With the development of offshore oil and gas resources,hydrates pose a significant challenge to flow assurance.Hydrates can form,accumulate,and settle in pipelines,causing blockages,reducing transport capacity,and lea...With the development of offshore oil and gas resources,hydrates pose a significant challenge to flow assurance.Hydrates can form,accumulate,and settle in pipelines,causing blockages,reducing transport capacity,and leading to significant economic losses and fatalities.As oil and gas exploration moves deeper into the ocean,the issue of hydrate blockages has become more severe.It is essential to take adequate measures promptly to mitigate the hazards of hydrate blockages after they form.However,a prerequisite for effective mitigation is accurately detecting the location and amount of hydrate formation.This article summarizes the temperature–pressure,acoustic,electrical,instrumental–response,and flow characteristics of hydrate formation and blocking under various conditions.It also analyzes the principles,limitations,and applicability of various blockage detection methods,including acoustic,transient,and fiber-optic-based methods.Finally,it lists the results of field experiments and commercially used products.Given their advantages of accuracy and a wide detection range,acoustic pulse reflectometry and transient-based methods are considered effective for detecting hydrate blockages in future underwater pipelines.Using strict backpressure warnings combined with accurate detection via acoustic pulse reflectometry or transient-based methods,efficient and timely diagnosis of hydrate blockages can be achieved.The use of a hydrate model combined with fiber optics could prove to be an effective method for detecting blockages in newly laid pipelines in the future.展开更多
By investigating the performance characteristics of the bio-based surfactant 8901A,a composite decontamination and injection system was developed using 8901A as the primary agent,tailored for application in low-permea...By investigating the performance characteristics of the bio-based surfactant 8901A,a composite decontamination and injection system was developed using 8901A as the primary agent,tailored for application in low-permeability and heavy oil reservoirs under varying temperature conditions.The results demonstrate that this system effectively reduces oil–water interfacial tension,achieving an ultra-low interfacial tension state.The static oil washing efficiency of oil sands exceeds 85%,the average pressure reduction rate reaches 21.55%,and the oil recovery rate improves by 13.54%.These enhancements significantly increase the system’s ability to dissolve oilbased blockages,thereby lowering water injection pressure caused by organic fouling,increasing the injection volume of injection wells,and ultimately improving oil recovery efficiency.展开更多
The appearance of flow instabilities like the blockage severity,impeller cut flaws,pitted cover plate flaws can cause to diminish the efficiency of centrifugal pump(CP),and may result in excessive vibration and noise,...The appearance of flow instabilities like the blockage severity,impeller cut flaws,pitted cover plate flaws can cause to diminish the efficiency of centrifugal pump(CP),and may result in excessive vibration and noise,and their failure may lead to the system imploding.To bridge the gap of downfall in the efficiency of CP,it is crucial that a system can be created to monitor the condition of the CP and must be maintained.The present work proposes at identifying and determining the severity of various blockage levels in the inlet pipe with three different kinds of pumps using three distinct sensors.One pump works faultlessly(healthy pump),another has cuts artificially made on the impeller blade,and the third has pits artificially created on the cover plate.The inlet pipe blockage mimics pump blockage which is made more severe step by step.As the blockage gets worse and the flow slows down,recirculation starts,causing vapor bubbles to form.Utilizing a mechanical modulating valve,the inlet flow area of the pipe is partitioned into six intervals(0%,16.7%,33.3%,50%,66.6%,and 83.33%)to replicate pump blockage.This obstruction directly influences vibrations,current line signals,and fluid dynamic pressure.To gather data across a spectrum of blockage levels and operational frequencies(30 Hz,35 Hz,40 Hz,45 Hz,50 Hz,55 Hz,and 60 Hz),a combination of a pressure transducer,accelerometer,and current probes were strategically employed in this investigation.Multiple sets of statistical features were extracted from the data,and through various algorithms,the most effective combined statistical feature set was determined.In this domain,the combination of standard deviation,mean,and entropy demonstrates superior performance compared to other features.This feature set was input into an ANN model,which is developed by optimizing parameters like hidden layer count,neurons,epochs and then the results of this investigation are then compared with existing literature.It has been noted that employing combinations of multiple sets of statistical features significantly improves the accuracy in identifying obstruction levels,often achieving near-perfect accuracy for various feature sets(nearly 100%across various combinations).In comparison to other SOTA methods,this approach achieves higher accuracy,ranging from 2.41%to 15.69%across different metrics.This study presents a method to classify inlet pipe blockages into various levels,enhancing maintenance prioritization and reducing downtime and repair costs,ensuring long-term equipment health and operational efficiency.The fault prediction methodology proves highly robust across various CP operating conditions.展开更多
This work focuses on the development and implementation of a simulation-based approach for the detection of partial and extended blockages within an edible oil pipeline system. Blockages, whether partial or extended, ...This work focuses on the development and implementation of a simulation-based approach for the detection of partial and extended blockages within an edible oil pipeline system. Blockages, whether partial or extended, pose a significant operational and safety risks. This study employs computational fluid dynamics (CFD) simulations to model the flow behaviour of edible oil through pipeline under varying conditions. It leverages advanced computational fluid dynamics (CFD) simulations to analyze pressure, velocity, and temperature variations along the pipeline. By simulating scenarios with different blockage characteristics, there is establishment of distinctive patterns indicative of partial and extended obstructions. Through extensive analysis of simulation data, sensing element, and monitoring system, processing signal input and response output, the system can accurately pinpoint the location and severity of blockages, providing crucial insights for timely intervention. The detection system represents a significant advancement in pipeline monitoring technology, offering a proactive and accurate approach to identify blockages and mitigate potential risks and ensure the uninterrupted flow of edible oil, thereby enabling timely intervention and maintenance.展开更多
Due to the uncertainties in formation mechanism of gas hydrate blockages in strings during the test of deep-water gas wells,inhibitors are either excessively consumed or inefficiently used when conventional prevention...Due to the uncertainties in formation mechanism of gas hydrate blockages in strings during the test of deep-water gas wells,inhibitors are either excessively consumed or inefficiently used when conventional prevention techniques are used.In this paper,a study was conducted on multi-phase flows,in terms of hydrate formation kinetics and hydrate particle migration and settlement kinetics.In this process,a model for quantitative prediction of hydrate blockage was built to predict when and where the blockage occurs in the strings and evaluate the severity of such blockage,in order to define the high-risk zones.Eventually,an innovative hydrate blockage prevention technique based on hydrate blockage free window(HBFW)was proposed to determine the optimal concentration and the flow rate of inhibitors.The study results are in the following four aspects.First,gas hydrates generated in the wellbore may deposit on the internal walls of strings.With the increase in thicknesses of such gas hydrate layers,the diameter of a pipe string decreases.Accumulation of gas hydrates generated around liquid film on pipe walls is the key contributor to the blockage in strings.Second,as the water depth increases or the gas production reduces,the HBFW turns to be narrower for production safety,and the time to initiate blockage is shorter.Third,application of hydrate inhibitors can effectively delay the occurrence of blockage and expand the window of safe production.Fourth,the innovative prevention technique can effectively reduce the volume and the flow rate of inhibitors(by 50%in the case study).The innovative technique effectively eliminates the problems related to the excessive consumption of inhibitors in the conventional methods and provides a valuable reference for the prevention of gas hydrates formation in deep-water gas well tests.展开更多
