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In recent times, renewable energy sources have gained significant popularity because of the dwindling reserves of fossil fuels and the significant environmental damage resulting from their use. Among the various renewable energy sources, hydrogen stands out as one of the most crucial technologies for the future. Hydrogen can be produced through several different methods, and electrolysis is among the most frequently used methods. This method employs electrical energy to decompose water into its constituent hydrogen and oxygen molecules. When this electrical energy is derived from renewable sources such as solar or wind, then green hydrogen is produced. Systems that use electrolysis to produce hydrogen are known as electrolyzers. One of the primary challenges in the electrolysis process is ensuring the purity of hydrogen; proper control of the levels and pressures of the gas tanks can improve this purity. Automatic control strategies are very important for regulating the levels and pressures of the oxygen and hydrogen tanks. Researchers have proposed various classical techniques for controller design to mitigate this issue. This study seeks to offer a comprehensive and up-to-date review of existing research on control methods for alkaline electrolyzers, which has attracted considerable attention in recent times. The findings of this review offer valuable insight for future studies aimed at developing new control strategies to enhance hydrogen purity. • Describe main control strategies applied to alkaline electrolyzers. • Comparison of control strategies applied to electrolyzers and finding gaps in the literature. • Describe the importance of hydrogen purity and its production control methods. • Identify applications of alkaline electrolyzers according to the control strategy. • Importance of electrolyzers with renewable energy sources as an energy vector. [ABSTRACT FROM AUTHOR]

The article presents the results of testing the validity of the hypothesis about the possibility of isolating the exhaust gases of the internal combustion engine (exhaust gas source). The objective was to conduct an experimental study of the "exhaust gas source - storage tank" system. In the experimental study, the following was performed: establishment of influencing factors and output parameters; selecting the number of experiments; methods and means of measurement; conducting an experiment at the stand. [ABSTRACT FROM AUTHOR]

Evaluating the integrity of liquefied natural gas (LNG) storage tanks is essential for safety and environmental conservation. In this study, which centered on an LNG storage tank on a specific island, we utilized 37 interferometric wide (IW) swath mode VV polarization Sentinel-1 images from the European Space Agency (August 2020-December 2023). Deformation data were obtained using persistent scatterer synthetic aperture radar (SAR) interferometry (PSInSAR) and small-baseline subset SAR interferometry (SBAS-InSAR) techniques, supplemented by dense point cloud data for 3D and 2D analyses. Results showed consistent deformation rates in the tank, with peaks between October 2021 and August 2022. Point cloud analysis revealed millimeter-level localized deformations (0.1 to 2.6 mm), corroborating InSAR findings. This underscores the importance of PS-InSAR, SBAS-InSAR, and point cloud modeling in monitoring LNG tank deformations, and offers insights into managing the impact of climate change on LNG storage stability. [ABSTRACT FROM AUTHOR]

As the integration of high-proportion renewable energy into the grid increases, the intermittency and uncertainty of renewable energy output significantly affect the safe and stable operation of the power system. Combining utility-scale energy storage technology with renewable coordination is one of the methods to address these issues. Compressed air energy storage (CAES) has garnered extensive attention due to its large capacity, long operational life, and clean, low-carbon advantages. Given the poor compressibility of air and its high critical point, using carbon dioxide as the working fluid in utility-scale energy storage systems can achieve higher energy storage density and cycle efficiency. Accordingly, this paper focuses on the study of utility-scale energy storage system modeling and scheduling methods considering carbon dioxide energy storage. It investigates Compressed Carbon Dioxide Energy Storage (CCES) systems, analyzes the operational framework of typical CCES systems, and sequentially establishes models for the energy storage process, energy release process, hot water tank operation, and gas storage tank operation. Based on this, it explores power system optimization dispatch methods considering CCES, incorporating the established models into an optimization dispatch model for power systems with high wind power penetration. Within the framework of a safe constraint unit commitment study, using the IEEE-30 nodes model, the effectiveness of the established models is validated. The case study results confirm the role of CCES in enhancing the absorption rate of renewable coordination. Moreover, under the same storage conditions, compared to, CCES offers greater charging and discharging power and higher energy storage density. [ABSTRACT FROM AUTHOR]

