Study on Radial Clearance Sealing Performance of Graphite Ring

Firstly, the suitable forming method of graphite ring was screened according to compression deformation test, considering the characteristics of radial clearance seal. Then, the compression resilience, radial contact stress and axial sealing performance of graphite packing rings with different density were researched by testing. Research shows: 25% compressibility is the limit of radial clearance compensation ability of graphite packing ring; And the radial contact stress of graphite packing ring on the pipe wall is linearly positively correlated with the axial load, density has little effect on it. Based on the porous media model of gaskets, axial leakage models of three kinds of graphite rings with different density were obtained by experimental fitting and the influence of external working conditions on leakage mode was analyzed, which provide a theoretical basis for the design of graphite ring seal based on leakage rate.

Stress-Deformed State of a Packing Ring with Eccentric Holes

Currently, various variants of physical and geometrical non-linear calculation of anisotropic bodies have been developed. In spite of the large and increasing number of studies on the theory of shells there are still many unsufficiently developed problems important both in scientific and applied fields, for example, development of practically convenient methods for calculating of anisotropic sealing composite materials weakened by eccentric holes under the influence of local loadings. Stress-deformed state of a packing ring with eccentric holes of sealing materials was studied. In composite materials, the Hooke’s equation was used for this purpose. Also, using Lurie’s symbolic method, the concrete solution of the sealing problem with eccentric holes was obtained.

Leakage Estimate in Nonuniformly Compressed Packing Rings

Characterizing the permeation performance of nanoporous material is an initial step toward predicting microflows and achieving acceptable designs in sealing and filtration applications. This study deals with analytical, numerical, and experimental studies of gaseous leaks through soft packing materials subjected to nonuniform axial compression in valve stuffing boxes. A new analytical model that accurately predicts gaseous leak rates through nanoporous packing materials assumed made of capillaries having an exponentially varying section. Based on Navier–Stokes equations with the first-order velocity slip condition for tapered cylinder capillaries, the analytical model is used to estimate gas flow through soft packing materials. In addition, computational fluid dynamic modeling using cfx software is used to test its capacity to estimate the permeation of compression packing ring materials assuming the fluid flow to follow Darcy's law. Helium gas is used as a reference gas in the experiments to characterize the porosity parameters. The analytical and cfx numerical leak predictions are compared to leak rates measured experimentally using different gas types (helium, nitrogen, air, and argon) at different pressures and gland stresses. The analytical and numerical models account for the porosity change with the stem axial distance because the packing ring set is subjected to an exponentially varying radial compression. The predictions from analytical model are in close agreement with the cfx model and in better agreement with experimental measurements.

Modeling Dry Wear of Piston Rod Sealing Elements of Reciprocating Compressors Considering Gas Pressure Drop Across the Dynamic Sealing Surface

The wear of dynamic sealing elements, i.e., elements that seal against a moving counter-surface, is highly complex. In dry-running reciprocating compressors, these sealing elements, commonly referred to as packing rings, have to seal the compressed gas against the environment along the reciprocating rod. Since the packing rings' seal effect arises from the differential pressure to be sealed, it is of paramount importance to take into account the gas pressure drop across the dynamic sealing surface. This paper presents a numerical model that allows us to calculate how the wear of such a packing ring evolves with time. An analytical solution is used to verify the numerical model.

Progressive Clearance Labyrinth Seal for Turbo-Machinery Applications

Turbomachinery sealing is a challenging problem due to the varying clearances caused by thermal transients, vibrations, bearing lift-off etc. Leakage reduction has significant benefits in improving engine efficiency and reducing emissions. Conventional labyrinth seals have to be assembled with large clearances to avoid rubbing during large rotor transients. This results in large leakage and lower efficiency. In this paper, we propose a novel Progressive Clearance Labyrinth Seal that is capable of providing passive fluidic feedback forces that balance at a small tip-clearance. A modified packing ring is supported on flexures and employs progressively tighter teeth from the upstream to the downstream direction. When the tip-clearance reduces below the equilibrium clearance, fluidic feedback forces cause the packing ring to open. Conversely, when the tip-clearance increases above the equilibrium clearance, the fluidic feedback forces cause the packing ring to close. Due to this self-correcting behavior, the seal provides high differential pressure capability, low leakage and non-contact operation even in the presence of large rotor transients. Theoretical models for the feedback phenomenon have been developed and validated by experimental results.

Evaluation of Loads on a Hypercompressor Plunger in Service Conditions

The plunger is a very critical component for the operation of hyper-compressors. To achieve long packing ring life it is necessary to select very hard materials for the plunger. As a consequence of the special materials used, the plunger is very brittle. To guarantee safe operation it is necessary to have perfect alignment to avoid bending stress that could cause plunger failure. The effects of the whole system, including packing rings and supporting crossheads were analyzed using a multi-body dynamic simulation to determine the maximum loads acting on the plunger. This analysis verified the viability of this critical component during abnormal machine operating conditions.