| The objective of this study is to develop an approximate thermohydrodynamic (THD, for short) model of lubrication for tilting pad journal and thrust bearings, which operate in either the laminar or the turbulent flow regime. It is further aimed that this model be simple enough to be solved on a personal computer, thereby placing computer aided design of pivoted pad bearings within reach of small manufacturers, yet it must contain all the essential parameters of the problem, thus assuring correct solution of the design problem. To reach the stage of simplification required, the equations governing the pressure and the temperature of the lubricant are reduced, via certain realistic assumptions, to ordinary differential equations. The ensuing non-linear system is then solved in iteration in such a manner that the required force and moment balance about the pivot are satisfied, and that energy is conserved globally.;Although the purpose of the model is the quick and accurate prediction of global performance parameters, such as bearing load, the model is often capable of providing local agreement for pressure and temperature with benchmark data. This is particularly true for journal bearings; these bearings are analyzed here for both static and dynamic behavior. The approximate model demonstrates excellent predictive capability of load carrying capacity and for maximum bearing temperature. The stability analysis, based on linearized spring and damping coefficients, shows that the THD model yields a higher threshold speed than does the isothermal model. Furthermore, the stability analysis demonstrates unconditional stability when including the motion of the pads, for a bearing which, for fixed pad, is only conditionally stable. For rotational speeds higher than threshold speed, the journal center reaches a limit cycle, while for rotational speeds less than the threshold speed for whirl, the perturbed journal center returns to its equilibrium position.;Only static analysis is performed for thrust bearings. Pad deformation is approximated as spherical crowning. When compared with results from more complete analysis, the approximate model is found to be acceptable. Comparison of calculated maximum pad temperature with experimental data, on the other hand, shows good agreement. |
