Search Results (32)

The increasing electrification in aircraft propulsion and assistant systems necessitates innovative approaches in battery safety design. This work presents an investigation into a lightweight, fire-resistant composite battery housing tailored for modular battery applications with potential for high-volume production. Utilizing the promising thermal capabilities of phenolic polymers, the housing parts were tailored around the identified fire protection baseline functions like bulkheads, outer walls and a venting concept consisting of burst valves and a venting channel. Component-level fire resistance tests were performed to close the testing gap between material and battery module-level testing. Full article

Centrifugal compressors are vital components in industrial applications, but they are prone to a disruptive phenomenon known as surge, which can lead to mechanical stress and temperature increase. Surge occurrence is influenced by machine design, plant layout, and geometry. Engineers often deploy long (cold) and short (hot) recycle valves to address this issue. To ensure surge prevention, a fluid dynamic model is indispensable. In this study, a 1D Computational Fluid Dynamics (1D-CFD) model was developed using Amesim for a two-section centrifugal compressor. The main objective was to investigate the impact of various parameters on surge occurrence and compare different plant layouts to determine the most suitable solution for the specific study case. Here, the focus is on the influence of vent valves over the plant performance. To achieve this comparison, transient simulations of emergency shutdown (ESD) operations were performed. This study contributes to a better understanding of how machine design and operational factors affect surge behavior. By systematically evaluating different plant layouts, we identified the most effective strategies for preventing surge and enhancing compressor performance. This research provides valuable insights for engineers and operators striving to optimize industrial processes and improve the reliability and efficiency of centrifugal compressor systems. Full article

This study investigates the sealing performance of marine vent valves in low-temperature environments (−30 °C to −40 °C) via thermo-mechanical coupling analysis. Polytetrafluoroethylene (PTFE) was selected as the sealing material for its excellent cryogenic toughness, corrosion resistance, and cost-effectiveness. The total minimum specific sealing pressure ($q_{total}$) of PTFE, corrected for marine vibrations (15–60 Hz), was 3.702 MPa. Using ANSYS Workbench 2022, finite element simulations of a DN200 globe valve showed that low temperatures caused non-uniform thermal contraction, reducing the gasket-poppet contact width (2.5 mm to 1.75 mm) and maximum specific pressure (16.967 MPa to 13.352 MPa), leading to leakage risks. Optimizing the stem preload to 36,000 N restored effective sealing: the maximum specific pressure rebounded to 16.601 MPa, with no pressure below 3.702 MPa. This research provides a method for evaluating low-temperature sealing performance and supports safe vessel operation in cold waters. Full article

To address the altitude control requirements of high-altitude latex balloons, this paper proposes a novel lightweight electromagnetically actuated valve design. The valve employs a permanent magnet–electromagnet–spring composite structure to achieve rapid opening/closing motions through electromagnetic force control, enabling precise regulation of balloon gas venting. 3D electromagnetic field simulations were conducted to validate the magnetic flux density distribution, while computational fluid dynamics (CFD) simulations based on the Reynolds-averaged Navier–Stokes equations were employed to evaluate the valve’s aerodynamic characteristics. The CFD results confirmed stable venting performance, with near-linear flow–pressure relationships and localized jet structures that support reliable operation under stratospheric conditions. A multidisciplinary optimization framework was further applied to achieve a lightweight structural design of critical components. Experimental results demonstrate that the optimized valve achieves a total mass of 984.69 g with an actuation force of 15.263 N, maintaining stable performance across a temperature range of −60 °C to 25 °C. This study provides an innovative and systematically validated solution for micro-valve design in lighter-than-air vehicles. Full article

The safety of pipeline transportation technology is the key to guaranteeing the development and application of CCUS. In the process of CO₂ pipeline transportation, manual pressure relief may be required due to equipment failure, overpressure, or other reasons. However, the sharp temperature drop in the evacuation process may lead to the formation of dry ice, which may cause a pipeline blockage and equipment damage. Although the multi-stage throttling method of pressure relief can effectively control the stability of the equipment, the effect on the low temperature of the pipeline needs to be further investigated. Therefore, in order to evaluate the safety of multi-stage throttling pressure relief, a comparative experiment of dense-phase venting with double-stage throttling was carried out based on an industrial-scale pipeline experimental device. The results show that the double-stage throttling pressure relief scheme can significantly reduce the pressure drop rate and improve the stability of the pressure relief structure. Moreover, the temperature drop limit upstream of the main pipeline is controlled under the double-stage throttling scheme, but it exacerbates the low temperature level downstream, which is not conducive to mitigating the risk of freeze-plugging of the pressure relief valve. Therefore, it is recommended that the double-stage throttling relief scheme be used to close the valve in time to return to the temperature and to adopt an intermittent means of pressure relief. Full article

