APPLICATION OF LASER-DOPPLER ANEMOMETRY TO MEASURE VELOCITY DISTRIBUTION INSIDE THE SCREW CHANNEL OF A TWIN-SCREW EXTRUDER

Velocity measurements inside the screw channels of a co-rotating, self -wiping twin-screw extruder (ZSK-30) have been carried out using the n oninvasive technique of Laser Doppler Anemometry. A two-dimensional Ar gon-ion laser Doppler system was used to measure tangential and axial velocity components in one of the screws, away from the intermeshing z one. Heavy corn syrup with naturally occurring particles was used in t he extrusion experiments. The measured tangential velocity distributio n agreed with the expected distribution for a Newtonian fluid. Measure ments also indicated that near the screw root and away from the flight s, shear rates were substantially lower as compared to the shear rates near the barrel. The results indicated that this technique is suitabl e for making velocity measurements in a twin-screw extruder using mode l fluids.