|¡¡|| Performance analysis of cryogenic hydrostatic journal bearing
Previous researches considered turbulent effect, pressure drop in recess boundary and changes of density or viscosity for pressure in extremely low temp. hydrostatic journal bearing This is why hydrostatic journal bearings in extreme low temperature are driven in turbulence region, and experience sudden velocity change in recess region, and also pressure change in the bearing is large. However, the performance analysis and the understanding of hydrostatic journal bearings in extreme low temperature is not enough due to the insufficient consideration about these parameters.
In this research, a numerical analysis is conducted about hydrostatic journal bearings in extreme low temperature having two columns¡® recess considering turbulence effect, pressure drop in recess boundary and the change of density or viscosity by pressure. We made a close investigation into an influence of each effect in static characteristics of hydrostatic journal bearings in extreme low temperature in this research.
Figure 1 shows pressure distribution in lubrication film. A longer direction is radial direction and other is axial direction. Recess locates in higher pressure region than a circumference. Recess is arranged in two column. each column has 10 recess.
Figure 2 shows the influence of each effect in performance analysis. Each case in Fig.2-(c) is classified in which effect is considered. Case 3 considering three effects is used as a reference in Fig 2-(a), (b).
The following things are the results of this research.
1. Turbulence effect exerts great influence on static performance analysis in extreme low temperature, so that this should be considered in an analysis.
2. Compared to turbulence effect, pressure drop effect is not large, but it is also considered when rotating speed is high or supplying pressure is large.
3. The change of density or viscosity by pressure has a small influence on performance analysis. Therefore, using mean density or viscosity value in middle pressure between supply and circumferential pressure is proper for exact analysis.
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