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As the number of FCEV vehicles increases, the importance of safe hydrogen fuel storage becomes larger. Hydrogen energy needs a high-pressure composite pressure vessel called a type 4 fuel tank. The type 4 fuel tank consists of a plastic liner and filament winding of composite fibers. During use, the hydrogen fuel tank is repeatedly charged and discharged, which causes damage to the composite region of the fuel tank. Therefore, to ensure the safe use of hydrogen fuel, it is necessary to monitor the condition of the hydrogen fuel tank. This article proposes a new, practical structural health monitoring (SHM) method based on the correlation between ultrasonic attenuation and crack density. The propagating ultrasonic wave attenuates by interaction with the damages in the composite materials of the fuel tank. Hydraulic cycle tests were performed to reproduce repeated damages in the fuel tanks. The micro-CT imaging method was used to verify the actual crack density of the fuel tank. The attenuation of the ultrasonic wave propagation and the crack density of fuel tanks were combined in one equation using the hydraulic test cycle as a parameter. With this practical SHM method, real-time structural health monitoring of type 4 fuel tanks can be done by measuring ultrasonic wave propagation on the fuel tank with the PZT active sensor network, offering hope for improved safety in the automotive and aerospace industries. [ABSTRACT FROM AUTHOR]

As a power generation fuel, high-pressure hydrogen gas is widely used in transportation, and significantly contributed to development of hydrogen fuel cell electric vehicles. However, obvious temperature rise generated during fast refueling causes serious safety risk to reliable operation of fuel cell stacks. Therefore, it is necessary to conduct in-depth research on fast filling process. Based on safety reasons, the SAE J2601/ISO 15869 strictly regulates the maximum temperature limit of 85 °C in specifications for refueling hydrogen gas tanks. In this study, a 70 MPa, Type IV on-board hydrogen storage tank is adopted as the research object, and a 2-dimensional axisymmetric numerical model is established to study the temperature rise of the vapor within storage tanks during fast refueling. The Realizable k - ε turbulence model is employed to simulate high intensity turbulent fluctuation during fast filling. Considering the compressibility of vapor, the state of equation for real hydrogen gas is used by obtaining fluid thermodynamic properties from the National Institute of Standards and Technology database. Three groups of fast filling experiments are selected to validate the developed numerical model. The comparison result shows that the numerical model has good prediction ability on hydrogen fast refueling. The final mass average temperature differences between numerical results and experimental data are 2.6 K, 4.3 K, and 0.03 K, respectively. Based on the developed numerical model, the influences of structure parameters and material properties on the temperature rise of hydrogen storage tanks are investigated. The results indicate that the inlet diameter and wall thickness of the inner and outer layers of the storage tank have weaken impacts on the temperature rise during rapid charging, with the maximum temperature differences of 1.8 K, 0.74 K, and 0.54 K, respectively. Due to the influence of heat capacity, the material properties of different layers exhibit a similar variation trend. This work can deepen researchers' understanding of the temperature rise of on-board hydrogen storage tanks during fast filling, and provide technical references for the structural optimal design of tanks and rapid refueling at hydrogen stations. • A 2-dimensional axisymmetric numerical model is constructed to predict the temperature rise during rapid charging. • Different structural parameters and material properties on the temperature rise performance are specially investigated. • Effects of inlet pipe diameter and wall thickness on the thermal behavior of hydrogen storage tanks are not so obvious. • The material properties of liner and laminate of storage tanks cause obvious impacts on the temperature rise control. [ABSTRACT FROM AUTHOR]

