Search Results (54)

The upstream pumping effect of mechanical face seals has a significant influence on their sealing performance. In order to reveal the effect of deep grooves on upstream pumping effects, an experimental and theoretical analysis is carried out in this study. The main novelty of this paper is to analyze the feasibility of deep grooves in a mechanical seal design from the perspective of cavitation and leakage rate. Firstly, an upstream pumping spiral groove is designed and fabricated, with different groove depths from 2 μm to 90 μm. Then, testing is performed with water as the sealing medium. Finally, the cavitation phenomena are captured, and leakage rates are measured during the experiment. The obtained results show that the groove with a depth of tens of microns can be designed according to the laminar flow hypothesis, and Reynolds equation is still valid to predict the cavitation and leakage rate theoretically. The spiral groove with a depth of tens of microns shows a significant upstream pumping effect. Both the theoretical and experimental analyses show that under certain working conditions, deep grooves can realize the zero-leakage sealing design of liquid, which might provide significant guidance for the sealing design of mechanical face seals to enhance sealing performance. Full article

Ultra-high-pressure hydrogen solenoid valves face a fundamental design challenge of operating across a wide pressure range from 2 MPa to 87.5 MPa. To address the conflicting requirements of effective sealing at low pressures and structural integrity at high pressures, this study proposes a novel concave contact geometry based on Hertzian contact theory. Finite element analysis examines the mechanical relationships between plunger curvature radius (R_ₚ), seat curvature radius (Rₛ), and eccentricity (e). Optimization utilizing Latin hypercube sampling and kriging metamodeling yields an optimal design (Rₚ = 5.73 mm, Rₛ = 4.68 mm, e = 0.95 mm) with an Rₚ/Rₛ ratio of 1.22. The optimized concave contact geometry achieves 23.7% higher contact pressure at 2.0 MPa and 42.7% lower maximum equivalent stress at 87.5 MPa compared to conventional rectangular geometry. Experimental validation confirms the concave contact geometry seals at 1.7 ± 0.2 MPa, below the AIS-195 standard requirement of 2.0 MPa and 69.6% lower than the rectangular design (5.6 ± 0.7 MPa). Structural analysis after 87.5 MPa high-pressure exposure reveals no measurable deformation in the concave design, while the rectangular design exhibits permanent deformation of 0.0580 ± 0.007 mm. This integrated methodology provides a framework for optimizing contact geometries in fluid control components operating under extreme pressure conditions, successfully reconciling contradictory requirements across the entire pressure range. Full article

For complex mechanical transmission equipment, shaft bearings are usually enclosed together with the shaft in the internal space of the housing to maintain good sealing and reliability. However, it is difficult to monitor the status of the shaft bearing through external sensors on the housing, while internal sensors face challenges in energy supply and data transmission. Therefore, a piezoelectric transducer ring-based energy harvesting microelectromechanical system (PTR-EH-MEMS) is proposed for the condition monitoring of shaft bearings. Specifically, the piezoelectric transducer ring is designed to convert mechanical vibrations into electrical energy, which simultaneously acts as a self-powered monitoring sensor through energy harvesting. In addition, the MEMS is embedded for piezoelectric data processing and condition monitoring of the shaft bearings. To verify the proposed PTR-EH-MEMS, an experimental investigation is implemented under different conditions. The experimental results demonstrate that the system can achieve the maximum DC output of 0.8 V and the root mean square power of 43.979 μW within 128 s, which can effectively identify early-stage bearing faults frequency through a self-powered mode. By combining energy harvesting with condition monitoring capability, the PTR-EH-MEMS offers a compact and sustainable approach for predictive maintenance in rotating machinery, reducing the reliance on external power sources and enhancing the reliability of industrial systems. Full article

Environmental and social governance targets, as well as the global transition to cleaner renewable energy sources, push for advancements in hydrogen-based solutions for energy generators due to their high energy per unit mass (energy density) and lightweight nature. Hydrogen’s energy density and lightweight nature allow it to provide an extended range of uses without adding significant weight, potentially revolutionizing many applications. Moreover, a variety of sources, including renewable energy, can produce hydrogen, making it a potentially more sustainable option for energy storage despite its main limitations in production and transportation costs. In this framework we are proposing an innovative energy generator that might merge the benefits of batteries and hydrogen. The energy generator is based on a worldwide patented solution introduced by MIEEG s.r.l. regarding the shape of the chambers. This innovative solution can be used to design a 100% H2-fed microturbine with a high power/weight/volume ratio that works as a range extender of battery packs for a comprehensive, high-efficiency hybrid powertrain. In fact, it runs at 100,000 rpm and is designed to deliver about 100 kW in about 15 L of volume and 15 kg of weight (alternator excluded). The system is highly complex due to high firing temperatures, long life requirements, corrosion protection, mechanical and vibrational stresses, sealing, couplings, bearings, and the realization of tiny blades. This paper analyzes the main design challenges to face in the development of such complex generators, focusing on the hot gas path components, which are the most critical part of gas turbines. The contribution of additive manufacturing techniques, the adoption of special materials, and coatings have been evaluated for system improvement. Full article

