Process Of Leakage Research Articles

The study of gas injection modes from a long tube to a channel filled with liquid

The results of experimental and numerical studies of the gas phase injection into the liquid column and sudden gas-liquid interaction are presented. Experimental study was performed by means of high-speed shadowgraph and analysis of signals of pressure transducers. The numerical part of the work was carried out using the OpenFOAM software. The data about void fraction distribution and pressure evolution are presented. In general, a good agreement between the experimental and calculated data was found. The data obtained can be used for verification and validation of different numerical codes, as example ones for the prediction of the process of the steam generation leakage on nuclear power plant.

The sealing of fixed joints

The article is devoted to the study of the seals of fixed joints. The mechanisms of leakage occurrence at different values of roughness and pressure on the joint surfaces are considered taking into account the real contact area. The estimation of deformations and forces in the contact zone was carried out taking into account the profile of surfaces, limit deviations of shape and location of surfaces, as well as physical and mechanical properties of materials of the sealed joint. The obtained theoretical dependence allows to evaluate the tightness of the fixed connection depending on the main parameters of the seal roughness, manufacturing errors and the location of the interfaces, their physical and mechanical properties and characteristics of sealed liquid, including differential pressure and the nominal pressure in the joint. A new law of probability density distribution is proposed, which more adequately describes the considered boundary conditions of the experiment. Relations for the probabilistic evaluation of the contact area and surface deformations taking into account the characteristics of the material are obtained. Simple engineering relations for the estimation of probability of contact of the projections and offset surfaces for the two profiles are obtained. The simulation of the process of leakage depending on these conditions is carried out. It is shown that the complete tightness of rigid joints is insufficient even with low roughness provided by the finishing methods of processing and in the absence of deviations in the shape of the joint surfaces. The comparison of experimental data with the obtained theoretical results showed that the proposed engineering dependences provide a good match with the experimental data.

Study on the influence of barriers in the diffusion process of liquid hydrogen leakage

Based on the computational fluid dynamics method, a numerical model of large-scale liquid hydrogen leakage and diffusion is established. By simulating the diffusion process of hydrogen cloud when the obstacle is located at different positions, we get the motion law of cloud and the important time parameters of Cloud Diffusion reaching the dangerous range (combustible concentration). Compared with the process of liquid hydrogen leakage and diffusion under barrier-free conditions, it was found that setting an obstacle in the wind direction of the leakage port can accelerate the diffusion speed of the hydrogen cloud. The time to reduce the cloud concentration below the flammable range is reduced by 15%, therefor, can decrease the risk of fire; however, setting barrier in the downwind direction will lead to the accumulation of hydrogen cloud near the ground, and the time when the cloud concentration drops below the flammable range is 64% longer than the barrier-free working conditions, the possibility of serious secondary accidents was increased.

Numerical simulation of CO2 leakage in a shallow subsurface layer from a CO2 geological storage site

In an effort to detect and quantify potential CO2 leakage from geologic storage sites, this work investigates the migration process of CO2 leaked in a shallow subsurface associated with the CO2 sequestration project at Shaanxi, China. A shallow subsurface model with aquifer and soil layers was established, and the sensitivities of leakage rate and geological conditions were analysed. The results show that the distribution morphology of the CO2 plume is generally mushroom-shaped when the leaked CO2 enters the formation as a point source. Maximum leakage occurs at the soil surface due to the comprehensive effects of pressure, concentration, and density differences between CO2 and soil gas. The mass fraction of CO2 in gas is approximately 0.38–0.48 near the surface leak point, and leaked CO2 moves laterally along the bottom of the soil vadose zone. The leakage rate of CO2 significantly affects the pressure build-up as observed for an increase in the CO2 leakage rate from 0.0002 to 0.02 kg/s. In addition to the loess beam area, the migration process of CO2 leakage in the valley terrace area was also studied. The results show that the CO2 concentration in the leakage centre area of the valley terrace is not much different from that in the loess beam. Moreover, the surface leakage range in the valley terrace is much smaller than that in the loess beam, which is because of the differences in the formation composition and thickness. Heterogeneity has limited effect on leakage.

