消光起伏光谱法高浓度效应的模拟计算

Simulation on High Concentration Effects of Transmission Fluctuation Spectrometry

消光起伏光谱法(TFS)是最近发展起来的颗粒测量技术,它可以同时测量颗粒粒径分布和浓度,并可用来进行在线、实时测量。在频率域内对透过率起伏信号进行频谱分析,信号分析系统采用品质因数为0.707的二阶低通滤波器。通过模拟计算得到有关单层与多层颗粒系统的归一化差值函数经验表达式,由此分析颗粒系统的高浓度效应(包括颗粒交叠效应和层结构)对消光起伏光谱的影响。结果表明,高浓度效应与颗粒系统的浓度、层数及光束-颗粒直径比Λ都有关系,它对消光起伏光谱特征函数的影响主要体现在频谱移动和阶高变化两个方面:一般来讲,消光起伏光谱的频率响应主要受颗粒交叠响应的影响,表现为向低频区移动;而消光起伏光谱特征函数的阶高则同时受层结构和颗粒交叠效应影响。

The transmission fluctuation spectrometry （TFS） is a new method developed in recent years, in which the particle size distribution and particle concentration can be measured simultaneously, and real-time online measurements can be realized. The spectral analysis of the transmission fluctuations in the frequency domain is presented and a 2nd order low pass filter with the quality of 0. 707 is employed. By numerical simulation, the empirical expression of the normalized deviation of the transition functions between the multi-layer particle system and the monolayer particle system is obtained. And the high concentration effects on the transmission fluctuation spectrum are discussed. The results show that the high concentration effects are related to the concentration of the suspension, number of layers and beam-to-particle diameter ratio. The high concentration effects can change the transition function of TFS in two aspects： the shift in frequency response and the step height. Generally, the shift in frequency of the transition function is domained by particle overlapping, while the step height is affected by both the monolayer structure and particle overlapping.