Seal Structure Research Articles

A mechanism leakage model of metal-bipolar-plate PEMFC seal structures with stress relaxation effects

This work addresses the issues of long-term leakage rate prediction, which is crucial for durability study of proton exchange membrane fuel cells (PEMFCs). A theoretical model is presented for the leakage rate of compressive seal structures in PEMFCs, based on the combination of three numerical techniques, namely Lattice-Boltzmann method (LBM) simulations for rough wall interfacial gaps, a numerical 3D rough-surface generation technique, and Finite-Element-Analysis (FEA) for micro-contact mechanics of single asperity. The model clearly reveals the quantitative influence of various factors on the leakage rate without any empirical regression coefficients, and therefore can be easily integrated with structural mechanics and aging mechanism analyses. Long term sealing performance comparisons with three types of rubber material identify liquid silicone rubber to have the optimal durability. When influences of water environment are taken into account, an accelerated degradation of sealing performance can be observed after approximately 3000 h of operation. In addition, the effect of stress loss on leakage rate can be effectively suppressed by reducing surface roughness, reducing gasket thickness and increasing strain level. The proposed theoretical model provides an effective approach for the design of metal-bipolar-plate PEMFCs seal structures.

Numerical Study on the Biomimetic Trailing Edge of a Turbine Blade Under a Wide Range of Outlet Mach Numbers

This study was carried out to investigate the loss mechanism of a blade with a harbor seal whisker structure on the trailing edge under different Mach numbers. The loss of high-pressure turbine blades with four different trailing edge geometries, including a prototype, an elliptical trailing edge (ETE), a sinusoidal trailing edge (STE), and a biomimetic trailing edge (BTE) at Mach numbers of 0.38–1.21 is studied. The delayed detached-eddy simulation method is used to predict the detailed flow of the four cascades. The result shows that, when the Mach number is less than 0.9, the BTE can effectively reduce the energy loss coefficient compared with the other three cases. As the Mach number increases, the three-dimensional characteristics of the wake behind the BTE weaken. The energy loss coefficient of the blade with the BTE is close to that of the blade with the ETE and STE when the Mach number is greater than 0.9. Besides this, by controlling the wake, the BTE can effectively suppress the dynamic movement of shock waves in the cascade at high Mach numbers.

Enhanced piezoelectric wind-induced vibration energy harvester via the interplay between cylindrical shell and diamond-shaped baffle

Energy harvesting from wind-induced vibrations is considered to be a promising solution for the power requirements of wireless sensor nodes. This paper proposes an enhanced piezoelectric wind-induced vibration energy harvester (EPWEH) via the interplay between the cylindrical shell and diamond-shaped baffle to improve reliability, environmental adaptability, and power generation performance. Different from the most existing hybrid piezoelectric wind energy harvesters where the interaction of vortex-induced vibration and galloping was mainly implemented by altering the cylinder geometry, this EPWEH realized the coupling between vortex-induced vibration and galloping through introducing a downstream diamond-shaped baffle to change the aeroelastic instability of the cylinder. Besides, the pre-bending vibrator only subjected to the unidirectional compressive stress was employed and embedded inside the hollow cylinder, thus avoiding the drawbacks of bidirectional deformation of the traditional piezoelectric vibrator and direct contact between piezoelectric element and fluid. The feasibility of the structure and principle of the EPWEH was proved through a series of experiments. The experimental results demonstrated that the compound-embedded structure led to a coupling phenomenon of VIV and galloping on the cylindrical shell. Besides, it exhibited that the structural parameters brought a significant impact on the vibration characteristics, power generation performance, and wind speed bandwidth of EPWEH as well. Thanks to the performance improvement effect of the baffle, the EPWEH could reach a maximum voltage output enhancement of 910.1% and provide a maximum output power density of 5.493 mW/cm 3 at an optimal load resistance of 200 kΩ. It is expected that this compound-embedded structure can provide a reference for performance improvement of the existing PWEHs. • A novel piezoelectric wind energy harvester with a combined structure is presented. • Sealed piezo-vibrator is indirectly excited by wind-induced vibration. • Reliability is improved by the combination of sealed and pre-bending structure. • High performance characteristics based on coupling of VIV and galloping is realized. • Voltage performance can be enhanced by 910.1% and the power is 5.493 mW/cm 3 .

