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This article describes a method that decouples hydrodynamic and hydrostatic pressure from total pressure in a dry gas seal, and analyses their functions and evaluates their contributions. It is applied to the pressure distributions of three typical symmetrical-groove dry gas seals – in particular the “fir tree” groove design – and is used to analyse the relationship between sealing performance and rotational speed. By separating the hydrodynamic and hydrostatic pressure distributions, their effects on sealing performance can be evaluated respectively. The hydrodynamic pressure of a symmetrical-groove dry gas seal is very weak because of the symmetry of the groove, which means that sealing performance is determined mainly by hydrostatic pressure. Therefore, when optimising the groove structure of such a seal, performance is improved by making the groove more receptive to high pressure. The first instalment of this article appears in the September 2020 issue of Sealing Technology (pages 4–9).

This article describes a method that decouples hydrodynamic and hydrostatic pressure from total pressure in a dry gas seal, and analyses their functions and evaluates their contributions. It is applied to the pressure distributions of three typical symmetrical-groove dry gas seals – in particular the “fir tree” groove design – and is used to analyse the relationship between sealing performance and rotational speed. By separating the hydrodynamic and hydrostatic pressure distributions, their effects on sealing performance can be evaluated respectively. The hydrodynamic pressure of a symmetrical-groove dry gas seal is very weak because of the symmetry of the groove, which means that sealing performance is determined mainly by hydrostatic pressure. Therefore, when optimising the groove structure of such a seal, performance is improved by making the groove more receptive to high pressure. The first instalment of this article, which appears here, provides the background and an introduction to the decoupling method and describes the numerical model. Part II will be published in the October 2020 issue of Sealing Technology.

Impregnated graphite has attracted considerable attention and has been widely used as an ideal friction material in many fields. However, the influence of the friction temperature on its tribological properties has not been clearly studied; furthermore, the evolution mechanism of transferred tribofilm is unknown. In this study, the tribological properties of impregnated graphite were investigated at different friction temperatures, and the evolution of the carbon-based tribofilm was also determined. The results revealed that the tribological properties significantly improved with an increase in friction temperature. The friction coefficient and wear depth of impregnated graphite reduced by 68% and 75%, respectively, at a high temperature of 160 °C compared with those of non-impregnated graphite. The significant properties of the impregnated graphite can be attributed to a transferred carbon-based tribofilm with an ordered structure induced by the friction temperature, which uniformly and stably adsorbs on friction interfaces. This study provides an important basis for designing graphite-based friction materials with improved properties suited for industrial applications.

This work presents a gas-liquid miscible backflow pumping seal (G-LMBPHS) aimed to seal lubricating oil in a high-speed bearing chamber as presented in this paper. The sealing mechanism and performance of the G-LMBPHS are numerically investigated and validated experimentally with a visualization test device, and the theoretical results fundamentally accord with the experimental values. The results reveal that G-LMBPHS uses high pressure fluid generated by the hydrodynamic effect of the groove to prevent the leakage of lubricating oil. When the shearing action generated by the rotational speed completely cancels out or even exceeds the pressure, G-LMBPHS can achieve perfect sealing with no any leakage of the lubricating oil. And G-LMBPHS designed in this study will have wide applications in engineering.

Polyvinylcarbazole(PVK) composites containing organic-inorganic hybrid polyhedral oligomeric silsesquioxane(POSS) PVK-POSS were prepared by free radical polymerization. POSS monomers reacted with vinylcarbazole and were completely dispersed at molecular level in PVK matrix and PVK-POSS nanocomposites display higher glass transition temperature(Tg) in comparison with neat PVK. Optical properties of PVK/POSS nanocomposites were investigated by UV-spectrum and PL-spectrum and the results show that the PVK-POSS nanoparticles have a good interface effect and improve color purity effectively. The maximum absorption wavelength bathochromically shifts gradually with the increasing of the content of POSS. The luminescent intensity becomes higher and higher with the increase of POSS content, and reaches its maximum luminescent intensity when the POSS content is 3% (mass fraction), while some POSS-rich nanoparticles are present in matrix when contents of POSS are beyond 5%.