Gypsum rocks are highly susceptible to mechanical deterioration under the coupled effects of wet-dry(W-D)cycles and flow rates,which significantly influence the stability of underground excavations.Despite extensive r...Gypsum rocks are highly susceptible to mechanical deterioration under the coupled effects of wet-dry(W-D)cycles and flow rates,which significantly influence the stability of underground excavations.Despite extensive research on the effects of W-D cycles,the coupling influence of flow rates and W-D cycles on gypsum rocks remains poorly understood.This study investigates the mechanical behavior and deterioration mechanisms of gypsum rocks subjected to varying W-D cycles and flow rate conditions.Axial compression tests,along with nuclear magnetic resonance(NMR)techniques,were employed to analyze the stress-strain response and microstructural changes.Based on the disturbed state concept(DSC)theory,a W-D deterioration model and a DSC-based constitutive model were developed to describe the degradation trends and mechanical responses of gypsum rocks under different conditions.The results demonstrate that key mechanical indices,elastic modulus,cohesion,uniaxial compressive strength(UCS),and internal friction angle,exhibit logarithmic declines with increasing W-D cycles,with higher flow rates accelerating the deterioration process.The theoretical models accurately capture the nonlinear compaction behavior,peak stress,and post-peak response of gypsum specimens.This study provides valuable insights for predicting the mechanical behavior of gypsum rocks and improving the stability assessments of underground structures under complex environmental conditions.展开更多
Offset-tracking is an essential method for deriving glacier flow rates using optical imagery.Sentinel-2(S2)and Landsat-8/9(L8/9)are popular optical satellites or constellations for polar studies,offering high spatial ...Offset-tracking is an essential method for deriving glacier flow rates using optical imagery.Sentinel-2(S2)and Landsat-8/9(L8/9)are popular optical satellites or constellations for polar studies,offering high spatial resolution with relatively short revisit time,wide swath width,and free accessibility.To evaluate and compare the precision of offset-tracking results yielded with these two kinds of data,in this study S2 and L8/9 imagery observed in Petermann Glacier in Greenland,Karakoram in High-Mountains Asia,and Amery Ice Shelf in the Antarctic are analyzed.Outliers and various systematic error sources in the offset-tracking results including orbital and strip errors were analyzed and eliminated at the pre-process stage.Precision at the off-glacier(bare rock)region was evaluated by presuming that no deformation occurred;then for both glacierized and the off-glacier regions,precision of velocity time series was evaluated based on error propagation theory.The least squares method based on connected components was used to solve flow rates time series based on multi-pair images offset-tracking.The results indicated that S2 achieved slightly higher precision than L8/9 in terms of both single-pair derived displacements and least square solved daily flow rates time series.Generally,the RMSE of daily velocity is 26%lower for S2 than L8/9.Moreover,S2 provided higher temporal resolution for monitoring glacier flow rates.展开更多
The qualitative and quantitative assessment of gas flow has become increasingly relevant in the use of everyday systems. The micro flow sensor, developed by Innovative Sensor Technology AG （Switzerland）, is by princ...The qualitative and quantitative assessment of gas flow has become increasingly relevant in the use of everyday systems. The micro flow sensor, developed by Innovative Sensor Technology AG （Switzerland）, is by principle a calorimetric flow sensor produced as a micro system on a glass substrate by means of photolithography and glass etching technology. These structures are arranged as a platinum micro heater and sensor in a Wheatstone bridge. The subsequent etching process produces an exposed area of polyimide membrane that is only a few microns thick and includes the resistive sensor structure as the active area. In addition, the RTD （resistance temperature detector） technology included on the sensor allows for the implementation of a variety of electronic biasing and signal processing modes. Since the sensor can be powered and the bridge can be measured in both CTA （constant temperature anemometer） and calorimetric mode, new possibilities are presented for both low and high flow rates with regard to temperature compensation, self-calibration and self-monitoring.展开更多
Lab scale biological treatment system was constructed from acrylic and operated using synthetic wastewater to evaluate the nitrification performance using different media. The media used for were Ceramic Ring A （CRA...Lab scale biological treatment system was constructed from acrylic and operated using synthetic wastewater to evaluate the nitrification performance using different media. The media used for were Ceramic Ring A （CRA）, Ceramic Ring B （CRB）, Japanese Filter Mat （JFM）, and Filter Wool （FW）. Laboratory studies were conducted, in order to evaluate the nitrification performance of different media types, at different synthetic wastewater flow rates, ranging from 0.03 to 0.045 m3/hr. The results from experiments suggest that at higher water flow rates, there was a decrease in nitrification for all media types. Based on the ammonia and nitrite removal rates, FW media gave the optimum nitrification, of up to 0.46 g/m2/day and 0.09 g/m2/day, respectively. Besides, in this study, the surface texture of the media is the main factor that affected the volumetric ammonia and nitrite conversion rates （VTR and VNR）. JFM gave the greatest VTR and VNR performance, compared with the other media展开更多
This paper discussed influences of flow rates of O_2, C_3H_8, and compressedair on the melting degree of particles during HVOF (high velocity oxy-fuel) sprayed CoCrW coating.The O_2 flow rate has the maximal effect on...This paper discussed influences of flow rates of O_2, C_3H_8, and compressedair on the melting degree of particles during HVOF (high velocity oxy-fuel) sprayed CoCrW coating.The O_2 flow rate has the maximal effect on the melting of particles, the C_3H_8 flow rate has thesecond, and the compressed air flow rate has the minimal effect. The bond strength of the HVOFsprayed CoCrW coating is over 54 MPa. The porosity ratio of the HVOF sprayed CoCrW coating afteroptimization of gas flow rates is less than 2%. The average microhardness of the coating is up toHV_(0.1) 545. The oxidation amount per unit area of the HVOF sprayed CoCrW coating increases withthe holding time increasing at 800℃. In the same way, the oxidation amount of the coating increasesas the temperature increases. Particularly, the oxidation of the coating drastically increases over850℃.展开更多
The flow velocity of gases in gobs directly influences the kinetics and intensity of gaseous components release during heating and cooling of coal.The assessment of fire hazard is performed on the basis of concentrati...The flow velocity of gases in gobs directly influences the kinetics and intensity of gaseous components release during heating and cooling of coal.The assessment of fire hazard is performed on the basis of concentrations of particular gases in a mine air.These concentrations differ in coal heating and cooling phase which was proven in the study.This paper presented the results of the experimental study on temperature distribution in a simulated coal bed in heating(50–250°C)and cooling(250–35°C)phases as well as its correlation to variations in concentration of gases released in these phases and flow rates of gases flowing through the coal bed.The research was performed on twenty-two samples of bituminous coals acquired from various coal beds of Polish coal mines.Considerable differences were observed between heating and cooling phases in terms of the concentrations of gases taken into account in calculations of self-combustion index.In the heating phase temperature increase resulted in the decrease of concentrations ratios of ethane,ethylene,propane,propylene and acetylene,while in the cooling phase these ratios increased systemically.The effect of air(in heating phase)and nitrogen(in cooling phase)flow rate on the self-ignition index CO/CO2 was also determined.展开更多
