**3. Experiment setup and experimental method**

The schematic of the experimental test rig is depicted in **Figure 3**. This rig consists of a rotor installed at its center and a rotating shaft supported by two bearings on its left- and right-hand sides. The right one is the test bearing for visualizations. It is manufactured while using transparent acryl, which allows us to observe the formation of the oil film and the generation of the gaseous phase. The shaft is driven with a DC motor that can control the rotational speed continuously by an inverter. The displacements in the horizontal and vertical directions of the journal are measured with eddy current-type proximity probes. The lubricating oil is supplied from the oil tank positioned on the top of the bearing through a control valve. The leaking oil from the side end of the bearing is returned using the pump. The VG22 oil is used and the oil temperature in the oil tank is fixed to 40°C with a heater.

**4. Results and discussions**

*Positions of thermocouples [2].*

**Figure 4.**

experimental result.

**199**

**4.1 Gaseous-phase area reproducibility**

*DOI: http://dx.doi.org/10.5772/intechopen.92421*

*4.1.1 Under flooded lubrication conditions in the journal bearing*

consequently, the main flow direction of lubrication oil is the same.

*n* = 3500 rpm. The volume of oil supply was *q* = 2.6 cm<sup>3</sup>

calculations and experiment are as shown below. The rotational speed was

*ε* = 0.54, and the attitude angle *ϕ* = 72.9°. These values are based on the

in good agreement with the experiment compared with the other cases.

In this study, four types of calculations were calculated to clarify the effects of vapor pressure and surface tension. Results of (i) analysis of the volume fraction *F* distribution of oil and (ii) experimental visualization under flooded lubrication conditions are depicted in **Figure 5**. The red color in **Figure 5(i)** indicates the phase of complete oil, whereas the blue color indicates that of complete gas. Further, the solid and dotted black lines perpendicular to the circumferential direction of the bearing indicate the maximum and the minimum clearance, respectively. The 0° means the position of the most upper part of the bearing and the oil-filler port of the bearing exists at this position. The black arrow means the rotational direction and,

*The Multiphase Flow CFD Analysis in Journal Bearings Considering Surface Tension and Oil…*

In this study, we have presented the results for the surface of the rotating shaft. Moreover, in **Figure 5(ii)** of the experimental result, the yellow areas represent the gaseous phase, and the remaining areas indicate the oil film. The conditions of these

In the case of VOF and VOF with surface tension as shown in **Figure 5(i-a, i-b)**, the volume fraction around the side end of the bearing decreases between 270° and 135°, and the volume fraction of the remaining area is approximately 1, which means complete oil. Around the oil-filler port, the volume fraction is most

decreased. In the case of VOF with vapor pressure as depicted in **Figure 5(i-c)**, the volume fraction around the side end of the bearing slightly decreases between 300 and 100°. The range of the volume-fraction decrease in this case is smaller than that observed in the case of VOF alone or in the case of VOF with surface tension. On the other hand, in the case of VOF with vapor pressure and surface tension as shown in **Figure 5(i-d)**, the volume fraction around the bearing side end is approximately 1 between 300 and 0°. This tendency is quite different from other cases. Moreover, between 0 and 135°, the value of volume fraction decreases, and the decreased area which means the gaseous-phase area is wider than that of VOF with vapor pressure shown in **Figure 5(c-1)**. The tendency found in **Figure 5(i-d)** of the gaseous-phase area is also found in the experiment. Therefore, it is concluded that **Figure 5(i-d)** is

/s, the eccentricity ratio

In this study, we also conducted the measurement of temperature distribution in the journal bearing clearance using sheathed thermocouples. **Figure 4** shows the positions of the thermocouples in the bearing. Two lines of bearing centerline and halfway between the center and side end of the bearing are installed, and they are positioned 45° apart on the bearing's circumference. Moreover, the thermocouples were only installed on one side of the bearing in order to be able to visualize the gaseous phase in the bearing clearance at the same time. It was found in the previous experiments that the temperature measurement error was almost negligible in the case of the obliquely installed thermocouple. The thermocouples were secured by feedthroughs, and oil leakage through the insertion hole was prevented by applying a sealant. As the experimental method, the temperature of the supplied oil was fixed at 40°C, while the rotating speed of the shaft was increased to 7500 rpm. Moreover, the ambient temperature was fixed at 25°C. In this study, the temperature in the bearing clearance was measured under two kinds of supply oil conditions.

**Figure 3.** *Geometry of an experimental test rig ([1] partially modified).*

*The Multiphase Flow CFD Analysis in Journal Bearings Considering Surface Tension and Oil… DOI: http://dx.doi.org/10.5772/intechopen.92421*

**Figure 4.** *Positions of thermocouples [2].*

of the oil-supply groove are open to the outside, the outside gas is easy to flow into the bearing and easy to generate the gaseous-phase cavitation at the position of negative-pressure generation. The surface tension was set to 0.04 N/m, which was

The schematic of the experimental test rig is depicted in **Figure 3**. This rig consists of a rotor installed at its center and a rotating shaft supported by two bearings on its left- and right-hand sides. The right one is the test bearing for visualizations. It is manufactured while using transparent acryl, which allows us to observe the formation of the oil film and the generation of the gaseous phase. The shaft is driven with a DC motor that can control the rotational speed continuously by an inverter. The displacements in the horizontal and vertical directions of the journal are measured with eddy current-type proximity probes. The lubricating oil is supplied from the oil tank positioned on the top of the bearing through a control valve. The leaking oil from the side end of the bearing is returned using the pump. The VG22 oil is used and the oil temperature in the oil tank is fixed to 40°C with a

In this study, we also conducted the measurement of temperature distribution in the journal bearing clearance using sheathed thermocouples. **Figure 4** shows the positions of the thermocouples in the bearing. Two lines of bearing centerline and halfway between the center and side end of the bearing are installed, and they are positioned 45° apart on the bearing's circumference. Moreover, the thermocouples were only installed on one side of the bearing in order to be able to visualize the gaseous phase in the bearing clearance at the same time. It was found in the previous experiments that the temperature measurement error was almost negligible in the case of the obliquely installed thermocouple. The thermocouples were secured by feedthroughs, and oil leakage through the insertion hole was prevented by applying a sealant. As the experimental method, the temperature of the supplied

oil was fixed at 40°C, while the rotating speed of the shaft was increased to

7500 rpm. Moreover, the ambient temperature was fixed at 25°C. In this study, the temperature in the bearing clearance was measured under two kinds of supply oil

measured while using the du Noüy method (ASTM 971–50).

**3. Experiment setup and experimental method**

*Computational Fluid Dynamics Simulations*

heater.

conditions.

**Figure 3.**

**198**

*Geometry of an experimental test rig ([1] partially modified).*