Inverse stochastic resonance(ISR)is a phenomenon in which the firing activity of a neuron is inhibited at a certain noise level.In this paper,the effects of potassium channel blockage on ISR in single Hodgkin-Huxley n...Inverse stochastic resonance(ISR)is a phenomenon in which the firing activity of a neuron is inhibited at a certain noise level.In this paper,the effects of potassium channel blockage on ISR in single Hodgkin-Huxley neurons and in small-world networks were investigated.For the single neuron,the ion channel noise-induced ISR phenomenon can occur only in a certain small range of potassium channel blockage ratio.Bifurcation analysis showed that this small range is the bistable region regulated by the external bias current.For small-world networks,the effect of non-homogeneous network blockage on ISR was investigated.The network blockage ratio was used to represent the proportion of potassium-channel-blocked neurons to total network neurons.It is found that an increase in network blockage ratio at small coupling strengths results in shorter ISR duration.When the coupling strength is increased,the ISR is more significant in the case of a large network blockage ratio.The ISR phenomenon is determined by the network blockage ratio,the coupling strength,and the ion channel noise.Our results will provide new perspectives on the observation of ISR in neuroscience experiments.展开更多
In order to safely,efficiently and economically remove the blockages of natural gas hydrate(NGH)in the wellbores of ultra-high pressure gas wells,this paper utilized the heat released from an independently developed a...In order to safely,efficiently and economically remove the blockages of natural gas hydrate(NGH)in the wellbores of ultra-high pressure gas wells,this paper utilized the heat released from an independently developed autogenetic heat based solid blockage remover through chemical reaction in the wellbore to dissolve NGH and prevent it from forming again.In addition,adjustable heat generation time and heat generation amount was realized by regulating the dosage of the blockage remover.Finally,the chemically autogenetic heat based blockage removal technology was applied to remove the blockages in ultra-high pressure sour gas wells in the Sichuan Basin.And the following research results were obtained.First,when the independently developed chemically autogenetic heat based solid blockage remover is adopted,the peak temperature(34.2e88.5℃)and time(24.2e884.0 min)of heat generation can be adjusted by its dosage.What's more,there is NGH inhibitor in the reaction product,which can inhibit the regeneration of NGH.Second,as the concentration of the blockage remover increases,the heat transfer speed increases,leading to an increase of NGH dissociation rate around the blockage remover.Third,blockage removal time increases with the increase of wellbore ID.In addition,the increasing rate of the blockage removal time as the wellbore ID increases from 64 mm to 76 mm is lower than that from 76 mm to 102 mm.Fourth,the coincidence rate between the simulation calculation result of heat diffusion and the on-site actual consumption is more than 85%,which indicates that the proposed model for the heat diffusion of chemically autogenetic heat based blockage remover is reliable and can be used to calculate the dosage of blockage remover.Fifth,solid reagent adding device with resistance to sulfur and pressure of 140 MPa is used to add autogenetic heat based solid blockage remover.This blockage remover has been applied in the ultra-high pressure sour gas wells in the Sichuan Basin three well times.Thanks to its application,NGH blockages in these wells are removed successfully and their production is resumed smoothly.In conclusion,this blockage removal technology has such advantages as effective blockage removal,safe and simple on-site operation and low cost,and a promising application prospect.展开更多
Detecting a pipeline's abnormal status,which is typically a blockage and leakage accident,is important for the continuity and safety of mine backfill.The pipeline system for gravity-transport high-density backfill...Detecting a pipeline's abnormal status,which is typically a blockage and leakage accident,is important for the continuity and safety of mine backfill.The pipeline system for gravity-transport high-density backfill(GHB)is complex.Specifically designed,efficient,and accurate abnormal pipeline detection methods for GHB are rare.This work presents a long short-term memory-based deep learning(LSTM-DL)model for GHB pipeline blockage and leakage diagnosis.First,an industrial pipeline monitoring system was introduced using pressure and flow sensors.Second,blockage and leakage field experiments were designed to solve the problem of negative sample deficiency.The pipeline's statistical characteristics with different working statuses were analyzed to show their complexity.Third,the architecture of the LSTM-DL model was elaborated on and evaluated.Finally,the LSTM-DL model was compared with state-of-the-art(SOTA)learning algorithms.The results show that the backfilling cycle comprises multiple working phases and is intermittent.Although pressure and flow signals fluctuate stably in a normal cycle,their values are diverse in different cycles.Plugging causes a sudden change in interval signal features;leakage results in long variation duration and a wide fluctuation range.Among the SOTA models,the LSTM-DL model has the highest detection accuracy of98.31%for all states and the lowest misjudgment or false positive rate of 3.21%for blockage and leakage states.The proposed model can accurately recognize various pipeline statuses of complex GHB systems.展开更多
When a ship model test is performed in a tank, particularly when the tank is small and the ship model is relatively large, the blockage effect will inevitably occur. With increased ship model scale and speed, the bloc...When a ship model test is performed in a tank, particularly when the tank is small and the ship model is relatively large, the blockage effect will inevitably occur. With increased ship model scale and speed, the blockage effect becomes more obvious and must be corrected. In this study, the KRISO 3600 TEU Container Ship (KCS) is taken as a model and computational fluid dynamics techniques and ship resistance tests are applied to explore the mechanism and correction method of the blockage effect. By considering the degrees of freedom of the sinkage and trim, the resistance of the ship model is calculated in the infinite domain and for blockage ratios of 1.5%, 1.8%, 2.2%, and 3.0%. Through analysis of the free surface, pressure distribution, and flow field around the ship model, the action law of the blockage effect is studied. The Scott formula and mean flow correction formula based on the average cross sectional area are recommended as the main correction methods, and these formulas are improved using a factor for the return flow velocity correction based on comparison of the modified results given by different formulas. This modification method is verified by resistance test data obtained from three ship models with different scale ratios.展开更多