Vanadium redox flow battery(VRFB)is considered one of the most potential large-scale energy storage technolo-gies in the future,and its electrolyte flow rate is an important factor affecting the performance of VRFB.To...Vanadium redox flow battery(VRFB)is considered one of the most potential large-scale energy storage technolo-gies in the future,and its electrolyte flow rate is an important factor affecting the performance of VRFB.To study the effect of electrolyte flow rate on the performance of VRFB,the hydrodynamic model is established and a VRFB system is developed.The results show that under constant current density,with the increase of electrolyte flow rate,not only the coulombic efficiency,energy efficiency,and voltage efficiency will increase,but also the capacity and energy discharged by VRFB will also increase.But on the other hand,as the flow rate increases,the power of the pump also increases,resulting in a decrease in system efficiency.The energy discharged by the system does not increase with the increase in flow rate.Considering the balance between efficiency and pump power loss,it is experimentally proved that 120 mL·min-1 is the optimal working flow rate of the VRFB system,which can maximize the battery performance and discharge more energy.展开更多
This study proposes an alternative approach to the investigation of high flow hydrogeological fractures within the basement in the Dabakala region of north-central Côte d’Ivoire. The used approach consists o...This study proposes an alternative approach to the investigation of high flow hydrogeological fractures within the basement in the Dabakala region of north-central Côte d’Ivoire. The used approach consists of exploring the subsurface by measuring electrical resistivity contrasts along the main shear direction within crystallophyllian rocks. Electrical resistivity profiling and vertical electrical sounding techniques, coupled with boreholes monitoring, have identified fractured aquifers whose best flow rates are around 96 and 116 m<sup>3</sup>/h. These aquifers mostly hosted in granodiorite have an average strength of 10 meters and are located at depth of around 100 meters. They are associated with open fractures created by tangential shear stresses that have affected the Dabakala volcano-sedimentary trench formations. The search for fractured aquifers along the main shear direction offers great perspective for obtaining high flow rates.展开更多
Critical erosionflow rate is the key factor restricting the injection/production capacity of an injection/production well.At present,it is commonly calculated according to API RP 14E standard and its calculation resul...Critical erosionflow rate is the key factor restricting the injection/production capacity of an injection/production well.At present,it is commonly calculated according to API RP 14E standard and its calculation result tends to be conservative.So far,however,there is no definite laboratory experiment orfield data that can prove that critical erosionflow rate can be increased on the basis of API RP 14E.To deal this end,the concept of critical erosionflow rate was proposed based on corrosion rate for thefirst time in this paper.Then,a laboratory equivalent simulation experiment under real injection and production conditions was carried out by comprehensively taking into account the factors influencing string erosion(including temperature,pressure,gas component,water content,solid particle content and string material)while introducing the wall shear stress.Accordingly,the critical erosion coefficient(C)under experimental working conditions was calculated.Finally,a C value chart for three kinds of strings that are commonly used onfield(N80,SM80S and S13Cr)was established.And the following research results are ob-tained.First,solid particle content,water content,CO_(2)differential pressure and wall shear stress are the main erosion controlling factors.Second,solid particle content is the most significant factor that affects the erosion of N80,SM80S and S13Cr strings,and erosion of N80 and SM80S strings is more sensitive to wall shear stress and water content.Third,as for S13Cr string,the C value can be 100 when the solid particle content is lower than 250 mg/L,180 when thefluid contains liquid but no solid particles,and 275 when thefluid is gas phase.Fourth,as for N80 and SM80S strings,the C value can be in the range of 100e180 based on different water content and wall shear stress when thefluid contains liquid but no solid particles,and 275 when thefluid is in gas phase.Fifth,in view that thefluid produced from the injection/production wells of Hutubi gas storage has a water content of 0.0010‰without solid particles,S13Cr is adopted as string material and the C value is set at 180.It is shown in the laboratory erosion experiments that no erosion trace occurs on the string samples under injection and production conditions and the erosion rate is extremely low without point erosion.In conclusion,the C value chart established in this paper is reliable and can provide the guidance for the scientific and reasonable determination of critical erosionflow rate.展开更多
Axial flow pumps are widely used in water conservancy,petrochemical and agricultural industries.Efficient operation is crucial for energy conservation and emission reduction.Improving efficiency under severe condition...Axial flow pumps are widely used in water conservancy,petrochemical and agricultural industries.Efficient operation is crucial for energy conservation and emission reduction.Improving efficiency under severe conditions requires studying the internal flow of axial-flow pumps,particularly at low flow rates where backflow vortices form near the impeller inlet.This study investigates the unsteady flow characteristics of backflow vortices at different flow rates in an axial-flow pump.Results show that backflow vortices form when the flow rate decreases to 0.59Q_(d).As the flow rate further declines,the backflow vortex progresses upstream,contracts,and rebounds.The flow rate range is divided into three stages:Stage Ⅰ with no backflow vortex,stage Ⅱ with initial vortex development extending upstream and relatively fragmented,and stage Ⅲ with vortex contraction and rebound forming a more coherent structure.Besides,backflow vortices induce significant pressure fluctuations and velocity oscillations with the primary frequency being 0.5 fb.They exhibit a three-dimensional spiral motion involving changes in axial length,self-rotation,and revolution around the pump axis,with an angular velocity of approximately half the impeller’s rotational speed.This work enhances insights into backflow vortex behaviors,which is essential for optimizing pump design and improving operational stability in challenging environments.展开更多
Production flow rates are crucial to make operational decisions,monitor,manage,and optimize oil and gas fields.Flow rates also have a financial importance to correctly allocate production to fiscal purposes required b...Production flow rates are crucial to make operational decisions,monitor,manage,and optimize oil and gas fields.Flow rates also have a financial importance to correctly allocate production to fiscal purposes required by regulatory agencies or to allocate production in fields owned by multiple operators.Despite its significance,usually only the total field production is measured in real time,which requires an alternative way to estimate wells'production.To address these challenges,this work presents a back allocation methodology that leverages real-time instrumentation,simulations,algorithms,and mathe-matical programming modeling to enhance well monitoring and assist in well test scheduling.The methodology comprises four modules:simulation,classification,error calculation,and optimization.These modules work together to characterize the flowline,wellbore,and reservoir,verify simulation outputs,minimize errors,and calculate flow rates while honoring the total platform flow rate.The well status generated through the classification module provides valuable information about the current condition of each well(i.e.if the well is deviating from the latest well test parameters),aiding in decision-making for well testing scheduling and prioritizing.The effectiveness of the methodology is demonstrated through its application to a representative offshore oil field with 14 producing wells and two years of daily production data.The results highlight the robustness of the methodology in properly classifying the wells and obtaining flow rates that honor the total platform flow rate.Furthermore,the methodology supports well test scheduling and provides reliable indicators for well conditions.By uti-lizing real-time data and advanced modeling techniques,this methodology enhances production monitoring and facilitates informed operational decision-making in the oil and gas industry.展开更多
