Pressures Research Articles

Characteristics of micron-scale pore-fracture modification in marine shale reservoirs with different combustion explosion energy

The combustion explosion fracturing of shale with in-situ methane is a revolutionary fracturing technique, but the modification characteristics of reservoir pores and fractures by combustion explosion energy level are still unclear. In order to study the transformation characteristics of micron-scale pore-fracture systems of marine shale reservoirs with different combustion explosion energies, this study selected a section of shale samples from the Longmaxi Formation in the Luzhou block in the southern Sichuan Basin to carry out different energy gradient combustion explosion test, named W1∼W5 (25–91 MPa). Based on micron CT scanning technology, the three-dimensional reconstruction of shale samples before and after combustion explosion was carried out to analyze the effect of combustion explosion energy on the transformation of the pore-fracture system characteristics. The results show that at the energy between 25 MPa and 45 MPa, the variation characteristics of cracks before and after explosion are not obvious. When the energy of the explosion is in the range of 61 MPa–91 MPa, the cracks gradually extend and become longer, and the distribution density of cracks becomes higher and more interconnected. After the explosion at 91 MPa, it can be seen that a number of annular cracks are generated at the edge of the sample, which are interconnected with radial cracks. Total porosity, connected porosity, pore number, and total pore volume of the shale increased after combustion explosion, where the total porosity at the combustion explosion energy of 91 MPa have the largest increment, while the connected porosity, pore number, and total pore volume in the combustion explosion energy of 71 MPa have the largest relative increments, indicating that there is a fracturing pressure value that strongly breaks through the bottleneck when the explosion pressure is between 61 MPa and 71 MPa. A comparison of different pore size sections before and after the combustion explosion pore volume share found that the explosion pressures of 25 MPa, 45 MPa and 91 MPa tend to expand from 100 to 200 μm pore size to form a larger volume share of >200 μm cracks, while at the explosion pressure of 71 MPa, more inclined to transform the 0–100 μm pores, so that the pores gradually transition to the 100–200 μm. Analysis shows that the gas explosion generates a large pressure, release a large amount of heat. Due to the high temperature and high pressure coupling effect, the pore-fracture in the shale changes significantly. Strong stress waves lead to stress concentration at the tip of shale and crack expansion and extension. At the same time, the local expansion force causes “pore expansion effect”. Various mineral particles in the shale undergo differential expansion, along the crystal rupture or through the crystal rupture. New pore fractures are also generated when the original pores keep expanding, which improves the shale pore connectivity. This understanding can provide a theoretical basis for the selection of the energy level of the in-situ methane combustion explosion in shale.

Pressure and Flame Propagation Characteristics of Suspended Coal Dust Explosions Induced by Gas Explosions.

In order to explore the pressure and flame propagation characteristics of gas-coal dust composite explosions, a semiclosed pipeline explosion test platform was built. The shock wave overpressure and explosion flame propagation law of different concentrations of suspended coal dust participating in gas explosions were studied in depth through experiments, and the coal dust motion law was simulated and analyzed based on Fluent software. The experimental results show that the peak pressure of gas-coal dust composite explosion is significantly higher than that of single-phase gas explosion, and the pressure peak increase ratio at the pipeline outlet is the highest; as the suspended coal dust concentration increases, the pressure rise rate at point 3 gradually decreases. Under the condition of 600 g/m3 coal dust participating in the explosion, the explosion pressure increase speed reduction ratio is 25.65%, the pressure wave secondary peak decreases, and the fluctuation frequency increases. When the explosion flame front passes through the suspended coal dust area, the flame shape changes from 'v' shape to 'finger' shape and propagates forward. The gas-coal dust composite explosion flame propagation speed shows a secondary acceleration phenomenon, after the flame front passes through the coal dust suspension area. As the coal dust concentration increases, the explosion core area moves away from the flame front. The coal dust cloud moves to the right, showing a concave rectangle; the larger the coal dust concentration, the smaller the moving speed. The experimental results and analysis provide an experimental basis for further exploring the mechanism and dynamic mechanism of gas-coal dust coupling explosion.

