Gas thermoelastohydrodynamic lubrication of face seals

Cavitation in micro-scale lubricating film could be determined by the fluid’s thermal properties, which impacts the hydrodynamic lubrication capacity dramatically. This study aimed to novelly investigate the impact of the thermal cavitation effect on the hydrodynamic performance of liquid face seals, employing the compressible cavitation model, viscosity–temperature effect, and energy equation. The finite difference method was adopted to analyze the thermal cavitation by calculating the pressure and temperature profiles of the lubricating film. The working conditions and geometric configuration of liquid face seals under different thermal cases were further studied to explore their effects on sealing performance. The results showed that thermal cavitation could reduce the temperature difference of liquid film at high speeds, and cavitation would be weakened under temperature gradients, which further dropped off the hydrodynamic performance. Contrary to the leakage rate, the opening forces tended to be lower with the increasing seal pressure and film thickness under high-temperature gradients. Furthermore, apart from the spiral angle of grooves, the hydrodynamic performance exhibited significant variation with increasing groove depth, number, and radius at high-temperature gradients, which meant that the thermal cavitation effect should be considered in the design of geometric grooves to obtain better hydrodynamic performance.

Section: Geometry Characterizationmentioning

confidence: 99%

“…The energy equation [39] for the thermo-hydrodynamic lubrication analysis could be written as follows:…”

Section: Geometry Characterizationmentioning

confidence: 99%

Section: Geometry Characterizationmentioning

confidence: 99%

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Thermal Cavitation Effect on the Hydrodynamic Performance of Spiral Groove Liquid Face Seals

Song,

Bai

2024

“…Fluid lubrication based on the Reynolds equation has been widely applied in the numerical analysis of face seals. For thermohydrodynamic lubrication analysis of face seals, the mathematical model mainly includes the Reynolds equation, energy equation, solid heat conduction equation [24] and cavitation equation [19,25].…”

Section: Governing Equationsmentioning

confidence: 99%

“…Based on numerous theoretical works about the upstream pumping effect of face seals, it was found that this effect was largely depends on the shear speed and fluid viscosity of the sealing medium [18][19][20]. Meanwhile, the upstream pumping effect is significantly affected by cavitation [21][22][23][24][25]. In experiments, Nau [26] observed the occurrence of cavitation in mechanical seals with tap-water or mineral oil at a speed of 530 rpm and summarized that the leakage rate relied on the circumferential extent of the cavitation, decreasing as it expanded.…”

Section: Introductionmentioning

confidence: 99%

Thermo-Hydrodynamic Lubricating Behaviors of Upstream Liquid Face Seals with Ellipse Dimples

Bai

Yang

et al. 2023

In order to obtain the leakage characteristics of an upstream pumping face seal with inclined ellipse dimples under high-temperature and high-speed liquid lubricating conditions, a thermo-hydrodynamic lubricating model is developed. The novelty of this model is that it takes the thermo-viscosity effect and cavitation effect into account. The influence of operating parameters, such as rotational speed, seal clearance, seal pressure, ambient temperature and structural parameters, such as dimple depth, inclination angle, slender ratio and dimple number on the opening force and leakage rate, is numerically calculated. The results obtained show that the thermo-viscosity effect makes the cavitation intensity decrease noticeably, leading to an increase in the upstream pumping effect of ellipse dimples. Moreover, the thermo-viscosity effect may make both the upstream pumping leakage rate and opening force increase by about 10%. It can also be found that the inclined ellipse dimples can produce an obvious upstream pumping effect and hydrodynamic effect. Based on the reasonable design of the dimple parameter, not only can the sealed medium achieve zero leakage, but the opening force can also increase by more than 50%. The proposed model has the potential to provide the theoretical basis for and guide the future designs of upstreaming liquid face seals.

Vaporization Phase Transition in Cryogenic Liquid Oxygen Sealing Film on Spiral Groove Faces

Chen,

Ma,

Bai

et al. 2024

The property of vaporization phase transition in liquid oxygen face seals is a key factor affecting the stability of mechanical face seals in many fields, especially under cryogenic conditions. Here, a numerical model based on the saturated vapor pressure is established to investigate the vaporization phase transition property of liquid oxygen sealing film. The novelty of this model is to take the influence of heat transfer and face distortions into consideration at the same time. The pressure and temperature distributions as well as face distortions are calculated, and then the property of vaporization phase transition and sealing performance are analyzed. It is found that spiral grooves may lead to the complex film temperature distributions and irregular vaporization distributions. With the increase in seal temperature and decrease in seal pressure, the vaporization area extends from the low-pressure side to the grooves area, and the vaporization rate increases rapidly. The more important thing is that the vaporization often brings a drastic fluctuation and non-monotonic change in opening force. Specifically, with the increase inin seal temperature from 55 K to 140 K, the opening force fluctuates violently, and the fluctuation range is more than 50%, showing an obvious instability. Finally, this study provides a design range of pressure and temperature values for liquid oxygen face seals. In these ranges, this kind of face seals can have a stable operation, which is beneficial to the practice engineering related to the complex properties of sealing fluid.