Seal Applications Research Articles

An approach simulating interacting solid, liquid, and gas domains for dynamic seal applications

AbstractIn seal applications a solid elastic body (the seal) ensures the separation of a liquid (e.g., hydraulic oil in one chamber) from a gas (e.g., air in another chamber). In the case of a dynamic seal, the rod is moving and transports a thin liquid film from the liquid chamber into the air chamber. The seal gap consists of a converging gap, a minimum distance between seal and rod and a diverging gap, where transported liquid detaches from the seal. Between the three states of matter (gas, liquid, gas) appear the following contact conditions: liquid‐to‐solid, gas‐to‐liquid, and gas‐to‐solid. A classical fluid‐structure‐interaction is technically possible with limited effort, but is not sufficient to distinguish between the liquid and the gas. A solution can make use of the fact, that the liquid has significant dimensions only in the liquid chamber and is pressurized only there. There is a thin liquid film on the rod in the air chamber, but it has dimensions clearly lower than the air chamber and has the same pressure as the air. Therefore a simulation is possible with the “variable viscosity approach”: Liquid and gas are modeled in one single fluid domain. Differences between liquid and gas are included by pressure‐dependent fluid parameters, especially viscosity and density. The resulting violation of the mass balance is very small as the low mass flow through the seal lip is low. The presented approach allows to apply a fluid‐structure simulation with special fluid properties to model a system with three states of matter. Advantages are a less complex model with less complex contact conditions and a reduced simulation time.

RELAXATION BEHAVIOR OF 3D PRINTED NBR-BASED RUBBER O-RINGS AS THE INNER PART OF ROD SEALS

ABSTRACT The viscoelastic properties of rubber polymer–based compounds are crucial for further applications but challenging in the manufacturing process using additive manufacturing techniques. The fact that the first layer is attached to the printing bed restricts free relaxation after extrusion and the part shows a strong contraction along the printing direction after release and especially after vulcanization. In this study, the molar mass distribution and the acrylonitrile (ACN) content of an NBR-based compound for the fabrication of O-rings for rod seal applications were varied to demonstrate the different degree of contraction resulting from three-dimensional printing. An ACN content of 34% and an average molar mass of 2.47·105 g·mol−1 with a dispersity index of 2.6 was found to be a suitable compromise between the degree of contraction and compression set as a criterion for the application as O-ring as the inner part of rod seals.

Strengthening mechanism of large-diameter magnetic particles on ferrofluid nanoparticle chaining

The magnetization of nano ferrofluid is lower than that of micrometer magnetorheological fluid, which limits its application in seals, dampers, and various other fields. To enhance the ferrofluid performance, this paper incorporates large-diameter magnetic particles into the ferrofluid to strengthen chaining among nanoparticles. A matrix discrete element method model is constructed to investigate the strengthening mechanism of large-diameter magnetic particles on ferrofluid nanoparticle chaining. Additionally, the chain formation process involving both large and small particles and the influence of large particle volume fractions on chain length, particle number, and yield strength are studied based on the simulation. The results show that small particles and large particles together constitute different complex structures, such as the columnar structure and column-net structure under the strong magnetic dipole force of the large particles, leading to the high chain structure strength. In addition, the chain formation speed, average chain length, average particle number, yield strength, and additional viscosity are influenced by the volume fractions and particle sizes of large particles. The method will enhance the ferrofluid sealing performance and expand the ferrofluid application areas.

Theoretical Expression and Screening of Real Gas Effect of Spiral Groove Dry Gas Seal

The emergence of dry gas seals has revolutionized the form of fluid sealing. The traditional research and analysis of dry gas seals is carried out by considering the lubricating medium gas as an ideal gas, but at this stage, the sealing application environment is complicated, so it is necessary to consider the real gas effect of the lubricating medium gas to expand and break through the design system of dry gas seals. We choose seven common lubricating media in dry gas seal applications and screen the optimal density expression of the real gas using different real gas equations of state. Then, we study the extent to which the compression factors of different lubricating gases deviate from the ideal gas and analyze the errors of different real gas equations of state. These results can provide an optimal expression to clarify the mechanism by which the real gas effect affects the dry gas seal performance, which helps to grasp the nature of dry gas seals, predict the dry gas seal behavior, and guide the dry gas seal application.

