• Journal of the Korean Society of Visualization
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• v.22 no.3
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• pp.54-59
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• 2024

Valves are devices used to control or stop the flow of fluids through pipelines. Among them, globe valves with a movable disk or plug experience a significant pressure drop due to the changes in fluid flow direction from horizontal to vertical and back to horizontal. This study analyzes the flow characteristics and cavitation in a globe valve, focusing on the effects of varying fuel viscosity due to changes in pressure and temperature. Simulations were conducted with IFO 380 fuel under constant and variable viscosity conditions. The Realizable k-ε model was applied, and cavitation was simulated through multiphase flow conditions. Results showed that at a 50% valve opening, significant pressure drops and cavitation occurred in narrow regions, while at 100%, pressure changes were more gradual. The WLF-Barus model revealed that higher pressures increased fuel viscosity, reducing cavitation compared to constant viscosity conditions. Flow coefficient (Kv) calculations showed minor differences between constant and variable viscosity, with the variable condition leading to a lower Kv at full valve opening. The study highlights the impact of viscosity changes on flow resistance and cavitation behavior.

• Tribology and Lubricants
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• v.14 no.1
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• pp.85-93
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• 1998

The Bair & Winer's limiting shear stress rheological model is incorporated into the Reynolds equation to successfully predict the traction and film thickness for an isothermal line contact using the primary rheological properties. The modified WLF viscosity model and Barus viscosity model are also adapted for the realistic prediction of EHD tractional behavior. The influences of the limiting shear stress and slide-roll ratio on the pressure spike, film thickness, distribution of shear stress and nonlinear variation of traction are examined. A good agreement between the disc machine experiments and numerical traction prediction has been established. The film thickness due to non-Newtonian effects does not deviate significantly from the fdm thicknesss with Newtonian lubricant.