HYDRO-DYNAMIC PRESSURE DISTRIBUTION IN TAPERED, STEPPED PARALLEL BOREAND COMPLEX-GEOMETRY PRESSURE UNITS - EXPERIMENTAL RESULTS

Hydro-dynamic action can generate very high pressure inside the passag e of particular shapes through which a fluid is flowing. A common situ ation is when the fluid is flowing through a converging surface (such as a journal bearing). The magnitude of this hydro-dynamic pressure is dependent on the viscosity of the fluid, the geometrical configuratio n of the confined passage and the relative speed of the solid surface. The effect of such action is less apparent for thin oil type fluids. Experimentally, it has been observed that when a solid wire is pulled through a stepped or conical bore passage that is filled with a viscou s fluid (such as polymer melt) then the pressure generated is so high that the outer casing may rupture if the wall thickness is not large e nough. Furthermore, if the casing is very strong, the rod may suffer p ermanent deformation if it is not made of a very hard material. The ma in objective of this study is to compare the performance of a complex geometry pressure unit to those of a simple tapered and a stepped para llel bore pressure unit in terms of pressure distribution, maximum pre ssure and axial stress and how the geometrical configuration of the un it affects the results. Results are presented in relation to the stain less steel and copper wires used for the experimental work. (C) 1998 E lsevier Science S.A. All rights reserved.