Rational allocation of water flow energy in river networks is essential to addressing water-related issues in river network areas.However,current methods of calculating the spatiotemporal distribution of flow energy i...Rational allocation of water flow energy in river networks is essential to addressing water-related issues in river network areas.However,current methods of calculating the spatiotemporal distribution of flow energy in river networks lack precision and efficiency.This paper introduces a novel hydrodynamic representation,the energy flow rate,defined as the product of the flow rate and kinetic energy head,to quantify the kinetic energy stored and transported in river networks.A linear equation system for the energy flow rate in a river network has been theoretically derived,enabling rapid calculations under steady flow conditions.A simplified equation is proposed to describe the exponential decay of the energy flow rate,accompanied by potential energy conversion.The coefficients in the linear equation system are determined using control equations at flow confluence and diversion nodes.This study provides foundational insights that can be used to develop new hydrodynamic modeling strategies to regulate water flow energy and achieve coordinated management of water-related issues in river networks.展开更多
This study involved numerical simulations of a double tube heat exchanger using the ANSYS FLUENT programversion 22.The study aims to examine methods for minimizing pressure loss and consequently enhancing the thermal ...This study involved numerical simulations of a double tube heat exchanger using the ANSYS FLUENT programversion 22.The study aims to examine methods for minimizing pressure loss and consequently enhancing the thermal performance index(TPI)of a heat exchanger fitted with wavy edge tape that is a heat recovery system(the hot air in simulation instead of t heat from the exhaust gases of the brick factory furnaces and return it to warm the heavy fuel oil by substituting the electrical heater with a heat exchanger to recuperate waste heat from the flue gases,so elevating the temperature of Heavy fuel oil(HFO)to inject from the roof nozzles of combustion chamber of the furnace furthermore reducing cost(by finding the optimal design of wavy edge tape))and energy consumption.Air was selected as the hot gas in the inner pipe instead of furnace exhaust gases due to their similar thermal characteristics.A numerical analysis was conducted to create a novel wavy edge tape with varying widths(50%Di,75%Di,and 95%Di),lengths(1000,1200,1400)mm,amplitudes(5,10,15)mm,and periods of wavy length(5,10,15)mm.The flow rate of the outer pipe fluid(oil)ranges from(0.06 to 0.1)kg/s,while the velocity of the hot fluid(air)varies from(1 to 27)m/s,Re_(air)(6957 to 187,837).The entrance temperature of the hot fluid can be either(200,225,and 250)℃.The study finds that wavy edge tape tubes are more effective than smooth tubes in terms of oil outlet temperature;results revealed that an increase in the oil mass flow rate leads to a decrease in the oil outlet temperature and an increase in the heat transfer rate,at the air temperature 250℃.Additionally,the results indicate that increasing the width,length,and amplitude also leads to an increase in the oil outlet temperature of(94-94.12)℃,the pressure drop of(568.3)Pa,and the Nusselt number(65.7-66.5)respectively on the oil side.Finally,the heat exchanger’s best thermal performance index was found by investigating temperature contour at amplitude(A=5),period(p=15),width(w=75%Di),and length(L=1200 mm).The values for these parameters are,in order(1.02,1.025,1.02,and 1.0077).展开更多
Experiments are conducted on the evacuation rate of pedestrians through exits with queued evacuation pattern and random evacuation pattern. The experimental results show that the flow rate of pedestrians is larger wit...Experiments are conducted on the evacuation rate of pedestrians through exits with queued evacuation pattern and random evacuation pattern. The experimental results show that the flow rate of pedestrians is larger with the random evacuation pattern than with the queued evacuation pattern. Therefore, the exit width calculated based on the minimum evacuation clear width for every 100 persons, which is on the assumption that the pedestrians pass through the exit in one queue or several queues, is conservative. The number of people crossing the exit simultaneously is greater in the random evacuation experiments than in the queued evacuation experiments, and the time interval between the front row and rear row of people is shortened in large-exit conditions when pedestrians evacuate randomly. The difference between the flow rate with a queued evacuation pattern and the flow rate with a random evacuation pattern is related to the surplus width of the exit, which is greater than the total width of all accommodated people streams. Two dimensionless quantities are defined to explore this relationship. It is found that the difference in flow rate between the two evacuation patterns is stable at a low level when the surplus width of the exit is no more than 45% of the width of a single pedestrian stream. There is a great difference between the flow rate with the queued evacuation pattern and the flow rate with the random evacuation pattern in a scenario with a larger surplus width of the exit. Meanwhile, the pedestrians crowd extraordinarily at the exit in these conditions as well, since the number of pedestrians who want to evacuate through exit simultaneously greatly exceeds the accommodated level. Therefore, the surplus width of exit should be limited especially in the narrow exit condition, and the relationship between the two dimensionless quantities mentioned above could provide the basis to some extent.展开更多
The two-fluid model coupled with population balance model was used for simulating the gas-liquid flow in the Ruhrstahl-Heraeus(RH)degasser.The predicted circulation flow rate was compared with that measured from a wat...The two-fluid model coupled with population balance model was used for simulating the gas-liquid flow in the Ruhrstahl-Heraeus(RH)degasser.The predicted circulation flow rate was compared with that measured from a water model experiment to validate the mathematical model.Then,influence of snorkel immersion depth on liquid circulation flow rate was numerically investigated under an atmospheric pressure of 101 and 84 kPa,respectively.Predicted result indicates that the circulation flow rate of the RH degasser in the high-altitude area was severely reduced because of the decrease in atmospheric pressure.However,increasing the snorkel immersion depth from 0.5 to 0.7 m can compensate for the decrease in atmospheric pressure.Industrial test result indicates that decarburization rate is significantly enhanced by increasing the snorkel immersion depth.Through optimization,the percentage of heats with a final carbon content less than 0.002 wt.%is significantly increased from 22.0%to 96.4%.展开更多
Geothermal energy has gained wide attention as a renewable alternative for mitigating greenhouse gas emissions.The advancements in enhanced geothermal system technology have enabled the exploitation of previously inac...Geothermal energy has gained wide attention as a renewable alternative for mitigating greenhouse gas emissions.The advancements in enhanced geothermal system technology have enabled the exploitation of previously inaccessible geothermal resources.However,the extraction of geothermal energy from deep reservoirs poses many challenges due to high‐temperature and high‐geostress conditions.These factors can significantly impact the surrounding rock and its fracture formation.A comprehensive understanding of the thermal–hydraulic–mechanical(THM)coupling effect is crucial to the safe and efficient exploitation of geothermal resources.This study presented a THM coupling numerical model for the geothermal reservoir of the Yangbajing geothermal system.This proposed model investigated the geothermal exploitation performance and the stress distribution within the reservoir under various combinations of geothermal wells and mass flow rates.The geothermal system performance was evaluated by the criteria of outlet temperature and geothermal productivity.The results indicate that the longer distance between wells can increase the outlet temperature of production wells and improve extraction efficiency in the short term.In contrast,the shorter distance between wells can reduce the heat exchange area and thus mitigate the impact on the reservoir stress.A larger mass flow rate is conducive to the production capacity enhancement of the geothermal system and,in turn causes a wider range of stress disturbance.These findings provide valuable insights into the optimization of geothermal energy extraction while considering reservoir safety and long‐term sustainability.This study deepens the understanding of the THM coupling effects in geothermal systems and provides an efficient and environmentally friendly strategy for a geothermal energy system.展开更多