In this paper, we perform an unprotected partial flow blockage analysis of the hottest fuel assembly in the core of the SNCLFR-100 reactor, a 100 MW_(th) modular natural circulation lead-cooled fast reactor, developed...In this paper, we perform an unprotected partial flow blockage analysis of the hottest fuel assembly in the core of the SNCLFR-100 reactor, a 100 MW_(th) modular natural circulation lead-cooled fast reactor, developed by University of Science and Technology of China. The flow blockage shall cause a degradation of the heat transfer between the fuel assembly and the coolant potentially,which can eventually result in the clad fusion. An analysis of core blockage accidents in a single assembly is of great significance for LFR. Such scenarios are investigated by using the best estimation code RELAP5. Reactivity feedback and axial power profile are considered. The crosssectional fraction of blockage, axial position of blockage,and blockage-developing time are discussed. The cladding material failure shall be the biggest challenge and shall be a considerable threat for integrity of the fuel assembly if the cross-sectional fraction of blockage is over 94%. The blockage-developing time only affects the accident progress. The consequence will be more serious if the axial position of a sudden blockage is closer to the core outlet.The method of analysis procedure can also be applied to analyze similar transient behaviors of other fuel-type reactors.展开更多
The blockage induced by particle migration and deposition is one of the main reasons for the decrease of reinjection capacity in the porous geothermal reservoir with a low and medium temperature.In this paper,a new dr...The blockage induced by particle migration and deposition is one of the main reasons for the decrease of reinjection capacity in the porous geothermal reservoir with a low and medium temperature.In this paper,a new drilled geothermal well in Xining basin China is taken as an example to investigate the formation blockage risk due to the movable clay and sand particles in pores.The physical properties of the reservoir rocks were analyzed,a series of pumping and reinjection tests were conducted,and the longterm reinjection performance of the well was predicted by numerical simulation based on the test fitting.The results show that the geothermal reservoir rocks are argillaceous and weakly cemented sandstones with a content of movable clay and sand particles up to 0.18–23.42 wt.%.The well presented a high productivity of 935–2186 m3?d-1 at a pressure difference of 0.7–1.62 MPa in the pumping tests associated with a large amount of clay and sand particles produced out,while in the reinjection test,only a low injectivity of 240–480 m3?d-1 was observed at an injection pressure of 0.2–0.6 MPa with the clay and sand particles near the wellbore move into deep.According to the prediction,under conditions of a blockage risk,the injectivity of the well will start to decline after 100 days of injection,and in the third year,it will decrease by 59.00%–77.09%.The influence of invasion of pretreated suspended particles and scale particles can be neglected.Under conditions of a high blockage risk,the injectivity of the well will decrease significantly in the first 20–30 days,with a decline of 75.39%–78.96%.Generally,the higher the injection pressure or rate,the greater the decrease in injectivity of the well caused by particle blockage.Pump lifting is an effective measure to remove the well blockage which can be used regularly.展开更多
To predict the thermal-hydraulic(T/H)parameters of the reactor core for liquid-metal-cooled fast reactors(LMFRs),especially under flow blockage accidents,we developed a subchannel code called KMC-FB.This code uses a t...To predict the thermal-hydraulic(T/H)parameters of the reactor core for liquid-metal-cooled fast reactors(LMFRs),especially under flow blockage accidents,we developed a subchannel code called KMC-FB.This code uses a time-dependent,four-equation,singlephase flow model together with a 3D heat conduction model for the fuel rods,which is solved by numerical methods based on the finite difference method with a staggered mesh.Owing to the local effect of the blockage on the flow field,low axial flow,increased forced crossflow,and backflow occur.To more accurately simulate this problem,we implemented a robust and novel solution method.We verified the code with a low-flow(~0.01 m/s)and large-scale blockage case.For the preliminary validation,we compared our results with the experimental data of the NACIE-UP BFPS blockage test and the KIT19ROD blockage test.The results revealed that KMC-FB has sufficient solution accuracy and can be used in future flow blockage analyses for LMFRs.展开更多
Chronic alcohol consumption is a major risk factor worldwide affecting significantly both mortality and years of life lost （YLL） （1）. Ca. 5% of the western world show risky alcohol consumption and in some countrie...Chronic alcohol consumption is a major risk factor worldwide affecting significantly both mortality and years of life lost （YLL） （1）. Ca. 5% of the western world show risky alcohol consumption and in some countries such as China a regional yearly increase of alcohol consumption of over 400% has been observed recently （2,3）. The liver is the major target organ of alcohol. According to the recently published ＇Global Burden of Disease Study 2010, liver cirrhosis and liver cancer are ranked at position 12 and 16 in the global deaths statistics （1）. Thus, in 2010, ca. 1 million people died from liver cirrhosis with one third directly attributable to alcohol. This is a considerable number when comparing with coronary heart disease with 7 million deaths and the leading cause of mortality. In central Europe, liver cirrhosis even ranks at the fourth position in YLL. Hepatocellular cancer （HCC） is now the most common fatal complication of patients with alcoholic cirrhosis. Moreover, it shows the second fastest increase of all tumors worldwide after kidney tumors and alcohol-associated HCC ranks on third position after HCCs caused by viral hepatitis B and C.展开更多
Asymmetric blockage of drainage systems occasionally occurs,which seriously threatens the safety of tunnel operation.Based on theoretical analysis,a calculation expression of tunnel water inflow involving clogging par...Asymmetric blockage of drainage systems occasionally occurs,which seriously threatens the safety of tunnel operation.Based on theoretical analysis,a calculation expression of tunnel water inflow involving clogging parameters was derived.Degradation of the analytical solution was analysed with the Taylor equation and series expansion theorem,and a tunnel under construction was considered to conduct field tests to verify the rationality of the established model and correctness of the derived expression.Studies have demonstrated that with increasing drainage system blockage degree,the amount of water inflow in the nonblocked area slowly increases,and the total amount of water in the tunnel gradually decreases.The hydrodynamic pressure in the blocked area non-linearly decreased,and the water inrush velocity and hydraulic gradient in the non-blocked area gradually increased.When the drainage system was not blocked,the result of tunnel water inflow calculated by the formula derived in this paper was 8.3% higher than the measured value.When the drainage system was blocked,the theoretical water inflow was 10.5% higher than the measured value.The difference between the measured value and the theoretical value is small,which verifies the effectiveness of the calculation formula of water inflow deduced in this paper.展开更多
The effect of lateral walls on fluid flow and heat transfer is investigated when a fluid passes a magnetic obstacle. The blockage ratio β that represents the ratio between the width of external magnet M y and the spa...The effect of lateral walls on fluid flow and heat transfer is investigated when a fluid passes a magnetic obstacle. The blockage ratio β that represents the ratio between the width of external magnet M y and the spanwise width L y is employed to depict the effect. The finite volume method （FVM） based on the PISO algorithm is applied for the blockage ratios of 0.2, 0.3, and 0.4. The results show that the value of Strouhal number St increases as the blockage ratio β increases, and for small β , the variation of St is very small when the interaction parameter and Reynolds number are increasing. Moreover, the cross-stream mixing induced by the magnetic obstacle can enhance the wall-heat transfer and the maximum value of the overall heat transfer increment is about 50.5%.展开更多
