Seal Structure Research Articles

Diagnostics of structural integrity violations of avionics during impact tests

Objectives. With the continuous development of modern radio equipment in the field of aviation and space instrumentation, the requirements for accuracy, stability, and reliability of electronic equipment operated on spacecraft are also on the increase. Spacecraft avionic units (SAU) operate under special conditions and malfunctions, as a rule, are impossible to repair. SAU are hermetically sealed structures, making it difficult to assess their technical condition. The aim of this study is to increase the efficiency and reliability of detecting latent defects in SAU using the diagnostic method involving exposure to mechanical shocks.Methods. Based on known methods, a new diagnostic method is proposed which simulates mechanical processes under shock effects at the design stage. The aim is to evaluate the presence of various latent defects in SAU. In a serviceable state, the amplitude-frequency characteristics (frequency response) of SAU differ from the frequency response of SAU with defects which affect mechanical characteristics. It was for this reason that the diagnostic model of evaluating the technical condition of SAU without removal of devices was developed.Results. This work simulates the mechanical processes in SAU in a serviceable state in the presence of a variety of defect. It also involves experimental studies of mechanical characteristics in both serviceable and faulty states. After measuring the mechanical characteristics under the impact of shock loads, the data obtained is compared with simulation results in the presence of various defects. The comparison result is a report on the technical condition of SAU.Conclusions. The method of diagnosing SAU under mechanical shock impact enhances the efficiency of diagnosing latent defects during the production and operation of SAU.

Reliability analysis and optimization design of magnetic fluid dynamic seal shell structure under thermal/mechanical load

In order to study the reliability of Magnetic fluid dynamic seal shell structure under thermal/mechanical load, the improving cooling structure, calculating fuzzy fatigue reliability, and collaborative optimization design of fatigue reliability and lightweight are studied in this paper. The temperature model of the shell structure under four temperature conditions is established to analyze the influence of the thermal deformation caused by excessive local temperature. The cooling structure is improved, and the maximum temperature under the maximum temperature condition is reduced by 40.154 °C. For the sake of calculating the reliability of the new shell structure, a strength analysis model under thermal/mechanical load is built, and the fuzzy fatigue reliability function is obtained based on Latin hypercube sampling and the second-order response surface method. Four kinds of reliability are acquired by coding the functional functions and four kinds of membership functions with MATLAB, but all of them are lower than 90 % of the industrial requirements. To improve the reliability of the new shell structure and carry out the anti-fatigue lightweight design at the same time, an approximate model was constructed based on the interval analysis method and second-order response surface method for analysis. The accuracy of the approximate model was verified by re-sampling and finite element analysis. Based on the non-dominated sorting genetic algorithm, the optimal solution is determined. The optimization results show that the stress target value is reduced by 19.3 %, the weight target value is reduced by 3 %, and the fuzzy fatigue reliability reaches 94.65 %, 94.58 %, 93.89 %, and 96.31 % respectively. A new cooling structure of the Magnetic fluid dynamic seal is obtained and the maximum temperature is reduced. Moreover, the reliability of the new shell structure under thermal/mechanical load coupling is improved.

Evolution mechanism and parametric investigation of relative negative pressure zone in spiral groove gas face seal for aero-engine at high rotational speed

As an advanced sealing technology, spiral groove gas face seal has excellent sealing performance. However, it is rarely used in aero-engine. Previous investigation proposed that the relative negative pressure zone (RNPZ) in the spiral groove gas face seal can regulate the sealing performance. In this paper, further numerical simulation work is carried out. By quantifying the obstruction effect, viscous pumping effect and shear effect, the evolution mechanism of RNPZ under different film thicknesses and groove depths is revealed. Then, the parametric analysis of spiral groove configuration and groove number is carried out. Through the sub-regional quantitative analysis of the groove, the influence mechanism of structural configuration on RNPZ is revealed. Finally, combined with the hydrodynamic performance analysis, the spiral groove seal structure under optimal conditions is obtained. It is found that under the condition of high speed and low inlet pressure of aero-engine, RNPZ is suppressed by adjusting the structure of the spiral groove to enhance the shear effect, the pumping effect at the top of the groove and reduce the pumping effect at the bottom of the groove. When the number of grooves is 20 and the groove depth is 3 μm, the stiffness-leakage ratio of structure B and C can be increased by 10.15 % and 12.68 %, and the sealing performance is the strongest. This work can provide a theoretical and data basis for the subsequent optimization design of aero-engine gas face seals.

