Influence of Wall Pressure on Power Reduction of Plug Conveying by Ultrasonic

Ultrasonic was applied to the horizontal line in plug conveyance of granular particles, and pressure drop was measured. As the result of this experimental research, pressure loss became smaller linearly with increasing of ultrasonic amplitude regardless of kinds of particles and flow conditions. Therefore, ultrasonic can cut the frictional resistance between packed particles and wall surface. Additionally the pressure sensor sheets were stuck inside the pipe at every 45 degree at a certain pipe cross section. Therefore 8 sheets were used. Measured values showed that the pressure against the pipe wall by particle bed have distribution in peripheral direction. Additionally pressure to the wall become smallest at the top of pipe cross section, and largest at the bottom. Then, the ratios of each pressure to the average value for all positions were calculated, and pressure distribution in peripheral direction was made clear. The ratio approached 1.0 as particle velocity in the packed bed become faster, and this means that pressure difference at each position become smaller. When particle velocity become faster, particles were pushed hard and the powder pressure against the pipe wall dominates for all pressure which works to the wall. This pressure is considered to affect the almost same value in all directions. Therefore the ratios approach 1.0. Additionally, the relationship of average pressure to the pipe wall and pressure loss reduction effect by ultrasonic was investigated. As a result, the pressure loss could not be reduced by ultrasonic as pressure of particle bed against the pipe wall become larger. This was assumed that it’s hard to float particles as particle pressure to the wall become larger and a lot of particles contact with pipe surface.