Combined Influence of Noncondensable Gas Mass Fraction and Mathematical Model on Cavitation Performance of Bearing

Lili Wang,Zengkai Liu,Yuliang Wei,Guoteng Yuan

doi:10.1155/2020/8409231

Abstract

The presence of cavitation in the oil film seriously affects the bearing lubrication performance and bearing capacity. Now the research of this phenomenon mostly focuses on the model of Reynolds equation (R-E equation) or Navier-Stokes equation (N-S), the influence of the two computation models is less analyzed, and the effect of noncondensable gas (NCG) mass fraction on the bearing performance is seldom studied. In the manuscript, the cavitation mechanism is studied using the mixed model of three-dimensional N-S equation and Jakobsson-Floberg-Olsson (JFO) condition of two dimensional Reynolds equation, and the influence of rotational speed and NCG mass fraction on the cavitationoil film pressure, and bearing capacity was studied. The results show that the change trend of cavitation with the rotational speed is basically consistent for N-S equation and R-E equation. The bearing capacity calculated by N-S equation is greater than that calculated by R-E equation. The peak pressure and bearing capacity of film can be improved by increasing the NCG mass fraction of lubricant and rotational speed.

Highlights

Numerical ModelInterpret the oil film reformation correctly and does not respect conservation of mass, and mass conserving boundary condition (JFO boundary condition) that is presented by Jakobsson, Floberg, Olsson considers mass conservation in oil film rupture and reformation location
Of noncondensing gas on the pressure field and phase field using a fully cavitated model
Air is a noncondensable gas under normal conditions, and the effect of NCG mass fraction on the bearing performance is seldom studied

Summary

Numerical Model

Interpret the oil film reformation correctly and does not respect conservation of mass, and mass conserving boundary condition (JFO boundary condition) that is presented by Jakobsson, Floberg, Olsson considers mass conservation in oil film rupture and reformation location In this manuscript, the JFO boundary condition with the cavitation pressure cav of −72139.79 Pa is used [17]. For using density as a dependent variable instead of pressure in Reynolds equation, the Elord algorithm treats lubricating oil as a compressible fluid with a large modulus of elasticity, introducing the nondimensional unit step function g into the relationship equation of density and pressure, 훽 = 휌휕푝/휕휌:. 휕푡 where is nondimensional elastic modulus of lubricant, h is nondimensional oil film thickness, is nondimensional axial direction, is width-diameter ratio, is bearing width, cav is cavitation density, and g is 0 in the cavitation region; g is 1 in the full oil film region. A er solving Equation (5) to obtain , the pressure distribution needs to be solved by Equation (4)

Numeral Calculations

Results and Discussion

Conclusion