Research Progress on the Dynamic Stability of Dry Gas Seals

Concerning the application of high-precision, enormous rotating equipment under harsh working conditions, the advantages of dry gas sealing technology are increasingly obvious. Herein, research on the dynamic stability of dry gas seals is reviewed based upon their operating mechanisms. The influence of the dry gas seal structure, vibration response, and dynamic followability on the reliability of the shaft end sealing system of rotating machinery is the focus of current dry gas sealing technology. This work reviews the research history; analyzes the key coefficient of the instability of the sealing system under external disturbances, and the existing research on stability models; discusses the influence of starting and stopping characteristics, working conditions, and groove parameters on the stability of dry gas seals; and points out the shortcomings in the existing research. In addition, potential developments in dynamic stability are proposed, including improving model accuracy, improving experimental techniques, or applying intelligent control and optimization methods to enhance the dynamic stability of the sealing system. Finally, the development prospects for dry gas sealing technology in intelligent monitoring and wide temperature range adaptations are discussed, and theoretical guidance for improving a dry gas seal system is provided.

Population genomics of harbour seal Phoca vitulina from northern British Columbia through California and comparison to the Atlantic subspecies.

The harbour seal Phoca vitulina is a ubiquitous pinniped species found throughout coastal waters of the Northern Hemisphere. Harbour seal impacts on ecosystem dynamics may be significant due to their high abundance and food web position. Two subspecies exist in North America, P. v. richardii in the Pacific Ocean and P. v. vitulina in the Atlantic. Strong natal philopatry of harbour seals can result in fine-scale genetic structure and isolation by distance. Management of harbour seals is expected to benefit from improved resolution of seal population structure and dynamics. Here, we use genotyping-by-sequencing to genotype 146 harbour seals from the eastern Pacific Ocean (i.e. British Columbia (BC), Oregon and California) and the western Atlantic Ocean (i.e. Québec, Newfoundland and Labrador). Using 12,742 identified variants, we confirm the recently identified elevated genetic diversity in the eastern Pacific relative to the western Atlantic and greatest differentiation between the subspecies. Further, we demonstrate that this is independent of reference genome bias or other potential technical artefacts. Coast-specific analyses with 8933 and 3828 variants in Pacific and Atlantic subspecies, respectively, identify divergence between BC and Oregon-California, and between Québec and Newfoundland-Labrador. Unexpected PCA outlier clusters were observed in two populations due to cryptic relatedness of individuals; subsequently, closely related samples were removed. Admixture analysis indicates an isolation-by-distance signature where Oregon seals contained some of the BC signature, whereas California did not. Additional sampling is needed in the central and north coast of BC to determine whether a discrete separation of populations exists within the region.

Numerical and experimental study on pole teeth interlaced divergent ferrofluid seals with single magnetic source

For the improvement of pressure resistance in ferrofluid seal with a small gap, a structure of divergent ferrofluid seal (FS) with alternating pole teeth (PT) was proposed in this paper. Distribution of the magnetic field in the seal gap (SG) is analyzed by using the magnetic field finite element method, and the theoretical pressure resistance (PR) is calculated by using the step ferrofluid seal PR theory. Effect of the number of pole teeth and seal gap on its sealing PR were studied experimentally. The PR of the interlaced divergent FS is compared to the experimental findings of a conventional ferrofluid seal structure. The results show that the actual pressure value of the interlaced divergent FS is consistent with its theoretical pressure value well. Compared to the common ferrofluid seal, the interlaced divergent FS has better PR.

