USING POROUS LUBRICATED NOZZLES TO PREVENT NOZZLE WEAR IN ABRASIVE WATER SUSPENSION JETS (AWSJ)

摘要

This paper reports on an on-going research to develop a method for preventing nozzle wear in abrasive water jets used for jet cutting. This method consists of using a nozzle made of a porous material, which is surrounded with a reservoir containing a high viscosity lubricant. The lubricant is forced continuously through the porous medium as a result of the pressure difference between the reservoir and the high-speed flow in the nozzle. The resulting oil film protects the walls of the nozzle from impact and shear caused by the abrasive particles. Previous tests with a two-dimensional, 0.145 mm wide nozzle with windows enabled observations and measurements of the liquid and abrasive particle velocities using PIV (Particle Image Velocimetry). We have established the proper material characteristics and EDM cutting parameters required to maintain the desired porosity. Over the past year we have been experimenting with an axisymmetric nozzle geometry. The effects of varying the lubricant flow rates and viscosities on the wear have been measured. It was found that the presence of oil substantially reduced the wear of the nozzle walls from 111 % to 10.5 % over the same period. The wear increased as the lubricant injection rate decreased. Lowering the viscosity of the oil for the same nozzle increased the lubricant flow rate, however it had little effect on the wear. The oil film also improved the jet coherence.