Research of the working body of an oil pumping device

Non-contact seals of a positive displacement pump for pumping of fluid are considered. Experimental studies confirmed the validity of application of non-contact seals in the form of a stepped comb. Empirical dependences of changes in fluid flow during forward and reverse movement of the piston are proposed. Keywords:non-contact seal, fluid flow, pressure, seal, positive displacement pump nga112001@list.ru

RELAXATION BEHAVIOR OF 3D PRINTED NBR-BASED RUBBER O-RINGS AS INNER PART OF ROD SEALS

ABSTRACT The viscoelastic properties of rubber polymer-based compounds are crucial for further applications but challenging in the manufacturing process using additive manufacturing techniques. The fact that the first layer is attached to the printing bed restricts free relaxation after extrusion, that the part shows a strong contraction along the printing direction after release and especially after vulcanization. In this study, the molar mass distribution and acrylonitrile (ACN) content of an NBR-based compound for the fabrication of O-rings for rod seal applications was varied to demonstrate the different degree of contraction resulting from 3D printing. An ACN content of 34% and an average molar mass Mw of 2.47·105 g·mol−1 with a dispersity index D of 2.6 was found to be a suitable compromise between the degree of contraction and compression set as a criterion for the application as O-ring as inner part of rod seals.

Nitrogen-Doped Diamond-like Carbon Buffer Layer Enhances the Mechanical and Tribological Properties of Diamond-like Carbon Films Deposited on Nitrile Rubber Substrate

The poor adhesion between the DLC film and rubber restricts its application of seals. Introducing a suitable interlayer can bolster the adhesion of the coating or film. In this study, nitrogen-doped diamond-like carbon (N-DLC) emerged as the optimal intermediate layer between rubber and DLC. A series of N-DLC/DLC multilayer films were fabricated via DC magnetron sputtering on nitrile rubber (NBR) substrates, varying the substrate bias voltage (0 V, 100 V, 200 V). A scanning electron microscopy analysis revealed that the composite film surface was smoother than the DLC film alone. The results of Raman spectroscopy and X-ray photoelectron spectroscopy indicated a robust bond between nitrogen and carbon atoms in the composite film, with nitrogen facilitating the conversion of sp3C-C bonds into sp2C=C. Mechanical tests demonstrated that the N-DLC interlayer improved film adhesion and reduced the CoF of the composite film to 0.2–0.3. Specifically, the CoF of the N-DLC/DLC film prepared at 100 V was as low as 0.20, with a wear amount of 1.13 mg. Consequently, the inclusion of the N-DLC interlayer substantially enhanced the mechanical and tribological properties of DLC-coated NBR, rendering this coating highly advantageous for various applications.

Numerical simulation study of high-speed lip seal considering eccentricity

PurposeThis paper aims to focus on the high-speed rotary lip seal in aircraft engines, combining its service parameters, its own structure and application conditions, to study the influence of different eccentric forms, eccentricity, rotational speed and other factors on the performance of the rotary lip seal.Design/methodology/approachA numerical simulation model for high-speed eccentric rotary lip seals has been developed based on the theory of elastic hydrodynamic lubrication. This model comprehensively considers the coupling of multiple physical fields, including interface hydrodynamics, macroscopic solid mechanics and surface microscopic contact mechanics, under the operating conditions of rotary lip seals. The model takes into account eccentricity and uses the hazardous cross-sectional method to quantitatively predict sealing performance parameters, such as leakage rate and friction force.FindingsEccentricity has a large impact on lip seal performance; lips are more susceptible to wear failure under static eccentricity and to leakage failure under dynamic eccentricity.Originality/valueThis study provides a new idea for the design of rotary lip seal considering eccentricity, which is of guiding significance for the engineering application of rotary lip seal.

