Numerical Investigation of Grooved Shaft Effects on the Rotary Lip Seal Performance with Relative Lip Motion

It is generally agreed that radial lip seals are used in systems with a rotating shaft and a stationary lip. However, according to previous work, it was demonstrated that relative motion between the shaft and the lip has substantial effects on the hydrodynamic lifting load and sealing performances. Nowadays, new generations of textured shafts have emerged in order to reduce friction torque and improve reverse pumping, but no study has confirmed the effect of the relative motion between the rough lip and the shaft grooves on the rotary lip seal performances. In this work, an isothermal hydrodynamic lubrication was performed in transient conditions to investigate the effect of the relative velocity between an oblique grooved shaft and a rough lip. After confirming the validity of the current model with respect to previous works, simulations have underlined the effect of the grooved shaft with relative lip motion on the rotary lip seal performance. Indeed, by keeping the same relative velocity between surfaces, it is shown that moving the shaft with a rate higher than that of the lip surface could produce an important reverse pumping and reduce the friction torque significantly, in comparison with cases where the shaft velocity is weaker.

Soft elastohydrodynamic analysis of rotary lip seals

The extensive literature on the elastohydrodynamic analysis of rotary lip seals is reviewed. Models that predict quantities such as film thickness and reverse pumping rate and that elucidate the physical processes governing the behaviour of rotary lip seals are described. Thermal effects, mixed lubrication, capillary effects, transients, viscoelasticity, statistical approaches, and so-called hydrodynamic seals are discussed.

Soft Elastohydrodynamic Analysis of Radial Lip Seals With Deterministic Microasperities on the Shaft

A numerical analysis is conducted to investigate the elastohydrodynamic effect of deterministic microasperities on the shaft of a lip seal. Various geometries of microasperities (triangular, square, hexagonal, and circular) are put into a 100×100μm2 unit cell and are investigated using Reynolds equation. For each shape, the area fraction of the microasperity is varied between 0.2 and 0.8, and the asperity height is varied between 0.3μm and 5μm. The calculation for load capacity and friction coefficient indicates that there are values for asperity height, where the load capacity and friction coefficient are optimized. These optimum heights were reached at 1–3μm. Although the lip seal surface is considered to be smooth, reverse pumping can still be obtained using an oriented triangular design. The Couette flow rate for this asperity showed lubricant is reverted back toward the seal side 2.6 times more than using a conventional lip seal. The addition of microasperities to the shaft surface shows significant improvement in lubrication characteristics for the lip seal in the form of a simultaneous reduction in friction coefficient and increase in the reverse pumping rate.

Surface Analysis of Radial Lip Seals With Deterministic Micro Cavities on the Shaft

Many approaches have been used to control the reverse pumping effect in radial lip seals. One of those is the use of oriented triangular micro-asperities on the shaft of the seal. This extended abstract presents areal surface parameter measurements from a lip seal with triangular micro-cavities oriented towards the direction of rotation. Surface parameters in the roughness, hybrid and functional groups are presented. The measurements are then discussed and placed in the context of radial lip seal performance.

Numerical Study of a Rotary Lip Seal With a Quasi-Random Sealing Surface

In all previous numerical simulations of the rotary lip seal, the sealing surface was modeled by regular periodic structures. In the present study, a more realistic quasirandom surface is used. A mixed elastohydrodynamic analysis is used to generate predictions of such seal operating characteristics as friction coefficient, reverse pumping rate, film thickness distribution, hydrodynamic and contact pressure distributions, contact area, and cavitation area. The results are in qualitative agreement with previous experimental observations. In the course of the simulations, a new physical mechanism of reverse pumping has been identified.