Design and manufacturing of modular self-compensating hydrostatic journal bearings

Abstract

In order to carry a load, a multi recess hydrostatic bearing supplied with a single pressure source requires compensation devices. These devices are also known as restricters and they allow the recess pressures to differ from each other. These devices, when properly selected and tuned, can deliver excellent bearing performance. However, these devices add to the complexity of the bearing and they are sensitive to manufacturing errors. These devices must often be tuned specifically for each bearing and are therefore expensive to install and maintain. Self-regulating or self-compensating bearings do not need any external devices to achieve load-carrying capability and they do not add to the total degrees of freedom of the system. However, in many cases the proposed designs require multiple precision manufacturing steps such as EDM and grinding in addition to precision shrink fit. In this work a self-compensating design, which eliminates all but one precision-manufacturing step, was manufactured and tested. Novel manufacturing methods for different sizes were introduced. The test results were compared with theoretical results and satisfactory agreement was achieved. The bearing sensitivity to manufacturing errors was analyzed computationally using statistical methods. These results were used to show that the introduced manufacturing methods are more cost effective than the applicable precision or semi precision manufacturing methods even when the performance variation is taken into account. When hydrostatic journal bearing is rotated hydrodynamic effects are introduced. Often, these effects are ignored by assuming them to be insignificant. Two non-dimensional parameters were derived to estimate the significance of the hydrodynamic effects and limits to these parameters were searched numerically. Design theory, along with first order equations to estimate bearing performance was developed.