Influence of diamond-like carbon coatings and micro-texturing on friction and wear of seal interfaces: Experiment and simulation study

For mechanical seal friction vice in dry friction conditions, due to friction wear serious failure, is the slurry pump and other instruments in the operation of the process of the urgent need to solve the problem. In this paper, in order to optimize and enhance the friction and wear problem of mechanical seal end face of slurry pump. Surface treatment of mechanical sealing rings with diamond-like carbon (DLC) coating and surface microtexturing, and at different rotational speeds and normal forces, the surface hardness, wear coefficient and dry friction coefficient of the sealing rings were analyzed by experimental comparison, and the wear morphology was collected by electron microscopy, having analyzed the results of the sets of, the end face structure of the mechanical seal was optimized. Based on Archard wear model simulation calculations, the seal ring wear depth and wear quality were obtained. The results show: under dry friction conditions, the synergistic effect of the DLC coating and the surface micro-texture (MT), the coefficient of friction is reduced by approx. 68% and the quality and depth of wear is minimized. Excessive speeds and normal forces are more prone to wear behavior caused by abrasive wear. Simulation results of surface treatment groups, DLC / MT group maximum wear depth is the smallest; wear quality test and simulation of the maximum error within 15.7%. The results of the study can provide a basis for a phosphoric acid plant slurry pump mechanical seal design.

Sealing Performance of Ethylene Propylene Diene Monomer Seals for Proton Exchange Membrane Fuel Cells

The reliability of the sealing system of a proton exchange membrane fuel cell (PEMFC) is a prerequisite for ensuring the efficient and safe operation of the cell stack. In consideration of the actual assembly process, a local model of single‐cell sealing structure is constructed using a rounded corner rectangular sealing gasket structure. Apart from that, the effects of fluid pressure, bipolar plate offset, sealing gasket size, steady‐state temperature field, and seal structure on the sealing performance of PEMFC are investigated. As shown by results, with the increase of fluid pressure and sealing gasket width, the contact pressure is increased and the sealing performance is also improved. However, the increase of sealing gasket height is unfavorable to the stability and sealing performance of the stack. Meanwhile, excessive offset error leads to a sharp decrease in contact length and contact pressure at the sealing interface, which reduces the stability of the stack. With the increase of the operating temperature, the thermal expansion of the gasket increases and the contact performance improves significantly. Seals with rectangular structure have some advantages in terms of contact stability and standard deviation of contact pressure.

Leakage performance of hybrid brush seals under high differential pressure conditions

A three-dimensional axial fluid-porous medium-flow field model was designed for the sealing properties of the hybrid brush seal (HBS) seal structure under complex operating conditions. Using a computational fluid dynamics model in view of non-Darcy porous media, the pressure and velocity distributions of the sealing medium in the flow path were simulated, and the flow characteristics of the hybrid brush seal were analysed to obtain the leakage of the hybrid seal structure. The results show the implication of pressure ratio (Rp) on the labyrinth brush seal leakage rate and pressure distribution. Compared with typical brush seal test results, as the inlet and outlet pressure ratio (Rp) increases, the more obvious the hybrid brush seal sealing effect is, when the pressure ratio is 3 bar, the spillage of the hybrid brush seal is reduced by about 39%.

Experimental Study on Non-contact Labyrinth Seal under Negative Pressure Intervention

The non-contact labyrinth seal structure of a high-speed gearbox was taken as the research object, a non-contact labyrinth seal structure under negative pressure intervention was designed, and its rationality was verified by simulation analysis. An airfoil-shaped acquisition device for collecting negative pressure was designed, and its rationality was analyzed by simulation. According to the design, a test platform for non-contact labyrinth seal under negative pressure intervention was built to measure the pressure data of each sealing chamber of the non-contact labyrinth seal under different working conditions. The results showed that it was effective to balance the internal and external pressure of the non-contact labyrinth seal by using the negative pressure collected by the airfoil-shaped device in the complex flow field of the high-speed gearbox. It also showed that the non-contact labyrinth seal structure under negative pressure intervention designed in this paper is an effective way to solve the leakage problem of the non-contact labyrinth seal used in high-speed gearbox.

