Search Results (5,678)

Zr is a common element in titanium alloys to enhance their mechanical properties; however, its role in combustion remains unknown. This study aimed to elucidate the effects of Zr on the ignition conditions and flame propagation of Ti_100−xZr_x alloys via promoted ignition-combustion (PIC) tests. Results indicated that increasing Zr content (from 30 at% to 70 at%) decreased the critical oxygen pressure, ignition temperature, and burning velocity of Ti_100−xZr_x alloys. The reduction in ignition conditions was attributed to a decrease in ignition activation energy (from 108.37 kJ/mol to 94.26 kJ/mol) and an increase in combustion heat (from 986.34 kJ/mol to 1049.84 kJ/mol) with Zr addition. Additionally, microstructural analysis indicated that the suppression of flame propagation was attributed to Zr promoting the formation of a dense oxide layer. This hindered oxygen diffusion, thereby suppressing the heat release of oxidation reactions in the oxide zone and the peritectic reaction in the melting zone. These findings provided new insights into optimizing the composition of burn-resistant titanium alloys to inhibit combustion kinetics. Full article

As a key zero-carbon energy carrier, the accurate measurement of liquid hydrogen flow in its industrial chain is crucial. However, the ultra-low temperature, ultra-low density and other properties of liquid hydrogen can introduce calibration errors. To enhance the measurement accuracy and reliability of liquid hydrogen flow, this study investigates the heat and mass transfer within a 1 m³ non-vented storage tank during the calibration process of a liquid hydrogen flow standard device that integrates combined dynamic and static gravimetric methods. The vertical tank configuration was selected to minimize the vapor–liquid interface area, thereby suppressing boil-off gas generation and enhancing pressure stability, which is critical for measurement accuracy. Building upon research on cryogenic flow standard devices as well as tank experiments and simulations, this study employs computational fluid dynamics (CFD) with Fluent 2024 software to numerically simulate liquid hydrogen flow within a non-vented tank. The thermophysical properties of hydrogen, crucial for the accuracy of the phase-change simulation, were implemented using high-fidelity real-fluid data from the NIST Standard Reference Database, as the ideal gas law is invalid under the cryogenic conditions studied. Specifically, the Lee model was enhanced via User-Defined Functions (UDFs) to accurately simulate the key phase-change processes, involving coupled flash evaporation and condensation during liquid hydrogen refueling. The simulation results demonstrated good agreement with NASA experimental data. This study systematically examined the effects of key parameters, including inlet flow conditions and inlet liquid temperature, on the flow characteristics of liquid hydrogen entering the tank and the subsequent heat and mass transfer behavior within the tank. The results indicated that an increase in mass flow rate elevates tank pressure and reduces filling time. Conversely, a decrease in the inlet liquid hydrogen temperature significantly intensifies heat and mass transfer during the initial refueling stage. These findings provide important theoretical support for a deeper understanding of the complex physical mechanisms of liquid hydrogen flow calibration in non-vented tanks and for optimizing calibration accuracy. Full article

During the actual service process, water-lubricated bearings on ships are often in complex operating environments such as low speed, heavy load and salt-sand water areas. To meet the requirements of high load-bearing capacity, long service life and the ability to discharge sand and dissipate heat during the service of bearings, research has been conducted on water-lubricated bearings made of polyetheretherketone (PEEK) with a semi-groove structure. Mathematical and physical models based on the averaged Reynolds equation have been established. By adopting the method of multi-physics field coupling, the lubrication characteristics of the bearings under the coupling influence of multiple factors in the salt-sand water environment (lubrication interface (the surface roughness of the bearing bush), different working conditions (water supply pressure, rotational speed, eccentricity)) are analyzed. Finally, a water-lubricated bearing test bench is set up to conduct bearing lubrication performance tests under multiple factors. The research shows that compared with liquid water, the salt-sand water environment exhibits better lubrication characteristics. The maximum water film pressure, the deformation amount of the bearing bush and the bearing capacity of the bearings increase with the increase of the rotational speed, water supply pressure and eccentricity, while the friction coefficient decreases. With the increase of the roughness of the bearing bush, these parameters decrease slightly and the friction coefficient increases. The presence of salt-sand particles can weaken the influence of roughness on the lubrication characteristics of the bearings. After considering the thermal effect, the mechanical load and thermal load act on the surface of the bearing bush together, resulting in an increase in the deformation amount of the bearing bush, a 0.11% drop in the water film pressure, and the highest temperature of the water film being concentrated at the outlet of the groove. The local semi-groove structure of PEEK can make the friction coefficient as low as 0.019. The comparison errors between the simulation and the experiment are within 10% (for water film pressure) and 2.6% (for friction coefficient), which verifies the reliability of the model. Full article