Pyrolysis as a Method for Processing of Waste from Production of Cultivated Tobacco (Nicotiana tabacum L.)

Because of the current energy crisis, researchers are looking into new potential substrates for production of biofuels and for possible ways to enhance their parameters. In line with such efforts, the current study focuses on the feasibility of processing waste from the production of cultivated tobacco. The aim of this study was to assess the potential of tobacco waste as a raw material for the production of solid biofuels, such as biochar produced through pyrolysis, and to determine its basic physicochemical properties, compared to other materials used for the production of green fuels. The analyses showed calorific values of 16.16 MJ kg−1 for the raw biomass and those in the range of 24.16–27.32 MJ kg−1 for the products of pyrolysis conducted at temperatures of 400–500 °C and with a heating time in the range of 5 to 15 min. To address the safety-related issues, the study also measured the explosion index (Kst max), which, in the raw biomass, amounted to 72.62 bar s−1 and in the biochar was in the range between 82.42 and 88.11 bar s−1. The registered maximum explosion pressure was 7.37 bar in the case of raw biomass, whereas in the biochars, the value ranged from 8.09 to 8.94 bar. The findings show that tobacco waste has parameters comparable to those identified in the case of other solid biofuels, whereas the process of pyrolysis enhances the energy-related parameters without increasing the explosion class of the product.

An underlying factor of increasing early winter precipitation in the Hokuriku region of Japan in recent decades

AbstractUsing a reanalysis dataset and large‐ensemble simulation results, this study examines a possible factor of increasing trend in early winter precipitation in recent decades in the Hokuriku region of Japan. Monthly precipitation in December has a significant increasing trend after the early 1990s, which is different from those in January and February. The increasing precipitation in December is related to that in the sea surface upward latent heat flux due to intensified winter monsoon circulation and warming sea surface temperatures (SSTs) over the Sea of Japan. December averaged SSTs show a trend pattern in recent decades that is similar to the negative phase of the interdecadal Pacific oscillation (IPO), accompanied by positive trends from the eastern Indian Ocean to the western tropical Pacific. The enhanced trend of convection over the Bay of Bengal is seen; suggesting a combined effect of climatologically high SSTs and IPO‐related warmed SSTs over the region. Trends in recent decades of an upper‐level wavy pattern from South Asia to near Japan along the subtropical jet associated with enhanced convection near the Bay of Bengal and the related pressure drop from Japan to the north are seen, which contribute to intensified winter monsoon circulation.

Explosion characteristics of HMX dust induced by ethanol vapor

Studying the explosion characteristics of HMX dust induced by ethanol vapor is an important foundation for the safe production of HMX. In this work, the explosion characteristics of HMX dust induced by ethanol vapor explosion were examined. The explosion pressure of pure ethanol vapor/air is 0.84 MPa. When the deposition mass concentrations of the HMX dust layer are 0.04, 0.08, and 0.16 g/L, the peak explosion pressures increase by 1.33, 1.43, and 1.58 times compared to pure ethanol vapor/air explosion. When the deposition mass concentration is 0.04 g/L, the burning duration is reduced by 38% and the ethanol at the bottom of the vessel begins to burn 8.72 ms later; however, though the ethanol at the top of the vessel also begins to burn 2 ms later, the burning duration increases to 16.67 times. When the deposition mass concentration of HMX is 0.08 g/L, dPdtpeak reaches the maximum value.