Dynamic Simulation and Quantitative Risk Assessment of Indoor Heavy Gas Diffusion

In order to study the dynamic diffusion process and risk of indoor liquid chlorine leakage, large-scale numerical simulation and risk calculation are carried out based on CFD method. Firstly, a full-scale model in 3km range is established based on CFD calculation, and then the chlorine diffusion process in six leakage scenarios is calculated and analyzed based on pool model. The individual risk and social risk of existing conditions and SIS increase are calculated respectively. The results show that the chlorine will diffuse slowly in the room when the small aperture leaks. In case of leakage of middle hole and larger hole diameter, chlorine gas will quickly fill the warehouse and leak to the outside of the warehouse. The influence of leakage pore size on the diffusion distance of chlorine is very obvious. The total diffusion distance of 900ppm chlorine is 24.2m-401.3m, and the diffusion time is 120s-670s respectively. Under the existing conditions, the individual risk and social risk do not meet the risk acceptance criteria. After sis is increased, the risk meets the acceptance criteria.

Experiment and simulation research of evolution process for LNG leakage and diffusion

The frequent occurrence of LNG leakage accidents has caused serious economic loss and environmental damage. Experiments and simulations can be combined to obtain the transient process of LNG leakage and diffusion. This paper analyzed LNG leakage diffusion rules with experiment results obtained by depleting 1.4t LNG. The vapor clouds and LNG concentration are measured, which can be a comparison with the simulation results. Computational fluid dynamics and gas diffusion theory were chosen as the theoretical basis, simulating the transient process of LNG gasification to obtain the diffusion concentration rules. The simulation of LNG diffusion is divided into two parts: LNG leakage at the source and atmospheric diffusion. The maximum concentration of methane in the experiment was 4.1%, and the maximum concentration in the simulation was 4.6%. The results show good agreement of the deviation statistics, which fall in the standard recommendation value range. Then we make a prediction of the dangerous concentration area and the flammability hazard zone of LNG leakage accident. The simulation results show that the range of the lower wind direction danger area firstly increases and then decreases, and the maximum distance of IDLH increases firstly and arrived at the peak of 52 m at 300s.

Analysis of Indoor Natural Gas Leakage Explosion

The safety accident of indoor natural gas supply system is the process of natural gas leakage and diffusion, most of which are turbulent processes affected by many factors. When the natural gas leaks into the indoor confined space, it will mix with the air to form a mixture. When the oxygen in the natural gas and the air reaches a certain concentration range, combustion or explosion will occur when it meets the ignition source. This paper mainly introduces the influencing factors and calculation methods of the explosion limit of natural gas, and analyzes the calculation methods of the explosion limit of multi-component combustible mixed gas.

Interaction of the bar-plate conveyor of the machine with mineral fertilizers

Annotation Purpose. Determining the impact and interaction of the bar-plate conveyor with the mass of fertilizers to justify the choice of its parameters and mode of operation, ensuring the stability of the process. Methods. Theoretical calculations, their analysis. Results. The structural scheme of the process of mineral fertilizers leakage by bar-plate conveyor through the unloading window is substantiated. The effectiveness of fertilizers largely depends on the correct combination of methods of their introduction into the soil. There are two ways to use fertilizers: continuous surface sifting and internal soil application. Depending on the terms and norms perform basic and pre-sowing application, as well as fertilization [1]. Centrifugal mineral fertilizer spreaders, which use disks with the possibility of making the working mixture on the surface at an angle to the horizon have become widespread. This is due primarily to the versatility of the tool, in which due to the reorientation of the disk you can get high quality fertilizers and achieve high widths of spread. Conclusions. The results of the kinematic analysis showed that the theoretically possible uneven distribution of mineral fertilizers can reach 34–60%, in fact it is less due to the elasticity and shedding of fertilizers. To reduce the uneven distribution in the design of the machine, we have provided an intermediate hopper with an inclined auger, due to which we were able to significantly reduce the intermittent supply of mass by the conveyor. Secondly, due to the auger, we have achieved the versatility of the machine: after removing the centrifugal working body, the machine can be used for other work. Keywords: mineral fertilizers, bar-plate conveyor, spreading and local fertilization.