Judging from the current global exploration trend, ultra-deep layers have become the main battlefield for energy exploration. China has made great progress in the ultra-deep field in recent decades, with the Tarim Basin and Sichuan Basin as the focus of exploration. The Sichuan Basin is a large superimposed gas-bearing basin that has experienced multiple tectonic movements and has developed multiple sets of reservoir–caprock combinations vertically. Notably, the multi-stage platform margin belt-type reservoirs of the Sinian–Lower Paleozoic exhibit inherited and superimposed development. Source rocks from the Qiongzhusi, Doushantuo, and Maidiping formations are located in close proximity to reservoirs, creating a complex hydrocarbon supply system, resulting in vertical and lateral migration paths. The structural faults connect the source and reservoir, and the source–reservoir–caprock combination is complete, with huge exploration potential. At the same time, the ultra-deep carbonate rock structure in the basin is weakly deformed, the ancient closures are well preserved, and the ancient oil reservoirs are cracked into gas reservoirs in situ, with little loss, which is conducive to the large-scale accumulation of natural gas. Since the Nvji well produced 18,500 cubic meters of gas per day in 1979, the study of ultra-deep layers in the Sichuan Basin has begun. Subsequently, further achievements have been made in the Guanji, Jiulongshan, Longgang, Shuangyushi, Wutan and Penglai gas fields. Since 2000, two trillion cubic meters of exploration areas have been discovered, with huge exploration potential, which is an important area for increasing production by trillion cubic meters in the future. Faced with the ultra-deep high-temperature and high-pressure geological environment and the complex geological conditions formed by multi-stage superimposed tectonic movements, how do we understand the special geological environment of ultra-deep layers? What geological processes have the generation, migration and enrichment of ultra-deep hydrocarbons experienced? What are the laws of distribution of ultra-deep oil and gas reservoirs? Based on the major achievements and important discoveries made in ultra-deep oil and gas exploration in recent years, this paper discusses the formation and enrichment status of ultra-deep oil and gas reservoirs in the Sichuan Basin from the perspective of basin structure, source rocks, reservoirs, caprocks, closures and preservation conditions, and provides support for the optimization of favorable exploration areas in the future. Full article

Battery mechanical properties degrade progressively with aging, manifesting as expansion pressure in module-constrained cells. Here, an in situ pressure operating system was developed to replicate the mechanical environment of lithium iron phosphate (LFP) prismatic batteries, enabling long-term monitoring under different loads and temperatures. Coupled with quasi-static compression tests on internal components, stress–strain curves and elasticity moduli were obtained to link microscopic behavior with macroscopic pressure response. Results show that irreversible pressure growth is jointly governed by state of health (SOH) and load: under low-load conditions, irreversible pressure increases nonlinearly with SOH, whereas higher loads yield more linear trends. A multilevel physical model encompassing electrodes, cells, and modules was proposed to explain these behaviors. This model takes into account the influence of external pressure on the modulus of the battery, and indicates that SOH and load influence reversible pressure curves through their effect on modulus. A theoretical method was derived to calculate in-module modulus, confirming its linear correlation with the fluctuation amplitude of reversible pressure. Differential pressure-capacity analysis further demonstrated that characteristic changes in expansion pressure reflect modulus evolution, and deviations from this relationship reveal degradation pathways such as gas generation, solid electrolyte interphase (SEI) growth, or lithium plating. This study establishes pressure signals as mechanistic indicators of modulus evolution and provides a framework for diagnosing mechanical degradation in batteries. Full article

