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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.

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.