Numerical Simulation and Experimental Study on Magnetorheological Fluid Seals With Flexible Pole Pieces

Magnetorheological fluid seal and brush seal are successful sealing forms. To address problems such as pole pieces colliding with spindles, precise sealing clearance in magnetic fluid seals, and inevitable leakage in brush seals, this article combines the advantages of magnetic fluid seal and brush seal and proposes a magnetorheological fluid seal with flexible pole pieces. The magnetic field of the seal was estimated using the finite-element method and the seal capacity was studied in theory. Single structural parameters of the seal that affect sealing capacity such as the relative permeability and thickness were discussed. The combined effects of various structural parameters were analyzed. The results show that an increase in the relative permeability and length of the flexible pole pieces leads to the enhancement of the seal capacity. The thickness of the flexible magnetic pole piece and the magnetic part of the flap and coating are inversely proportional to the sealing pressure value. The experimentally obtained seal capacity agrees with the value calculated through the simulation. This article presents a structure of the magnetorheological fluid seal and comparative results of the seal capacity obtained from both experimental studies and numerical simulation calculations.

About the possibility of creation of sealed strong structures of rocket and space equipment FDM printing methods

The work shows the possibility of manufacturing products for rocket and space technology using the additive FDM-printing technology. The object of research is the nozzle plugs of the "membrane" type. Taking into account the specific-strength properties of the product during its operation during operation, as well as the features of the FDM-process, the design was optimized, the regularities of the formation of its properties were established. An impregnation technology has been developed to seal the product. The equipment was designed and pneumatic tests were carried out. The properties of materials were investigated taking into account their guaranteed shelf life for 12 years of operation under accelerated climatic tests. It is shown that the production of products by FDM-printing methods is promising and expedient, since the properties being formed are predictable, achievable and stable.

ПРОБЛЕМНІ ПИТАННЯ ТА ШЛЯХИ ЇХ ВИРІШЕННЯ ПРИ ПРОЕКТУВАННІ КОМПОЗИЦІЙНИХ ПАЛИВНИХ БАКІВ

To reduce of the rocket constructions weight is one of the topical issues of space technology. The preliminary calculations showed that reducing the fuel tanks mass by 20 % allows to increase the cargo by 4-5% for a given launch weight, or to reduce the launch vehicle mass by about the same amount. The one of ways to solution the problem is the use of modern composite materials like a carbon fiber reinforced plastics. However, the improvement of the mass parameters exacerbates the problem of ensuring tightness of the load-bearing shell and the flange joints with the main pipelines and nozzles for supplying fuel components. This problem is especially relevant for manhole structures. The tightness in modern designs of composite fuel tanks is ensured by the load-bearing shell itself, however, the flange connections tightness, which made of composite materials, remains under the question. In the proposed work, various options for constructive and technological solutions to this problem are analysed. Considering that depressurization occurs along the joints of the flange assembly structures, the main attention is paid to the special sealants as well as to the quality of joint surfaces processing and the compensation of residual deformations by elastic elements of the seal structures. The rheological processes under the influence of external power loads should also take into account in analyzing the functionality of flange assemblies design. The proposed constructive solutions for ensure the tightness of composite fuel tanks can be used not only in the design of launch and space vehicles, but also in all areas of application of cryogenic and high-toxic chemicals.

Performance of cryogenic demountable indium seal at high pressures.