Weld lines in injection-molded plastics often act as structural weak points that reduce mechanical performance. Enhancing weld line strength is therefore essential to improve product reliability and service life. This study aims to develop and validate an injection mold system capable of localized cavity temperature control to strengthen weld line regions. A specialized mold with an integrated cooling layer was designed to enable rapid thermal response during molding. The Taguchi method was applied to optimize three key parameters—part thickness, melt temperature, and injection pressure—to maximize weld line flexural strength. Experiments based on an L25 orthogonal array revealed that weld line stress varied significantly across parameter combinations, with a maximum of 109.23 MPa. A subsequent validation test conducted under the optimal conditions (250 °C melt temperature, 1.5 mm part thickness, and 16 MPa injection pressure) achieved an enhanced weld line stress of 121.88 MPa, confirming the reliability of the Taguchi-based optimization. Among the factors studied, part thickness had the greatest influence, followed by injection pressure, while melt temperature had the smallest effect. These results demonstrate that combining cavity temperature control with systematic parameter optimization provides an effective strategy to enhance weld line strength in high-performance plastic components. Full article

This article presents experimental results for motive nozzles with profiled supersonic parts of parabolic, hyperbolic, and elliptical shapes, compared to conical nozzles with unprofiled supersonic parts. This study examined the effect of nozzle geometry and profile on thermodynamic and flow parameters of the vaporization process. The measured parameters included outlet pressure, flow velocity, and mass vapor content, along with dimensionless efficiency indicators, such as relative outflow velocity and the velocity coefficient. Graphical dependencies of these parameters on the relative initial underheating, (1 − ε_s0), were obtained. This parameter represents the ratio of the pressure difference between inlet and saturation conditions (at inlet temperature) to the inlet pressure. The results show that profiled nozzles operate effectively over a wider range of (1 − ε_s0) = 0.20–0.45, compared to conical unprofiled nozzles. The vaporization constant for profiled nozzles remained at b_n ≈ (2/3)^0.5 along their length. The velocity coefficients for profiled designs were 4–6% higher, and the volumetric vapor content at the outlet was also greater, indicating a more efficient vaporization process. Overall, the findings demonstrate that profiling the supersonic section of a motive nozzle improves the operating range, flow characteristics, and vaporization quality compared to conventional conical designs. Full article

This study investigates the flow field and temperature field characteristics of a certain type of aerospace tail-thrust clutch friction plate under engagement conditions. A thermo–fluid–solid coupled convective heat transfer model was established based on the velocity distribution of lubricating oil within the groove cavities. The model was applied to analyze the surface temperature distribution of a single friction pair (friction plate and steel plate) under different operating parameters. The results reveal that both the inlet temperature and flow rate of the lubricating oil have a mitigating effect on temperature rise. However, due to the geometric constraints of the groove structure, the maximum wetted area and the actual inflow are inherently limited. Consequently, the temperature evolution during engagement is more significantly influenced by rotational speed and applied pressure. In particular, once these parameters exceed certain critical values, the surface temperature exhibits a sharp increase. Furthermore, the optimization of lubricating flow is constrained by friction materials. A higher flow rate does not necessarily yield greater lubrication benefits; instead, the optimal flow rate solution tailored to the friction pair should be pursued. This work provides theoretical insights into parameter control for aerospace tail-thrust clutches in practical operation. Full article

This study examined engine combustion characteristics of the plastic diesel produced through pyrolysis of waste plastics as an eco-friendly source of engine fuel. We extensively measured and compared the key fuel properties based on various diesel fuel standards. Distillation and hydrotreatment processes were used to improve the quality of the pyrolysis oil, resulting in distilled plastic diesel (DPD) and hydrotreated plastic diesel (HPD). DPD and HPD were blended at 10:90 and 20:80 (vol%) ratios with commercial diesel, resulting in fuel blends termed as DPD10, DPD20, HPD10, and HPD20, respectively, to analyse their engine combustion characteristics. A full-scale 4-cylinder, 4-stroke diesel engine was used in this study. There are virtually no studies available in the literature where engine combustion characteristics have been tested with both distilled and hydrotreated plastic pyrolytic oil. This study comprehensively investigated the combustion behaviours of all four fuel blends under full-load conditions and at an engine operating speed of 1500 rpm, except engine exhaust gas temperature which was measured at varying engine speeds from 1200 rpm to 2400 rpm at an interval of 300 rpm. The study found notable differences in engine combustion characteristics between the commercial diesel and plastic diesel blends under identical operating conditions. The HPD blends had higher exhaust gas temperatures (EGTs) than the DPD blends, particularly at lower blend ratios, whereas the DPD10 and HPD10 blends had higher peak cylinder pressures than DPD20 and HPD20. The HPD10 blend exhibited the highest heat release rate (HRR) of 120.41 J/°CA. The engine combustion characteristics using a full-scale engine with distilled and hydrotreated plastic diesel and their comparison are not fully studied in the literature yet. Full article