Effect of process parameters on characteristics and pore structure of foam ceramics prepared from granite sawing dust

Foam ceramics made from solid waste have recently attracted considerable interest because of their environmentally friendly and sustainable properties. This study examines the manufacturing of foam ceramics through the direct sintering of granite sawing dust. An orthogonal experimental design was employed to explore the impact of the foaming-agent content, sintering temperature, holding time, and moulding pressure on the characteristics of foam ceramics. The experimental and analytical results show that under the given conditions involving a foaming agent content of 0.8 wt%, a sintering temperature of 1200 °C, a holding time of 30 min and a moulding pressure of 5 MPa, the produced foam ceramics have excellent properties. These included a bulk density of 0.892 g/cm³, water absorption of 0.130 %, porosity of 59.67 %, high compressive strength of 10.721 MPa, and thermal conductivity of 0.247 W/(m·K). Analysis of the pore structure revealed that the samples had an evenly distributed and sealed pore structure, which effectively increased the porosity and bulk density. This study effectively demonstrates the viability of producing porous ceramics from granite sawing dust, presenting a green and economically sustainable method for waste management and the creation of high-functioning materials. These findings offer promising prospects for the greater implementation of granite waste in the construction sector.

Experimental and Numerical Investigations into the Effects of Rim Seal Structure on Endwall Film Cooling and Flow Field Characteristics

During the practical operation of gas turbines, relatively cooled air from the compressor and the rim seal is applied in order to prevent mainstream ingestion into the space between the rotor and stator disc cavities, which can prolong the service life of hot components. On the one hand, the purge flow from the rim seal will inevitably interact with the mainstream and result in secondary flow on the endwall. On the other hand, it can also provide an additional cooling effect. In this paper, four rim seal structures, including an original single-tooth seal (ORI), a double-tooth seal (DS), a single-tooth seal with an adverse direction of the coolant purge flow and mainstream (AS) and a double-tooth seal with an adverse direction of the coolant purge flow and mainstream (ASDS), are experimentally and numerically investigated with mass flow ratios of 0.5%, 1.0% and 1.5%. The flow orientation of the coolant from the rim seal is considered as one of the main factors. The pressure-sensitive paint technique is used to experimentally measure the film cooling effectiveness on the endwall, and flow field analysis is conducted via numerical simulations. The results show that the cooling effect decreases in the cases of DS and ASDS. AS and ASDS can achieve a better film cooling performance, especially under a higher mass flow ratio. Furthermore, the structural changes in the rim seal have little impact on the aerodynamic performance. AS and ASDS can both achieve a better aerodynamic and film cooling performance.

Frost-Preventing Design for Space Station Refrigerator

Different preservation temperatures for sample storage in space stations and corresponding refrigerator devices have been designed. In the below-freezing environment, frost will occur on the inner wall surface and the sealing place of the refrigerator device, which may have an impact on the operating performance and sealing performance of the refrigerator device. This paper analyzes the impact of frost on refrigerator storage devices, and designs and verifies a scheme of air cooling with a hollow seal method to reduce the impact of frost. The designed refrigerator was tested for air cooling, sealing, and long-term performance. The tests show that the air-cooling structure designed in this paper can effectively reduce the frost on the sample surface. A cumulative helium mass spectrometry leak detection method is applied to verify that the hollow seal structure designed has a better sealing property, which can prevent the diffusion of water vapor and frosting at the sealing position. The design with air cooling and hollow sealing has less frost and more stable performance for long-term operation. The results demonstrate this refrigerator would have the capability of operating on-orbit. The frost-preventing method for space station refrigerator designed in this paper has significance for the design of similar cryogenic equipment in microgravity environments.