An essential challenge in seal designis to provide an ultra-low leak rate at cryogenic temperatures and high pressures. In this paper, the performance of demountable indium seals under a charging pressure of 8.5 MPa A and at cryogenic temperatures down to -190°C was investigated. Three indium seal structures with a diameter of 30mm were specifically designed and tested. All three structures went through both room temperature and cryogenic temperature tests in cycles with a pressure of up to 8.5 MPa A. In addition, leak rate experiments regarding the creep relaxation effect of the indium ring were conducted. The results showed that the leak rates of all three structures were lower than 1 × 10-10 Pa m3s-1 at both room temperature and cryogenic temperature with the pressure up to 8.5 MPa A when the torque was 8 or 12 N m. It was concluded that the linear loads for achieving a successful indium seal were 163, 171, and 220 N mm-1 alongside its circumference for the 2mm indium M-T structure, the 3mm indium M-T structure, and the Z-shaped seal structure, respectively. Furthermore, although the torque slightly dropped after the assembly due to the creep relaxation effect, the leak rates of the structure were still lower than 1 × 10-10 Pa m3s-1 three days after the assembly. The present work is helpful for designing ultra-low leak rate demountable indium seals at cryogenic temperatures and high pressures.

Underwater Crawling Robot With Hydraulic Soft Actuators.

Benthic operation plays a vital role in underwater applications, where crawling robots have advantages compared with turbine-based underwater vehicles, in locomotion accuracy, actuation efficiency, current resistance, and in carrying more payloads. On the other hand, soft robots are quickly trending in underwater robotic design, with their naturally sealed body structure and intrinsic compliance both desirable for the highly unstructured and corrosive underwater environment. However, the limitations resulting directly from the inherent compliance, in structural rigidity, actuation precision, and limited force exertion capability, have also restricted soft robots in underwater applications. To date soft robots are adopted mainly as grippers and manipulators for atraumatic sampling, rather than as locomotion platforms. In this work, we present a soft-robotic approach to designing underwater crawling robots, with three main innovations: 1) using rigid structural components to strategically reinforce the otherwise omni-directionally flexible soft actuators, drastically increasing their loading capability and actuation precision; 2) proposing a rigid–soft hybrid multi-joint leg design, with quasi-linear motion range and force exertion, while maintaining excellent passive impact compliance by exploiting the inherent flexibility of soft actuators; 3) developing a novel valve-free hydraulic actuation system with peristaltic pumps, achieving a compact, lightweight, and untethered underwater crawling robot prototype with a 5:1 payload-to-weight ratio and multi-gait capability. The prototype was tested for design verification and showcasing the advantages of the proposed hybrid mechanism and actuation approach.

Study on Self-compensation Design of Main Seal Structure of High Temperature and High Pressure Ball Valve

Study on Self-compensation Design of Main Seal Structure of High Temperature and High Pressure Ball Valve

Influence of undersea vehicle shafting offset on contact stress and temperature of spherical stern shaft seal

In order to solve the problem that the sealing surface can not adapt itself due to the change of the stern shaft seal of the stern shaft of undersea vehicle. A spherical stern shaft seal structure was proposed in this paper. In order to lay a foundation for the analysis of the sealing performance of the spherical stern shaft seal, a three-dimensional thermal-structural coupling finite element model of the spherical stern shaft seal and the Stern Shaft was established by using ANSYS software. The distribution of contact stress and temperature on the surface of the spherical stern shaft seal was simulated when the Stern Shaft was moving in a series of 0,1,2mm in the vertical direction. The influence of shaft motion on contact stress and temperature on surface of spherical stern shaft seal is analyzed.

A Sliding-Window Principal Component thermography reconstruction approach for enhancement and identification of electronic components internal structure