To investigate the influence of salt transport in water–steam mixtures on flow and heat transfer and to ensure the operational safety of steam injection boilers, this study simulated the behavior of high-dryness steam carrying salts in U-tubes. The analysis focused on three representative substances—silica, hematite, and calcium carbonate—to evaluate their effects on flow and heat transfer characteristics under varying conditions. The simulation results show that under specified operating conditions, vortices induced by rotational flow lead to complex flow behavior in U-tubes, with transitions from stratified flow to annular flow and back to stratified flow. The effects of salt precipitation on the temperature, velocity, and pressure fields of the boiling flow were also examined. The findings indicate that for pure water, large gradients and multiple vortices adversely affect flow stability, whereas the introduction of small amounts of salts provides localized stabilization in regions of the fluid away from the wall. Full article

Qatar’s arid and semi-arid landscapes subject native plants to severe abiotic stresses, including salinity, drought, intense solar radiation, and high temperatures, along with biotic challenges such as herbivory, microbial pathogens, and competition. The ways in which plants coordinate responses to these simultaneous pressures remain insufficiently understood, creating a knowledge gap in desert persistence strategies. This study investigates the integrated defence mechanisms that enable survival under dual stress conditions. We analyse chemical responses such as the synthesis of antimicrobial and phenolic compounds, structural adaptations including thickened cuticles, trichomes, and reinforced cell walls, and physiological trade-offs affecting water-use efficiency and gas exchange. Emphasis is placed on the regulatory role of abscisic acid, which links abiotic stress responses to enhanced pathogen resistance through interconnected biochemical pathways. The study also evaluates the benefits and costs of these structural and biochemical defences. Our findings reveal that native desert species employ adaptive strategies that integrate structural, physiological, and biochemical processes to withstand simultaneous abiotic and biotic pressures. These coordinated mechanisms enhance plant persistence under extreme conditions and play a crucial role in maintaining biodiversity, ecological resilience, and the long-term stability of Qatar’s fragile desert ecosystems. Full article

Thermal properties significantly affect extrusion energy efficiency and polymer processing. Relevant parameters include melt temperature, viscosity, and specific heat impact energy consumption, while thermal degradation limits processing temperatures within the screw and barrel. Traditional empirical methods used in polymer extrusion are often hindered by the complex relationship between screw speed and energy efficiency. Numerical simulations, particularly those using ANSYS Polyflow, offer a more precise approach for visualizing temperature, pressure, and shear rate distributions in the molten polymer, enabling better control of extrusion conditions. The screw’s geometric configuration, which includes sections for conveying, compressing, kneading, and mixing, plays a key role in determining flow behavior and performance. Studies on polymers using various screw configurations have revealed that screw designs with lower compression ratios enhance throughput and reduce melt temperature. Additionally, barrier screw designs improve the polymer melting efficiency. In this study, ANSYS Polyflow simulations were applied to analyze the flow behavior of molten PVC in a counter-rotating twin-screw extruder, focusing on the effects of screw speed and inlet flow rate on pressure, temperature, and velocity distributions. The results indicated optimal extrusion conditions for preventing degradation, with an ideal outlet rate of 439 kg/h at a screw rotational speed of 43 rpm. The pumping pressure of molten PVC by a twin-screw approach would be enough for entering the extrusion die. Full article