Employing Jute as Agrotextiles in improving water use efficiency and wheat growth in sandy soil

Egypt is one of the largest wheat importing countries in the Middle East. It is one of the strategic crops that is deficient in its production capacity to meet the consumer needs of the community. Therefore, there are many attempts to reach practical solutions to increase local production and reduce imports to increase self-sufficiency. These solutions include the cultivation of wheat in the reclaimed sandy soil, but it is poor in its properties and requires many agricultural seasons and treatments to be arable soil. The most important problems are that the soil granules are loose and cannot hold water. The importance of using cellulose fabrics as Agrotextiles in the form of mats to improve the functions of soil and reduce the process of evaporation and leakage and thus increase the retention of soil water and provide appropriate moisture for the process of germination and growth of wheat crop. The use of jute fibers, as mats has been greater importance to water retention. Agricultural experiments were conducted to test the effect of jute mats through three weights per square meter with different irrigation rates to improve the properties of sandy soil and the growth of cultivated wheat plant. The results showed improved plant growth compared to the sandy soil studied without the use of tissue mats. The results of dry weight of the plant with jute mats gave an increase in the dry weight of wheat 251% with the highest level of weight per square meter of the mats, when using the normal rate of irrigation (100% Of the plant's need for water) while the increase was equivalent to 160.1% at the rate of irrigation 75% and 39.3% with irrigation rate of 50% of the water used when compared to the results of soil without textile mats.

Simulation and safety analysis of the leakage of liquefied hydrogen from high-pressure container

In this paper, the leakage and diffusion of liquefied hydrogen which is stored in high-pressure container were investigated and the safety arrangement in cosmodrome focused on the effects of external flow on the above process was proposed. The phase transition process of leakage of liquefied hydrogen at the initial stage was first analyzed by considering the motion of single particle and particle group. Furthermore, the rule of leakage and diffusion of liquefied hydrogen under different conditions was thoroughly examined by CFD modelling. Through this work, the leakage pressure, leakage location, external air-flow direction and external air-flow velocity are found to have great effects on the diffusion of leaking hydrogen. By increasing the leakage pressure and putting leakage port closer to ground, the diffusion and dilution of leaking hydrogen would be strongly expedited to spread much further away. By adopting upper air blow and raising the external air speed, the concentration can be fairly reduced.

Effect of fracture on gas migration, leakage and CO2 enhanced shale gas recovery in Ordos Basin

Although the CO2 enhanced shale gas recovery (CO2-ESGR) has been studied to respond to energy shortages and climate changes, previous studies have not examined the effect of fracture on the process of gas migration and leakage. Therefore, this study presents a 3-D numerical model base on geological data of Ordos basin. The leakage of CH4 happens at the beginning of shale gas production in SGR scenario, and the injection of CO2 in CO2-ESGR scenario can reduce the leakage of CH4. The higher CO2 injection rate will promote the leakage of CO2 and prevent the leakage of CH4 in CO2-ESGR scenario. Higher permeability will make the CH4 gas leak from shale reservoir to aquifer easier and faster in both scenarios, but it can relatively prevent the leakage of CO2 in CO2-ESGR scenario.

