**5. Conclusion**

from the oil-filler port. Hence, it is believed that the oil film at the center position was cooled down by an inflow air. Comparing with it, the position of between center and side, oil phase exists. Therefore, the cooling effect is lower than that of

From the abovementioned results, the authors considered that the internal flow of the oil-filler port influenced the temperature characteristics of starved lubrication conditions. Therefore, we focused on the calculation results in the oil-filler port

**Figure 14** shows the calculation results of the oil-filler port. **Figure 14(a)** indicates the results of the internal oil-filler port at the center of the bearing width of starved lubrication condition. **Figure 14(i-a)** indicates the volume fraction, while **Figure 14(i-b)** indicates the temperature. Moreover, **Figure 14(ii)** indicates the analytical results in the front view of the oil-filler port. From **Figure 14(ii)**, the temperature is high near the shaft, and the volume fraction decreases in that area. From the above, it is considered that the gas phase in this region is a circulating flow. In contrast, the gas phase exists in the wide area in the inside of the oil-filler port, while the temperature of the gaseous phase is smaller than the temperature of supply oil. Moreover, it is found that the temperature of oil is commensurate with the temperature of supply oil or less than. Furthermore, the temperature of the gaseous phase from the bearing clearance is about 40°C at the center of the oil-filler port. In **Figure 14(ii)**, the gaseous phase exists in the wide area in the inside of the oil-filler port as with **Figure 14(i)**, while it exists also in the oil-supply groove. The temperature of gaseous phase around the side end of the oil-supply groove is the same as the ambient atmosphere temperature set on the analysis; thus, it is found that outside air counterflows the oil-supply groove. From these results, in the case of the starved lubrication condition, it is considered that the outside air flows from

*Calculation results in the oil-filler port under starved lubrication conditions [2]. (i) Results in the center surface from the view of the side ((a) Volume fraction; (b) Temperature). (ii) Results in the front view ((a) Volume*

bearing center position.

*4.4.2 Results in oil-filler port*

**Figure 14.**

**208**

*fraction; (b) Temperature).*

under starved lubrication conditions.

*Computational Fluid Dynamics Simulations*

In this chapter, using a two-phase flow CFD analysis, the calculation of gaseousphase areas in journal bearings under flooded and starved lubrication conditions was conducted, and the surface tension effect on multiphase flow CFD analysis of journal bearing especially generating the gaseous-phase area was studied.

As a result of comparing the calculation results and the experimental results, the VOF calculation considering the surface tension and vapor pressure was observed to be in good agreement under both lubrication conditions.

Furthermore, under starved lubrication, the calculation results of the interface of the oil film and gaseous phase during oil-film rupture agree rather well with experimental visualization result if they consider both vapor pressure and surface tension. While using these results, the effect of surface tension was discussed from the viewpoint of the Weber number, and it is concluded that the Weber number is strongly lower than one by using the supply oil speed as the representative speed and strongly influenced.

Moreover, thermal CFD analysis of a two-phase flow was conducted under two conditions of supply oil, and they were compared with the experiment. As a result, it is believed that in the case of the starved lubrication conditions, the air flowing outside of the oil-supply groove created a circulating flow; thus, the temperature in the bearing is controlled.

It is concluded that the two-phase VOF CFD analysis considering the vapor pressure and surface tension is applicable in reproducing the gaseous phase on the journal bearing.