It is a common phenomenon during CBM drilling and production that reservoir damage is not eliminated completely.In view of this,a technical idea of composite pulsating hydraulic fracturing of radial horizontal wells w...It is a common phenomenon during CBM drilling and production that reservoir damage is not eliminated completely.In view of this,a technical idea of composite pulsating hydraulic fracturing of radial horizontal wells which is conducive to blockage removing and stimulation was put forward in this paper.Speaking of the hydraulic jetting in a multi-branch radial well,it is to conduct pulsating hydraulic fracturing moderately through a high-diversion radial hole,so as to crush and break coal beds near the main hole to the uttermost.Thus,an extensive pressure relief and permeability increase area where high-diversion pathways are combined with fracture networks is formed.Then,to verify its technical principles,laboratory tests on pulsating hydraulic fracturing of radial wells were designed and carried out.Besides,the relationships of the features of acoustic emission(AE)response during the formation of fractures by composite fracturing of radial horizontal wells vs.coal breaking degree and macro fracture morphology were experimentally studied by using a pulse servo fatigue testing machine and an acoustic emission detector.And the following research results were obtained.First,under experimental conditions,fractures initially occur when the pressure of composite pulsating hydraulic fracturing of radial horizontal wells is 1/3–1/4 of the peak pressure of conventional fracturing,and the amount of its AE events is 1.38–7.07 times that of conventional fracturing.Second,when composite pulsating hydraulic fracturing of radial horizontal wells is conducted,AE emission signals respond strongly,the peak pressure for macro fracturing is lower and a larger fracture network can be generated more easily under the same condition.Third,radial laterals amount,borehole length,dynamic loading frequency and amplitude are the important factors affecting the effect of composite pulsating hydraulic fracturing of radial horizontal wells.In conclusion,composite pulsating hydraulic fracturing of radial horizontal wells provides a new idea of removing the blockages in CBM reservoirs and developing CBM efficiently,realizing effective blockage removing and stimulation of CBM wells.展开更多
Drainage pipe system is the requisite component of the traffic tunnels in Karst area.To reveal the dynamic process of crystallization blockage in drainage pipes,a novel hydrodynamics and hydrochemistry coupled simulat...Drainage pipe system is the requisite component of the traffic tunnels in Karst area.To reveal the dynamic process of crystallization blockage in drainage pipes,a novel hydrodynamics and hydrochemistry coupled simulation model was developed for calculating the deposition rate of CaCO_(3) fouling in pipeline surface.Sediments adhering to the pipe walls involve a deformable domain with moving geometric boundaries,and moving mesh and level set methods are proposed for simulation of for tunnel turbulence and crystallization fouling process.The simulation results are compared with the experimental results showing similar trend.The effects of temperature,flow velocity,and solution concentration on crystallization blockage were analyzed by comparative simulation studies.The simulation results show that:(1)the moving mesh method simulated nozzle shrinkage caused by crystalline deposition,without accounting for geometric topology shape changes.However,the level set method tracked the moving topology and thus can simulate the process of complete blockage;(2)the flow velocity in the longitudinal pipe generally exceeded that in the transverse pipe,and the CaCO_(3) crystal concentration in the transverse pipe eclipsed that in the longitudinal pipe,which meant crystallization blockages primarily occurred in the transverse pipe;(3)the temperature and concentration correlated positively with the crystallization rate,while the crystal precipitation value decreases with the increasing of inlet flow velocity increases.This study advances a hydrodynamics and hydrochemistry coupled crystallization blockage model to provide technical support for the early identification of crystallizationinduced pipe blockage in the drainage system in karst tunnel sites.展开更多
The present study aims to plumb blockage of the deep-sea mining pump transporting large particles with different shapes. A numerical work was performed through combining the computational fluid dynamics(CFD) technique...The present study aims to plumb blockage of the deep-sea mining pump transporting large particles with different shapes. A numerical work was performed through combining the computational fluid dynamics(CFD) technique and the discrete element method(DEM). Six particle shapes with sphericity ranging from 0.67 to 1.0 were selected. A velocity triangle is built with the absolute, relative, and circumferential velocities of particles. Velocity triangles with absolute velocity angles ranging from 90° to 180° prevail in the first-stage impeller. With declining sphericity, more particles follow the velocity triangle with absolute velocity angles ranging from 0° to 90°, which weakens the ability of particles to pass through the flow passage. Furthermore, the forces acting on the particles traveling in the impeller passage are analyzed. Large particles, especially non-spherical ones, suffer from high centrifugal force and therefore move along the suction surface of the impeller blades. Non-spherical particles undergo great drag force as a result of large surface area. The distribution of drag force angles is featured by two peaks, and one vanishes due to blockage.As particle sphericity declines, both magnitude and angle of the pressure gradient force decrease. Variation of the drag force and the pressure gradient force causes clockwise deflection of the centripetal force, resulting in deflection and elongation of particle trajectory, which increases the possibility of blockage.展开更多
Stream blockage by the debris flow from tributary valleys is a common phenomenon in mountainous area,which takes place when large quantities of sediment transported by debris flow reaches a river channel causing its c...Stream blockage by the debris flow from tributary valleys is a common phenomenon in mountainous area,which takes place when large quantities of sediment transported by debris flow reaches a river channel causing its complete or partial blockage.The dam formed by debris flow may causes upstream and downstream flooding,and presents great threat to people and property.Because of the catastrophic influence on people and property,debris-flow dam has attracted many attentions from the researchers and local adm...展开更多
Various sources of solid particles might exist in the coolant flow of a liquid metal cooled fast reactor(e.g.,through chemical interaction between the coolant and impurities,air,or water,through corrosion of structura...Various sources of solid particles might exist in the coolant flow of a liquid metal cooled fast reactor(e.g.,through chemical interaction between the coolant and impurities,air,or water,through corrosion of structural materials,or from damaged/molten fuel).Such particles may cause flow blockage accidents in a fuel assembly,resulting in a reduction in coolant flow,which potentially causes a local temperature rise in the fuel cladding,cladding failure,and fuel melt.To understand the blockage formation mechanism,in this study,a series of simulated experiments was conducted by releasing different solid particles from a release device into a reducer pipe using gravity.Through detailed analyses,the influence of various experimental parameters(e.g.,particle diameter,capacity,shape,and static friction coefficient,and the diameter and height of the particle release nozzle)on the blockage characteristics(i.e.,blockage probability and position)was examined.Under the current range of experimental conditions,the blockage was significantly influenced by the aforementioned parameters.The ratio between the particle diameter and outlet size of the reducer pipe might be one of the determining factors governing the occurrence of blockage.Specifically,increasing the ratio enhanced blockage(i.e.,larger probability and higher position within the reducer pipe).Increasing the particle size,particle capacity,particle static friction coefficient,and particle release nozzle diameter led to a rise in the blockage probability;however,increasing the particle release nozzle height had a downward influence on the blockage probability.Finally,blockage was more likely to occur in non-spherical particles case than that of spherical particles.This study provides a large experimental database to promote an understanding of the flow blockage mechanism and improve the validation process of fast reactor safety analysis codes.展开更多
基金supported by the National Natural Science Foundation of China(52476058,U21B2065,52006024,and 52306188)the National Key Research and Development(2022YFC2806200).