A Generalised Method for Friction Optimisation of Surface Textured Seals by Machine Learning

Friction behaviour is an important characteristic of dynamic seals. Surface texturing is an effective method to control the friction level without the need to change materials or lubricants. However, it is difficult to put the manual prediction of optimal friction reducing textures as a function of operating conditions into practice. Therefore, in this paper, we use machine learning techniques for the prediction of optimal texture parameters for friction optimisation. The application of pneumatic piston seals serves as an illustrative example to demonstrate the machine learning method and results. The analyses of this work are based on experimentally determined data of surface texture parameters, defined by the dimple diameter, distance, and depth. Furthermore friction data between the seal and the pneumatic cylinder are measured in different friction regimes from boundary over mixed up to hydrodynamic lubrication. A particular innovation of this work is the definition of a generalised method that guides the entire machine learning process from raw data acquisition to model prediction, without committing to only a few learning algorithms. A large number of 26 regression learning algorithms are used to build machine learning models through supervised learning to evaluate the suitability of different models in the specific application context. In order to select the best model, mathematical metrics and tribological relationships, like Stribeck curves, are applied and compared with each other. The resulting model is utilised in the subsequent friction optimisation step, in which optimal surface texture parameter combinations with the lowest friction coefficients are predicted over a defined interval of relative velocities. Finally, the friction behaviour is evaluated in the context of the model and optimal value combinations of the surface texture parameters are identified for different lubrication conditions.

SiC‐bonded diamond ceramics for extreme conditions in subsea applications

AbstractExtremely reliable and wear‐resistant components are required for subsea pump applications. For this purpose, materials and components were developed and qualified within the framework of a joint project1, which under media lubrication with water containing particles, exhibit the highest possible wear resistance and can thus achieve the longest possible service life. The developed SiC‐bonded diamond ceramics have diamond contents of up to 60 % by volume and can be manufactured in the form of a solid material or as graded components containing diamonds only in the tribologically stressed areas. The results show that the investigated diamond‐containing ceramics are very suitable for media‐lubricated sliding bearings and mechanical seals in subsea applications. The friction values under media lubrication are very stable and independent of tribological loads. In mechanical seal application, SiC‐bonded diamond shows significantly better friction performance than the reference material SiC. An outlook is given on demonstrator tests that are currently in preparation.

FORENSIC DATING OF OFFICIAL DOCUMENTS: UTILIZING FTIR ANALYSIS OF STAMP PAD INK DEGRADATION FOR DOCUMENT AUTHENTICATION

This study delves into the deterioration of stamp pad ink found on official documents and explores its potential in dating these documents. The credibility of official documents relies on the application of an official seal or stamp using stamp pad ink. However, individuals with malicious intent may seek to manipulate the ink's appearance to deceive the document's perceived age. To counteract this, we propose a non-destructive method employing Fourier Transform Infrared (FTIR) analysis in Attenuated Total Reflection (ATR) mode to analyze the degradation of stamp pad ink. Through the application of FTIR analysis in ATR mode and the utilization of chemometric approaches like Principal Component Analysis (PCA), we have effectively established a connection between the degradation of stamp pad ink and the document's age. This methodology stands as a crucial tool in authenticating official documents and identifying fraudulent attempts to alter their purported preparation date. The implications of these findings extend to the realms of forensic document examination and legal contexts, offering a dependable means of dating documents through the analysis of ink degradation patterns.

