The experimental equipment of lawn sweeper for scavenging volcanic ash was composed with a belt conveyer, dust collector and Root's blower. The conveyer belt was pasted on with an artificial lawn. The investigation in 1997 was intended for explication of scattering behavior of ash particles from a lawn by blowing air jets. The next purpose in 1998 was to investigate the flow of particles in the sweeper models. In those experiments, flow visualization techniques were used and their pictures were analyzed with micro-computers. Their results are as follows.
1. Blowing ash particles on a plane with an air jet through a blow tube, scattering position of ash in front of a blow tube recedes in the distance from a tube, scattering velocities of particles increase and scattering angles decrease from 80 to 70 degrees, with increasing blowing air velocity from 50 to 90 m/s. When a belt speed is large, a part of scattered particles which roll up and return to a blow tube increase.
2. On an artificia
l lawn with an air jet through a blow tube, a part of scattered ones rolling up and returning to a blow tube is less. In front of a blow tube, scattering position increases further than the above case 1, scattering velocities increase and scattering angles decrease from 55 to 30 degrees, with increasing blowing air velocity from 50 to 90 m/s.
3. On an artificial lawn with air jets through three blow tubes, scattering behavior in front of a blow tube is resemble to above case 2. But in the frontal intermediate plane between rubes, scattering position is near tubes, scattering velocities is low and scattering angles is high, about 80 degrees, independently of a blowing velocity When a belt speed increases, scattering position recedes in the distance, scattering velocities increase considerably and scattering angles decrease, on the contrary of above cases 1 and 2.
4. According to the above results, three ash sweeper models with 30, 45, or 60 degrees inclined suction duct were produced and flowing pattern of particles in them was investigated.
Their results are as follows.
(1) When a suction duct angle is 30 degrees, a part of blown up particles collide against an horizontal upper wall of blowing tubes area, then whole particles flow , up through a suction duct, like a serpentine motion.
(2) When a suction duct angle is 60 degrees, a part of blown up particles collide against an lower wall of suction duct, then whole particles flow through it, like a serpentine motion.
(3) When a suction duct angle is 45 degrees, whole blown up particles flow into a suction duct smoothly and then transfer through it almost parallel to it's wall.
(4) The above scattering behavior of particles with air jets through the blow tubes appear in such a narrow ash sweeper duct, so the flowing behavior in the ash sweeper is interpreted by them. Less