Effects of tank sloshing on submerged oil leakage from damaged tankers

In order to gain advanced understanding of the mechanism of the submerged oil leakage from damaged tankers subjected to wave-excited motions, a three-dimensional (3D) full scale numerical model is developed in this paper. The model is based on the three-phase Navier-Stokes equation and the continuity equation, which are solved by using the finite volume method (FVM). The volume of fluid (VOF) method is implemented to identify the interfaces between different phases and the k-ε turbulence model is employed to approximate the turbulence effects. The prototype of the oil tanker is taken as the side tank of VLCC, which is subjected to a periodically forced motions yielding a liquid sloshing inside the tank. After being validated by comparing its prediction with experimental data, the present model is utilized to a systematic investigation with wide range of applications including different motion amplitudes and periods. The dynamic characteristics of both the macroscopic parameters, e.g. the volume of the oil/water, and the microscopic parameters, e.g. the velocity distributions, are analyzed. The results fill the gap in the existing numerical and experimental work, in which the tank is assumed to be stationary, and produce a more reliable prediction on the dynamic process of the oil leakage and the stability of the damaged oil tankers subjected to wave actions.

Transient liquid leakage during plunger lifting process in gas wells

Plunger lift is an economical method to solve the liquid loading problem in wells. Following our previous research (Zhao et al., 2018), which focused on the steady-state process of liquid leakage during lifting, the transient variations of plunger velocity, liquid leakage and stress conditions during plunger lifting process are investigated theoretically and experimentally in this paper. Based on the force analysis and finite difference method, the transient physical model for the mass and gas volume fraction of gas-liquid column above plunger is proposed. Combining the similarity experiments and infrared measuring technology, the proposed transient model is verified quantitatively with the relative deviation less than ±10%. The results show that both the liquid leakage and the gas volume fraction of gas-liquid column above plunger cannot be neglected during plunger lifting. The transient change rules of lifting differential pressure, plunger velocity, gas volume fraction of gas-liquid column and liquid leakage flow rate during lifting process are obtained. The influences of liquid loading condition and gas production rate on transient plunger lifting process are discussed. Through the dimensionless analysis, a dimensionless correlation for transient gas volume fraction of gas-liquid column is developed.

Elementary processes of antimicrobial peptide PGLa-induced pore formation in lipid bilayers

Antimicrobial peptide PGLa induces the leakage of intracellular content, leading to its bactericidal activity. However, the elementary process of PGLa-induced leakage remains poorly understood. Here, we examined the interaction of PGLa with lipid bilayers using the single giant unilamellar vesicle (GUV) method. We found that PGLa induced membrane permeation of calcein from GUVs comprised of dioleoylphosphatidylcholine (DOPC) and dioleoylphosphatidylglycerol (DOPG) and its rate increased with time to reach a steady value, indicating that PGLa induced pores in the bilayer. The binding of PGLa to the GUV membrane raised its fractional area change, δ. At high PGLa concentrations, the time course of δ showed a two-step increase; δ increased to a value, δ1, which was constant for an extended period before increasing to another constant value, δ2, that persisted until aspiration of the GUV. To reveal the distribution of PGLa, we investigated the interaction of a mixture of PGLa and carboxyfluorescein (CF) -labeled PGLa (CF-PGLa) with single GUVs. The change of the fluorescence intensity of the GUV rim, I, over time showed a two-step increase from a steady value, I1, to another, I2, concomitant with the entering of CF-PGLa into the lumen of the GUV prior to AF647 leakage. The simultaneous measurement of δ and I indicated that their time courses were virtually the same and the ratios (δ2/δ1 and I2/I1) were almost 2. These results indicated that CF-PGLa translocated across the bilayer before membrane permeation. Based on these results, the elementary processes of the PGLa-induced pore formation were discussed.