INFLUENCE OF THE MIXTURE VISCOSITY ON MECHANICAL ANISOTROPY AND PROCESSABILITY OF AN NBR-BASED RUBBER MIXTURE FOR ADDITIVE MANUFACTURING

ABSTRACT Rubber-based polymers with high carbon black content can be three-dimensionally (3D) printed using the additive manufacturing of elastomers process. However, high-viscosity materials limit printing resolution, making it difficult to produce fine structures and high-precision parts, especially two-component (2K) parts. The viscosity of a rubber compound used for rod seal applications was reduced and adjusted using Nipol® 1312 liquid rubber and the alkyl sulfonic phenyl ester Mesamoll® II as plasticizers to lower the torque level during extrusion when a reduced nozzle diameter of 0.4 mm is used in 3D printing. In addition, the flowability of the compound was enhanced prior to vulcanization of the part, which could increase the layer–layer bond and thus reduce the mechanical anisotropy typically induced by fused filament fabrication. Using a viscosity-optimized rubber compound, a 2K rod seal consisting of a thermoplastic polyurethane with elastomeric properties and an acrylonitrile rubber-based O-ring was produced and dynamically tested for leakage.

Research Status and Development Trend of Cylindrical Gas Film Seals for Aeroengines

High-performance aeroengine design is an important component of modern industry, and advanced sealing technology is a key technology to meet the engine fuel consumption rate, thrust-to-weight ratio, pollutant emission, durability, and lifetime. Reducing the internal airflow leakage of the engine through a sealing technology can improve the performance and efficiency of the engine. In this paper, the typical sealing technology for an aeroengine is introduced in more detail, including the structural characteristics and use limitations of the labyrinth seal, brush seal, honeycomb seal, gas film face seal, and cylindrical gas film seal. It focuses on the development history, typical structure type, working principle, basic technology research method, steady-state performance, dynamic characteristics, multi-physical field coupling, structural deformation, experimental testing, processing technology. Finally, it summarizes the problems and future development trends of the current application of the cylindrical gas film seal in aeroengines, and points out that the seal performance test and evaluation based on advanced composite sensor technology and the innovative design of the seal based on new material, a new principle, and a new structure will be the new research direction.

Possibilities of Legal Mechanisms to Counteract Greenwashing to Achieve the Principles of Sustainable Development

Objective: The paper examines the practice where companies use environmental advertising or statements about their environmental responsibility to promote their products or services (greenwashing). The objective of the study is to analyze the main signs of greenwashing and develop recommendations for countering environmental offenses. Methods: The research methods are based on the analysis of a limited number of studies that were selected according to special parameters and comprehensively considered. Methods of analogy and comparative analysis were also used. Results: The main signs of greenwashing, the negative consequences to which greenwashing can lead, and the main measures to control this kind of environmental offense are considered. According to the results of the study, it has been concluded that at the international level, greenwashing should be defined as a socially dangerous culpable act that contradicts the norms of law and harms society, the state, individual citizens, and the environment. Conclusion: To counteract greenwashing, it is necessary to introduce a ban on the application of seals that are not introduced by state bodies and are not based on a certification system; a ban on eco-friendly labeling without providing evidence, and without certificates; and a ban on eco-friendly statements about the product, if they relate only to a certain aspect of the product. Furthermore, a system of public reports needs to be introduced where manufacturers can publish reports about their production processes and product test results. This will help consumers make informed decisions about the purchase of products. Besides that, environmental, social, and governance principles need to be implemented in the contract system, together with a penalty system.

Evolution and Action Mechanism of Relative Negative Pressure Zone in Spiral Groove Gas Face Seal for Aero-Engine

