Search

Abstract: Grease is commonly used to lubricate various machine components such as rolling bearings and seals. In this paper the flow of lubricating grease passing restrictions is described. Such flow occurs in rolling bearings during relubrication events where the grease is flowing in the transverse (axial) direction through the bearing and is hindered by guide rings, flanges etc, as well as in seals where transverse flow occurs, for example during so-called breathing caused by temperature fluctuations in the bearing. This study uses a 2D flow model geometry consisting of a wide channel with rectangular cross-section and two different types of restrictions to measure the grease velocity vector field, using the method of Micro Particle Image Velocimetry. In the case of a single restriction, the horizontal distance required for the velocity profile to fully develop is approximately the same as the height of the channel. In the corner before and after the restriction, the velocities are very low and part of the grease is stationary. For the channel with two flow restrictions, this effect is even more pronounced in the “pocket” between the restrictions. Clearly, a large part of the grease is not moving. This condition particularly applies to the cases with a low-pressure drop and where high consistency grease is used. In practice this means that grease is not replaced in such “corners” and that some aged/contaminated grease will remain in seal pockets. [Copyright &y& Elsevier]

A numerical study of the grease friction losses in three different configurations of axial and radial labyrinth seals under different rotational speeds was conducted. The results showed the grease rheology has a significant effect on the viscous torque. On the other hand, the number of labyrinth grooves does not affect substantially the torque for axial configuration but influences significantly the torque for radially oriented seals. Axially oriented seals have shown a better lubrication efficiency than radial labyrinths, especially when a non-Newtonian grease with small yield stress and index of consistency was used. The numerical model was also compared with a proposed analytical solution in which the differences were within an error band of 15%. • A numerical study of different lubricating greases inside axial and radial labyrinth seals was carried out. • Axially oriented seals showed better lubrication efficiency when compared to radial configurations. • The viscous torque dependence on the number of labyrinth grooves is negligible for axial but significant for radial seals. • The viscous torque varies approximately with rotational speed to the power of n. [ABSTRACT FROM AUTHOR]