Weather effects on natural surface trail use in an urban wilderness multi-use trail system

Previous research has concluded weather conditions can influence physical activity (PA) on trails. However, these studies focused primarily on mixed-use paved surface trails. Many recreational areas use natural surface trails for mountain biking, trail running, and walking. The purpose of this study was to analyze the association between weather conditions and the use of natural surface trails for PA. In addition, this investigation sought to determine if the type of trail surface material, gravel vs. dirt, impacted PA differently by weather factors. Infrared trail counters were used to measure hourly trail use within Knoxville's Urban Wilderness in Knoxville, TN. An onsite weather station was used to obtain hourly weather variables. Negative binomial regression models were used to analyze the relationship between trail use and weather conditions. Both trail locations experienced bi-modal peaks in usage with Spring and Fall months showing the highest usage. As temperature increased, so did trail use (β = 0.115, p = 0.00); however, gravel trail use began to decrease at temperatures above 86 °F. Precipitation negatively impacted trail use on both gravel (β = −3.114, p = 0.00) and dirt (β = −2.281, p = 0.00) trails. Relative humidity and had a negative relationship with trail use on both trails. UVRI (β = −0.036) was only significantly associated with dirt trail use. The direction of the effect of weather measures on natural surface trail use is similar to previous studies on paved trails; however, the magnitude of the effect varies. Gravel trail use was more sensitive to temperature and precipitation, while relative humidity, absolute pressure, and UVRI had a greater impact on dirt trail use. The variations in the magnitude of the effect may be a function of the activity performed on the different trail surfaces. Trail surface material should be considered to fully understand the impact weather has on trail use. Management implicationsBy understanding the behaviors of natural surface trail users in response to various weather conditions, managers can adapt their trail planning (i.e., type of trail, surface material), maintenance, and funding for various projects. Managers could collect weather-related information in conjunction with trail surface conditions to inform users of more user-friendly trails during adverse weather events. This could decrease trail maintenance by shifting users to trails that can tolerate more use in poor weather. Additionally, this information would enable managers to develop programs more effectively (e.g., special events, learning clinics) and thus engage more people in outdoor recreation.

Evaluation of Aortic Hemodynamics Using Four-Dimensional Flow of Magnetic Resonance Imaging in Rabbits with Liver Fibrosis.

Liver fibrosis (LF) precipitates systemic hemodynamic alterations, however, its impact on the aorta remaining undefined. To assess aorta hemodynamics changes during LF development in a rabbit model. Prospective, experimental. Thirty 7-month-old male rabbits underwent bile duct ligation (BDL) to induce LF. Biweekly four-dimensional (4D) flow imaging incorporating a 3D gradient-echo at 3.0 T scanner for 14 weeks post-BDL. Histopathological exams for 2-5 rabbits were performed at each time point, following each MRI scan. LF was graded using the Metavir scale by a pathologist. 4D flow was analyzed by two radiologists using dedicated postprocessing software. They recorded 4D flow parameters at four aorta sections (aortic sinus, before and after bifurcation of aortic arch, and descending aorta). The linear mixed model; Bonferroni correction; Pearson correlation coefficient (r); receiver operating characteristic (ROC) curve; Delong test. The level of significance was set at P < 0.05. Following BDL, the wall shear stress (WSS) (0.23-0.32 Pa), energy loss (EL) (0.27-1.55 mW) of aorta significantly increased at the second week for each plane, peaking at the sixth week (WSS: 0.35-0.49 Pa, EL: 0.57-2.0 mW). So did the relative pressure difference (RPD) (second week: 1.67 ± 1.63 mmHg, sixth week: 2.43 ± 0.63 mmHg) in plane 2. Notably, the RPD in plane 2 at the second week displayed the highest area under ROC curve of 0.998 (specificity: 1, sensitivity: 0.967). LF were found at the second, fourth, and sixth week after BDL, with grade F2, F3, and F4, respectively. The RPD in plane 2 was most strongly correlated with the severity of LF (r = 0.86). The occurrence of LF could increase WSS, EL, and RPD of aorta as early as the second week following BDL. 1 TECHNICAL EFFICACY: Stage 2.

Effect Analysis of the Venting Direction on Explosion Pressure in LPG Pipelines.