The COVID-19 pandemic raised global concerns about the shortage of ventilators and revealed the challenges of rapidly scaling up production to meet emergency needs. In response, numerous teams worldwide attempted to develop emergency and simple mechanical ventilators. Among these, the CoroVent ventilator was developed to meet the urgent need for ventilatory support in the Czech Republic. The aim of this study was to describe the innovative and simple design of the CoroVent emergency ventilator, evaluate its compliance with international safety and performance standards, verify its reliability under simulated clinical conditions, and demonstrate its suitability for use in crisis scenarios. CoroVent was designed with a focus on the clinical needs of patients with COVID-19 respiratory failure and to ensure safe ventilation while maintaining a simplified design. It features volume-controlled, pressure-limited mandatory ventilation and supports key adjustable parameters such as tidal volume, respiratory rate, inspiratory-to-expiratory time ratio, inspired oxygen fraction, and positive end-expiratory pressure (PEEP). The ventilator incorporates robust safety mechanisms, including alarms and a safety relief valve, to protect against excessive airway pressures. Results confirmed the ability to maintain consistent tidal volumes, stable PEEP, and precise pressure limitation over extended periods of use. The results showed that CoroVent met the essential international standards for accuracy, including those set by the UK Medicines and Healthcare products Regulatory Agency, U.S. Food and Drug Administration, and ISO 80601-2-12. Although production of these ventilators was stopped in 2021 as the Czech Republic managed the crisis and shortage of ventilators, the results validate their reliability as emergency ventilators and indicate their potential to support critical care needs in crisis situations. Full article

The venting process is one of the most important events during the thermal runaway (TR) of lithium-ion batteries (LIBs) in determining fire accidents, while different ambient pressures will exert an influence on the venting events as well as the TR. Ternary nickel–cobalt–manganese (NCM) batteries with a 75% state of charge (SOC) were employed to conduct TR tests under different ambient pressures in a sealed chamber with dilute oxygen. It was found that elevated ambient pressure results in milder ejections in terms of jet temperature and mass loss. Gas venting characteristics were also obtained. Additionally, the amount of carbon dioxide (CO₂), hydrogen (H₂), methane (CH₄), and ethylene (C₂H₄) released increase with ambient pressure, while carbon monoxide (CO) varies inversely with ambient pressure. The higher the ambient pressure is, the greater the flammability risk is. The molar amount of C, H, O, and total gases released shows a positive correlation with the maximum battery temperature and ambient pressure. This study will support the design of safety valves and help reveal the effects of venting events on the evolution of TR. Full article

Background: PCBs are persistent organic chemicals that have serious impacts on sustainability from the perspectives of health and the environment. We investigated the impact of apartment size in combination with residential and behavioural factors on PCB concentrations in indoor air within contaminated apartments. Methods: Fifty-one apartments from a Danish complex were investigated for PCBs in 2017, including self-reported information about cleaning and ventilation. Results: Linear regressions showed that a high resident and pet density (m² per person/pet) and, to some extent, a high resident density, were significantly correlated with lower indoor air concentrations of PCBs. Low indoor air temperature, high cleaning frequency, and open vent valves (ventilation) were other significant reducing factors. The average concentrations of PCBs in apartments with a resident density of 25 m² per resident were 2000 ng/m³ and 1844 ng/m³ per resident/pet. These concentrations increased by 0.37% for each additional m² per resident and by 0.70% for each additional m² per resident/pet. Conclusions: Resident/pet density and, to some extent, resident density are significant modifiers of the indoor air content of PCBs in the investigated complex. Temperature, cleaning frequency, and blocking or unblocking of vent valves (ventilation) are behavioural factors related to residential and residential/pet density and significant modifying factors of the PCB indoor air concentration. This study confirms the importance of cleaning and ventilation. Full article