Developing a novel drop counter by introducing the Internet of Things concept has been vigorously conducted in recent years. Understanding the newly introduced drop counter’s flow rate control accuracy and flow rate ...Developing a novel drop counter by introducing the Internet of Things concept has been vigorously conducted in recent years. Understanding the newly introduced drop counter’s flow rate control accuracy and flow rate count feature is essential for improving safety in infusion management. This study aimed to verify if the new drop counters could secure accurate flow rate and drip count by conducting actual flow rate measurements using gravimetry and functional evaluation. A drop counter was attached to each drip chamber of the infusion set, and an IV drip was conducted at the 100 ml/h flow rate. The weight of discharged physiological saline was measured to plot trumpet curves. Next, three different types of drop counters were evaluated to determine if they maintained drip count accuracy according to the changes in their position angles. The flow rate errors in all conditions indicated trumpet-like curves, exhibiting an overall error range within ±10% in all observation windows. Although every drop counter successfully detected and measured dripping, it was challenging in some counters to detect dripping when the drip chamber was tilted. In comparing adult and pediatric IV sets, the adult IV set was found to be less likely to detect dripping in the angled position. No significant differences in results were confirmed between high and low flow rates, suggesting that the drop count function would not be affected by the flow rate in the ranges of typical infusion practices. Doppler sensors have a wide range of measurements and high sensitivity;the dripping was detected successfully even when the drip chamber was tilted, probably due to the advantages of these sensors. In contrast, miscounts occurred in those equipped with infrared sensors, which could not detect light intensity changes in tilted positions. Understanding the tendencies in flow rate errors in infusion can be valuable information for infusion management.展开更多
The advancement in endoscopic technology and techniques has increased its use in the diagnosis and treatment of gastrointestinal diseases.Reprocessing of reusable endoscopes remains a challenge.Inadequate reprocessing...The advancement in endoscopic technology and techniques has increased its use in the diagnosis and treatment of gastrointestinal diseases.Reprocessing of reusable endoscopes remains a challenge.Inadequate reprocessing leads to bacterial contamination of the endoscope,a significant cause of endoscope-related infections.To thoroughly address the complexities of cleaning a flexible endo-scope,various cleaning methods have been devised and tested across different studies.This letter evaluates one such method,spray flushing for flexible gastro-scopes,developed and tested in a randomized controlled trial by Du et al.Based on the post-processing test results for this method,Du et al conclude that there is improved cleaning efficacy and reduced damage compared to manual brush cleaning.The validity and reliability of the results could be further enhanced by carefully considering the study design and a few underlying concepts that contribute to the reprocessing quality of different types of endoscopes.展开更多
Developing low-permeability Coalbed Methane(CBM)reservoirs can significantly benefit from a comprehensive understanding of hydraulic fracture nucleation and propagation mechanisms,particularly in anthracite CBM reserv...Developing low-permeability Coalbed Methane(CBM)reservoirs can significantly benefit from a comprehensive understanding of hydraulic fracture nucleation and propagation mechanisms,particularly in anthracite CBM reservoirs.This study employs true-triaxial hydraulic fracturing experiments to investigate these mechanisms,with variables including injection flow rate,horizontal stress difference(σH-σh),and bedding orientation.Additionally,we conduct corresponding numerical cases to validate the experimental conclusions.The research also considers re-fracturing instances.For the first time,we utilize a combination of Kaiser tests and the stress transfer function in ANSYS Workbench finite element analysis to accurately restore the confining pressure of the coal sample.The findings suggest that a high initial injection flow rate during hydraulic fracturing can promote fluid leakage and aid in maintaining substantial fracture pressure.Enhanced fracturing efficiency can be achieved through higher injection rates,and it can ensure optimal fracturing efficiency,minimizing roof and floor fracturing in coal reservoirs to prevent fracturing fluid leakage.The presence of a high horizontal stress difference facilitates hydraulic fracture propagation along the direction of the maximum horizontal compressive stress,requiring a greater hydraulic pressure to produce more fracture systems in coal reservoirs.Additionally,a minor deviation in the wellbore injection direction from the bedding orientation assists in creating a complex hydraulic fractured network,although this also requires higher hydraulic pressure to initiate new fractures.In the case of multiple hydraulic fracturing,the second initiation pressure tends to be significantly higher than the first,indicating that a sequential increase in hydraulic pressure aids the formation of additional fractures.Moreover,a simplified numerical simulation has been conducted to corroborate the experimental findings.These insights are crucial in optimizing hydraulic fracturing processes to enhance the permeability of anthracite CBM reservoirs.展开更多
With the widespread use of polyethylene(PE)materials in gas pipelines,the problem related to the aging of these pipes has attracted increasing attention.Especially under complex environmental conditions involving temp...With the widespread use of polyethylene(PE)materials in gas pipelines,the problem related to the aging of these pipes has attracted increasing attention.Especially under complex environmental conditions involving temperature,humidity,and pressure changes,PE pipes are prone to oxidative degradation,which adversely affects their performance and service life.This study investigates the aging behavior of PE pipes used for gas transport under the combined effects of temperature(ranging from 80℃to 110℃)and pressure(0,0.1,0.2,and 0.3 MPa).By assessing the characteristics and thermal stability of the aged pipes,relevant efforts are provided to explore the performance variations during the aging process and develop methods for evaluating thermal stability.The results indicate that an increase in aging factors,specifically temperature and pressure,significantly reduces theMeltMass Flow Rate(MFR)of polyethylene pipes,suggesting a decline in the material’s flowability during the aging process.Oxidative Induction Time(OIT)tests show that with increasing temperature and pressure,the oxidative induction time of the aged polyethylene pipes progressively shortens,indicating a significant reduction in the material’s oxidative stability.The application of the Arrhenius equation further demonstrates that the aging reaction rate of polyethylene pipes in high-temperature environments is closely related to both temperature and activation energy,thereby laying the foundation of a new approach for the development of an initial model that can reflect the microscopic behavior of polyethylene pipes in aging environments.展开更多
基金Projects(52378392,52478390)supported by the National Natural Science Foundation of ChinaProject(2024J08213)supported by the Natural Science Foundation of Fujian Province,China+1 种基金Project(00387088)supported by the“Foal Eagle Program”Youth Top-notch Talent Project of Fujian Province,ChinaProject(GY-Z23072)supported by the Scientific Research Foundation of Fujian University of Technology,China。
文摘Gypsum rocks are highly susceptible to mechanical deterioration under the coupled effects of wet-dry(W-D)cycles and flow rates,which significantly influence the stability of underground excavations.Despite extensive research on the effects of W-D cycles,the coupling influence of flow rates and W-D cycles on gypsum rocks remains poorly understood.This study investigates the mechanical behavior and deterioration mechanisms of gypsum rocks subjected to varying W-D cycles and flow rate conditions.Axial compression tests,along with nuclear magnetic resonance(NMR)techniques,were employed to analyze the stress-strain response and microstructural changes.Based on the disturbed state concept(DSC)theory,a W-D deterioration model and a DSC-based constitutive model were developed to describe the degradation trends and mechanical responses of gypsum rocks under different conditions.The results demonstrate that key mechanical indices,elastic modulus,cohesion,uniaxial compressive strength(UCS),and internal friction angle,exhibit logarithmic declines with increasing W-D cycles,with higher flow rates accelerating the deterioration process.The theoretical models accurately capture the nonlinear compaction behavior,peak stress,and post-peak response of gypsum specimens.This study provides valuable insights for predicting the mechanical behavior of gypsum rocks and improving the stability assessments of underground structures under complex environmental conditions.