Abstract As an advanced sealing technology, the application of gas face seal in aero-engine is few; if possible, lower specific fuel consumption, higher thrust-weight ratio, and effective secondary flow control at minimal cost would be brought. A relative negative pressure zone (RNPZ) was found in the spiral groove gas face seal, and the evolution and action mechanism of RNPZ was investigated in detail, which may promote the above application. Three film thicknesses of spiral groove gas face seals at different rotational speeds and inlet pressures were numerically compared to obtain the pressure field in the groove area and the formation of RNPZ. Then, the radial and circumferential velocities in the groove were calculated to quantify the impact of the obstruction effect, viscous pumping, and shear effect, which revealed the evolution mechanism of the RNPZ stage by stage. At last, the action mechanism of RNPZ was clarified through the hydrodynamic performance analysis. It is found that the pressure field evolution in the gas face seal is in stage Ⅲ under the high rotational speed and low inlet pressure conditions in an aero-engine. Under the same film thickness, RNPZ can suppress leakage to a certain extent in stage Ⅱ, while in stage Ⅲ, it increases the opening force and stiffness-leakage ratio. This work can provide theory and data to help with the subsequent optimization design of gas face seals for aero-engine.

INFLUENCE OF THE MIXTURE VISCOSITY ON MECHANICAL ANISOTROPY AND PROCESSABILITY OF AN NBR-BASED RUBBER MIXTURE FOR ADDITIVE MANUFACTURING

ABSTRACT Rubber-based polymers with high carbon black content can be three-dimensionally (3D) printed using the additive manufacturing of elastomers process. However, high-viscosity materials limit printing resolution, making it difficult to produce fine structures and high-precision parts, especially two-component (2K) parts. The viscosity of a rubber compound used for rod seal applications was reduced and adjusted using Nipol® 1312 liquid rubber and the alkyl sulfonic phenyl ester Mesamoll® II as plasticizers to lower the torque level during extrusion when a reduced nozzle diameter of 0.4 mm is used in 3D printing. In addition, the flowability of the compound was enhanced prior to vulcanization of the part, which could increase the layer–layer bond and thus reduce the mechanical anisotropy typically induced by fused filament fabrication. Using a viscosity-optimized rubber compound, a 2K rod seal consisting of a thermoplastic polyurethane with elastomeric properties and an acrylonitrile rubber-based O-ring was produced and dynamically tested for leakage.

Solid Oxide Cell Technology for Power Generation, Hydrogen Production and Energy Storage

The progress in maturation of solid oxide cell technology has led to development of new applications that would explode its presence in many areas, far beyond power generation. The solid oxide cell technology has the potential to have a formidable presence in production of hydrogen and, eventually, long duration storage of electric power.Following the successful operation of a 200 kW SOFC system under a project supported by Department Energy/NETL, FuelCell Energy (FCE) is pursing the development of SOC based plant configurations from subMW to electrolysis, and further, to energy storage.Multi-faceted evolution of the technology has been underway since the earlier demonstration of SOFC power plant. FCE has developed state-of-the-art lightweight Compact SOFC Architecture (CSA) stacks that are packaged in compact modules with adaptability for use in a variety of configurations and capacities. The CSA stacks can operate directly on a variety of fuels - natural gas, biogas, and hydrogen- without any modification. FCE’s existing fuel cell pilot manufacturing line for CSA cells and stacks includes robotics and automation such as cell screen printing, interconnect subassembly, seal application, QC, as well as stack assembly and conditioning. Via a design for manufacturing approach, as well as focus on minimization of raw material, recent detailed cost studies show a path to low factory stack production cost (<100/kW) at high volumes (1,000 MW/year). The large market existing for power generation equipment, in the range of 200-300kW, is a significant driver for development of high efficiency SOFC products that would easily cater to early-adopters prior to wide-spread acceptance. The accelerated interest in hydrogen as the fuel source will widen the market for SOFC deployment even more. Under a project supported by DOE, FCE is working on design of MW-class SOFC power plants as future extension of the subMW SOFC plant products.FCE is developing a first-of-a-kind 250kW Solid Oxide Electrolyzer Cell (SOEC) system with the hydrogen production capacity of 150kg/day. The overarching goal of the project is to verify that the integration of Solid Oxide Electrolysis Cell (SOEC) systems within nuclear plants will maximize the plants’ efficiency and flexibility and will increase their revenue by switching between electric power generation and hydrogen production. Hybrid nuclear-hydrogen production operations are expected to help the present and future nuclear plants diversify and increase profitability.The 250kW SOEC system is planned to be demonstrated and operated at Idaho National Laboratory (INL). The project will culminate in verification and validation testing and solidify SOEC technology as a low cost and efficient means for hydrogen production integrated within the nuclear power plant environment. The SOEC system will be interfaced with a High-Level front-end Controller (HLC) simulating communications from a nuclear plant and the electric grid. The HLC will determine an optimized hydrogen production schedule to meet all contractual obligations, while maximizing revenue from the integrated operations.FCE is also developing energy storage systems based on the Company’s Solid Oxide Fuel Cell (SOFC) technology. Reversible Solid Oxide Fuel Cell (RSOFC) technology is suitable for medium to long-duration energy storage achieving high round trip electric efficiencies near 70% (electricity-in to electricity-out) at an expected levelized cycle cost of ≤ $0.05 / kWh-cycle.FCE is currently conducting operational tests of an RSOFC prototype system to accomplish the of validation and verification of engineering/pilot-scale RSOFC technology in a relevant environment. A bread-board pilot demonstration system is being utilized to verify cell materials and stack design improvements as well as to validate power electronics and system control strategies that will be utilized for optimization of efficiency, transient response, and lifetime characteristics.