文摘With the development of offshore oil and gas resources,hydrates pose a significant challenge to flow assurance.Hydrates can form,accumulate,and settle in pipelines,causing blockages,reducing transport capacity,and leading to significant economic losses and fatalities.As oil and gas exploration moves deeper into the ocean,the issue of hydrate blockages has become more severe.It is essential to take adequate measures promptly to mitigate the hazards of hydrate blockages after they form.However,a prerequisite for effective mitigation is accurately detecting the location and amount of hydrate formation.This article summarizes the temperature–pressure,acoustic,electrical,instrumental–response,and flow characteristics of hydrate formation and blocking under various conditions.It also analyzes the principles,limitations,and applicability of various blockage detection methods,including acoustic,transient,and fiber-optic-based methods.Finally,it lists the results of field experiments and commercially used products.Given their advantages of accuracy and a wide detection range,acoustic pulse reflectometry and transient-based methods are considered effective for detecting hydrate blockages in future underwater pipelines.Using strict backpressure warnings combined with accurate detection via acoustic pulse reflectometry or transient-based methods,efficient and timely diagnosis of hydrate blockages can be achieved.The use of a hydrate model combined with fiber optics could prove to be an effective method for detecting blockages in newly laid pipelines in the future.
文摘By investigating the performance characteristics of the bio-based surfactant 8901A,a composite decontamination and injection system was developed using 8901A as the primary agent,tailored for application in low-permeability and heavy oil reservoirs under varying temperature conditions.The results demonstrate that this system effectively reduces oil–water interfacial tension,achieving an ultra-low interfacial tension state.The static oil washing efficiency of oil sands exceeds 85%,the average pressure reduction rate reaches 21.55%,and the oil recovery rate improves by 13.54%.These enhancements significantly increase the system’s ability to dissolve oilbased blockages,thereby lowering water injection pressure caused by organic fouling,increasing the injection volume of injection wells,and ultimately improving oil recovery efficiency.
文摘The appearance of flow instabilities like the blockage severity,impeller cut flaws,pitted cover plate flaws can cause to diminish the efficiency of centrifugal pump(CP),and may result in excessive vibration and noise,and their failure may lead to the system imploding.To bridge the gap of downfall in the efficiency of CP,it is crucial that a system can be created to monitor the condition of the CP and must be maintained.The present work proposes at identifying and determining the severity of various blockage levels in the inlet pipe with three different kinds of pumps using three distinct sensors.One pump works faultlessly(healthy pump),another has cuts artificially made on the impeller blade,and the third has pits artificially created on the cover plate.The inlet pipe blockage mimics pump blockage which is made more severe step by step.As the blockage gets worse and the flow slows down,recirculation starts,causing vapor bubbles to form.Utilizing a mechanical modulating valve,the inlet flow area of the pipe is partitioned into six intervals(0%,16.7%,33.3%,50%,66.6%,and 83.33%)to replicate pump blockage.This obstruction directly influences vibrations,current line signals,and fluid dynamic pressure.To gather data across a spectrum of blockage levels and operational frequencies(30 Hz,35 Hz,40 Hz,45 Hz,50 Hz,55 Hz,and 60 Hz),a combination of a pressure transducer,accelerometer,and current probes were strategically employed in this investigation.Multiple sets of statistical features were extracted from the data,and through various algorithms,the most effective combined statistical feature set was determined.In this domain,the combination of standard deviation,mean,and entropy demonstrates superior performance compared to other features.This feature set was input into an ANN model,which is developed by optimizing parameters like hidden layer count,neurons,epochs and then the results of this investigation are then compared with existing literature.It has been noted that employing combinations of multiple sets of statistical features significantly improves the accuracy in identifying obstruction levels,often achieving near-perfect accuracy for various feature sets(nearly 100%across various combinations).In comparison to other SOTA methods,this approach achieves higher accuracy,ranging from 2.41%to 15.69%across different metrics.This study presents a method to classify inlet pipe blockages into various levels,enhancing maintenance prioritization and reducing downtime and repair costs,ensuring long-term equipment health and operational efficiency.The fault prediction methodology proves highly robust across various CP operating conditions.
文摘This work focuses on the development and implementation of a simulation-based approach for the detection of partial and extended blockages within an edible oil pipeline system. Blockages, whether partial or extended, pose a significant operational and safety risks. This study employs computational fluid dynamics (CFD) simulations to model the flow behaviour of edible oil through pipeline under varying conditions. It leverages advanced computational fluid dynamics (CFD) simulations to analyze pressure, velocity, and temperature variations along the pipeline. By simulating scenarios with different blockage characteristics, there is establishment of distinctive patterns indicative of partial and extended obstructions. Through extensive analysis of simulation data, sensing element, and monitoring system, processing signal input and response output, the system can accurately pinpoint the location and severity of blockages, providing crucial insights for timely intervention. The detection system represents a significant advancement in pipeline monitoring technology, offering a proactive and accurate approach to identify blockages and mitigate potential risks and ensure the uninterrupted flow of edible oil, thereby enabling timely intervention and maintenance.
基金Project supported by the National Program on Key Basic Research Project(973 Program)"Basic research on safe and efficient drilling and completion of marine deepwater oil and gas wells"(No.:2015CB251204)the National Science Foundation for Distinguished Young Scholars“Theory and application of multiphase flow of oil and gas wells”(No.:51622405).
文摘Due to the uncertainties in formation mechanism of gas hydrate blockages in strings during the test of deep-water gas wells,inhibitors are either excessively consumed or inefficiently used when conventional prevention techniques are used.In this paper,a study was conducted on multi-phase flows,in terms of hydrate formation kinetics and hydrate particle migration and settlement kinetics.In this process,a model for quantitative prediction of hydrate blockage was built to predict when and where the blockage occurs in the strings and evaluate the severity of such blockage,in order to define the high-risk zones.Eventually,an innovative hydrate blockage prevention technique based on hydrate blockage free window(HBFW)was proposed to determine the optimal concentration and the flow rate of inhibitors.The study results are in the following four aspects.First,gas hydrates generated in the wellbore may deposit on the internal walls of strings.With the increase in thicknesses of such gas hydrate layers,the diameter of a pipe string decreases.Accumulation of gas hydrates generated around liquid film on pipe walls is the key contributor to the blockage in strings.Second,as the water depth increases or the gas production reduces,the HBFW turns to be narrower for production safety,and the time to initiate blockage is shorter.Third,application of hydrate inhibitors can effectively delay the occurrence of blockage and expand the window of safe production.Fourth,the innovative prevention technique can effectively reduce the volume and the flow rate of inhibitors(by 50%in the case study).The innovative technique effectively eliminates the problems related to the excessive consumption of inhibitors in the conventional methods and provides a valuable reference for the prevention of gas hydrates formation in deep-water gas well tests.
