】 Theoretical researches are carried out to measure the mean size distribution of spherical particle group as found in the low pressure stages of wet steam turbines using optical instruments incorporating a He-Ne laser. The deviation presented is analysed between several distribution functions in ordinary use and practical particle distribution. Finally, it is decided to employ an improved method using upper limit distribution function (ULDF) to optimize the distribution parameters. In the design of the experimental system, an anti-Gaussian filter is used to eliminate the effect of the Gaussian beam, and a Fourier transformation lens of high precision is also applied to eliminate the spherical aberration. In addition, a photosensitive detector is manufactured as a unit to receve the power spectrum of scattering light. This apparatus is calibrated by directly measuring the diameters of glass beads suspended in water. The results are compared with those obtained by microphotographic statistical method and with those obtained by using a Malvern instrument. The experimental results indicate that this light scattering apparatus has a higher precision than that of Malvern’s, and a wide range of particle size (5～200μm) for measuroment.更多还原