Gas–Liquid Mass Transfer Behavior of Upstream Pumping Mechanical Face Seals

Abstract

For gas–liquid medium isolation seals in aero-engines, the upstream pumping function of directional grooves provides an effective way to realize the design of longer service life and lower leakage rate. However, this produces a new problem for gas–liquid mass transfer in the sealing clearance. This study establishes an analytical model to investigate the gas–liquid mass transfer behavior and the change rule for the opening force of mechanical face seals with elliptical grooves. Compared with traditional studies, this model considers not only the gas–liquid transfer but also the cavitation effect. The results obtained show that with the increase of rotational speed, the gas medium transferred from the inner low-pressure side to the outer high-pressure side. In addition, the leakage rate of the liquid medium from the outer high-pressure side to the inner low-pressure side increased with the growth of sealing clearance, rotational speed and seal pressure. The upstream pumping effect of the gas medium with elliptical grooves not only led to a state of gas–liquid mixed lubrication in the sealing surfaces, but also significantly increased the opening capacity of the seal face. This research may provide a reasonable basis for the design of upstream pumping mechanical face seals.

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

“…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].…”

“…where h is the thickness of the lubricating film, p is the pressure of the lubricating film, ω is the rotating speed of the rotor, ρ is the density of the lubricating medium, r and θ are the radials and circumferential coordinates of the selected calculation area, η is the viscosity of the lubricating medium, Q θ is the circumferential pressure flow factor, Q r is the radial pressure flow factor, Q s is the shear flow factor. As discussed in works [19,25], in the cavitation region, the compressible of fluid (the density variation) is considered, and the pressure distribution in the cavitation region can be solved. The following density equation can be used to describe the cavitation effect in the liquid lubrication analysis.…”

“…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].…”

Computational fluid dynamics modeling and mass transfer study of an in situ gas production process

“…Moreover, many modeling approaches, including analytical models, 21 empirical correlations, [22][23][24][25][26] and computational fluid dynamics (CFD) simulations, 27,28 have been developed to predict the gas-liquid masstransfer coefficient in different reactor configurations. For example, Abiev et al developed an empirical model correlating the masstransfer coefficient and circulation frequency in liquid slugs.…”

“…Experimental studies have been conducted to explore the effects of various parameters, such as the flow rates of liquid and gas phases, the reactor geometry, and the physical properties of the fluids, on the mass‐transfer coefficient. Moreover, many modeling approaches, including analytical models, 21 empirical correlations, 22–26 and computational fluid dynamics (CFD) simulations, 27,28 have been developed to predict the gas–liquid mass‐transfer coefficient in different reactor configurations. For example, Abiev et al developed an empirical model correlating the mass‐transfer coefficient and circulation frequency in liquid slugs 23 .…”