基金the National Natural Science Foundation of China(No.12175080)the Fundamental Research Funds for the Central Universities(No.CCNU22JC009),China.
文摘Inverse stochastic resonance(ISR)is a phenomenon in which the firing activity of a neuron is inhibited at a certain noise level.In this paper,the effects of potassium channel blockage on ISR in single Hodgkin-Huxley neurons and in small-world networks were investigated.For the single neuron,the ion channel noise-induced ISR phenomenon can occur only in a certain small range of potassium channel blockage ratio.Bifurcation analysis showed that this small range is the bistable region regulated by the external bias current.For small-world networks,the effect of non-homogeneous network blockage on ISR was investigated.The network blockage ratio was used to represent the proportion of potassium-channel-blocked neurons to total network neurons.It is found that an increase in network blockage ratio at small coupling strengths results in shorter ISR duration.When the coupling strength is increased,the ISR is more significant in the case of a large network blockage ratio.The ISR phenomenon is determined by the network blockage ratio,the coupling strength,and the ion channel noise.Our results will provide new perspectives on the observation of ISR in neuroscience experiments.
基金Project supported by the Scientific Research and Technology Development Project of PetroChina Southwest Oil and Gas Field Company“Research on Hydrate plugging removal Technology for Ultra-high pressure Gas Wells”(No.20180303-03).
文摘In order to safely,efficiently and economically remove the blockages of natural gas hydrate(NGH)in the wellbores of ultra-high pressure gas wells,this paper utilized the heat released from an independently developed autogenetic heat based solid blockage remover through chemical reaction in the wellbore to dissolve NGH and prevent it from forming again.In addition,adjustable heat generation time and heat generation amount was realized by regulating the dosage of the blockage remover.Finally,the chemically autogenetic heat based blockage removal technology was applied to remove the blockages in ultra-high pressure sour gas wells in the Sichuan Basin.And the following research results were obtained.First,when the independently developed chemically autogenetic heat based solid blockage remover is adopted,the peak temperature(34.2e88.5℃)and time(24.2e884.0 min)of heat generation can be adjusted by its dosage.What's more,there is NGH inhibitor in the reaction product,which can inhibit the regeneration of NGH.Second,as the concentration of the blockage remover increases,the heat transfer speed increases,leading to an increase of NGH dissociation rate around the blockage remover.Third,blockage removal time increases with the increase of wellbore ID.In addition,the increasing rate of the blockage removal time as the wellbore ID increases from 64 mm to 76 mm is lower than that from 76 mm to 102 mm.Fourth,the coincidence rate between the simulation calculation result of heat diffusion and the on-site actual consumption is more than 85%,which indicates that the proposed model for the heat diffusion of chemically autogenetic heat based blockage remover is reliable and can be used to calculate the dosage of blockage remover.Fifth,solid reagent adding device with resistance to sulfur and pressure of 140 MPa is used to add autogenetic heat based solid blockage remover.This blockage remover has been applied in the ultra-high pressure sour gas wells in the Sichuan Basin three well times.Thanks to its application,NGH blockages in these wells are removed successfully and their production is resumed smoothly.In conclusion,this blockage removal technology has such advantages as effective blockage removal,safe and simple on-site operation and low cost,and a promising application prospect.
基金financially supported by the China Postdoctoral Science Foundation (No.2021M690362)the National Natural Science Foundation of China (Nos.51974014 and U2034206)。
文摘Detecting a pipeline's abnormal status,which is typically a blockage and leakage accident,is important for the continuity and safety of mine backfill.The pipeline system for gravity-transport high-density backfill(GHB)is complex.Specifically designed,efficient,and accurate abnormal pipeline detection methods for GHB are rare.This work presents a long short-term memory-based deep learning(LSTM-DL)model for GHB pipeline blockage and leakage diagnosis.First,an industrial pipeline monitoring system was introduced using pressure and flow sensors.Second,blockage and leakage field experiments were designed to solve the problem of negative sample deficiency.The pipeline's statistical characteristics with different working statuses were analyzed to show their complexity.Third,the architecture of the LSTM-DL model was elaborated on and evaluated.Finally,the LSTM-DL model was compared with state-of-the-art(SOTA)learning algorithms.The results show that the backfilling cycle comprises multiple working phases and is intermittent.Although pressure and flow signals fluctuate stably in a normal cycle,their values are diverse in different cycles.Plugging causes a sudden change in interval signal features;leakage results in long variation duration and a wide fluctuation range.Among the SOTA models,the LSTM-DL model has the highest detection accuracy of98.31%for all states and the lowest misjudgment or false positive rate of 3.21%for blockage and leakage states.The proposed model can accurately recognize various pipeline statuses of complex GHB systems.
基金financially supported by the National Natural Science Foundation of China(Grant No.51679052)the Natural Science Foundation of Heilongjiang Province of China(Grant No.E2018026)the Defense Industrial Technology Development Program(Grant No.JCKY 2016604B001)
文摘When a ship model test is performed in a tank, particularly when the tank is small and the ship model is relatively large, the blockage effect will inevitably occur. With increased ship model scale and speed, the blockage effect becomes more obvious and must be corrected. In this study, the KRISO 3600 TEU Container Ship (KCS) is taken as a model and computational fluid dynamics techniques and ship resistance tests are applied to explore the mechanism and correction method of the blockage effect. By considering the degrees of freedom of the sinkage and trim, the resistance of the ship model is calculated in the infinite domain and for blockage ratios of 1.5%, 1.8%, 2.2%, and 3.0%. Through analysis of the free surface, pressure distribution, and flow field around the ship model, the action law of the blockage effect is studied. The Scott formula and mean flow correction formula based on the average cross sectional area are recommended as the main correction methods, and these formulas are improved using a factor for the return flow velocity correction based on comparison of the modified results given by different formulas. This modification method is verified by resistance test data obtained from three ship models with different scale ratios.
文摘In this paper, we perform an unprotected partial flow blockage analysis of the hottest fuel assembly in the core of the SNCLFR-100 reactor, a 100 MW_(th) modular natural circulation lead-cooled fast reactor, developed by University of Science and Technology of China. The flow blockage shall cause a degradation of the heat transfer between the fuel assembly and the coolant potentially,which can eventually result in the clad fusion. An analysis of core blockage accidents in a single assembly is of great significance for LFR. Such scenarios are investigated by using the best estimation code RELAP5. Reactivity feedback and axial power profile are considered. The crosssectional fraction of blockage, axial position of blockage,and blockage-developing time are discussed. The cladding material failure shall be the biggest challenge and shall be a considerable threat for integrity of the fuel assembly if the cross-sectional fraction of blockage is over 94%. The blockage-developing time only affects the accident progress. The consequence will be more serious if the axial position of a sudden blockage is closer to the core outlet.The method of analysis procedure can also be applied to analyze similar transient behaviors of other fuel-type reactors.