基金supported by the National Natural Science Foundation of China(Grant no.42371136)the Guangdong Basic and Applied Basic Research Foundation(Grant no.2021B1515020032)the Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(Grant no.311022003).
文摘Offset-tracking is an essential method for deriving glacier flow rates using optical imagery.Sentinel-2(S2)and Landsat-8/9(L8/9)are popular optical satellites or constellations for polar studies,offering high spatial resolution with relatively short revisit time,wide swath width,and free accessibility.To evaluate and compare the precision of offset-tracking results yielded with these two kinds of data,in this study S2 and L8/9 imagery observed in Petermann Glacier in Greenland,Karakoram in High-Mountains Asia,and Amery Ice Shelf in the Antarctic are analyzed.Outliers and various systematic error sources in the offset-tracking results including orbital and strip errors were analyzed and eliminated at the pre-process stage.Precision at the off-glacier(bare rock)region was evaluated by presuming that no deformation occurred;then for both glacierized and the off-glacier regions,precision of velocity time series was evaluated based on error propagation theory.The least squares method based on connected components was used to solve flow rates time series based on multi-pair images offset-tracking.The results indicated that S2 achieved slightly higher precision than L8/9 in terms of both single-pair derived displacements and least square solved daily flow rates time series.Generally,the RMSE of daily velocity is 26%lower for S2 than L8/9.Moreover,S2 provided higher temporal resolution for monitoring glacier flow rates.
文摘The qualitative and quantitative assessment of gas flow has become increasingly relevant in the use of everyday systems. The micro flow sensor, developed by Innovative Sensor Technology AG （Switzerland）, is by principle a calorimetric flow sensor produced as a micro system on a glass substrate by means of photolithography and glass etching technology. These structures are arranged as a platinum micro heater and sensor in a Wheatstone bridge. The subsequent etching process produces an exposed area of polyimide membrane that is only a few microns thick and includes the resistive sensor structure as the active area. In addition, the RTD （resistance temperature detector） technology included on the sensor allows for the implementation of a variety of electronic biasing and signal processing modes. Since the sensor can be powered and the bridge can be measured in both CTA （constant temperature anemometer） and calorimetric mode, new possibilities are presented for both low and high flow rates with regard to temperature compensation, self-calibration and self-monitoring.
文摘Lab scale biological treatment system was constructed from acrylic and operated using synthetic wastewater to evaluate the nitrification performance using different media. The media used for were Ceramic Ring A （CRA）, Ceramic Ring B （CRB）, Japanese Filter Mat （JFM）, and Filter Wool （FW）. Laboratory studies were conducted, in order to evaluate the nitrification performance of different media types, at different synthetic wastewater flow rates, ranging from 0.03 to 0.045 m3/hr. The results from experiments suggest that at higher water flow rates, there was a decrease in nitrification for all media types. Based on the ammonia and nitrite removal rates, FW media gave the optimum nitrification, of up to 0.46 g/m2/day and 0.09 g/m2/day, respectively. Besides, in this study, the surface texture of the media is the main factor that affected the volumetric ammonia and nitrite conversion rates （VTR and VNR）. JFM gave the greatest VTR and VNR performance, compared with the other media
文摘This paper discussed influences of flow rates of O_2, C_3H_8, and compressedair on the melting degree of particles during HVOF (high velocity oxy-fuel) sprayed CoCrW coating.The O_2 flow rate has the maximal effect on the melting of particles, the C_3H_8 flow rate has thesecond, and the compressed air flow rate has the minimal effect. The bond strength of the HVOFsprayed CoCrW coating is over 54 MPa. The porosity ratio of the HVOF sprayed CoCrW coating afteroptimization of gas flow rates is less than 2%. The average microhardness of the coating is up toHV_(0.1) 545. The oxidation amount per unit area of the HVOF sprayed CoCrW coating increases withthe holding time increasing at 800℃. In the same way, the oxidation amount of the coating increasesas the temperature increases. Particularly, the oxidation of the coating drastically increases over850℃.
基金This work was supported by the Ministry of Science and Higher Education,Poland(No.14303018).
文摘The flow velocity of gases in gobs directly influences the kinetics and intensity of gaseous components release during heating and cooling of coal.The assessment of fire hazard is performed on the basis of concentrations of particular gases in a mine air.These concentrations differ in coal heating and cooling phase which was proven in the study.This paper presented the results of the experimental study on temperature distribution in a simulated coal bed in heating(50–250°C)and cooling(250–35°C)phases as well as its correlation to variations in concentration of gases released in these phases and flow rates of gases flowing through the coal bed.The research was performed on twenty-two samples of bituminous coals acquired from various coal beds of Polish coal mines.Considerable differences were observed between heating and cooling phases in terms of the concentrations of gases taken into account in calculations of self-combustion index.In the heating phase temperature increase resulted in the decrease of concentrations ratios of ethane,ethylene,propane,propylene and acetylene,while in the cooling phase these ratios increased systemically.The effect of air(in heating phase)and nitrogen(in cooling phase)flow rate on the self-ignition index CO/CO2 was also determined.