As humans expanded across the globe, the Americas were the last continents to be colonized. While debates persist regarding the timing and mechanisms of this process, it is widely accepted that by the Pleistocene–Holocene transition, the New World was populated from Alaska to Tierra del Fuego. During this period, hunter-gatherer societies demonstrated remarkable cultural and adaptive diversity, particularly in subsistence strategies and technological innovations. The colonization of the Americas offers valuable insights into population dynamics, human–environment interactions, species extinctions, and adaptive capacities. From an interdisciplinary perspective that combines an isotopic analysis of megafaunal remains with archaeological evidence, this study examines human interactions with Pleistocene fauna in the south–central region of South America’s Southern Cone. Isotopic analyses provide information about the diets, adaptations, and climatic challenges faced by megafaunal communities. Archaeological evidence reveals that humans utilized megafauna and other Pleistocene species for food and tool production. These findings are supported by evidence such as cut marks and bone tools, but also by sealed sediment layers and/or indisputable associations of lithic artifacts. This research contributes to our understanding of human dispersal in the Southern Cone during the colonization of the Americas, shedding light on the regional environments and adaptive strategies of early populations. Full article

For the exploration and development of oil and gas reservoirs in shallow, cold regions and deep oceans, oil well cement (OWC) pastes face the challenge of slow cement hydration reactions and the low early-strength development of cement stone at low temperatures, which can cause the risk of fluid channeling and the defective isolation of the sealing section during the cementing construction process. To address the above challenges, a nanoscale hydrated calcium silicate (C-S-H) crystal nucleus, DRA-1L, was synthesized. Its application performance and action mechanism were studied. The structural characterization of DRA-1L revealed that its crystal structure resembles that of amorphous C-S-H gel, with a size distribution ranging from 20 to 200 nm. The addition of DRA-1L significantly shortens the transition time of static gel strength, preventing the channeling of OWC paste and promoting the strength development of cement stone at low temperatures. Moreover, the mechanism by which DRA-1L enhances the early strength of cement stone was studied. Results indicated that the nanoscale DRA-1L with nucleation effect reduces the barrier to C-S-H gel formation and accelerates cement hydration, which leads to the increased compactness and early strength of cement stone. Full article

Antibacterial stainless steels have been widely used in biomedicine, food, and water treatment. However, the current antibacterial stainless steels face challenges in balancing corrosion resistance and antibacterial effectiveness, limiting their application range and lifespan. In this study, an oxide layer sealed with antibacterial Ag particles was constructed on the surface of 304 stainless steel through anodizing and electrodeposition, and the process parameters were optimized for achieving long-term antibacterial properties. The electrochemical tests demonstrated that the composite coating effectively enhanced the corrosion resistance of 304 stainless steel. The X-ray photoelectron spectroscopy analysis revealed the close binding mechanism between the Ag particles and the micropores in the oxide layer. Furthermore, the antibacterial stainless steel has an antibacterial rate of 99% against Escherichia coli (E. coli) and good biocompatibility. This study provides an effective approach for designing efficient, stable, and safe antibacterial stainless steel. Full article

This paper reviews the current state of dynamic sealing technologies, examining the challenges faced by conventional sealing methods under complex working conditions, such as high temperature, high pressure, and corrosive environments. It also provides a concise overview of the status and developmental trends in sealing inspection technologies. From the perspective of obstruction mechanisms, this study reinterprets the concept of sealing science by redefining the classification of sealing types based on solid-phase medium obstruction, fluid hydrostatic and hydrodynamic obstruction, fluid pumping obstruction, fluid energy dissipation obstruction, and fluid impact obstruction. Comparative analyses of sealing structures across these obstruction mechanisms are presented. The sealing technology based on fluid impact medium obstruction, newly proposed by this paper, represents an innovative sealing approach. It offers distinct advantages such as zero wear, structural simplicity, and high stability, addressing longstanding issues in high-speed, large-clearance non-contact seals, including low leakage suppression efficiency, system complexity, and poor stability. Since its introduction, this novel sealing structure has garnered significant attention and recognition from both the academic and industrial sealing communities. With the potential to revolutionize the field, this groundbreaking sealing design is poised to lead the next wave of technological advancements in sealing science. Full article