When loading liquefied natural gas (LNG) onto a dual-fuel LNG container ship fuelled by LNG, there is a considerable temperature difference between LNG and the fuel tank at room temperature. The current solution is to pre-cool the tank with LNG through a spray line but the cooling process, if not correctly handled, can result in excessive cooling rates and Boil-Off Gas (BOG), which can expose the tank to increased temperature stress and gas pressure. Therefore, this paper takes the Mark III fuel tank of a specific type of LNG container ship as the object and realises a real-time predictive control system by writing a UDF (User Defined Function) to simulate and analyse the influence of LNG spray rate on the change of cooling effect, cooling time and cooling cost under the unidirectional LNG spray cooling mode. Compared with the results of the fuel tank gas experiment, the deviation of numerical model simulation results is less than 5%. Under the same cooling rate, the real-time control scheme can achieve a more uniform cooling rate and reduce the total LNG consumption by 25%. With the increase in LNG cooling rate, the cooling time, LNG usage, and the total BOG exhaust volume all decrease; however, the decreased range gradually decreases as well. The results of this paper provide parameters and suggestions for optimising and improving the LNG fuel tank cooling monitoring and control system. [ABSTRACT FROM AUTHOR]

The finite volume method (FVM) is used to numerically investigate the sloshing behaviors of dual liquid tanks with gas inflow in this study. The sloshing process of a single liquid tank is simulated to verify the feasibility of the numerical method. Three different inlet boundary conditions are then discussed in order to obtain a reasonable gas flow rate. The sloshing process of a dual liquid tank with the gas inflow is simulated, and the effects of three different factors on the sloshing behaviors are investigated. The results indicate that the overload, flow rate, and filling ratio can affect the peak value of the impact force acting on the tank wall. The impact force is positively proportional to the overload (1G, 3G, or 5G). An increase in flow rate (50 g/s, 1000 g/s, or 5000 g/s) or a decrease in filling ratio (99.52%, 75.64%, or 63.69%) can increase the size and number of bubbles, leading to intensified sloshing behavior and increased impact force. [ABSTRACT FROM AUTHOR]

The inorganic water-based non-expanding fireproof coating was taked as the research object, and the coating thickness as the main influencing factor, the thermal response tests of liquefied petroleum gas tanks were conducted in a pool fire environment. The wall temperature response, damage time, and failure mode of storage tanks after spray fireproof coatings were studied in pool fire environments. The results show that the inorganic water-based non-expansion fireproof coatings have a significant delayed effect on the explosion time of storage tanks under fire action. For civilian liquefied petroleum gas storage tanks, when the filling level is the same, the tank which coating thickness is 2 cm is 6.91 times that of bare tanks in a pool fire environment, the tank which coating thickness is 3 cm is 1.20 times that of the tank which coating thickness is 2 cm, and the tank which coating thickness is 4 cm is 1.05 times that of the tank which coating thickness is 3 cm. The delayed effect of increasing coating thickness on the damage time of storage tanks in a pool fire environment gradually decreases, so it is suggest that to the coating thickness of 3 cm is suitable for storage tank. The research results have certain significance for the safety protection application of storage tanks in a pool fire environment and the study of fireproof coating. [ABSTRACT FROM AUTHOR]

An improved impact damage model is proposed, which can be used to analyze the progressive failure behavior of fiber-reinforced composites. The model is constructed based on the 3D Hashin failure criterion. However, the difference is that the strain component along the thickness direction in the matrix energy evolution model is introduced, and the effects of and on impact damage are added. Rigid-body and bird-body impact problems are studied, which validates the accuracy of the numerical model by comparison with experiments. A 3D numerical model of light aircraft fuel tank impact is constructed, and the SPH-FEM coupling method is used to predict the bird strike failure problem. The structural damage and impact behavior of a light aircraft fuel tank under impact loading are analyzed. The results show that, under different impact energies, the damage to the matrix is more serious and expands along the fiber direction, and the structure presents different damage forms. This paper provides an effective research model for the study of drop shock and the airworthiness of composite fuel tanks. [ABSTRACT FROM AUTHOR]