Electronic supply chain vulnerability has been threatened by counterfeits for decades and as a result, the authentication and quality of Electronic Components (ECs) are highly valued by stakeholders for safety-critical industrial systems. Thermography Nondestructive Testing (NDT), offering a rapid inspection while covering a large area within a short time frame, is a promising technique to inspect the integrity of ECs. However, recognising the internal structural layout directly through a packaged EC from thermography images is still a challenge due to its sealed and cramped structure. In this research, we propose a Pulsed Thermography (PT) based data analysis method for enhancement and identification of the layout of die and lead frame in ECs. The proposed solution combines the Sliding Window (SW) concept, Thermographic Signal Reconstruction (TSR) and Principal Component Thermographic (PCT) technique, named SWPCT, to enhance the contrast of die, die substrate and lead frame. Compared to the conventional full-scale PT image analysis, the proposed method presents its superior sensitivity in small thermal features by reducing the spatial thermal information redundancy benefiting from the sliding window PCT analysis. It overcomes the structural thermograms obstruction from the thick packaging, reveals the hidden die and lead frame layout and suppresses the noise simultaneously. By selecting a proper window size, this paper reveals that SWPCT can reconstruct the position and dimension of die and die substrate in ECs, and spatially distinguish the lead frame layout. Two groups of typical OpAmps chip samples with internal structure diversity (X-ray observed) were tested using PT to demonstrate the effectiveness of the proposed method. Simulation data were also used to verify this approach. This research could unlock the challenge of thermography-based inspection for key internal structure in the encapsulated integrated components.

Application of the response-surface method and CFD simulations in the matching optimization of spiral sealing for a high-speed cone bit

ABSTRACT The cone bit is an important rock-breaking tool in oil and gas mining. Sealing plays a crucial role in determining the high rotational speed and service life of the bit. The traditional seal structure is passive and wears out rapidly. Under the high-speed rotation of the drill, it has a short sealing service life. This paper describes a spiral-seal active sand discharge structure that incorporates a new type of sealing for the cone bit. Because traditional matching optimization methods are not suitable for this type of sealing, the response-surface method (RSM) was applied to optimize the spiral seal structure for a high-speed cone bit. The optimization significantly improved the service life of the bit. The working conditions and the effect of the spiral-seal structure were studied through computational fluid dynamics (CFD) simulations that revealed the sealing mechanism of this structure. Additionally, the RSM was used to perform matching and optimization of the spiral-seal structure for a high-speed cone bit and to study the dependence of the spiral structure parameters on the sand discharge performance at different rotation speeds. This not only provides more accurate theoretical data for actual production, but also provides a means to optimize other mechanical structures.

Foldable Glistening-Free Acrylic Intraocular Lens Biomaterials with Dual-Side Heterogeneous Surface Modification for Postoperative Endophthalmitis and Posterior Capsule Opacification Prophylaxis.

Hydrophobic acrylic intraocular lenses (IOLs) are widely used in cataract treatment for posterior capsule opacification (PCO) prophylaxis. However, undesired glistening and postoperative endophthalmitis are two major potential risks. Hence, a series of poly(2-phenoxyethyl methacrylate-co-2-phenoxyethyl acrylate-co-2-ethylhexyl methacrylate) (PPPE) acrylic IOL materials were synthesized for "glistening-free" optimization. The selected PPPE with 2% 2-ethylhexyl methacrylate showed excellent optical, foldable, and thermomechanical properties. The anterior surface of PPPE was coated with polydopamine followed by gentamycin conjugation (PDA/GS). It inhibited bacterial adhesion by 74% and decreased the biofilm thickness by 87%. In inflammatory mimicking conditions, bacterial proliferation was restrained, with acidic-dependent GS release behavior. The surface of PPPE toward the posterior capsule remained hydrophobic. It was conducive to human lens epithelial cell adhesion, collagen IV and fibronectin adsorption, and the following "sealed sandwich structure" formation. In summary, the PPPE with a dual-side heterogeneous surface displayed good application prospects in postoperative endophthalmitis and PCO prevention.