Neutralization of placental growth factor as a novel treatment option in diabetic retinopathy

The current standard of care in clinical practice for diabetic retinopathy (DR), anti-vascular endothelial growth factor (VEGF) therapy, has shown a significant improvement in visual acuity. However, treatment response can be variable and might be associated with potential side effects. This study was designed to investigate inhibition of placental growth factor (PlGF) as a possible alternative therapy for DR. The effect of the anti-PlGF antibody (PL5D11D4) was preclinically evaluated in various animal models by investigating different DR hallmarks, including inflammation, neurodegeneration, vascular leakage and fibrosis. The in vivo efficacy was tested in diabetic streptozotocin (STZ) and Akimba models and in the laser induced choroidal neovascularization (CNV) mouse model. Intravitreal (IVT) administration of the anti-PlGF antibody was compared to anti-VEGFR-2 antibody (DC101), anti-VEGF antibody (B20), VEGF-Trap (aflibercept) and triamcinolone acetonide (TAAC). Vascular leakage was investigated in the mouse STZ model by fluorescein isothiocyanate labeled bovine serum albumin (FITC-BSA) perfusion and in the Akimba model by fluorescein angiography (FA). Repeated IVT administration of the anti-PlGF antibody reduced vascular leakage, which was comparable to a single administration of VEGFR-2 inhibition in the mouse STZ model. PL5D11D4 treatment did not alter retinal ganglion cell (RGC) density, as demonstrated by Brn3a staining, whereas DC101 significantly reduced RGC number with 20%. Immunohistological stainings were performed to investigate inflammation (CD45, F4/80) and fibrosis (collagen type 1a). In the CNV model, IVT injection(s) of PL5D11D4 dose-dependently reduced inflammation and fibrosis, as compared to PBS treatment. Equimolar single administration of the anti-PlGF antibody and aflibercept (21 nM) and TAAC decreased leukocyte and macrophage infiltration with 50%, whereas DC101 and B20 (21 nM) had no effect on the inflammatory response. Similar results were observed in the mouse STZ model on the number of microglia and macrophages in the retina. Repeated administration of PL5D11D4 (21 nM) and TAAC similarly reduced fibrosis, while no effect was observed after equimolar DC101, B20 nor aflibercept administration (21 nM). In summary, the anti-PlGF antibody showed comparable efficacy as well-characterized VEGF-inhibitor on the process of vascular leakage, but differentiates itself by also reducing inflammation and fibrosis, without triggering a neurodegenerative response.

Optimization of Ventilation and Alarm Setting During the Process of Ammonia Leak in Refrigeration Machinery Room Based on Numerical Simulation

In order to optimize the ventilation effect of ammonia leakage in the refrigeration machinery room, a food processing enterprise is selected as the subject investigated. The velocity and concentration field distribution during the process of ammonia leakage are discussed through simulation of refrigeration machinery room using CFD software. The ventilation system of the room is optimized in three aspects which are named air distribution, ventilation volume and discharge outlet. The influence of the ammonia alarm system through ventilation is also analyzed. The results show that it will be better to set the discharge outlet at the top of the plant than at the side of the wall, and the smaller of the distance between the air outlet and the ammonia gathering area, the better of the effect of ventilation will be. The air flow can be improved and the vortex flow can be reduced if the ventilation volume, the number of air vents and the exhaust velocity are reasonably arranged. Not only the function of the alarm could be ensured, but also the scope of the detection area could be enlarged if the detectors are set on the ceiling of the refrigeration units or the ammonia storage vessel.

Remote Visualization of Screen Images Using a Pseudo-Antenna That Blends Into the Mobile Environment

This paper presents a potential threat of remote visualization for screen displays of various mobile devices used in public spaces via electromagnetic waves (electromagnetic (EM) screen remote visualization). The traditional EM screen remote visualization uses nonportable equipment on a specific target device, and requires sufficient time to estimate the parameters related to information leakage of each target. In contrast, this paper proposes a method that allows for real-time estimation of information leakage parameters without requiring to know the target of remote visualization in details. The proposed method models the process of information leakage for each device, and consequently determines the frequency that leaks screen information faster than ever before. In addition, in this paper, portable equipment and a pseudo-antenna that blends into the mobile environment were used to implement the proposed method. The experiment shows that the screen image can be reconstructed from EM emanation obtained from the areas near some target devices. Furthermore, we discuss the measures against EM remote visualization of mobile devices.