The hydrogen gas storage tank market includes passenger cars and heavy-duty trucks. However, there is insufficient economic analysis of these tanks, which is the key element for achieving market expansion. Theoretical studies have investigated the cost of carbon composites in automotive and aerospace applications and hydrogen storage tanks. However, there is insufficient analysis based on actual technological and cost data. Moreover, there is limited analysis of the material, labor, and expense costs and equipment investments based on production quantities. The objective of this study is to analyze the costs related to hydrogen tanks in passenger cars and heavy-duty trucks on the basis of the manufacturing technologies, tank volume, type, and annual production. Furthermore, this study uses a cost – profit modeling approach to identify the cost, price, investment, and key cost drivers and provide target costs, effective manufacturing technologies, and strategies to meet the demands of the hydrogen tank market. [ABSTRACT FROM AUTHOR]

Automotive evaporative emission inventory is continuously increasing with less stringent evaporative emission norms and lack of control measures. Uncontrolled refuelling emissions from huge fleet of two-wheelers with high environmental temperature make this situation worst. Motorcycles are typically equipped with metallic fuel tanks which are exposed to direct sunlight causing very high temperature conditions inside them. In this work, two motorcycle fuel tanks are used to record the temperature of liquid gasoline, vapour in headspace and surface of fuel tank through data logger to closely assess the vapour generation environment. Also, fuel consumption behaviour determines the liquid-to-vapour ratio inside fuel tank and promotes the refuelling losses in the absence of onboard refuelling vapour recovery control technology in two-wheelers. Liquid-to-vapour ratio inside fuel tank depends on prefill gasoline volume and the quantity of gasoline refuelled. Experiments are conducted to develop understanding on the mechanism of vapour generation during refuelling. This paper focuses on studying the impact of refuelling quantity, prefill volume and ambient temperature conditions on the vapour generation during refuelling of two-wheeler fuel tanks. Also, interaction between these control factors with influence of individual factor is studied using regression analysis and Minitab. Analysis of variance study reveals that temperature has strong influence on vapour generation (61.5%) and refuelling quantity (21.18%) also affects it significantly with least influence of prefill volume (14.19%). Combined effect of prefill volume and refuelling quantity on vapour generation is found interesting in interaction plots. Further assessment of interaction between various control factors is suggested to develop optimized control solutions for two-wheeler refuelling emissions. [ABSTRACT FROM AUTHOR]

In recent years, due to the frequent occurrence of accidents in confined space operations, horizontal ammonia tank trucks with higher accident frequencies were selected for numerical simulation research through comparative analysis. The ammonia concentration variation characteristics of horizontal ammonia tank cars were simulated under four conditions: natural ventilation with 0° incoming air, natural ventilation with 45° incoming air, mechanical ventilation with extraction, and mechanical ventilation with compression. The results indicate that natural ventilation requires 48 h to reduce the ammonia concentration to a safe range for operation, while mechanical ventilation reduces the ammonia concentration to infinity and approaches zero within 30 min according to regulations, making the working environment safer; Set up monitoring points inside the tank to monitor the gas disturbance inside the tank at different wind speeds. Based on the ammonia concentration cloud map and the monitoring point wind speed, it can be concluded that local ammonia accumulation is more likely to occur on both sides of the tank due to poor ventilation. Comparing and analyzing the simulated values with theoretical calculations and experiments, it was found that there are differences in the degree of gas change but the overall trend is the same. This indicates that ventilation simulation and the determination of ammonia migration characteristics have practical significance for guiding on-site operations. [ABSTRACT FROM AUTHOR]