In order to study the effect of the venting direction on explosion pressure in liquefied petroleum gas pipelines, explosion accident scenarios are experimentally tested and numerically simulated in a pipeline model with different explosion venting directions. In addition, the effect characteristic is analyzed through the pressure field varying with time and peak pressure varying with the distance. Results show that the pressure in the vertical branch decreases sharply, while the pressure in the horizontal branch does not show an obvious decrease with explosion venting of the vertical branch. However, the pressure decreases obviously in both branches with explosion venting of the horizontal branch, and the biggest reduction of peak pressure of monitoring points is 73.55% compared with that without venting. In addition, large areas of negative pressure appear in both branches with explosion venting of the vertical branch; however, a large area of negative pressure area appears in the horizontal branch with explosion venting of the horizontal branch. What is more, the arrival time of peak pressure in the main pipe of the explosion pipeline is significantly reduced with explosion venting, which is caused by the different generation ways of peak pressure. The effect analysis result of the venting direction on explosion pressure could aid the optimal layout design of LPG pipelines with the location of venting and important facilities as well as with the selection of negative-pressure-resistant material and higher-accuracy sensors.

Effect of polyurethane foam and carbon dioxide on the suppression of hydrogen/air explosion

This study examines the influence of polyurethane porous materials and carbon dioxide on hydrogen/air explosions within an enclosed vessel. Through analysis of peak overpressure, maximum rate of pressure rise, and shock wave propagation velocity, the suppression effects on explosions in hydrogen-air mixtures with different equivalence ratios at room temperature and atmospheric pressure are investigated. Findings indicate that porous materials with a PPI (pores per inch) of 60 significantly mitigate hydrogen/air explosions across all equivalence ratios. Conversely, a PPI below 60 exacerbates the explosions. Simultaneous presentation of PPI60 porous material and a CO2 addition level of x = 2 (carbon dioxide to oxygen ratio) reduces hydrogen explosion pressure to only 13.7 kPa at "Φ = " 1.2, representing an attenuation rate of 84% and falling well below the human safety threshold of 28 kPa. Independent effects of carbon dioxide and porous materials on hydrogen explosions across various equivalence ratios are also explored. The experimental design encompasses a broad range of equivalence ratios, covering hydrogen's explosive limits. These results contribute to the design of flame arrestors and enhance understanding of explosion suppression in hydrogen systems.

A short-cut methodology for the spatial assessment of the biochemical river quality

The deterioration of superficial water quality is a significant concern in water management. Currently, most European rivers do not achieve qualitative standards defined by Directive 2000/60/EC (Water Framework Directive, WFD), while the health status of many surface water bodies remains unknown. Within this context, we propose a new methodology to perform a semi-quantitative analysis of the pressure state of a river, starting from easily accessible data related to anthropic activities. The proposed approach aims to address the endemic scarcity of monitoring records. This study proposes a procedure to (i) evaluate the relative pressure of different human activities, (ii) identify allocation points of different pollutant sources along the river using a raster-based approach, and (iii) determine a spatial biochemical water quality index. The developed index expresses the overall biochemical state of surface water induced by pollutant sources that may simultaneously impact a single river segment. This includes establishments under the so-called Seveso Directive, activities subjected to the IPPC-IED discipline, wastewater treatment plants, and contaminated sites. The methodology has been tested over three rivers in Northern Italy, each exposed to different industrial and anthropogenic pressures: Reno, Enza, and Parma. A comparison with monitored data yielded convincing results, proving the consistency of the proposed index in reproducing the spatial variability of the river water quality. While additional investigations are necessary, the developed methodology can serve as a valuable tool to support decision-making processes and predictive studies in areas lacking or having limited water quality monitoring data.

