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 Transmission fluctuation spectrometry is a new method for measurements on large particles.Radiated by a narrow beam,the flowing particle system at a uniform velocity causes the transmission signal fluctuate violently.The transmission fluctuation signal is averaged within a variable time interval in the time domain and is then expressed in terms of the expectancy of transmission square.By changing the time constant,the transmission fluctuation spectrum is obtained,which includes the information of particle... Transmission fluctuation spectrometry is a new method for measurements on large particles.Radiated by a narrow beam,the flowing particle system at a uniform velocity causes the transmission signal fluctuate violently.The transmission fluctuation signal is averaged within a variable time interval in the time domain and is then expressed in terms of the expectancy of transmission square.By changing the time constant,the transmission fluctuation spectrum is obtained,which includes the information of particle size distribution and particle concentration.In this work,the theoretical expression is deduced,which also takes account of the influence from the particle concentration.  利用层模型得到消光起伏光谱及其数学表达式,光谱转折点的位置给出了颗粒的粒径信息,而光谱的深度则与颗粒系统的浓度有关.所得结果考虑了颗粒浓度对消光起伏光谱的影响.  Spectral analysis on the transmission fluctuations is a new method for measurements on large particles. Radiated by a narrow beam, the flowing particle system at a uniform velocity causes the transmission signal fluctuate violently. Both the average transmission and the spectrum of transmission fluctuations can be obtained statistically, which include the complete information on particle size distribution and particle concentration (volume fraction). By using the inverse algorithm, the particle size distribution... Spectral analysis on the transmission fluctuations is a new method for measurements on large particles. Radiated by a narrow beam, the flowing particle system at a uniform velocity causes the transmission signal fluctuate violently. Both the average transmission and the spectrum of transmission fluctuations can be obtained statistically, which include the complete information on particle size distribution and particle concentration (volume fraction). By using the inverse algorithm, the particle size distribution may be extracted from the spectrum of transmission fluctuations and consequently the particle concentration can be achieved from the average transmission. The theoretical expression of the transmission fluctuation spectrum is established, for monolayer of monodispersed particles. The theory is then extended to a 3dimensional system of monodispersed particles and further to that of polydispersed particles. Experimental test and simulation on dilute particle systems with particle diameters in the range 32～425 μm are performed, which shows that the method is valid to measure the particle size distribution and particle concentration simultaneously.  提出的透过率起伏光谱分析法是一种新的颗粒测量方法。采用一细小光束照射匀速流动的颗粒系统,通过采集透射光起伏信号,经统计处理得到透过率的平均值与起伏谱。通过求解逆问题,从透过率的起伏谱中得到颗粒粒径分布信息,再结合透过率的平均值得到颗粒的体积分数信息。给出了关于单层颗粒透过率的平均值与起伏谱的理论表达式,并推广到三维单分散和多分散的颗粒系统。对粒径在32~425μm内的稀薄颗粒系进行了部分实验测试和模拟计算,结果表明该方法可同时对颗粒粒径分布和体积分数进行有效测量。  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 realtime 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 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 realtime 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 multilayer 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 beamtoparticle 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.  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。   << 更多相关文摘 
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