One of the primary causes of mechanical face seal failure is rotor vibration. Traditional dynamic seal models often cannot fully explain failure mechanisms. The dynamic models of seals proposed in this paper, including those developed by the authors, are valuable for predicting seal dynamics during operation in specific turbomachinery and for explaining the causes of seal failure. The single-mass dynamic model is suitable for analyzing the dynamics of contact mechanical face seals and simply designed dry gas seals. The two-mass dynamic model is used to investigate the operational dynamics processes of classical dry gas seals under complex loading conditions. The three-mass dynamic model is used to study various complex types of mechanical face seals. This model can determine the normal operating condition range and explain leakage mechanisms in the presence of excessive rotor vibrations. Full article

Firmly, the bearing capacity test of 1:1 equal ratio pillar under different constraint forms and different filling medium conditions was carried out. The results show that the binding pillar-forming effect is relatively good. The constraint ability of unconstrained, metal mesh, polyester mesh, hooked iron flat-hoop bushing, bellows, and spiral iron pipe is enhanced, in turn, and the carrying capacity is improved successfully. The homogeneity of high-water materials is better than concrete, and they have better compressibility, but their carrying capacity is relatively weak. The carrying capacity of concrete pillars is generously higher than that of high-water materials, but the compressibility is poor. Second, the migration characteristics of the surrounding rock structure of the gob-side entry retaining and the rule of side support are analyzed, the requirements of the side support are pointed out, and the side-support technology of the binding pillar is proposed. Taking Hijiata Mine’s 50108 working face gob-side entry retaining as an example, the bellows pump-filled concrete pillar is used as the side support body, supplemented by handling steel mesh and air-duct cloth, and toughness material is sprayed between the pillars to seal the goaf, meeting the requirements of side support and road stability. The pillar has the characteristics of high early strength, strong final consolidation carrying capacity, good crimping effect, high mechanism degree, fast construction speed, less concrete consumption, low comprehensive cost, etc., and it has a good application prospect in the gob-side entry retaining or rapid advanced working face. Full article

Urban trees are known for their ability to settle fine particulate matter (PM_2.5), yet the effects of historical pollution exposure on their dust-retention capacity and stress memory remain underexplored. Therefore, we selected Euonymus japonicus Thunb. var. aurea-marginatus Hort. and Photinia × fraseri Dress, which are two common urban greening tree species in the Yangtze River Delta, a highly urbanized region in China facing severe air pollution challenges, characterized by dense urban forests, and we employed an aerosol generator to perform controlled experiments aiming to simulate PM_2.5 pollution exposure in a sealed chamber. The experiments encompassed a first pollution treatment period P1 (15 days), a recovery period R (15 days), and a second pollution treatment period P2 (15 days). The study investigates the historical impacts of pollution exposure by simulating controlled environmental conditions and assessing the morphological and physiological changes in trees. The main results are as follows: V_d of Euonymus japonicus Thunb. var. aurea-marginatus Hort. significantly decreased on the 10th day during P2 compared with that on the same day during P1, whereas V_d of Photinia × fraseri Dress significantly decreased on the 15th day. Compared with those during P1, the specific leaf area of both plants significantly decreased, the specific leaf weight significantly increased, the wax layer significantly thickened, the stomata decreased, and the content of photosynthetic pigments remained stable during P2. Furthermore, the air pollution tolerance index (APTI) generally increased during both P1 and P2. This study contributes to international knowledge by examining stress memory in urban trees and underscores the role of stress memory in enhancing plant resistance to periodic particulate pollution, offering insights into the adaptive mechanisms that can be applied globally, not just regionally. Full article

To address the lack of reliable measurement methods for identifying wear mechanisms and predicting the state of mechanical seal tribo-parts, this study proposes a method for characterizing tribological behavior based on measuring face vibration acceleration. It aims to uncover the source mechanism of mechanical seal face vibration acceleration influenced by tribology and dynamic behavior. This research delves into the dynamic behavior characteristics and vibration acceleration of the mechanical seal stationary ring. We explored the variation pattern of face vibration acceleration root mean square (RMS) with rotation speed, sealing medium pressure, and face surface roughness. The results indicate that under constant medium pressure, an increase in rotation speed leads to a decrease in acceleration RMS and an increase in face temperature. Similarly, under constant rotation speed, an increase in medium pressure results in nonlinear changes in acceleration RMS, forming an “M” shape, along with an increase in face temperature. Furthermore, under conditions of constant medium pressure and rotation speed, an increase in the surface roughness of the rotating ring face corresponds to an increase in acceleration RMS and face temperature. Upon starting the mechanical seal, both acceleration RMS and temperature initially increase before decreasing, a trend consistent with the Stribeck curve. Full article