Effects of injection timing on mixture formation, combustion, and emission characteristics in a n-butanol direct injection spark ignition engine

The impact of injection timings on the in-cylinder flow field intensity, mixture formation process, combustion, and emission characteristics are analyzed. The range of injection timing is set between −320°CA and −260°CA. The research results indicate: Delaying the injection timing causes the spray plumes increasingly align with the tumble direction, consequently enhancing the in-cylinder tumble intensity and the turbulence near the spark timing. The mixture homogeneity is influenced by both the formation time and the in-cylinder flow field intensity. Moreover, combustion performance is linked to the homogeneity of the mixture and turbulence intensity near the spark timing. Despite the fact that postponed injection may augment both turbulence intensity and the equivalent ratio around the spark plug at the moment of spark, achieving higher explosion pressure, but the higher viscosity of n-butanol impedes droplet break-up, and its low volatility decelerates the evaporation rate, leading to poorer mixture homogeneity, reduced BMEP, and increased CO and soot emissions. However, at −300°CA start of injection, the extended mixing time optimizes the fuel-air mixture homogeneity, thus improving combustion quality and reducing CO, soot, and HC emissions, albeit leading to increased NOx emissions.

Shale gas completion fracturing technology based on FAE controlled burning explosion

The existing fracturing technology in shale gas production lacks compatibility between efficiency and environmental concerns, which significantly hinders the industrial production of shale gas. Therefore, based on the distinctive characteristics of fuel-air explosives (FAE), this paper proposes an advanced shale gas completion fracturing technology utilizing FAE controlled burning explosion, which can effectively achieve a balance between efficiency and environmental considerations. Research and numerical simulations demonstrate that various factors or ways in the FAE burning explosion can exert controllable effects: the higher the zero oxygen equilibrium value and the uniformity of FAE, the greater the initial pressure, and the greater the filling mass of FAE, thereby the stronger the explosion power; the larger inertness coefficient leads to lower sensitivity and intensity of FAE; etc. Additionally, the research and numerical simulation also show that the controllability of FAE burning explosion fracturing on shale reservoirs can be achieved through a variety of factors and ways: an increased explosion pressure results in a larger fracturing zone; the deeper the fractured rock layer leads to higher fracture pressures but a smaller fracturing zone; larger Poisson’s ratio reduces crushed zone while enlarging both crack zone and the fracturing zone.

Insight into energy release characteristics of TiH2 dust explosion through ignition experiments and molecular dynamic simulations

TiH2 is an efficient hydrogen storage material with high energy density and relatively stable chemical quality, which is commonly used in metal sponge production, hydrogen storage, battery technology, rocket propellants, etc. In this study, TiH2 dust explosion is systematically investigated by integrating ignition experiments with reactive force field molecular dynamics simulation. Findings show that when the TiH2 dust concentration is 750 g·m−3, both the explosion pressure and explosion pressure rise rate reach their maximum values under airtight and venting conditions. There are three stages in the whole combustion process: the combustion development stage, the stable combustion stage, and the decay stage. The flame length (L) and flame propagation velocity (v) grow with the increase of dust concentration. TiH2 dust explosion with different concentrations in macroscopic tests is approximated by simulating the combustion behaviors of the TiH2 system with different densities. The combustion reaction rate of TiH2 grows with an increase in system density, and the simulation results are consistent with experimental findings.

Thermodynamic Reactivity Study during Deflagration of Light Alcohol Fuel-Air Mixtures with Water

In this paper, a thermodynamic and reactivity study of light alcohol fuels was performed, based on experimental and numerical results. We also tested the influence of water addition on fundamental properties of the combustion reactivity dynamics in closed vessels, like the maximum explosion pressure, maximum rate of pressure rise and the explosion delay time of alcohol–air mixtures. The substances that we investigated were as follows: methanol, ethanol, n-propanol and iso-propanol. All experiments were conducted at initial conditions of 323.15 K and 1 bar in a 20 dm3 closed testing vessel. We investigated the reactivity and thermodynamic properties during the combustion of liquid fuel–air mixtures with equivalence ratios between 0.3 and 0.7 as well as some admixtures with water, to observe water mitigation effects. All light alcohol samples were prepared at the same initial conditions on a volumetric basis by mixing the pure components. The volumetric water content of the admixtures varied from 10 to 60 vol%. The aim of water addition was to investigate the influence of thermodynamic properties of light alcohols and to discover to which extent a water addition may accomplish mitigation of combustion dynamics and thermodynamic reactivity.