This article presents a comprehensive review of the current landscape and prospects of large-scale hydrogen storage technologies, with a focus on both onshore and offshore applications, and flexibility. Highlighting the evolving technological advancements, it explores storage and compression techniques, identifying potential research directions and avenues for innovation. Underwater hydrogen storage and hybrid metal hydride compressed gas tanks have been identified for offshore buffer storage, as well as exploration of using metal hydride slurries to transport hydrogen to/from offshore wind farms, coupled with low pressure, high flexibility electrolyser banks. Additionally, it explores the role of metal hydride hydrogen compressors and the integration of oxyfuel processes to enhance roundtrip efficiency. With insights into cost-effectiveness, environmental and technology considerations, and geographical factors, this review offers insights for policymakers, researchers, and industry stakeholders aiming to advance the deployment of large-scale hydrogen storage systems in the transition towards sustainable energy. [Display omitted] • Underwater H 2 buffer storage is proposed for deepwater floating wind installations. • Hybrid metal hydride – H 2 gas buffer stores are attractive for offshore locations. • Potential of thermal compression recognised for large-scale H 2 storage (LSHS). • Explore use of oxyfuel processes to improve roundtrip efficiency of LSHS. [ABSTRACT FROM AUTHOR]

The liquefied natural gas (LNG) fuel tank in a large container ship is loaded with liquid LNG at an ultra-low temperature (-163°C), there is a significant temperature difference in the cargo hold area where the entire fuel tank is located, which will have an important impact on the steel grade design and structural safety of the cargo tank in container ship. This paper develops two heat transfer models using Computational Fluid Dynamics method (CFD method) and an analytical method to analyze the temperature distribution in a large container ship equipped with Type-B LNG fuel tank. These models incorporate the arrangement and heat transfer characteristics of LNG fuel tanks. The temperature field analysis is conducted under typical the environmental conditions specified in the Code for the Construction and Equipment of Ships Transporting Liquefied Gas in Bulk (IGC Code) and the United States Coast Guard Code (USCG Code), based on the CFD method and the analytical method, and the results of temperature field distribution are compared. Additionally, a parametric analysis of the hull temperature field is further carried out, the results show that the thermal conductivity of the insulation layer in LNG storage tanks and the types of the loaded liquid cargo have a limited impact on the final temperature field distribution in hull structure. However, the selection of steel grade in the local structure of the cargo hold, especially in the inner hull part, may lead to significant changes. [ABSTRACT FROM AUTHOR]

Most space shuttle fuel tanks use a center column to hold the Propellant Management Device (PMD). This paper analyzes the gas–liquid interface state in the tanks with a central column during microgravity experiments conducted in the Chinese Space Station. It launches an extended study to investigate the gas–liquid interface state under different gravity conditions. Using the perturbation method and boundary layer theory, we numerically calculated the morphology of the gas–liquid interface under varying gravity conditions based on the Young–Laplace equation. The results were then compared to those obtained from existing commercial software and were found to be consistent. Based on this, the study develops two types of calculation procedures. The first procedure generates the corresponding shape of the liquid surface by inputting the height of the liquid surface endpoints and the gravity level. The second procedure is based on the targeting method and generates the corresponding liquid surface by inputting the volume of the liquid in the storage tank and the gravity level. The procedures were used to analyze the variation of gas–liquid interface properties under different gravity conditions. This study offers theoretical support for liquid management in aerospace engineering fuel tanks. [ABSTRACT FROM AUTHOR]

The 2219 aluminum alloy thin-walled complex components manufactured by spin forming are frequently applied to the bottom end of rocket fuel tanks. However, fracture and quality problems (large part-mold contact gap, low roundness, thickness accuracy) are prone to occur during their multi-pass spin forming. While the material anisotropy, complicated components geometry and the complex stress state evolution make it difficult to obtain the appropriate forming process parameters in spin forming. With the help of finite element methods, it is possible to solve this difficulty. Thus, based on the anisotropic Barlat89 yield function and the DF2016 fracture criterion, a spin forming finite element model considering material anisotropy and damage evolution is established first for the components. Then, a method by using multi-pass involute spinning track with variable diameter base circle to form the components is proposed, and also the spinning passes are determined. Finally, taking the non-fracture as the constraint condition and the forming quality indexes (part-mold contact gap, roundness, and thickness accuracy) as the optimization objectives, a multi-objective optimization model based on orthogonal experimental design and response surface model is established. The optimized process parameters are solved and determined by a combination of the Archive-Based Micro Genetic Algorithm, and the optimized results are verified by the experiments. [ABSTRACT FROM AUTHOR]

