5. Investigations of the temperature distribution

Tested apparatuses for the temperature distribution of the ball bearing have been built up as shown in Figure 2. There are three temperature sensors attached to the outer ring of the test bearing and one more temperature sensor on the inner ring. A data acquisition system is also employed to collect and transmit the data to a computer for further analysis.

#### 5.1 Temperature variations of the bearing

Figure 10 shows simulated outer ring temperature with the consideration of the nonuniform air-oil two-phase distribution under a bearing speed at 10,000 r/min. The oil flow rate is 3.0 l/min, which is equivalent to a jet speed about 10 m/s. The bearing is imposed with an axial load of 5.0 kN in the test. Table 6 shows the comparison between the test measurements and simulation results. It is shown that the relative tolerance between the tests and the simulations is smaller than 5%,

#### Figure 10.

The simulated temperature of the outer ring.


#### Table 6.

Measured and simulated outer ring temperatures.

Figure 11. Temperature distribution of the fluid-solid coupling heat transfer area.

Figure 12. Temperature distribution of the oil flow field inside the bearing.

#### Figure 13.

Simulation of average circumferential temperature and oil volume fraction distributions: (a) average oil temperature and (b) average outer ring temperature.

#### Flow and Heat Transfer in Jet Cooling Rolling Bearing DOI: http://dx.doi.org/10.5772/intechopen.84702

which indicates that the simulated results are in good agreements with the experimental results and sufficient in preforming quantitative analyses, since the research focuses are the overall heat transfer effects of the air-oil flow inside the bearing.

Figure 11 shows the simulation result of radial temperature distribution of both the fluid and solid domains inside the rolling bearing. The temperature distribution along the radial direction is inhomogeneous. The inner ring shows a relatively high temperature compared to that of the rolling elements. It is reasonable since the distribution of cooling oil around the inner ring is less, as most of the cooling oil is forced to leave the inner ring for the outer ones due to the strong centrifugal effect under high rotating speed. The accumulation of cooling oil near the outer ring surface leads to a better heat transfer effect that contributes to the lower temperature of the outer ring. Owing to the large heat-generating rate between roller and raceway, the temperature in these contact regions is of the highest level.

The 3D display of the simulated temperature distribution shown in Figure 12 confirms the nonuniformity of the temperature distribution inside the bearing. As shown in Figure 13, the temperature distribution of the flow field has a close

#### Figure 14.

The temperature distribution at different speeds: (a) bearing temperature distributions and (b) simulated and measured outer ring temperatures around the circumferential direction.

Figure 15.

The temperature distributions at different oil flow rates: (a) Bearing temperature distributions and (b) simulated inner ring temperature and measured inner ring temperature variations.

Figure 16. The temperature distributions at different oil-jet speeds.

Flow and Heat Transfer in Jet Cooling Rolling Bearing DOI: http://dx.doi.org/10.5772/intechopen.84702

association with the distribution of oil and gas. It is known that the heat transfer capacity of oil is considerably higher than that of air. That explains the reason that the lower temperature always achieves at positions with higher oil volume fractions, such as the positions that are close to the jet position. In general, the temperature near the nozzle is the lowest and increases gradually along the direction of rotation. It drops on the other side of the nozzle. This is because the low-temperature oil is discharged from the nozzle, and the low-temperature oil is constant. More oil supplement is the key factor in achieving better heat convection and lower temperatures.

#### 5.2 Parametric studies on the temperature distribution

Figure 14 shows the temperature distribution of the ball bearing at different speeds. The operating speeds of the bearing are 6000, 8000, and 10,000 r/min, respectively. The flow rate is 3.0 L/min and the oil injection speed is 10 m/s. It seems that the bearing temperature varies obviously at different speeds. With the increase of the speed, the bearing temperature rises, especially at a higher speed. Different from the average circumferential temperature distribution in the internal ring, the circumferential temperature difference exists in the outer ring. Further, the average temperature of the internal ring is higher than that of the outer ring.

Figure 15 shows the temperature distribution of the ball bearing under different oil flow rates. The oil flow rates are 1, 3, and 6 L/min with a speed of 10,000 r/min. The internal ring rotating direction is clockwise. The result indicates that the oil volume fraction of the flow field increases gradually. The convection heat transfer coefficient of the bearing boundary will also increase correspondingly. The heat dissipation condition becomes better. It is because that the amount of the oil entering the flow field in a unit time increases. At a constant speed, the stirring ability of the roller and cage changes little. Thus, the internal flow field of the bearing is distributed with more oil. The average temperatures of the rings and the flow field decrease, as shown in Figure 15(b).

Figure 16 shows the temperature distribution of the ball bearing at different jet speeds. The jet speeds are 5, 10, and 40 m/s with an operating speed of 10,000 r/min. The lubrication flow rate is 3.0 L/min. With the increase of the jet speed, the oil volume fraction of the flow field inside the bearing reduces gradually. The temperature of the bearing also rises. The variation of the outer ring temperature is not apparent compared with the inner ring. It is because that the convective heat

Figure 17. The temperature distributions with different nozzle numbers.


#### Table 7.

The measured temperatures with different nozzle numbers and speeds.

transfer capacity of the bearing boundary decreases, especially around the inner ring. The heat dissipation condition becomes worse with a higher jet speed.

Figure 17 shows the temperature distribution of the ball bearing under different nozzle numbers. The nozzle numbers are 1, 2, and 4 with an operating speed of 10,000 r/min. The oil-jet speed is 10 m/s and the oil flow rate is 3.0 L/min. The bearing temperature is decreased with a larger nozzle number. The heat convection coefficient inside the bearing increases. The experiments of the bearing with one nozzle and two nozzles have been carried out.

Table 7 presents the experimental results. The measured temperatures were presented. The axis load is 5 kN and the radial load is 10 kN. It can be seen that the increase of the nozzle number can improve the heat dissipation effect under a constant flow rate. The experimental results are consistent with the calculated results.