Influence of Inlet and Outlet Area Ratio on Intake Port Flow Capacity

The flow capacity of the intake port has a great influence on the charging efficiency of the internal combustion engine, affecting the engine’s performance, so it is critical to improve the intake port flow capacity. In this paper, the intake port numerical model was established, and the influence of the inlet and outlet area ratio on intake port flow capacity was studied. The results show that, under the same condition of relative pressure difference, the intake port discharge coefficient increases sharply and then slowly with an increase in area ratio. Under the same condition of area ratio, the discharge coefficient is only determined by relative pressure difference and decreases with an increase of relative pressure difference when the inlet and outlet area ratio&gt;1. The optimal area ratio decreases and then converges with an increase in relative pressure difference. When the intake port is designed, the optimal area ratio under the working condition of a smaller relative pressure difference should be applied in order to ensure the discharge coefficient is optimal under all working conditions.

Effects of ignition location on CH4/air explosion characteristic in a spherical bomb

To build methane anti-explosion storage equipment, the influence of the ignition location on the CH4/air explosion in a spherical equipment was investigated. A two-step CH4/air reaction mechanism was developed and it considered the effect of heat transfer on the explosion. The effect of methane explosion pressure on heat loss was studied. The results show that the maximum explosion pressure of central ignition is 0.72 MPa under the heat loss simulation. The peak pressure of the upper and lower end-wall explosion is about 79.2 % and 83.3 % of the central ignition explosion, respectively, and the experimental results verifies the simulation results. Therefore, the reason for the highest peak pressure of central ignition methane explosion is that the reaction speed of central ignition methane explosion is the fastest, and the heat loss is the lowest. The difference in peak pressure between the upper and lower wall surfaces is due to the buoyancy effect accelerates the reaction rate of the lower end-wall ignition. In the simulation time range, the heat radiation at different ignition locations accounts for more than 70 % of the total heat loss, and radiation heat transfer plays a leading role in the total heat loss.

The Variation in Atmospheric Turbidity over a Tropical Site in Nigeria and Its Relation to Climate Drivers

Atmospheric turbidity exhibits substantial spatial–temporal variability due to factors such as aerosol emissions, seasonal changes, meteorology, and air mass transport. Investigating atmospheric turbidity is crucial for climatology, meteorology, and atmospheric pollution. This study investigates the variation in atmospheric turbidity over a tropical location in Nigeria, utilizing the Ångström exponent (α), the turbidity coefficient (β), the Linke turbidity factor (TL), the Ångström turbidity coefficient (βEST), the Unsworth–Monteith turbidity coefficient (KAUM), and the Schüepp turbidity coefficient (SCH). These parameters were estimated from a six-month uninterrupted aerosol optical depth dataset (January–June 2016) and a one-year dataset (January–December 2016) of solar radiation and meteorological data. An inverse correlation (R = −0.77) was obtained between α and β, which indicates different turbidity regimes based on particle size. TL and βEST exhibit pronounced seasonality, with higher turbidity during the dry season (TL = 9.62 and βEST = 0.60) compared to the rainy season (TL = 0.48 and βEST = 0.20) from May to October. Backward trajectories and wind patterns reveal that high-turbidity months align with north-easterly air flows from the Sahara Desert, transporting dust aerosols, while low-turbidity months coincide with humid maritime air masses originating from the Gulf of Guinea. Meteorological drivers like relative humidity and water vapor pressure are linked to turbidity levels, with an inverse exponential relationship observed between normalized turbidity coefficients and normalized water vapor pressure. This analysis provides insights into how air mass origin, wind patterns, and local climate factors impact atmospheric haze, particle characteristics, and solar attenuation variability in a tropical location across seasons. The findings can contribute to environmental studies and assist in modelling interactions between climate, weather, and atmospheric optical properties in the region.

Enhanced echocardiographic assessment of intracardiac flow in congenital heart disease.

