Principal normal stress cavitation criterion for CFD analysis of loading capacity in journal bearings

Abstract

Purpose Shear stresses have a considerable influence on the characteristics of lubricants and become significant at high rotating speeds. This study aims to investigate the influences of shear cavitation (SC) on loading capacity of journal bearings. Design/methodology/approach A principal normal stress cavitation criterion based on the stress applied to flowing lubricant in journal bearings is developed and used to investigate SC in journal bearings. A computational fluid dynamic (CFD) model for calculating the loading capacity is established using this criterion. After validation with experimental results, the loading capacity is calculated under different conditions. Findings The calculation results indicate that SC intensifies when viscosity, speed and eccentricity increase. Angle of loading capacity with SC is larger than that without SC. The magnitude of loading capacity with SC is smaller than that without SC due to the decrease in the ultimate pressure. In addition, the magnitude difference between the loading capacity with and without SC increases when viscosity, speed and eccentricity increases. Originality/value Present research can provide some guidance for calculating the loading capacity when a journal bearing is operating at high speed or with a high viscosity lubricant.

Stability Analysis of the Rotor-Journal Bearing System Considering Shear and Gaseous Cavitation

“…In vaporous cavitation, the shear stress affects the amplitude of the incipient cavitation pressure in the oil film. A stress cavitation criterion is proposed and verified [31], and the ultimate principal stress cavitation criterion equations are as follows:…”

“…Based on the full cavitation model, Li et al [30] put forward the transient calculation method to analyze the transient flow field of a journal bearing in a rotor-bearing system. Furthermore, Li et al [31] made a detailed derivation of shear stress cavitation and found that the magnitude of the loading capacity of shear stress cavitation is smaller than the loading capacity without shear stress cavitation due to the decreased ultimate pressure. For gaseous cavitation, Lin et al [32] described the relationship between gas phase volume and pressure through linear functions and established a thermoelastic fluid dynamic pressure lubrication model for journal bearings.…”

An active control for hydrostatic journal bearing using optimization algorithms

“…Several authors focus to improve load-carrying capacity (Zhang et al, 2019;Li et al, 2019). The efficiency and performance of hydrostatic bearing are measured in terms of its load-carrying capacity.…”