Hydrocarbon exploration and extraction increasingly rely on drilling fluids that guarantee operating safety and efficiency, particularly in ultra-deep, high-temperature, and unconventional reservoirs. Traditional drilling fluids, especially for water-based muds (WBMs), have several problems, including excessive fluid loss, severe swelling in shale and instability in high-pressure/high-temperature (HPHT) conditions. Polymer nanocomposites (PNCs) are new types of drilling fluid additives that combine the vast surface area and reactivity of nanoparticles (NPs) with the structural flexibility and stability of polymers. This combination enhances rheology, reduces filtrate loss, and, most importantly, creates hydrophobic and pore-blocking barriers that prevent shale from swelling. This review highlights important improvements in drilling fluids with PNCs regarding exceptional rheological properties, low fluid loss, and improved suppression of the shale swelling. The particular focus was placed on the specific mechanisms and role that PNCs play in enhancing shale stability, as well as their responsibilities in improving rheology, heat resistance, and salt tolerance. Current advancements, persistent hurdles, and prospective prospects are rigorously evaluated to emphasize the scientific and industrial trajectories for the development of next-generation, high-performance drilling fluids. Moreover, the current challenges and future opportunities of PNCs in drilling fluids are discussed to motivate future contributions and explore new possibilities. Full article

Understanding gas–water two-phase flow mechanisms in deep tight gas reservoirs is critical for improving production performance and mitigating water invasion. However, the effects of pore-throat-fracture multiscale structures on gas–water flow remain inadequately understood, particularly under high-temperature and high-pressure conditions (HT/HP). In this study, we developed visualizable multiscale throat-pore and throat-pore-fracture physical nanofluidic chip models (feature sizes 500 nm–100 μm) parameterized with Keshen block geological data in the Tarim Basin. We then established an HT/HP nanofluidic platform (rated to 240 °C, 120 MPa; operated at 100 °C, 100 MPa) and, using optical microscopy, directly visualized spontaneous water imbibition and gas–water displacement in the throat-pore and throat-pore-fracture nanofluidic chips and quantified fluid saturation, front velocity, and threshold pressure gradients. The results revealed that the spontaneous imbibition process follows a three-stage evolution controlled by capillarity, gas compression, and pore-scale heterogeneity. Nanoscale throats and microscale pores exhibit good connectivity, facilitating rapid imbibition without significant scale-induced resistance. In contrast, 100 μm fractures create preferential flow paths, leading to enhanced micro-scale water locking and faster gas–water equilibrium. The matrix gas displacement threshold gradient remains below 0.3 MPa/cm, with the cross-scale Jamin effect—rather than capillarity—dominating displacement resistance. At higher pressure gradients (~1 MPa/cm), water is efficiently expelled to low saturations via nanoscale throat networks. This work provides an experimental platform for visualizing gas–water flow in multiscale porous media under ultra-high temperature and pressure conditions and offers mechanistic insights to guide gas injection strategies and water management in deep tight gas reservoirs. Full article

Ammonia is an ideal candidate for clean energy in the future, and its large-scale production has long relied on the Haber–Bosch process, which operates at a high temperature and pressure. However, this process faces significant challenges due to the growing demand for ammonia and the increasing need for environmental protection. The high energy consumption and substantial CO₂ emissions associated with the Haber–Bosch method have greatly limited its application. Consequently, increasing research efforts have been devoted to developing green ammonia synthesis technologies. Among these, the electrocatalytic nitrogen reduction reaction (NRR), which uses water and nitrogen as raw materials to synthesize NH₃ under mild conditions, has emerged as a promising alternative. This method offers the potential for carbon neutrality and decentralized production when coupled with renewable electricity. However, it is important to note that the current energy efficiency and ammonia production rates of NRR under ambient aqueous conditions generally lag behind those of modern Haber–Bosch processes integrated with green hydrogen (H₂). As the core of the NRR process, the performance of electrocatalysts directly impacts the efficiency, energy consumption, and product selectivity of the entire reaction. To date, significant efforts have been made to identify the most suitable electrocatalysts. In this paper, we focus on the current research status of metal catalysts—including both precious and non-precious metals—as well as non-metal catalysts. We systematically review important advances in performance optimization, innovative design strategies, and mechanistic analyses of various catalysts. We clarify innovative optimization strategies for different catalysts and summarize and compare the catalytic effects of various catalyst types. Finally, we discuss the challenges facing electrocatalysis research and propose possible future development directions. Through this paper, we aim to provide guidance for the preparation of high-efficiency NRR catalysts and the future industrial application of electrochemical ammonia synthesis. Full article