In the process of tunnel construction, problems such as high-stress rockburst, large deformation of soft rock, water inrush and mud gushing, secondary cracking of linings, blasting interference, man-made damage, and mechanical damage are often encountered. These pose a great challenge to the installation of monitoring equipment and line protection. In order to solve these problems, the 2# inclined shaft of Muzhailing Tunnel in the Gansu Province of China, which exists under high stress, water bearing, and bias conditions, was taken as the research object in this paper. By assembling a string, drilling grouting and sealing, and introducing multiple modes of protection, new fiber grating sensor group installation and line protection methods were proposed. The automatic continuous monitoring of the deep deformation of surrounding rock and the automatic continuous monitoring of steel arch stress were realized. The field monitoring results showed that: (1) the fiber grating displacement sensor group could be used to verify the authenticity of the surface displacement results monitored by the total station; (2) the NPR anchor cable coupling support effectively limited the large deformation of soft rock and the expansion of surrounding rock in a loose circle, and the range of the loose circle was stable at about 1 m; and (3) the main influence range of blasting was at a depth of 0~5 m in surrounding rock, and about 25 m away from the working face. In addition, to secure weak links in the steel arch due to the hardening phenomenon, a locking tube was set at the arch foot. In the support design, the fatigue life of the steel was found to be useful as the selection index for the steel arch frame to ensure the stability of the surrounding rock and the long-term safety of the tunnel. The present research adopted a robust method and integrates a variety of sensor technologies to provide a multifaceted view of the stresses and deformations encountered during the tunneling process, and the effective application of the above results could have certain research and reference value for the design and monitoring of high stress, water-bearing, and surrounding rock supports in tunnels. Full article

Spring-energized seals demonstrate good sealing performance over a wide range of pressures and temperatures and can compensate for installation eccentricity, high-temperature aging, etc. However, as a contact seal, its polytetrafluoroethylene (PTFE) jacket material is easily worn during the rotation of the end face, which leads to a decline in sealing performance and, ultimately, seal failure. Based on the Archard wear model, a performance prediction model of the spring-energized seal was established by combining tests and numerical analyses. In order to improve the tribological performance of spring-energized seals made of PTFE, varied fillers were added to modify the PTFE, and the tribological and mechanical properties of PTFE composites with varied fillers were measured in experiments. Using a performance prediction model for spring-energized seals, the variation in the friction performance of seals made of these filled PTFEs during the operating cycle was analyzed. The results showed that the performance prediction model can accurately simulate this variation. After a certain amount of wear, the deviation between the simulated data and the experimental data was within ±5%. Compared with spring-energized seals made of pure PTFE, the friction torque of spring-energized seals made of GF/PTFE was reduced by 28.97% at most, and the friction torque reduction rate was lowered by 22.25%. Full article

Low carbon and high performance have become key trends in the development of construction materials. Understanding the mechanism by which curing conditions affect the mechanical properties of high-ductility geopolymer concrete (HDGC) is of significant importance. This study investigated three sealing curing temperatures (room temperature, 45 °C, and 60 °C) and four curing durations (1 day, 3 days, 5 days, and 7 days), while considering two final curing ages (7 days and 28 days) to explore their effects on the axial tensile and compressive properties of HDGC. The results showed that both 45 °C and 60 °C could improve the brittle failure of HDGC under axial compressive loading. However, curing at 60 °C and for durations longer than 1 day in an oven would catalyze the formation of eight-faced zeolite crystals within the slag–fly ash geopolymer matrix, and it could weaken the matrix’s pore structure and subsequently affect the material’s later strength development. Nevertheless, oven heat curing enhanced the bridging effect between the fibers and the matrix, partially compensating for the reduction in the initial tensile strength of HDGC. This follows the pseudo-strain-hardening material’s saturation cracking criterion to enhance the strain-hardening behavior of HDGC and improve its tensile energy absorption capacity. A curing condition of 45 °C for 5 days is recommended to maximize the ductility of HDGC. This study provides important theoretical support for the design and promotion of green, low-carbon, high-ductility composite materials. Full article