Performance analysis of rotating externally pressurized air bearings

Abstract

The developed numerical method for solving the isothermal compressible Reynolds equation, which governs the equation of air-bearing analysis, is presented in this study. By using the assumption of mass flow continuity between the bearing clearance and orifices, the non-linear Reynolds equation is derived with the shaft-rotating effect. Newton's method is employed to linearize the Reynolds equation and an iterative successive relaxation process is used to solve for the air film pressure. The proposed method is valid for the analysis of film pressure distribution and load capability. This study gives a theoretical basis for the design of a pocket orifice externally pressurized bearing with the shaft-rotating effect considered, where the aerodynamic and aerostatic effects are coupled. Also, the numerical results indicate the difference between the two kinds of bearings mentioned above.

Performance analysis of Pareto optimal bearings subject to surface error variations

“…This effect is also referred to as the pressure depression effect [26] However, if manufacturing errors result in longitudinal convexity of the bearing surface, it can have deleterious effects on the stiffness as shown by negative stiffness regions in Figure 4(b). Although this phenomenon has been mostly attributed to journal aerostatic bearings [27], It has also been observed in flat pad aerostatic bearings [28]. It can be seen from the graph that it occurs at low values of gap heights and for maximum allowable value of surface deviation.…”

Characterization and Measurement of Hybrid Gas Journal Bearings

“…The results at this CFD microscope level were sketchy. As far as can be determined (excepting reference [5]), virtually no effort has been made to describe or characterize the hydrostatic pressure wave or the combined hybrid pressure wave. This thesis corrects this.…”

“…Reference [5] is an exception to that. It contains a graph of the load capacity versus eccentricity ratio for the feedhole hybrid bearing with data sets for the various speeds of operation including a zero-RPM curve.…”

“…This method is used to identify the development and movement of the pressure extrema in the pressure waves with increased hydrodynamic activity (rotation speed and eccentricity) for geometrically identical hydrodynamic bearings and hybrid bearings with porous liner-type mass addition and two rows of 6 feedholes-type mass addition over two orders of magnitude of "apples-to-apples" mass addition compensation. Due to the vastly increased computational and graphical power of the modern computer this examination provides much richer detail for the hydrodynamic bearing than was previously possible in earlier work as well providing apparently the first such examination (with the exception of Zhang and Xu [5] who do some similar analysis on feedhole bearings with two rows of 8 feedholes) of hydrostatic gas journal bearings and hybrid gas journal bearings.…”

“…Other names for  are simply another bearing number [23] or bearing number for transient analysis [5]. Thus the results of the study of purely hydrodynamic gas journal bearings are expressed in terms of the eccentricity ratio,  , , and L/D and are extendable as the clearance, c, is implicit or scaled into both the bearing number and the squeeze term such that they are both inversely proportional to the square of the clearance.…”