Flow of a wood pulp suspension through sudden expansion ducts and dispersion control of a high-consistency pulp-fibers

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An experimental investigation of the flow of wood pulp suspensions in a modeled hydraulic headbox of papermaking machines was performed. In the experiments, we investigate the flow characteristics in three sudden-expansion ducts and examine the influences of the expansion ratio and the flow rate on the behavior of the pulp fibers. The changes in the distributions of time-averaged concentration and the fluctuations of the concentration along the duct axis are illustrated for the pulp suspensions with various concentrations. Moreover, we discuss the degree of nonuniformity of the fiber concentration. The results obtained from this study are useful basic data and are expected to contribute to improving and optimizing headbox of the papermaking machines.