This research presents a comprehensive dynamic finite element analysis (FEA) of a cryogenic fuel tank made from an innovative aluminium/lithium–graphene nano-composite material, assessing its suitability for aerospace launch vehicles carrying cryogenic hydrogen and oxygen. The study focuses on the effects of lightweighting, utilizing 0.5 wt.% reinforced graphene in the Al 2195 matrix, a material poised to revolutionize the aerospace industry. Objectives include developing a digital twin of the fuel tank, CAD modeling to aerospace standards, and conducting ANSYS simulations under launch conditions to evaluate stress, strain, and deformation. Numerical results reveal a significant weight reduction of approximately 19,420 kg and a notable maximum stress reduction of 1.3% compared to traditional Al 2195 alloy tanks. The novelty of this research lies in its pioneering analysis of aluminium/lithium–graphene composites for lightweighting in cryogenic fuel tanks under space launch conditions. Conclusions affirm the composite's viability, advocating for the development of lighter yet robust aerospace structures and fostering innovation in spacecraft design and materials science. [ABSTRACT FROM AUTHOR]

Jet fuel in aircraft fuel tanks moves due to acceleration resulting from maneuvers. The movement mentioned here directly impacts the Center of Gravity (CG). The aircraft's flight mechanics are significantly affected by the deviation of its CG on the aircraft body, and excessive deviation is undesirable. Preventing CG deviation is achieved by designing various baffles within the fuel tank. In this study, design details of the baffles were investigated with the help of an artificial neural network (ANN) model, 1D simulations, and computational fluid dynamics (CFD) calculations. The 1D simulations, which model the fuel movement, were used to understand the general behavior of the fluid in the tank. CFD calculations simulating turbulent fluid flow in three dimensions were used to confirm the results of the 1D simulations and provide more detailed information. A simulation set is created utilizing five parameters: barrier usage, volume fraction, cutout diameter, number of cutouts, and cutout location. Compared to the barrierless design, the barrier usage as a parameter changes either on baffle number 1, 3, and 6, or on baffle number 2, 4, and 7. The fuel volume fraction parameter accounts for 30%, 45%, and 60% of the interior volume. The diameters of the cutout holes vary between 30 mm and 156 mm and are used as categorized among the baffles. Cutout holes are applied on baffles in single, twin, and triplet forms and their locations are subjected to a divergence of either −20 mm or +20 mm from the z-axis. Based on these parameters, the maximum deviation and the retreat time of CG constitute the output parameters. The importance of the input parameters on the outputs was obtained with the help of an ANN algorithm created from the results of all possible combinations of a sufficient number of 1D simulations. To obtain more detailed results and confirm the importance of input parameters on outputs, selected cases were simulated with CFD. As a result of all analyses, it was revealed that barrier usage is the most dominant input parameter on CG deviation followed by volume fraction, cutout hole diameter, cutout divergence, and finally, the number of cutout holes. This study identifies the dominant input parameters to control fuel sloshing, specifically CG deviation and retreat time in the fuel tank, and proposes baffle designs to promote robust flight stability. [ABSTRACT FROM AUTHOR]