Selective use of political opportunity: a case of environmental protest in rural China

This paper explores the selective and instrumental use of political opportunity in Chinese contentious politics through the study of a rural environmental protest. By considering the transmission of political opportunity through different levels of government, it also analyses the phenomenon of leakage of political opportunity. We argue that political opportunities can be divided into soft and hard types, which are weighted differently by activists. In the protest we examine, the villagers had various political opportunities at their disposal. They used them selectively, preferring the opportunities arising from changes to land policy, which were relatively hard and had a higher level of operability than environmental political opportunities—despite their grievances being largely connected with environmental damage. The hard, land-oriented opportunities, however, went through a process of leakage and then became merely symbolic, due to the local government’s manipulation of policy implementation. However, although they were well aware that the symbolic political opportunities were not genuine, the protesters still acted as if they were real and exploited them instrumentally.

Design of Real Time Monitoring System for Dangerous Goods Transportation Based on DSP

To solve the hazardous goods transportation equipment state real-time monitoring and control system with TMS320F2812 of TI company as the core, through the shaping of the sensor into the alcohol gas signal, filtering, amplification, a / D conversion, A / D conversion using F2812 comes with 12 bit A / D converter, continuous sampling signal monitoring gas concentration change and through the acquisition of temperature and humidity signal, the gas concentration data were temperature and humidity compensation, accurate measurement, calibration gas data can be secondary sound and light alarm, and the MAX232 and PC data transfer, at any time to check and call history. Good monitoring and control to make the system more stable. System mainly includes sensor for gas detection, temperature detection pass, humidity sensor, signal conversion and processing unit, A / D conversion circuit, sound and light alarm unit, RS232 communication module, the battery monitoring unit, a gas pump control unit. DSP main program using modular programming, completed the DSP initialization of the main program module, real-time communication with the PC module and system function module test program design. Laboratory research on gas monitoring and control system scheme is designed in this paper for tankers physical model. and on this basis, focusing on the completion of the core part of the control system in the control card design and implementation. This system can realize the monitoring of the whole process of leakage of hazardous goods transport equipment, once dangerous goods transport vehicles of hazardous chemicals spill occurred, the system can real-time detection to the leakage and alarm, the modern crisis of goods logistics provides a security solution.

Lack of evidence for tissue hypoxia as a contributing factor in anastomotic leak following colon anastomosis and segmental devascularization in rats.

Current surgical dogma dictates that tissue ischemia and hypoxia are major contributing factors in anastomotic leak despite scant evidence. The aim of this study was to determine if tissue hypoxia is a feature of anastomotic leakage in rats following colon resection and segmental devascularization. Rats were randomly assigned to undergo sham operation, segmental colon devascularization alone, colectomy alone, or segmental devascularization plus colectomy. Tissue hypoxia present at the colon anastomosis site across the various treatment groups was determined at sacrifice on postoperative day 6. Pimonidazole HCl was injected 30min prior to sacrifice. Anastomotic tissues were examined and scored for healing versus leakage using an anastomotic healing score (AHS). Collagen content, hypoxia, enteric smooth muscle and periendothelial stromal patterning, and apoptosis were evaluated histologically. No differences in tissue hypoxia were noted in the 16% of anastomotic tissues with poor healing compared to the remaining 84% of rats whose anastomoses healed well. No significant changes were found in cell death in the submucosa of any group. Consistent with previous findings, poor healing was associated with lower collagen content. Submucosal thickness correlated with increased arteriole diameter (R 2=0.25, p<0.005). These results demonstrate that tissue hypoxia is not a distinctive feature of anastomotic tissues that fail to heal and leak, even when their blood supply is interrupted. These findings suggest that compensatory factors may mitigate the effects of ischemia and hypoxia during healing of anastomotic tissues and that the process of leakage involves factors beyond their acute effects.