Abstract
Motivated by the use of aerodynamic bearings lubricated with high-pressure gases in energy conversion cycles, the Reynolds equation is adapted in order to include effects of real-gas and turbulence. Three geometries (Rayleigh-step slider, plain and herringbone-grooved journal bearing) serve to investigate real-gas effects on the static and dynamic properties with a wide variety of lubricants and nondimensional operating conditions. Computational results show a depreciation of the load capacity of journal bearings, with cases reaching a reduction of 50% with unequally affected force components. Stability can be affected both positively and negatively. Some stability losses reach nearly 100%, while improvements of several orders of magnitude with the grooved bearing are reported. Results are fluid-independent for similar reduced pressure and temperature.
Highlights
Schiffmann and Favrat[6] investigated the real-gas effects on the 18 properties of herringbone-grooved journal bearings (HGJB) using the Nar19 row Groove Theory (NGT) and addressed the consequences on the optimal 20 design of such bearings
159 The model developed above is applied for different geometries of aero160 dynamic bearings in order highlight the real-gas effects on the lubrication 161 performance in terms of load capacity and stability
The real gas consideration leads to a redistribution of the pressure, with a lowered peak pressure compared to the pressure when the ideal-gas law is
Summary
44 The Reynolds equation is adapted to express the density field in aero dynamic bearings, with the bulk modulus as a parameter accounting for 46 the real-gas effect. Since real-gas effects are associated with high-density fluids, the Reynolds number in the bearing can reach a level where turbulence has to be included in the constitutive lubrication equation. The load capacity W is computed from the static pressure field from the reaction force acting on the bearing in both directions: Wx = −R2Pa Wy = −R2Pa. 134 The equations regrouping terms of first order are linear with respect to the perturbed density. A first-order perturbation is applied to this equation following Equations 17 to 21 and zeroth- and first-order equations are segregated to be solved successively with the same numerical scheme indicated above
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