During the tank filling process with gaseous hydrogen, gas and tank temperatures rise due to the significant pressure surge (up to 700–800 bar) and the short duration (i.e. around 3 min) of the filling. These high temperatures pose a risk to the structural integrity of the storage system and may damage the material of the tank and the valves. One effective strategy to mitigate this temperature rise is pre-cooling the hydrogen prior to its injection into the tank. A zero-dimensional model has been validated in order to predict the average tank temperature during the filling for two different types of tank. The model has been then used to study the effect of different hydrogen inlet temperature and of the tank aspect ratio (L/D). • Fast refuelling times is essential to enhance the convenience and flexibility of the use of FCVs. • During fast filling, compression process results in H2 temperature increase within the tank. • Zero-dimensional models provide valuable insights into temperature profiles within the tanks. • Higher L/D ratios facilitate more efficient heat exchange. • Type III and type IV tanks revealed different temperature evolution during filling. [ABSTRACT FROM AUTHOR]

Recommendations are given for choosing the optimal schemes for the process of inerting cargo tanks of ships carrying liquefied gases. It was determined that one of the tasks that arise during the transportation of hydrocarbon cargoes (crude oil, petroleum products, and liquefied gases) is to ensure fire safety and prevent accidental explosions of cargo vapors in cargo tanks. Processes that occur during cargo operations on ships transporting oil products and liquefied gases are considered. The critical composition of the mixture of oxygen (entering the cargo tanks with air) and cargo vapors (remaining in the tanks after the cargo is unloaded) is indicated, at which a flash and explosion may occur. It was determined that the main technological operation that prevents spontaneous ignition of cargo vapors in cargo tanks is their inerting using nitrogen. The main advantages and disadvantages of the schemes for inerting cargo tanks are considered and determined: cascade, semi-cascade and parallel. The effective use of these schemes is based on the consumption of nitrogen, the amount of which is necessary for inerting, as well as the duration of the inerting process. The results of determining these indicators for a group of gas carriers with a cargo capacity of 38,646–62,233 m³ are given. At the same time, it is stated that the lowest consumption of nitrogen is necessary to ensure the process of inerting according to the cascade scheme. It was established that semi-cascade and parallel inerting schemes require an increase in the amount of nitrogen by 1.74–2.42 times and by 1.28–1.83 times, respectively. It was also established that the cascade scheme of inerting requires more time for its implementation. The duration of inerting according to the semi-cascade and parallel scheme is reduced and is 0.43–0.64 and 0.58–0.75 times in comparison with the cascade scheme. [ABSTRACT FROM AUTHOR]

During the fabrication of fuel tanks by adopting friction stir welding (FSW), welding defects were almost unavoidable. The multi-pass repair FSW is the preferred repair welding technique for fuel tanks. However, the effect of muti-pass repair FSW on the microstructure and mechanical properties of dissimilar FSW 2219Al/2195Al joints lacks of investigation. In the present study, 2219Al-T8/2195Al-T8 plates were subjected to 1 ~ 3 passes repair FSW under 600 rpm–200 mm min−1 based on the initial joint 800 rpm–200 mm min−1 with placing 2219Al-T8 plates on the advancing side (AS). The results showed that, sound 1–3 passes repair FSW joints were obtained. The low hardness zone (LHZ) on the 2219Al-T8 side, characterized by the dissolution/coarsening of θ′ (Al2Cu) precipitates, showed the minimum hardness in the initial joint. Compared to the initial joint, the 1–3 passes repair FSW resulted in the moving of the location of LHZs far away from the weld center and coarser θ precipitates with higher density, and the hardness of the LHZ therefore decreased on the 2219Al-T8 side. The joint strength at − 196 °C was much higher than that at room temperature for both the initial and repair FSW joints. The 1 pass repair FSW weakened the joint strength at both the room temperature and − 196 °C. When increasing the repair pass from 1 to 2 and 3, the joint strength further decreased at room temperature but was unchanged at − 196 °C. The enlarged hardness gap between the nugget zone (NZ) and LHZ caused the narrowing of the necking zone at the LHZ on the 2219Al-T8 side for the multi-pass repair FSW joints. The material flow uniformity at the top of the NZ was improved by the 1 ~ 3 passes repair FSW, making the up bending failure location changing from the "S" line for the initial joint to the HAZ on the 2195Al-T8 side for the repair FSW joints. [ABSTRACT FROM AUTHOR]