4D flow magnetic resonance imaging (4D flow MRI) can assess and measure the complex flow patterns of the right ventricle (RV) in congenital heart diseases, but its limited availability makes the broad application of intracardiac flow assessment challenging. Color Doppler imaging velocity reconstruction from conventional echocardiography is an emerging alternative, but its validity against 4D flow MRI needs to be established. To compare intracardiac flow parameters measured by color Doppler velocity reconstruction (DoVeR) against parameters measured from 4D flow MRI. We analyzed 20 subjects, including 7 normal RVs and 13 abnormal RVs (10 with repaired Tetralogy of Fallot, and 3 with atrial-level shunts). Intracardiac flow parameters such as relative pressure difference, vortex strength, total kinetic energy, and viscous energy loss were quantified using DoVeR and 4D flow MRI. The agreement between the two methods was determined by comparing the spatial fields and quantifying the cross-correlation and normalized difference between time-series measurements. The hemodynamic parameters obtained from DoVeR and 4D flow MRI showed similar flow characteristics and spatial distributions. The time evolutions of the parameters were also in good agreement between the two methods. The median correlation coefficient between the time-series of any parameter was between 0.87 and 0.92, and the median L2-norm deviation was between 10% to 14%. Our study shows that DoVeR is a reliable alternative to 4D flow MRI for quantifying intracardiac hemodynamic parameters in the RV.

Dynamic response and performance assessment of subsea sandwich pipelines with different interlayer subjected to underwater explosion

The sandwich pipelines have been developed and applied in subsea due to their better resistance than single-layer pipelines. Explosive shock loads can cause fatal damage to subsea pipelines, thus the objective of this paper is to systematically evaluate the safety of subsea sandwich pipelines under explosion loading. The uniqueness of this study is to analyze the dynamic response of sandwich pipeline filled with different interlayer materials subjected to underwater explosion, especially considering the fluid-solid interaction (FSI) effect. Based on the Arbitrary Lagrangian-Eulerian (ALE) algorithm, the propagation of the blast shock wave in sea water and the FSI effect with the pipeline were investigated by using LS-DYNA code. The accuracy of the numerical method was verified, and then the evolution of the explosive pressure in sandwich pipes with different interlayer material was simulated. The energy absorbing capacity of each layer was analyzed. The structural dynamic response and deformation of the subsea sandwich pipelines was investigated by considering the influencing factors including the diameter-to-thickness ratio (λ) of the inner pipe and outer pipe, the interlayer material, and the explosive charge (Me). The results show that with the increase of λ and Me, the ovality of the pipe increase correspondingly. Moreover, the results demonstrate that with different material as the interlayer, each layer of the sandwich pipe shows different ability to absorb the internal energy caused by explosive shock wave, thus the deformation of the pipe differs significantly. This study can provide a reference for the optimized design of subsea sandwich pipelines to support the operational safety of deep-sea pipeline systems.

Polyacrylonitrile and polyacrylonitrile/cellulose‐based activated carbon nanofibers obtained from acrylic textile wastes for carbon dioxide capture

AbstractThe aim of this study is to develop nanofibrous CO2 adsorbents by using of textile wastes as precursor materials. Therefore, polyacrylonitrile (PAN) and PAN/cell nanofibers were produced from acrylic textile wastes. Nanofibrous membranes were subjected to stabilization, carbonization, and chemical activation processes, respectively, to produce activated carbon nanofiber (ACnF) structures. Elemental analysis, scanning electron microscope, FTIR, and Braunauer, Emmett, and Teller analyses were carried out and CO2 adsorption performance was tested. It was observed that all samples, except PAN/cell nanofibers carbonized at 900°C, preserved their nanofibrous structure. PAN ACnFs had a lower surface area; on the other hand, they were shown to have higher carbon dioxide adsorption values compared with PAN/cell ACnFs. Reasonable adsorption capacities as high as 3.53 and 2.99 mmol/g (at 298 K at a relative pressure of 0.989) were achieved by PAN and PAN/cell ACnFs, respectively. As a result, it was investigated that sustainable ACnF‐based carbon dioxide adsorbents could be produced by the thermochemical processing of electrospun nanofibers obtained from textile wastes.