基金supported by the Special Fund for the Construction of Innovative Province in Hunan Province,China(2020RC3038)the Changsha City Fund for Distinguished and Innovative Young Scholars,China(kq1802007).
文摘Vanadium redox flow battery(VRFB)is considered one of the most potential large-scale energy storage technolo-gies in the future,and its electrolyte flow rate is an important factor affecting the performance of VRFB.To study the effect of electrolyte flow rate on the performance of VRFB,the hydrodynamic model is established and a VRFB system is developed.The results show that under constant current density,with the increase of electrolyte flow rate,not only the coulombic efficiency,energy efficiency,and voltage efficiency will increase,but also the capacity and energy discharged by VRFB will also increase.But on the other hand,as the flow rate increases,the power of the pump also increases,resulting in a decrease in system efficiency.The energy discharged by the system does not increase with the increase in flow rate.Considering the balance between efficiency and pump power loss,it is experimentally proved that 120 mL·min-1 is the optimal working flow rate of the VRFB system,which can maximize the battery performance and discharge more energy.
文摘This study proposes an alternative approach to the investigation of high flow hydrogeological fractures within the basement in the Dabakala region of north-central Côte d’Ivoire. The used approach consists of exploring the subsurface by measuring electrical resistivity contrasts along the main shear direction within crystallophyllian rocks. Electrical resistivity profiling and vertical electrical sounding techniques, coupled with boreholes monitoring, have identified fractured aquifers whose best flow rates are around 96 and 116 m<sup>3</sup>/h. These aquifers mostly hosted in granodiorite have an average strength of 10 meters and are located at depth of around 100 meters. They are associated with open fractures created by tangential shear stresses that have affected the Dabakala volcano-sedimentary trench formations. The search for fractured aquifers along the main shear direction offers great perspective for obtaining high flow rates.
基金supported by PetroChina Major Scientifie Research&Techno-logical Development Project"Research on Key Technologies of Injection and Production Engincering of Underground Gas Storage"(No:2015E-4004).
文摘Critical erosionflow rate is the key factor restricting the injection/production capacity of an injection/production well.At present,it is commonly calculated according to API RP 14E standard and its calculation result tends to be conservative.So far,however,there is no definite laboratory experiment orfield data that can prove that critical erosionflow rate can be increased on the basis of API RP 14E.To deal this end,the concept of critical erosionflow rate was proposed based on corrosion rate for thefirst time in this paper.Then,a laboratory equivalent simulation experiment under real injection and production conditions was carried out by comprehensively taking into account the factors influencing string erosion(including temperature,pressure,gas component,water content,solid particle content and string material)while introducing the wall shear stress.Accordingly,the critical erosion coefficient(C)under experimental working conditions was calculated.Finally,a C value chart for three kinds of strings that are commonly used onfield(N80,SM80S and S13Cr)was established.And the following research results are ob-tained.First,solid particle content,water content,CO_(2)differential pressure and wall shear stress are the main erosion controlling factors.Second,solid particle content is the most significant factor that affects the erosion of N80,SM80S and S13Cr strings,and erosion of N80 and SM80S strings is more sensitive to wall shear stress and water content.Third,as for S13Cr string,the C value can be 100 when the solid particle content is lower than 250 mg/L,180 when thefluid contains liquid but no solid particles,and 275 when thefluid is gas phase.Fourth,as for N80 and SM80S strings,the C value can be in the range of 100e180 based on different water content and wall shear stress when thefluid contains liquid but no solid particles,and 275 when thefluid is in gas phase.Fifth,in view that thefluid produced from the injection/production wells of Hutubi gas storage has a water content of 0.0010‰without solid particles,S13Cr is adopted as string material and the C value is set at 180.It is shown in the laboratory erosion experiments that no erosion trace occurs on the string samples under injection and production conditions and the erosion rate is extremely low without point erosion.In conclusion,the C value chart established in this paper is reliable and can provide the guidance for the scientific and reasonable determination of critical erosionflow rate.
基金Project supported by the National Natural Science Foundation of China(Grant No.U22B6010)supported by the International Partnership Program of Chinese Academy of Sciences(Grant No.025GJHZ2022118FN)the Hainan Provincial Joint Project of Sanya Yazhou Bay Science and Technology City(Grant No.2021CXLH0003).
文摘Axial flow pumps are widely used in water conservancy,petrochemical and agricultural industries.Efficient operation is crucial for energy conservation and emission reduction.Improving efficiency under severe conditions requires studying the internal flow of axial-flow pumps,particularly at low flow rates where backflow vortices form near the impeller inlet.This study investigates the unsteady flow characteristics of backflow vortices at different flow rates in an axial-flow pump.Results show that backflow vortices form when the flow rate decreases to 0.59Q_(d).As the flow rate further declines,the backflow vortex progresses upstream,contracts,and rebounds.The flow rate range is divided into three stages:Stage Ⅰ with no backflow vortex,stage Ⅱ with initial vortex development extending upstream and relatively fragmented,and stage Ⅲ with vortex contraction and rebound forming a more coherent structure.Besides,backflow vortices induce significant pressure fluctuations and velocity oscillations with the primary frequency being 0.5 fb.They exhibit a three-dimensional spiral motion involving changes in axial length,self-rotation,and revolution around the pump axis,with an angular velocity of approximately half the impeller’s rotational speed.This work enhances insights into backflow vortex behaviors,which is essential for optimizing pump design and improving operational stability in challenging environments.
文摘Production flow rates are crucial to make operational decisions,monitor,manage,and optimize oil and gas fields.Flow rates also have a financial importance to correctly allocate production to fiscal purposes required by regulatory agencies or to allocate production in fields owned by multiple operators.Despite its significance,usually only the total field production is measured in real time,which requires an alternative way to estimate wells'production.To address these challenges,this work presents a back allocation methodology that leverages real-time instrumentation,simulations,algorithms,and mathe-matical programming modeling to enhance well monitoring and assist in well test scheduling.The methodology comprises four modules:simulation,classification,error calculation,and optimization.These modules work together to characterize the flowline,wellbore,and reservoir,verify simulation outputs,minimize errors,and calculate flow rates while honoring the total platform flow rate.The well status generated through the classification module provides valuable information about the current condition of each well(i.e.if the well is deviating from the latest well test parameters),aiding in decision-making for well testing scheduling and prioritizing.The effectiveness of the methodology is demonstrated through its application to a representative offshore oil field with 14 producing wells and two years of daily production data.The results highlight the robustness of the methodology in properly classifying the wells and obtaining flow rates that honor the total platform flow rate.Furthermore,the methodology supports well test scheduling and provides reliable indicators for well conditions.By uti-lizing real-time data and advanced modeling techniques,this methodology enhances production monitoring and facilitates informed operational decision-making in the oil and gas industry.
