Powder flow in a screw feeder unit is experimentally investigated with X-ray visualization. Metal minute particle tracers with high absorption ratios are injected into the powder flow, and the motion of tracers is observed using X-ray penetration. We evaluate four kinds of powder flows transmitted with different shaped screws in a screw feeder unit. To study the flow structure precisely, image-processing techniques are adopted to measure the diffusion coefficient and transmitted velocity of the flow and to visualize path line. The following results are obtained :(i) Increasing pitch width of the screw yields decreased transmitted velocity and a larger diffusion coefficient. (ii) Double screw provides the largest transmitted velocity and the smallest diffusion coefficient. Uncertainty analysis is applied to the method of measuring the diffusion coefficient to achieve a more accurate method.

View full abstract