Unveiling the Potential of HVOF Coatings for Mechanical Seal Applications

Unveiling the Potential of HVOF Coatings for Mechanical Seal Applications

Comparison of asphalt emulsion-based chip seal and hot rubber asphalt-based chip seal

The use of asphalt emulsion chip seal and hot rubber chip seal as pavement preservation techniques has been gaining popularity. This study aims to compare the laboratory performance of asphalt emulsion and hot rubber asphalt used in chip seal applications. Interlayer shear strength (ISS) and interlayer tensile strength (ITS) tests were designed to evaluate the bond quality of the chip seal samples prepared for both materials. The sweep test was used to estimate the aggregate loss of the chip seal on the asphalt pavement. The universal testing machines were used to evaluate the deterioration of the ISS and ITS values under cyclic load conditions, while the tensile and shear bond properties of chip seals under wet-freeze conditions were evaluated using freeze-thaw cycles. Results showed while both materials experienced a decline in their ISS and ITS values following repeated cycles of load and freeze-thaw, the hot rubber chip seal demonstrated significantly higher ISS and ITS values than the asphalt emulsion chip seal (48–111% and 36–102%, respectively). Moreover, the hot rubber chip seal exhibited better performance in terms of aggregate retention and cohesive strength. The aggregate gradation would affect the aggregate retention and cohesive strength. Nonetheless, both treatments are deemed acceptable for pavement maintenance. The weak bond between hot rubber asphalt or asphalt emulsion and aggregate could be attributed to cyclic load and freeze-thaw conditions.

Start-up test of ferrofluid seal based on rheometer

Sealing is one of the most successful applications of ferrofluid. However, the seal often has a sudden change in speed during the start-up process, which causes unstable vibration of the system and may result in accidental failure of the seal. In this work, we designed a ferrofluid seal test equipment based on rheometer to study the start-up characteristics of ferrofluid seal. We scan the rotational speed of the ferrofluid seal to determine the torque range of the fixed torque start, and found that the magnetic field strength and the number of pole teeth will affect the torque value and the slope of the curve. We experimentally analyzed three start-up modes of ferrofluid seal. During the start-up process at a fixed rotating speed, the torque fluctuates periodically, and the fluctuation amplitude increases with the increase of magnetic field strength or the number of pole teeth. During the start-up process of fixed torque, the rotating speed fluctuates periodically, and the fluctuation amplitude declines with the increase of torque. In the process of variable torque start-up, as the number of torque changes increases, the rotation speed increases more slowly and the fluctuation range is smaller, which leads to a more stable start-up of the ferrofluid seal. Ultimately, we believe that variable torque starting will be used to promote the application of ferrofluid seals in high-end precision applications.