基金supported by the National Natural Science Foundation of China(Grant No.U2340221)the National Key R&D Programof China(Grant No.2022YFC3202602)+1 种基金the NaturalScience Foundation of Jiangsu Province(Grant No.BK20230036)the 111 Project(Grant No.B17015)。
文摘Rational allocation of water flow energy in river networks is essential to addressing water-related issues in river network areas.However,current methods of calculating the spatiotemporal distribution of flow energy in river networks lack precision and efficiency.This paper introduces a novel hydrodynamic representation,the energy flow rate,defined as the product of the flow rate and kinetic energy head,to quantify the kinetic energy stored and transported in river networks.A linear equation system for the energy flow rate in a river network has been theoretically derived,enabling rapid calculations under steady flow conditions.A simplified equation is proposed to describe the exponential decay of the energy flow rate,accompanied by potential energy conversion.The coefficients in the linear equation system are determined using control equations at flow confluence and diversion nodes.This study provides foundational insights that can be used to develop new hydrodynamic modeling strategies to regulate water flow energy and achieve coordinated management of water-related issues in river networks.
文摘This study involved numerical simulations of a double tube heat exchanger using the ANSYS FLUENT programversion 22.The study aims to examine methods for minimizing pressure loss and consequently enhancing the thermal performance index(TPI)of a heat exchanger fitted with wavy edge tape that is a heat recovery system(the hot air in simulation instead of t heat from the exhaust gases of the brick factory furnaces and return it to warm the heavy fuel oil by substituting the electrical heater with a heat exchanger to recuperate waste heat from the flue gases,so elevating the temperature of Heavy fuel oil(HFO)to inject from the roof nozzles of combustion chamber of the furnace furthermore reducing cost(by finding the optimal design of wavy edge tape))and energy consumption.Air was selected as the hot gas in the inner pipe instead of furnace exhaust gases due to their similar thermal characteristics.A numerical analysis was conducted to create a novel wavy edge tape with varying widths(50%Di,75%Di,and 95%Di),lengths(1000,1200,1400)mm,amplitudes(5,10,15)mm,and periods of wavy length(5,10,15)mm.The flow rate of the outer pipe fluid(oil)ranges from(0.06 to 0.1)kg/s,while the velocity of the hot fluid(air)varies from(1 to 27)m/s,Re_(air)(6957 to 187,837).The entrance temperature of the hot fluid can be either(200,225,and 250)℃.The study finds that wavy edge tape tubes are more effective than smooth tubes in terms of oil outlet temperature;results revealed that an increase in the oil mass flow rate leads to a decrease in the oil outlet temperature and an increase in the heat transfer rate,at the air temperature 250℃.Additionally,the results indicate that increasing the width,length,and amplitude also leads to an increase in the oil outlet temperature of(94-94.12)℃,the pressure drop of(568.3)Pa,and the Nusselt number(65.7-66.5)respectively on the oil side.Finally,the heat exchanger’s best thermal performance index was found by investigating temperature contour at amplitude(A=5),period(p=15),width(w=75%Di),and length(L=1200 mm).The values for these parameters are,in order(1.02,1.025,1.02,and 1.0077).
基金Project supported by the Special Funds for Basic Operating Expenses of the Centre University of China (Grant No.23ZYJS006)。
文摘Experiments are conducted on the evacuation rate of pedestrians through exits with queued evacuation pattern and random evacuation pattern. The experimental results show that the flow rate of pedestrians is larger with the random evacuation pattern than with the queued evacuation pattern. Therefore, the exit width calculated based on the minimum evacuation clear width for every 100 persons, which is on the assumption that the pedestrians pass through the exit in one queue or several queues, is conservative. The number of people crossing the exit simultaneously is greater in the random evacuation experiments than in the queued evacuation experiments, and the time interval between the front row and rear row of people is shortened in large-exit conditions when pedestrians evacuate randomly. The difference between the flow rate with a queued evacuation pattern and the flow rate with a random evacuation pattern is related to the surplus width of the exit, which is greater than the total width of all accommodated people streams. Two dimensionless quantities are defined to explore this relationship. It is found that the difference in flow rate between the two evacuation patterns is stable at a low level when the surplus width of the exit is no more than 45% of the width of a single pedestrian stream. There is a great difference between the flow rate with the queued evacuation pattern and the flow rate with the random evacuation pattern in a scenario with a larger surplus width of the exit. Meanwhile, the pedestrians crowd extraordinarily at the exit in these conditions as well, since the number of pedestrians who want to evacuate through exit simultaneously greatly exceeds the accommodated level. Therefore, the surplus width of exit should be limited especially in the narrow exit condition, and the relationship between the two dimensionless quantities mentioned above could provide the basis to some extent.
基金supported by the National Natural Science Foundation of China (Grant No.52104321)the Natural Science Foundation of Chongqing,China (Grant No.CSTB2023NSCQ-MSX0871)the Science and Technology Research Program of Chongqing Municipal Education Commission (Grant No.KJQN202101404).
文摘The two-fluid model coupled with population balance model was used for simulating the gas-liquid flow in the Ruhrstahl-Heraeus(RH)degasser.The predicted circulation flow rate was compared with that measured from a water model experiment to validate the mathematical model.Then,influence of snorkel immersion depth on liquid circulation flow rate was numerically investigated under an atmospheric pressure of 101 and 84 kPa,respectively.Predicted result indicates that the circulation flow rate of the RH degasser in the high-altitude area was severely reduced because of the decrease in atmospheric pressure.However,increasing the snorkel immersion depth from 0.5 to 0.7 m can compensate for the decrease in atmospheric pressure.Industrial test result indicates that decarburization rate is significantly enhanced by increasing the snorkel immersion depth.Through optimization,the percentage of heats with a final carbon content less than 0.002 wt.%is significantly increased from 22.0%to 96.4%.
基金supported by the financial support from the National Natural Science Foundation of China(52204084)Project funded by the China Postdoctoral Science Foundation(2021M700388).
文摘Geothermal energy has gained wide attention as a renewable alternative for mitigating greenhouse gas emissions.The advancements in enhanced geothermal system technology have enabled the exploitation of previously inaccessible geothermal resources.However,the extraction of geothermal energy from deep reservoirs poses many challenges due to high‐temperature and high‐geostress conditions.These factors can significantly impact the surrounding rock and its fracture formation.A comprehensive understanding of the thermal–hydraulic–mechanical(THM)coupling effect is crucial to the safe and efficient exploitation of geothermal resources.This study presented a THM coupling numerical model for the geothermal reservoir of the Yangbajing geothermal system.This proposed model investigated the geothermal exploitation performance and the stress distribution within the reservoir under various combinations of geothermal wells and mass flow rates.The geothermal system performance was evaluated by the criteria of outlet temperature and geothermal productivity.The results indicate that the longer distance between wells can increase the outlet temperature of production wells and improve extraction efficiency in the short term.In contrast,the shorter distance between wells can reduce the heat exchange area and thus mitigate the impact on the reservoir stress.A larger mass flow rate is conducive to the production capacity enhancement of the geothermal system and,in turn causes a wider range of stress disturbance.These findings provide valuable insights into the optimization of geothermal energy extraction while considering reservoir safety and long‐term sustainability.This study deepens the understanding of the THM coupling effects in geothermal systems and provides an efficient and environmentally friendly strategy for a geothermal energy system.