基金supported by the Basic Research Program Project of Qinghai Province(No.2020-ZJ-758)the Special Fund on the Exploration of Clean Energy and Mineral Products in Qinghai Province(20181317146sh 007)partially financed by the General Project of Shandong Natural Science Foundation(ZR2020ME090)。
文摘The blockage induced by particle migration and deposition is one of the main reasons for the decrease of reinjection capacity in the porous geothermal reservoir with a low and medium temperature.In this paper,a new drilled geothermal well in Xining basin China is taken as an example to investigate the formation blockage risk due to the movable clay and sand particles in pores.The physical properties of the reservoir rocks were analyzed,a series of pumping and reinjection tests were conducted,and the longterm reinjection performance of the well was predicted by numerical simulation based on the test fitting.The results show that the geothermal reservoir rocks are argillaceous and weakly cemented sandstones with a content of movable clay and sand particles up to 0.18–23.42 wt.%.The well presented a high productivity of 935–2186 m3?d-1 at a pressure difference of 0.7–1.62 MPa in the pumping tests associated with a large amount of clay and sand particles produced out,while in the reinjection test,only a low injectivity of 240–480 m3?d-1 was observed at an injection pressure of 0.2–0.6 MPa with the clay and sand particles near the wellbore move into deep.According to the prediction,under conditions of a blockage risk,the injectivity of the well will start to decline after 100 days of injection,and in the third year,it will decrease by 59.00%–77.09%.The influence of invasion of pretreated suspended particles and scale particles can be neglected.Under conditions of a high blockage risk,the injectivity of the well will decrease significantly in the first 20–30 days,with a decline of 75.39%–78.96%.Generally,the higher the injection pressure or rate,the greater the decrease in injectivity of the well caused by particle blockage.Pump lifting is an effective measure to remove the well blockage which can be used regularly.
文摘To predict the thermal-hydraulic(T/H)parameters of the reactor core for liquid-metal-cooled fast reactors(LMFRs),especially under flow blockage accidents,we developed a subchannel code called KMC-FB.This code uses a time-dependent,four-equation,singlephase flow model together with a 3D heat conduction model for the fuel rods,which is solved by numerical methods based on the finite difference method with a staggered mesh.Owing to the local effect of the blockage on the flow field,low axial flow,increased forced crossflow,and backflow occur.To more accurately simulate this problem,we implemented a robust and novel solution method.We verified the code with a low-flow(~0.01 m/s)and large-scale blockage case.For the preliminary validation,we compared our results with the experimental data of the NACIE-UP BFPS blockage test and the KIT19ROD blockage test.The results revealed that KMC-FB has sufficient solution accuracy and can be used in future flow blockage analyses for LMFRs.
文摘Chronic alcohol consumption is a major risk factor worldwide affecting significantly both mortality and years of life lost （YLL） （1）. Ca. 5% of the western world show risky alcohol consumption and in some countries such as China a regional yearly increase of alcohol consumption of over 400% has been observed recently （2,3）. The liver is the major target organ of alcohol. According to the recently published ＇Global Burden of Disease Study 2010, liver cirrhosis and liver cancer are ranked at position 12 and 16 in the global deaths statistics （1）. Thus, in 2010, ca. 1 million people died from liver cirrhosis with one third directly attributable to alcohol. This is a considerable number when comparing with coronary heart disease with 7 million deaths and the leading cause of mortality. In central Europe, liver cirrhosis even ranks at the fourth position in YLL. Hepatocellular cancer （HCC） is now the most common fatal complication of patients with alcoholic cirrhosis. Moreover, it shows the second fastest increase of all tumors worldwide after kidney tumors and alcohol-associated HCC ranks on third position after HCCs caused by viral hepatitis B and C.
基金sponsored by the Research Project on the Damage Mechanism and Performance Recovery of Carbon Phyllite in the Basement of HighSpeed Railway Tunnels in Cold Regions(51978668)the Key Technology of Green Construction of the Hongtu Extra Tunnel(DFH(201904)ys1-001)。
文摘Asymmetric blockage of drainage systems occasionally occurs,which seriously threatens the safety of tunnel operation.Based on theoretical analysis,a calculation expression of tunnel water inflow involving clogging parameters was derived.Degradation of the analytical solution was analysed with the Taylor equation and series expansion theorem,and a tunnel under construction was considered to conduct field tests to verify the rationality of the established model and correctness of the derived expression.Studies have demonstrated that with increasing drainage system blockage degree,the amount of water inflow in the nonblocked area slowly increases,and the total amount of water in the tunnel gradually decreases.The hydrodynamic pressure in the blocked area non-linearly decreased,and the water inrush velocity and hydraulic gradient in the non-blocked area gradually increased.When the drainage system was not blocked,the result of tunnel water inflow calculated by the formula derived in this paper was 8.3% higher than the measured value.When the drainage system was blocked,the theoretical water inflow was 10.5% higher than the measured value.The difference between the measured value and the theoretical value is small,which verifies the effectiveness of the calculation formula of water inflow deduced in this paper.
基金the National Natural Science Foundation of China(Grant No.51176073)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20103218110027)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD),China
文摘The effect of lateral walls on fluid flow and heat transfer is investigated when a fluid passes a magnetic obstacle. The blockage ratio β that represents the ratio between the width of external magnet M y and the spanwise width L y is employed to depict the effect. The finite volume method （FVM） based on the PISO algorithm is applied for the blockage ratios of 0.2, 0.3, and 0.4. The results show that the value of Strouhal number St increases as the blockage ratio β increases, and for small β , the variation of St is very small when the interaction parameter and Reynolds number are increasing. Moreover, the cross-stream mixing induced by the magnetic obstacle can enhance the wall-heat transfer and the maximum value of the overall heat transfer increment is about 50.5%.