Leakage problems occur from time to time due to the large number of equipment and complex processes during oil and gas production and transportation. The traditional detection methods highly depend on manpower with large workload and are prone to missed and false alarms, which seriously affects the efficiency and safety of oil and gas production and transportation. With the continuous improvement of information technology and the rapid advancement of artificial intelligence (AI), the research on leakage detection technology based on AI methods has attracted more and more attention. This paper discusses the application scenarios of an AI agent based on the recently emerged large language model (LLM) technology in oil and gas production leakage detection: (1) Compared with the traditional leakage detection methods, this paper innovatively employs a combination of AI-based diagnostics and infrared temperature measurement technologies to develop a specialized small model for oil and gas leakage detection, which has been proven to significantly improve the accuracy of detecting industrial venting events in natural gas valve chambers; (2) By employing retrieval-augmented generation (RAG) technology, a knowledge vector library is constructed, utilizing a series of leakage-related documents, assisting the LLM to carry out knowledge questioning and inference. Compared with the traditional SimBERT, the accuracy can be improved by about 15% in the Q&A search ability test. The correct rate is about 70% higher than the SimBERT in the Chinese complex reasoning quiz. Also, it can still remain stable under high load conditions, with the interruption rate of retrieval closing to zero. (3) By combining the specialized small model and the knowledge Q&A tool, the natural gas valve chambers’ leakage detection AI agent based on the open-source LLM model was designed and developed, which preliminarily achieved the leakage detection based on the specialized small model, and the automatic processing of the retrieval reasoning process based on the knowledge Q&A tool and the intelligent generation of corresponding leakage disposal scheme. The effectiveness of the method has been verified by actual project data. This article conducts preliminary explorations into the in-depth applications of AI agents based on LLMs in the oil and gas energy industry, demonstrating certain positive outcomes. Full article

With the widespread application of lithium-ion batteries (LIBs) energy storage stations in high-altitude areas, the impact of ambient pressure on battery thermal runaway (TR) behavior and venting flow characteristics have aroused wide research attention. This paper conducts a lateral heating experiment on 280 Ah lithium iron phosphate batteries (LFPs) and proposes a method for testing battery internal pressure using an embedded pressure sensor. This paper analyzes the battery characteristic temperature, internal pressure, chamber pressure, and gas components under different chamber pressures. The experiment is carried out in a N₂ atmosphere using a 1000 L insulated chamber. At 40 kPa, the battery experiences two instances of venting, with a corresponding peak in temperature on the battery’s side of 136.3 °C and 302.8 °C, and gas generation rates of 0.14 mol/s and 0.09 mol/s, respectively. The research results indicate that changes in chamber pressure significantly affect the center temperature of the battery side (T_s), the center temperature of the chamber (T_c), the opening time of the safety valve (t_open), the triggering time of TR (t_TR), the time difference (Δt), venting velocity, gas composition, and flammable limits. However, the internal pressure and gas content of the battery are apparently unaffected. Considering the TR characteristics mentioned above, a safety assessment method is proposed to evaluate the TR behavior and gas hazard of the battery. The results indicate that the risk at 40 kPa is much higher than the other three chamber pressures. This study provides theoretical references for the safe use and early warning of energy storage LIBs in high-altitude areas. Full article

The boiling point of liquid hydrogen is very low, at −253 °C under atmospheric pressure, which causes boil-off gas (BOG) to occur during storage and transport due to heat penetration. Because the BOG must be removed through processes such as re-liquefaction, venting to the atmosphere, or incineration, related studies are required to estimate the heat transfer of storage and transport devices and to improve insulation to reduce BOG generation. In this study, a vaporization analysis was performed on a vacuum-jacketed valve used in liquid hydrogen storage and transport devices to calculate the amount of BOG generation considering the flow characteristics at the vena contracta and the saturation temperature. At a pressure of 1 bar in the liquid hydrogen storage tank, the maximum fluid flow velocity and minimum static pressure occurred at the vena contracta, with values of 62.9 m/s and −0.4 bar, respectively, and the BOG generation rate was estimated as 0.132 m³/h, where the saturation temperature was minimized at 19.3 K. Furthermore, through case studies, when the pressure in the liquid hydrogen storage tank increased to 1.5 and 2 bar, the static pressure and saturation temperature decreased, and the BOG generation rate increased to 0.221 and 0.283 m³/h, respectively. Full article