Coaxiality prediction for aeroengines precision assembly based on geometric distribution error model and point cloud deep learning

Assembly accuracy of aeroengines influences operation performance and service life. The coaxiality of the aeroengine is the main index of assembly accuracy and is also a core index to represent assembly quality. However, direct measurement of coaxiality is a difficult technical problem due to the sealed structure of the aeroengine casing system. A coaxiality prediction method is proposed to obtain coaxiality and assist assembly by geometric distribution error modeling and point cloud deep learning. The prediction process consists of three steps. In the beginning, the geometric distribution error model is established to construct the accurate dense point cloud of aeroengine part surfaces by the non-uniform rational B-splines (NURBS) method based on the coordinate measuring machine collecting information. Then, the mapping between the dense point cloud and coaxiality is established to obtain an assembly dataset by the virtual assembly. Finally, the dataset is fed to a new point cloud deep learning backbone, Self-channel cross attention point network, and realizes end-to-end coaxiality prediction based on the aeroengine surface point cloud. The geometric distribution error model is tested on the aeroengine simulated parts with 0.001 mm accuracy. The prediction method is verified on the aeroengine simulated parts and compared with other point cloud deep learning baselines. The method proposed in this paper realizes 93.17% prediction accuracy with 0.01 mm coaxiality precision which is a high performance and meets the requirements of industrial measurement. This paper provides an effective coaxiality prediction model for the aeroengine casing system, to improve the accuracy and efficiency of the aeroengine assembly.

ИСТОРИЯ ФОРМИРОВАНИЯ ЗАЛЕЖЕЙ УГЛЕВОДОРОДОВ В ПЛАСТАХ МАЛЫШЕВСКОЙ СВИТЫ НА ТЕРРИТОРИИ КАРСКО-ЯМАЛЬСКОГО РЕГИОНА

The paper describes the characteristics of source beds, considers the structure of fluid seals and formation stages of anticline structures within Kara-Yamal region, bounded from the south by the Messoyakha inclined ridge. Investigations were carried out on the basis of comprehensive generalization of published geological and geochemical materials. It is shown that all formations of the Lower and Middle Jurassic containing aquagene, terragene and mixed types of kerogen in various proportions, possessed oil and gas generating properties. The significant implementation of generation potential due to the high OM catagenetic transformation in rocks of the Middle and especially Lower Jurassic caused the formation of mainly condensate gas accumulations in reservoirs of the Malyshevka Formation. The stages of formation of clay fluid seal in the process of lithogenesis are considered, it was determined by the feature of subsequent transgressive-regressive sediment filling relative to the deep–sea basin in the Late Berriasian – Early Aptian. The history of the anticline structure formation in the roof of the Jurassic structural stage is analyzed separately. According to the results of this analysis, it was found that hydrocarbon accumulations matured within the structures whose main stages of development coincided with the Jurassic period and Early Cretaceous epoch. The beginning time of filling traps with hydrocarbons was defined on the basis of information comparison about the time of compaction of clay strata of the Late Bathonian – Kellovian to the state of fluid seal and time of implementation of the HC main generation phases by oil –and- gas generating rocks. It is concluded that the lithification asynchrony of the fluid seal clay deposits predetermined the time diversity of the HC accumulation generation in the Malyshevka Formation in geological past.

Analysis of sealing performance of combined seal structure with metal C-ring with built-in spring

The built-in spring reinforced metal C-shaped sealing ring is a high-performance static sealing component. Its metal combination sealing structure is designed to meet the sealing requirements of all metal graded cementing tools. To analyze and study the sealing performance of this combination sealing structure under complex underground application conditions, a three-dimensional simulation analysis model of the metal C-shaped ring combination sealing structure was established using ANSYS finite element analysis software, Simulate and analyze the stress and deformation of the combined sealing structure under different working conditions (room temperature and high temperature), and discuss the influence of external load conditions, including underground working medium pressure, temperature, and pre compression amount, on the sealing performance of the combined sealing structure. Calculate the variation law of contact pressure and equivalent stress under specific external conditions, providing some reference basis for the design and application of sealing rings and combined sealing structures.

Undulating Seal Whiskers Evolved Optimal Wavelength-to-Diameter Ratio for Efficient Reduction in Vortex-Induced Vibrations.

