Measurement of fiber suspension flow and forming jet velocity profile by pulsed ultrasonic doppler velocimetry.

Abstract

The flow of wood fiber suspensions plays an important role during the pulp and paper manufacture process. Considerable research has been carried out in the past 50 years to characterize the fiber suspension flow behavior and to monitor the fiber suspension flow during paper manufacture. However, the above research has been hampered by the lack of techniques to directly characterize fiber suspension flow fields because fibers and fiber flocs tend to interfere with instruments inserted into the flow. The fundamental studies in this thesis concentrated on three parts: (1) examine the feasibility of measuring wood fiber suspension flow by Pulsed Ultrasonic Doppler Velocimetry (PUDV), (2) apply PUDV to characterize fiber suspension flow behavior in a rectangular channel, (3) apply PUDV to measure the forming jet velocity profile along the jet thickness direction (ZD). In the first part, it is demonstrated that PUDV is an accurate technique for the velocity profile measurement of fiber suspension flow. The measurement has high repeatability and sensitivity. Suitable parameters should be selected in order to obtain the optimum measuring results.