REDUCTION OF UNCERTAINTIES IN LASER STRIPE MEASUREMENT OF SOLID PARTICLES CONCENTRATION

Abstract

Laser stripe measurement (LSM) is a relatively novel method for measuring a local concentration of coarse particles in a mixture with fluid. It is based on an analysis of camera records of the laser sheet penetration in to the mixture. We report on our measurements of the concentration of suspended particles in a fluidization cell and focus on the parameters affecting the evaluation procedure for the measured data. A high sensitivity of the measured concentration to the correction for the position of the wall and to the threshold brightness for data filtering is demonstrated. The uncertainty in the wall position is reduced by applying a rectification procedure based on an identification of the position of a laser stripe drawn at the wall of the fluidization cell. The main motivation for the presented study was to find guidelines for the determination of the threshold brightness, absence of which can be considered a serious weakness of the LSM when particles of non-ideal optical properties are tested. Histograms of the brightness of laser stripes drawn on a surface of suspended particles are analysed with the aim to find a connection between the histograms and the threshold brightness. The threshold brightness is shown to be proportional to a position of the second of the two peaks identified in a histogram. Based on the results of the analysis, a method is proposed for the determination of the threshold brightness.