Seals are well-known for their remarkable hydrodynamic trail-following capabilities made possible by undulating flow-sensing whiskers that enable the seals to detect fish swimming as far as 180m away. In this work, the form-function relationship in the undulating whiskers of two different phocid seal species, viz. harbor and gray seals, is studied. The geometry and material properties of excised harbor and grey seal whiskers are systematically characterized using blue light 3D scanning, optical and scanning electron microscopy, and nanoindentation. The effect of the undulating geometry on the whiskers' vibration in uniform water flow is studied using both experimental (piezoelectric MEMS and 3D-printed piezoresistive sensors developed in-house) and numerical (finite element method) techniques. The results indicate that the dimensionless ratio of undulation wavelength to mean whisker diameter (λ/Dm ) in phocid seals may have evolved to be in the optimal range of 4.4-4.6, enabling an order-of-magnitude reduction in vortex-induced vibrations (compared to a similarly-shaped circular cylinder) and, consequently, an enhanced flow sensing capability with minimal self-induced noise. The results highlight the importance of the dimensionless λ/Dm ratio in the biomimetic design of seal whisker-inspired vibration-resistant structures, such as marine risers and wake detection sensors for submarines.

Experimental study of self-locking seal structure based on full ocean depth sediment pressure retaining sampler

The full ocean depth environment is characterized by high pressure, low temperature, and high corrosiveness, making it difficult for the current deep-sea sampling equipment to obtain pressure-retaining sediment samples from the seafloor. A new self-locking seal structure is designed with an automatic centering plus floating valve core structure to ensure that the long needle valve core only carries the axial load and autonomously fits the sealing cone of the pressure retaining device. The novel self-locking seal design makes the sampler seal more reliable under high pressure. We conducted a series of experiments to verify the sealing performance of the self-locking seal structure, and the test results show that the self-locking seal structure has better sealing performance when the pressure difference between the inside and outside is larger. This new self-locking seal structure has been used for the full ocean depth sediment sampler during the TS-21 cruise in 2021 and was tested in situ at a depth of 7700 m in the West Philippine Basin, retrieving pressure-retaining sediment samples with 94 % pressure retention.

Design and experimental investigation of symmetrical embedded magnetic fluid rotary seal with small gap

A novel symmetrical embedded magnetic fluid seal (SEMFS) structure was designed with the aim of enhancing the pressure resistance of the magnetic fluid (MF) seal with small gap under vacuum condition. The magnetic field distribution in the sealing gap (SG) was studied by numerical simulation, and the theoretical pressure resistant-withstanding of the SEMFS was obtained by combining the pressure resistance theories of stepped MFS. An experimental study was conducted to investigate the effects of magnetic fluid injection volume (MFIV), number of pole teeth, SG, and rotational speed of the rotating shaft on the seal's pressure resistance. The pressure resistant-withstanding values obtained were compared with those theoretically projected for the (SEMFS) and the ordinary magnetic fluid seal (OMFS), based on numerical analysis. The results indicate that the measured pressure value for the SEMFS matches well with the calculated pressure value. Furthermore, the SEMFS exhibits superior pressure resistance capabilities compared to the OMFS when subjected to the same parameters, which fully reflects the superiority of SEMFS structure. With an augment in the injection volume of MF, the pressure-withstanding performance of the SEMFS exhibits an initial upward trend followed by a gradual stabilization. Moreover, the pressure-withstanding performance of the SEMFS demonstrates a progressive enhancement with an increase in the number of radial pole teeth (RPT) and a corresponding increment in the number of axial pole teeth (APT). The ability to resist pressure of SEMFS decreases as the radial sealing gap (RSG) and axial sealing gap (ASG) increase. At low shaft speeds, the SEMFS's pressure resistance capability is not impacted by rotational speed and can be considered similar to a static seal.

Characteristics and Experimental Research on Performance of the Seal Structure of Deepwater Collet Connector

The sealing reliability of collet connectors is essential within underwater production systems. This paper is based on the lens gasket sealing mechanism and Hertzian contact theory, establishing mechanical models for the core sealing components in preloaded and working states and analyzing the minimum required axial preload force for sealing. According to the sealing principles of the connector, the force characteristics of each sealing element are analyzed in both preloaded and working states. The interplay of forces between these elements is subsequently determined. Furthermore, the amplification of axial preload force within the sealing structure is confirmed through simulations of contact characteristics. Finally, the accuracy of theoretical and simulated results is confirmed through experimental validation.