A New THL Model for High Accuracy of Predicted Journal Surface Temperature

A thermo-hydrodynamic lubrication (THL) theory is applied to journal bearings that support large-sized high-speed rotary machineries and it is confirmed that the maximum pad surface temperature under operation is below an allowable limit value. The temperature predicted by the traditional THL model is in good agreement with the measurement. However, the predicted journal surface temperature is not comparable with the measurement. In the present paper, it is firstly shown that the amount of heat, which is generated by the shear flow in the oil film and is discharged out of the film, is evaluated appropriately in the film near the pad surface while it is evaluated excessively in the film near the journal surface. Secondly, a new THL model is proposed that the oil film temperature near the pad surface and the temperature near the journal surface are obtained independently, that is, the conventional energy equation for the oil film is solved for the former temperature while the equation described in the relative coordinate system with the journal surface as the reference one is used for the latter temperature. Lastly, it is shown that the THL model can predict the journal surface temperature comparable with the measurement without deteriorating the accuracy of the predicted maximum pad surface temperature.