Particulate concentration measured from scattered light fluctuations

Development of a tunable diode laser absorption sensor for online monitoring of industrial gas total emissions based on optical scintillation cross-correlation technique

We report the first application of gas total emission using a DFB diode laser for gas concentration measurements combined with two LEDs for gas velocity measurements. In situ gas total emissions and particle density measurements in an industrial pipeline using simultaneous tunable diode laser absorption spectroscopy (TDLAS) and optical scintillation cross-correlation technique (OSCC) are presented. Velocity mean values obtained are 7.59 m/s (OSCC, standard deviation is 1.37 m/s) and 8.20 m/s (Pitot tube, standard deviation is 1.47 m/s) in a steel plant pipeline for comparison. Our experiments demonstrate that the combined system of TDLAS and OSCC provides a new versatile tool for accurate measurements of total gas emissions.

Measurement of particle concentration in flow by statistical analyses of optical coherence tomography signals

We present a statistic method to measure the concentration of particles in flow by the use of optical coherence tomography (OCT). This method is based on the fact that the fluctuating numbers of particles contained within a small OCT detection volume caused by Brownian motion are governed by Poissonian distribution. Particle concentration is evaluated from the statistical analyzes of the OCT intensity signals that are backscattered by the moving particles. The method is experimentally verified with flow phantoms of polymer microspheres. Experimental results are in good agreement with the theoretical ones for low concentrations while relatively large discrepancies emerge for high concentrations.