| This research work introduces a novel solution for preventing nozzle wear in Abrasive Water Suspension Jets. It uses a porous nozzle surrounded by a reservoir containing a high-viscosity lubricant, which is exposed to the same driving pressure as the flow in the nozzle. The pressure difference between the reservoir and the nozzle interior, created by the high-speed flow in the nozzle, continuously forces lubricant through the porous medium. The thin lubricant film that forms on the interior walls of the nozzle protects them from the impact and shear of abrasive particles, substantially reducing nozzle wear.;Porous nozzles in the present study were manufactured using Electric Discharge Machining. The optimum material characteristics and machining parameters required to maintain the desired porosity have been established by observations using Scanning Electron Microscopy.;Two test-facilities were used for evaluating the porous lubricated nozzles. A two-dimensional facility, supporting a 145mum wide nozzle with windows on both sides, which enabled visualization of the oil-film and measurements of the liquid and abrasive-particle velocities using Particle Image Velocimetry. The velocity measurements showed that the centerline liquid velocity was not significantly affected by injection of oil. The measured velocities of the slurry-particles relative to the liquid, i.e. the slip-velocities, compared well with the computed values from a simple numerical model near the entrance to the straight-section of the nozzle, but were substantially lower near the nozzle exit. In fact, near the exit the measured slip-velocity decreased to less than 2% of the local liquid velocity, essentially to a negligible level. When the particles gouged the oil-layer, it immediately replenished itself and maintained its integrity.;The second facility used a 200 mum axisymmetric nozzle to determine the extent of nozzle wear under different conditions. It was found that the presence of an oil-film substantially reduced the wear, from 111% of the diameter, when the nozzle was not lubricated, to 4%, when oil-viscosity was 1800 mm 2/s and oil flow-rate ratio was only 2.4% (over the same period of time). The wear increased as the lubricant flow-rate and viscosity decreased. The presence of the oil-film also improved the coherence of the jet. |
