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A Thermal Equilibrium Analysis of Line Contact Hydrodynamic Lubrication Considering the Influences of Reynolds Number, Load and Temperature.

Yu X, Sun Z, Huang R, Zhang Y, Huang Y - PLoS ONE (2015)

Bottom Line: These variations have caused some inconsistencies in the conclusions of different researchers regarding the relative contributions of these thermal effects.The results indicate that the contribution of each thermal effect sharply varies with the Reynolds number and temperature.Convective effect could be dominant under certain conditions.

View Article: PubMed Central - PubMed

Affiliation: Department of Energy Engineering, Zhejiang University, Hangzhou, 310027, China.

ABSTRACT
Thermal effects such as conduction, convection and viscous dissipation are important to lubrication performance, and they vary with the friction conditions. These variations have caused some inconsistencies in the conclusions of different researchers regarding the relative contributions of these thermal effects. To reveal the relationship between the contributions of the thermal effects and the friction conditions, a steady-state THD analysis model was presented. The results indicate that the contribution of each thermal effect sharply varies with the Reynolds number and temperature. Convective effect could be dominant under certain conditions. Additionally, the accuracy of some simplified methods of thermo-hydrodynamic analysis is further discussed.

No MeSH data available.


The variations of Qb, Qf, Qconv and Qvis with different oil inlet temperature Tinlet.
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pone.0134806.g008: The variations of Qb, Qf, Qconv and Qvis with different oil inlet temperature Tinlet.

Mentions: The results are shown in Fig 8. With increasing Tinlet, the effect of Qconv in the thermal effects changes from dissipating heat to bringing heat into the oil film. The point of conversion depends on the difference of Tinlet and Tb: If Tinlet >> Tb, Qconv brings heat; If Tinlet << Tb, Qconv dissipates heat; however, if the difference between Tinlet and Tb is small, it is difficult to deduce the direction (in or out) of heat flow without careful calculations. The calculation results for Qb reflect the same situation. With increasing Tinlet, the value of Qvis decreases slightly, but the proportion of Qvis in the thermal effects changes dramatically. These results can be explained as follows: According to the research of Harigaya et al. [19], the minimum oil film thickness δ0 decreases with increasing Tinlet due to decreasing oil viscosity as shown in Fig 9. However, the decrease of δ0 results in an increase of the shear rate in the oil film. Combining these two factors, the total amount of Qvis fluctuates slightly. Meanwhile, other effects fluctuate rapidly with variation of δ0, resulting in the fluctuation of the proportion of Qvis with temperature.


A Thermal Equilibrium Analysis of Line Contact Hydrodynamic Lubrication Considering the Influences of Reynolds Number, Load and Temperature.

Yu X, Sun Z, Huang R, Zhang Y, Huang Y - PLoS ONE (2015)

The variations of Qb, Qf, Qconv and Qvis with different oil inlet temperature Tinlet.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4526673&req=5

pone.0134806.g008: The variations of Qb, Qf, Qconv and Qvis with different oil inlet temperature Tinlet.
Mentions: The results are shown in Fig 8. With increasing Tinlet, the effect of Qconv in the thermal effects changes from dissipating heat to bringing heat into the oil film. The point of conversion depends on the difference of Tinlet and Tb: If Tinlet >> Tb, Qconv brings heat; If Tinlet << Tb, Qconv dissipates heat; however, if the difference between Tinlet and Tb is small, it is difficult to deduce the direction (in or out) of heat flow without careful calculations. The calculation results for Qb reflect the same situation. With increasing Tinlet, the value of Qvis decreases slightly, but the proportion of Qvis in the thermal effects changes dramatically. These results can be explained as follows: According to the research of Harigaya et al. [19], the minimum oil film thickness δ0 decreases with increasing Tinlet due to decreasing oil viscosity as shown in Fig 9. However, the decrease of δ0 results in an increase of the shear rate in the oil film. Combining these two factors, the total amount of Qvis fluctuates slightly. Meanwhile, other effects fluctuate rapidly with variation of δ0, resulting in the fluctuation of the proportion of Qvis with temperature.

Bottom Line: These variations have caused some inconsistencies in the conclusions of different researchers regarding the relative contributions of these thermal effects.The results indicate that the contribution of each thermal effect sharply varies with the Reynolds number and temperature.Convective effect could be dominant under certain conditions.

View Article: PubMed Central - PubMed

Affiliation: Department of Energy Engineering, Zhejiang University, Hangzhou, 310027, China.

ABSTRACT
Thermal effects such as conduction, convection and viscous dissipation are important to lubrication performance, and they vary with the friction conditions. These variations have caused some inconsistencies in the conclusions of different researchers regarding the relative contributions of these thermal effects. To reveal the relationship between the contributions of the thermal effects and the friction conditions, a steady-state THD analysis model was presented. The results indicate that the contribution of each thermal effect sharply varies with the Reynolds number and temperature. Convective effect could be dominant under certain conditions. Additionally, the accuracy of some simplified methods of thermo-hydrodynamic analysis is further discussed.

No MeSH data available.