Abrasion testing that follows the ASTM G65-04(2010) test method involves the delivery of a test sand to an abrasion wheel that removes material from a test specimen. The sand flow is controlled by a supply valve and delivered to a nozzle in order to form a uniform "curtain." It has been found that as the nozzle exit area is increased, the sand flow becomes widely dispersed and unstable. An experimental study was performed to determine the cause of this effect and to identify a means to mitigate it. By visualizing the inlet and outlet flow of different nozzles it was found that the dispersed flow occurs when the feed tube does not completely fill with sand. This sparsely packed flow in the nozzle is able to exit with a wide range of exit angles and yields the dispersed flow pattern as well as a higher flow rate. It was found that when the flow is controlled at the nozzle outlet, allowing the system to completely fill with sand before the flow is initiated, a desirable narrow sand curtain forms because the particles are more closely packed and thus their motion is more constrained. The narrow curtain is associated with lower flow rates than the dispersed pattern for the same geometry and once established will remain stable until the flow is terminated.
Title
The Control of Sand Curtains Used in Abrasion Testing