Purpose: To ensure the safety of aircraft fuel tanks, the FAA issued an airworthiness clause (25.981(b)) suggesting that the risk of combustion and explosion be reduced by installing a Flammability Reduction Means or an Ignition Mitigation Means. The airflow distribution method has a significant effect on the inerting performance. Therefore, this study aims to determine an optimum airflow distribution method of the inerting system. Design/methodology/approach: This paper establishes the calculation model of the oxygen concentration in the ullage of a multi-bay fuel tank, calculates the oxygen concentration in the ullage of an aircraft tank in single-flow and dual-flow modes under series and parallel ventilation methods and analyses the inerting performance of the tank under different airflow distribution methods. Findings: The results show that: (1) the bleed flow rate required to achieve whole process inerting of multi-bay fuel tank in dual-flow mode is lower than that in single-flow mode; (2) under the parallel ventilation method, the decrease of oxygen concentration and the uniformity of each bay are better than that in the series ventilation method; (3) dual-flow mode staged ventilation method can be used to achieve the whole process inerting of the tanks under the minimum engine bleed consumption. Originality/value: The novelty of this paper is to analyze and optimize the airflow distribution method of the inerting system under the whole flight envelope to minimize the engine bleed consumption. [ABSTRACT FROM AUTHOR]

In light of escalating global energy demands and the imperative to reduce greenhouse gas emissions, the efficient transportation of liquefied natural gas (LNG) has become increasingly critical. As the evaporation of LNG from storage tanks represents a significant energy loss, improving tank insulation is crucial to optimize storage efficiency. This paper conducts a structural assessment of a smaller-sized Type C independent tank made of AISI 304L steel and examines the impact of two insulation techniques—vacuum and perlite—on their heat, structural, and fatigue behavior. Utilizing the finite element method (FEM), this study performs a heat transfer analysis followed by a structural analysis under combined loads in accordance with the International Gas Carrier (IGC) code. The subsequent fatigue analysis follows IGC procedures and is performed using third-party software. This article presents a detailed analysis of the heat transfer throughout the entire LNG tank and the stress levels under various combined load scenarios while providing insights into the critical stress points and the areas with the lowest fatigue life. Finally, this study confirms the viability of using both novel materials, perlite as an insulation material and Durolight for the tank support, because they meet the required limits. [ABSTRACT FROM AUTHOR]

The seismic response of underground liquefied natural gas (LNG) storage tanks has been a significant focus in both academic and engineering circles. This study utilized Ansys (2021R1) to conduct seismic analyses of large-capacity LNG tanks, considering the fluid–structure–soil coupling interaction (FSSI), and it was solved using the Volume of Fluid model (VOF) and Finite Element Method (FEM). The mechanical properties of both the LNG tank structure and soil were simulated using solid elements, and seismic acceleration loads were applied. An analysis of liquefied natural gas was performed using fluid elements within FLUENT. Initially, a modal analysis of the tank was conducted, which revealed lower frequencies for a full-liquid tank (3.193 Hz) compared to an empty tank (3.714 Hz). Subsequently, the seismic responses of both the aboveground and underground LNG tank structures were separately simulated, comparing the acceleration, stress, and displacement of the tank wall structures. The findings indicate that the peak relative displacement of the aboveground empty tank wall is 122 mm, less than that of a full tank (136 mm), while the opposite holds true for underground tanks. The period and wave height of LNG liquid shaking in underground tanks are lower than those in aboveground tanks, which is more conducive to tank safety. The deformation and acceleration of underground tanks are lower than those of aboveground tanks, but the Mises stress is higher. The results indicate that underground LNG tank structures are safer under earthquake conditions. [ABSTRACT FROM AUTHOR]