文摘Developing a novel drop counter by introducing the Internet of Things concept has been vigorously conducted in recent years. Understanding the newly introduced drop counter’s flow rate control accuracy and flow rate count feature is essential for improving safety in infusion management. This study aimed to verify if the new drop counters could secure accurate flow rate and drip count by conducting actual flow rate measurements using gravimetry and functional evaluation. A drop counter was attached to each drip chamber of the infusion set, and an IV drip was conducted at the 100 ml/h flow rate. The weight of discharged physiological saline was measured to plot trumpet curves. Next, three different types of drop counters were evaluated to determine if they maintained drip count accuracy according to the changes in their position angles. The flow rate errors in all conditions indicated trumpet-like curves, exhibiting an overall error range within ±10% in all observation windows. Although every drop counter successfully detected and measured dripping, it was challenging in some counters to detect dripping when the drip chamber was tilted. In comparing adult and pediatric IV sets, the adult IV set was found to be less likely to detect dripping in the angled position. No significant differences in results were confirmed between high and low flow rates, suggesting that the drop count function would not be affected by the flow rate in the ranges of typical infusion practices. Doppler sensors have a wide range of measurements and high sensitivity;the dripping was detected successfully even when the drip chamber was tilted, probably due to the advantages of these sensors. In contrast, miscounts occurred in those equipped with infrared sensors, which could not detect light intensity changes in tilted positions. Understanding the tendencies in flow rate errors in infusion can be valuable information for infusion management.
文摘The advancement in endoscopic technology and techniques has increased its use in the diagnosis and treatment of gastrointestinal diseases.Reprocessing of reusable endoscopes remains a challenge.Inadequate reprocessing leads to bacterial contamination of the endoscope,a significant cause of endoscope-related infections.To thoroughly address the complexities of cleaning a flexible endo-scope,various cleaning methods have been devised and tested across different studies.This letter evaluates one such method,spray flushing for flexible gastro-scopes,developed and tested in a randomized controlled trial by Du et al.Based on the post-processing test results for this method,Du et al conclude that there is improved cleaning efficacy and reduced damage compared to manual brush cleaning.The validity and reliability of the results could be further enhanced by carefully considering the study design and a few underlying concepts that contribute to the reprocessing quality of different types of endoscopes.
基金funded by the National Natural Science Foundation of China(No.42202155)China Postdoctoral Science Foundation(No.2021MD703807)+7 种基金Heilongjiang Provincial Postdoctoral Science Foundation(No.LBH-Z20121)financial support from the China Scholarship Council(No.202008230018)the Research Fund Program of Hubei Key Laboratory of Resources and Eco-Environment Geology(No.HBREGKFJJ-202309)funding by the DGICYT Spanish Project(grant no.PID2020-118999GB-I00)funded by the MCIN/AEI/10.13039/501100011033funding by the Ramón y Cajal fellowship(grant no.RyC-2018-026335-I)funded by the MCIN/AEI/10.13039/50110001103the European Social Fund-Investing in Your Future.
文摘Developing low-permeability Coalbed Methane(CBM)reservoirs can significantly benefit from a comprehensive understanding of hydraulic fracture nucleation and propagation mechanisms,particularly in anthracite CBM reservoirs.This study employs true-triaxial hydraulic fracturing experiments to investigate these mechanisms,with variables including injection flow rate,horizontal stress difference(σH-σh),and bedding orientation.Additionally,we conduct corresponding numerical cases to validate the experimental conclusions.The research also considers re-fracturing instances.For the first time,we utilize a combination of Kaiser tests and the stress transfer function in ANSYS Workbench finite element analysis to accurately restore the confining pressure of the coal sample.The findings suggest that a high initial injection flow rate during hydraulic fracturing can promote fluid leakage and aid in maintaining substantial fracture pressure.Enhanced fracturing efficiency can be achieved through higher injection rates,and it can ensure optimal fracturing efficiency,minimizing roof and floor fracturing in coal reservoirs to prevent fracturing fluid leakage.The presence of a high horizontal stress difference facilitates hydraulic fracture propagation along the direction of the maximum horizontal compressive stress,requiring a greater hydraulic pressure to produce more fracture systems in coal reservoirs.Additionally,a minor deviation in the wellbore injection direction from the bedding orientation assists in creating a complex hydraulic fractured network,although this also requires higher hydraulic pressure to initiate new fractures.In the case of multiple hydraulic fracturing,the second initiation pressure tends to be significantly higher than the first,indicating that a sequential increase in hydraulic pressure aids the formation of additional fractures.Moreover,a simplified numerical simulation has been conducted to corroborate the experimental findings.These insights are crucial in optimizing hydraulic fracturing processes to enhance the permeability of anthracite CBM reservoirs.
基金supported by the Sponsored by Natural Science Foundation of Xinjiang Uygur Autonomous Region(no.2022D01C389)the Xinjiang University Doctoral Start-up Foundation(no.620321029)the Science and Technology Planning Project of State Administration for Market Regulation(no.2022MK201).
文摘With the widespread use of polyethylene(PE)materials in gas pipelines,the problem related to the aging of these pipes has attracted increasing attention.Especially under complex environmental conditions involving temperature,humidity,and pressure changes,PE pipes are prone to oxidative degradation,which adversely affects their performance and service life.This study investigates the aging behavior of PE pipes used for gas transport under the combined effects of temperature(ranging from 80℃to 110℃)and pressure(0,0.1,0.2,and 0.3 MPa).By assessing the characteristics and thermal stability of the aged pipes,relevant efforts are provided to explore the performance variations during the aging process and develop methods for evaluating thermal stability.The results indicate that an increase in aging factors,specifically temperature and pressure,significantly reduces theMeltMass Flow Rate(MFR)of polyethylene pipes,suggesting a decline in the material’s flowability during the aging process.Oxidative Induction Time(OIT)tests show that with increasing temperature and pressure,the oxidative induction time of the aged polyethylene pipes progressively shortens,indicating a significant reduction in the material’s oxidative stability.The application of the Arrhenius equation further demonstrates that the aging reaction rate of polyethylene pipes in high-temperature environments is closely related to both temperature and activation energy,thereby laying the foundation of a new approach for the development of an initial model that can reflect the microscopic behavior of polyethylene pipes in aging environments.