A hybrid piezoelectric-electromagnetic wave energy harvester based on capsule structure for self-powered applications in sea-crossing bridges

The ocean is a huge kinetic energy field with considerable energy harvesting potential. Harvesting renewable ocean wave energy and using it to power electric facilities such as sensors for sea-crossing bridges in real time could be an effective strategy to promote sustainable development of the oceans. In this paper, we propose a piezoelectric-electromagnetic wave energy harvester (PEWEH) based on a sealed capsule structure for self-powered applications in sea-crossing bridges. The proposed system consists of three main components: piezoelectric module, electromagnetic module, and energy storage module. The piezoelectric module is mainly composed of two piezoelectric sheets which can be deformed by continuous wave motion to generate electricity. The electromagnetic module includes a fixed coil and a core that moves back and forth to cut the magnetic line to generate electricity. The electrical energy recovered by the piezoelectric module and electromagnetic module will be stored in the energy storage module after being rectified and stabilized. Experiment results showed that output voltage up to 7 V and power of 162 mW can be obtained by the PEWEH, validating that the proposed wave energy harvesting system is promising for self-powered applications in low-power monitoring sensors for sea-crossing bridges.

Sealing Tröger base/ZIF-8 mixed matrix membranes defects for improved gas separation performance

Manufacturing defect-free mixed matrix membranes (MMMs) especially with high nanoparticle concentrations exceeding 40 wt% is still an ongoing challenge. Desired performance improvements are often unfulfilled in MMMs with high filler loading because nanoparticles with increasing contents are prone to aggregating, forming non-selective cavities, and deteriorating membrane's mechanical properties. To address this key issue, our work develops MMMs using Tröger base (TB) polymer with more hydrogen bond acceptors, polydopamine (PDA), and ZIF-8 fillers. The PDA modified ZIF-8 to create TB/ZIF-8 MMMs especially with high ZIF-8 loading over 40 wt% improves membrane mechanical properties and completely seals structural defectives to demonstrate encouraging gas selectivities. Hydrogen bonding between CN:NH and CN:OH groups within TB polymers and PDA enhances ZIF-8 interactions and reduces particle agglomeration within the polymer matrix. A TB/ZIF-8@PDA MMM containing 50 wt% ZIF-8 has H2 and CO2 permeabilities of 664.1 and 277.3 Barrer. Its ideal H2/CH4 and CO2/CH4 selectivities are 37.7 and 15.5, respectively. Equal molar CO2/CH4 mixed gas tests at various pressures demonstrate strong CO2 plasticization resistance and enhanced CO2/CH4 gas selectivity over ideal selectivity within the membranes. The combination of PDA modification technique on filler surfaces and a polymer with many hydrogen bonds acceptors is not only a feasible route to fabricate high filler loading MMMs with sealed defective structures, but also demonstrates positive impacts on membrane mechanical properties.

Effect of heat‐sealing parameters on the thermal profile and seal strength of multilayer films and non‐woven

AbstractHeat sealing is one of the most common techniques for sealing food packages. In this study, the effects of sealer parameters such as dwell time (0.5–2 s), jaw temperature (225–250°C) and pressure (69–345 KPa) and the seal contaminants (coffee particles [0.70–0.85 mm]) were studied on polymer materials used in coffee capsules: (1) lidding, poly(ethylene terephthalate) (PET)/Al/linear low‐density poly(ethylene) (LLDPE); (2) wall, polystyrene (PS)/ethylene‐vinyl alcohol copolymer (EVOH)/PS; and non‐woven filter, NW1 (mono‐component fibre) or NW2 (bicomponent fibre [core/sheath]). The presence of NW1 and NW2 non‐woven in the seal structures decreased the interfacial temperature by 5°C and 11°C, respectively in comparison to seal structures without non‐woven. The degradation of the seal bonding caused a decline in the seal strength at elevated temperature (NW: >240°C without NW: >235°C) and longer dwell time (NW: >1 s, without NW: >1.5 s). The core and sheath structure of NW2 (969 N/mm) was responsible for higher seal strength in comparison to NW1 and without NW, as the core remained intact during the sealing, increasing the material strength. The minimum pressure of 207 KPa was required for creating enough contact between films to achieve proper sealing. The coffee particles buried under the opaque layer of lidding films created visible thermal artefacts when observed under thermal camera. The contaminated region differed by 30–38°C from the surrounding sound region after cooling for 3.5 s. The seal strength was stronger when a single coffee particle was in the middle compared to a sample with multiple particles.