Layered ternary materials with high nickel content are regarded as the most promising cathode materials for high-energy-density lithium-ion batteries, owing to their advantages of high capacity, low cost, and relatively good safety. However, as the nickel content increases in ternary layered materials, their thermal stability noticeably decreases. It is of paramount importance to explore the characteristics of thermal runaway for lithium-ion batteries. In this study, two high-nickel LiNi_0.9Co_0.05Mn_0.05O₂ batteries were laterally heated to thermal runaway in a sealed chamber filled with nitrogen to investigate the thermal characteristics and gas compositions. The temperature of the battery tabs was measured, revealing that both batteries were in a critical state of thermal runaway near 120 degrees Celsius. A quantitative analysis method was employed during the eruption process, dividing it into three stages: ultra-fast, fast, and slow; the corresponding durations for the two batteries were 3, 2, 27 s and 3, 3, 26 s. By comparing the changes in chamber pressure, it was observed that both batteries exhibited a similar continuous venting duration of 32 s. However, the pressure fluctuation ranges of the two samples were 99.5 and 68.2 kPa·m·s⁻¹. Compared to the other sample, the 211 Ah sample exhibited larger chamber pressure fluctuations and reached higher peak pressures, indicating a higher risk of explosion. In the experimental phenomenon captured by a high-speed camera, it took only 1 s for the sample to transition from the opening of the safety valve to filling the experimental chamber with smoke. The battery with higher energy density exhibited more intense eruption during thermal runaway, resulting in more severe mass loss. The mass loss of the two samples is 73% and 64.87%. The electrolyte also reacted more completely, resulting in a reduced number of measured exhaust components. The main components of gaseous ejections are CO, CO₂, H₂, C₂H₄, and CH₄. For the 211 Ah battery, the vented gases were mainly composed of CO (41.3%), CO₂ (24.8%), H₂ (21%), C₂H₄ (7.4%) and CH₄ (3.9%), while those for the other 256 Ah battery were mainly CO (30.6%), CO₂ (28.5%), H₂ (21.7%), C₂H₄ (12.4%) and CH₄ (5.8%). Comparatively, the higher-capacity battery produced more gases. The gas volumes, converted to standard conditions (0 °C, 101 kPa) and normalized, resulted in 1.985 L/Ah and 2.182 L/Ah, respectively. The results provide valuable guidance for the protection of large-capacity, high-energy-density battery systems. The quantitative analysis of the eruption process has provided assistance to fire alarm systems and firefighting strategies. Full article

Respiratory dysfunction often decreases arterial oxygen content. Four common oxygen delivery techniques—flow-by, nasal prongs, a tight-vented mask, and a tight mask connected to a Venturi valve—were evaluated for their effectiveness in increasing the oxygen reserve index (ORi), a dimensionless index of oxygen content that provides additional information compared to traditional pulse oximetry (SpO₂) during hyperoxia (PaO₂ 100–200 mmHg), and that ranges from 0 to 1. Thirty-two dogs sedated with dexmedetomidine and an opioid were evenly divided into four groups based on the technique for oxygen administration. Each dog received oxygen at 1, 2, and 3 L/min by a single technique, and the amount of inhaled oxygen (FiO₂) was measured at the level of the cervical trachea. At each flow rate, ORi and SpO₂ were recorded. The flow-by method minimally increased the FiO₂, and ORi reached its highest value only in 3 out of 8 dogs at the maximum flow rate. Other methods exhibited direct correlations between the oxygen flow rate and ORi (p < 0.001). These methods effectively increased FiO₂ and ORi, with over half of the values exceeding 40% and 0.4, respectively. The tight-vented mask showed variable increases in FiO₂, ranging between 22 and 90%. Despite method-dependent variations, all devices increased SpO₂ > 98% as the FiO₂ increased (p = 0.002). In conclusion, nasal prongs and the mask connected to the Venturi valve showed the highest correlation between the oxygen flow rate and the ORi. These results suggest that using these two techniques in conjunction with ORI can help in optimizing oxygen therapy. Full article

Dry dust collectors are a typical dust and gas coexistence space. Dust explosion risk assessments should be performed for effective prevention and control of dust explosion accidents. In this paper, a dust explosion risk assessment index system for dust removal systems was constructed following the dust characteristics and the actual operation of a dry dust collector. The proposed system consisted of three first-level indexes (dust explosion characteristic parameters, environmental parameters in the dust collector box, use state of explosion prevention and control device) and seven second-level indexes (dust explosion sensitivity, dust explosion severity, temperature in the dust collector box, pressure difference between inlet and outlet, operating state of spark detection, operating the explosion venting disc, and operating state of the lock gas ash discharge valve). The analytic hierarchy process was adapted to calculate the weight of each index. Additionally, a dust explosion risk assessment model for the dust removal system was constructed using the fuzzy comprehensive evaluation method to form a set of dust explosion risk assessment methods suitable for dry dust collectors. The risk of explosion was assessed at level II through the use of paper powder with a particle size of 75 $\mathsf{\mu }$m, which means this method is reliable. Full article

The risks associated with unsteady two-phase flows in pressurized pipe systems must be considered both in system design and operation. To this end, this paper summarizes experimental tests and numerical analyses that highlight key aspects of unsteady two-phase flows in water pipelines. The essential dynamics of air–water interactions in unvented lines are first considered, followed by a summary of how system dynamics change when air venting is provided. System behaviour during unsteady two-phase flows is shown to be counter-intuitive, surprising, and complex. The role of air valves as protection devices is considered as is the reasonableness of the usual assumptions regarding air valve behaviour. The paper then numerically clarifies the relevance of cavitation and air valve performance to both the predicted air exchanges through any installed air valves and their role in modifying system behaviour during unsteady flows. Full article