基金supported by National Natural Science Foundation of China-General Program“Study on fracturing control mechanism for radial drilling through water jet in coal rocks”(No.:51674275)National Natural Science Foundation of China-Major Program“Theory of safe and quality drilling for shale oil and gas development under the mode of multi-coupling”(No.:51490652)。
文摘It is a common phenomenon during CBM drilling and production that reservoir damage is not eliminated completely.In view of this,a technical idea of composite pulsating hydraulic fracturing of radial horizontal wells which is conducive to blockage removing and stimulation was put forward in this paper.Speaking of the hydraulic jetting in a multi-branch radial well,it is to conduct pulsating hydraulic fracturing moderately through a high-diversion radial hole,so as to crush and break coal beds near the main hole to the uttermost.Thus,an extensive pressure relief and permeability increase area where high-diversion pathways are combined with fracture networks is formed.Then,to verify its technical principles,laboratory tests on pulsating hydraulic fracturing of radial wells were designed and carried out.Besides,the relationships of the features of acoustic emission(AE)response during the formation of fractures by composite fracturing of radial horizontal wells vs.coal breaking degree and macro fracture morphology were experimentally studied by using a pulse servo fatigue testing machine and an acoustic emission detector.And the following research results were obtained.First,under experimental conditions,fractures initially occur when the pressure of composite pulsating hydraulic fracturing of radial horizontal wells is 1/3–1/4 of the peak pressure of conventional fracturing,and the amount of its AE events is 1.38–7.07 times that of conventional fracturing.Second,when composite pulsating hydraulic fracturing of radial horizontal wells is conducted,AE emission signals respond strongly,the peak pressure for macro fracturing is lower and a larger fracture network can be generated more easily under the same condition.Third,radial laterals amount,borehole length,dynamic loading frequency and amplitude are the important factors affecting the effect of composite pulsating hydraulic fracturing of radial horizontal wells.In conclusion,composite pulsating hydraulic fracturing of radial horizontal wells provides a new idea of removing the blockages in CBM reservoirs and developing CBM efficiently,realizing effective blockage removing and stimulation of CBM wells.
基金jointly supported by the National Key Research and Development Program of China(No.2019YFC1804304)the National Natural Science Foundation of China(No.U2167212)。
文摘Drainage pipe system is the requisite component of the traffic tunnels in Karst area.To reveal the dynamic process of crystallization blockage in drainage pipes,a novel hydrodynamics and hydrochemistry coupled simulation model was developed for calculating the deposition rate of CaCO_(3) fouling in pipeline surface.Sediments adhering to the pipe walls involve a deformable domain with moving geometric boundaries,and moving mesh and level set methods are proposed for simulation of for tunnel turbulence and crystallization fouling process.The simulation results are compared with the experimental results showing similar trend.The effects of temperature,flow velocity,and solution concentration on crystallization blockage were analyzed by comparative simulation studies.The simulation results show that:(1)the moving mesh method simulated nozzle shrinkage caused by crystalline deposition,without accounting for geometric topology shape changes.However,the level set method tracked the moving topology and thus can simulate the process of complete blockage;(2)the flow velocity in the longitudinal pipe generally exceeded that in the transverse pipe,and the CaCO_(3) crystal concentration in the transverse pipe eclipsed that in the longitudinal pipe,which meant crystallization blockages primarily occurred in the transverse pipe;(3)the temperature and concentration correlated positively with the crystallization rate,while the crystal precipitation value decreases with the increasing of inlet flow velocity increases.This study advances a hydrodynamics and hydrochemistry coupled crystallization blockage model to provide technical support for the early identification of crystallizationinduced pipe blockage in the drainage system in karst tunnel sites.
基金financially supported by the Science and Technology Plan Project of State Administration for Market Regulation of China (Grant No. 2021MK060)the National Key Research and Development Program of China (Grant No. 2021YFC2801600)+1 种基金the Postgraduate Research and Practice Innovation Program of Jiangsu Province (Grant No. KYCX20_3082)the Science and Technology Innovation Project from China State Shipbuilding Corporation Limited。
文摘The present study aims to plumb blockage of the deep-sea mining pump transporting large particles with different shapes. A numerical work was performed through combining the computational fluid dynamics(CFD) technique and the discrete element method(DEM). Six particle shapes with sphericity ranging from 0.67 to 1.0 were selected. A velocity triangle is built with the absolute, relative, and circumferential velocities of particles. Velocity triangles with absolute velocity angles ranging from 90° to 180° prevail in the first-stage impeller. With declining sphericity, more particles follow the velocity triangle with absolute velocity angles ranging from 0° to 90°, which weakens the ability of particles to pass through the flow passage. Furthermore, the forces acting on the particles traveling in the impeller passage are analyzed. Large particles, especially non-spherical ones, suffer from high centrifugal force and therefore move along the suction surface of the impeller blades. Non-spherical particles undergo great drag force as a result of large surface area. The distribution of drag force angles is featured by two peaks, and one vanishes due to blockage.As particle sphericity declines, both magnitude and angle of the pressure gradient force decrease. Variation of the drag force and the pressure gradient force causes clockwise deflection of the centripetal force, resulting in deflection and elongation of particle trajectory, which increases the possibility of blockage.
基金Supported by 973 Program (2003CB415206)China Postdoctoral Science Fetmdation and National Natural Science Foundation (49831010)
文摘Stream blockage by the debris flow from tributary valleys is a common phenomenon in mountainous area,which takes place when large quantities of sediment transported by debris flow reaches a river channel causing its complete or partial blockage.The dam formed by debris flow may causes upstream and downstream flooding,and presents great threat to people and property.Because of the catastrophic influence on people and property,debris-flow dam has attracted many attentions from the researchers and local adm...
基金supported by the Basic and Applied Basic Research Foundation of Guangdong Province(Nos.2021A1515010343,2022A1515011582)the Science and Technology Program of Guangdong Province(Nos.2021A0505030026,2022A0505050029).
文摘Various sources of solid particles might exist in the coolant flow of a liquid metal cooled fast reactor(e.g.,through chemical interaction between the coolant and impurities,air,or water,through corrosion of structural materials,or from damaged/molten fuel).Such particles may cause flow blockage accidents in a fuel assembly,resulting in a reduction in coolant flow,which potentially causes a local temperature rise in the fuel cladding,cladding failure,and fuel melt.To understand the blockage formation mechanism,in this study,a series of simulated experiments was conducted by releasing different solid particles from a release device into a reducer pipe using gravity.Through detailed analyses,the influence of various experimental parameters(e.g.,particle diameter,capacity,shape,and static friction coefficient,and the diameter and height of the particle release nozzle)on the blockage characteristics(i.e.,blockage probability and position)was examined.Under the current range of experimental conditions,the blockage was significantly influenced by the aforementioned parameters.The ratio between the particle diameter and outlet size of the reducer pipe might be one of the determining factors governing the occurrence of blockage.Specifically,increasing the ratio enhanced blockage(i.e.,larger probability and higher position within the reducer pipe).Increasing the particle size,particle capacity,particle static friction coefficient,and particle release nozzle diameter led to a rise in the blockage probability;however,increasing the particle release nozzle height had a downward influence on the blockage probability.Finally,blockage was more likely to occur in non-spherical particles case than that of spherical particles.This study provides a large experimental database to promote an understanding of the flow blockage mechanism and improve the validation process of fast reactor safety analysis codes.