Analysis of Piston Seal Performance of Pure Water Cylinder of Hydraulic Support

Taking the piston seal of pure water hydraulic cylinder of hydraulic support as the research object, the sealing performance and damage characteristics are compared and analyzed for mountain seal and drum seal structures under different compressions and working medium pressures by the ANSYS Workbench. The two-dimensional axisymmetric models for the two structures are established. The compression deformation and stress of mountain seal ring and drum seal ring are simulated by setting different amount of compression and medium pressure. Findings showed that the most vulnerable area of the mountain seal ring is in the middle of the contact surface with the cylinder, and that of the drum seal ring is in its outer edge. The maximum contact stress of both the structured sealing rings increased with the increase of the medium pressure, and is always greater than the medium pressure, indicating good sealing performance. With the increase of compression and working medium pressure, the sealing performance of both kinds of rings decreased. When applied to the same piston, the sealing performance of mountain seal is better than that of drum seal under the same compression amount and medium pressure.

Analysis and Improvement of Sealing Structure of Transfer Valve on FADECs Channel Switching

Analysis and Improvement of Sealing Structure of Transfer Valve on FADECs Channel Switching

Vapor condensation with low air mass fraction inside water seal branch tube under free convection

The pressure vessel has used a newly designed water seal structure, and the sealed water is from condensation at low hydrogen concentration. To get the condensation capacity of the water seal branch tube under the pressure vessel normal operation, the experimental loop named WASETEL was constructed, which is aimed at studying the heat transfer during the process of air-steam mixture condensation inside the inclined branch tube at the condition of low air mass fraction. The inner tube is diameter 0.134 m with length 0.68 m which is connected with diameter 1.4 m, high 2.5 m pressure vessel. A canon camera was set to record the images and videos of the condensate height through glass tube in communicating vessel liquidometer. The experiment was conducted under the pressure ranged from 0.2 to 0.6 MPa, air mass concentration ranged from 0.49 to 6.42% and wall subcooling ranged from 11 to 40 K. The test showed HTC (heat transfer coefficient) would sharply deteriorate with the small air fraction, compared with pure steam condensation, about 0.49% mass fraction of the air will reduce heat transfer coefficient by 70–80%. When air concentration is relatively small, those widely used relations can not predict the condensation well, therefore, a new heat transfer empirical correlation with air mass fraction, pressure and subcooling is proposed, covered all the experimental data within the error band ±13%.

Evaluation of CO2 sequestration and circulation in fault-bounded thin geothermal reservoirs in North Oman using response surface methods

In the past decade, techno-economic feasibility of using CO2 as a working fluid to harvest geothermal energy has been studied and demonstrated in both hot-dry rock and deep brine aquifers. Potential geothermal resources have been suggested by hydrogeological surveys in North Oman area. Many depleting petroleum reservoirs in this area provide excellent candidates as CO2 geologic storage and geothermal reservoirs, considering well-characterized and sealed geological structures and existing on-site infrastructure. In this study, we aim to conduct a comprehensive evaluation of reservoir performances during CO2 sequestration and circulation with possible field conditions in North Oman foreland basin. Continuous response surfaces of performance indicators are developed using 1000 CO2 sequestration-circulation models. Each model input file is assigned a set of values sampled using Latin-Hypercube method from high-dimensional parameter space bounded by ranges of key property parameters of reservoirs, including reservoir dip angle, depth, permeability, thickness, lateral boundaries, bounded fault permeability, and geothermal temperature gradient. Using response surfaces, key performance indicators, including CO2 injection, production, storage, fault leakage, well space, pressure, temperature, produced thermal flux, and lifespan, are quantitatively evaluated corresponding to various reservoir conditions represented by input parameters. The findings provide a quantitative guidance on site selection, geothermal field development and operation, and associated leakage risk assessment and techno-economic analysis for potential CO2 sequestration, geothermal exploration and utilization in North Oman foreland basin and other similar fields.