In order to solve the issue that the combustible objects for cased telescoped ammunition (CTA) didn't burn completely during the combustion process, the microcellular combustible objects were foamed with numerous ...In order to solve the issue that the combustible objects for cased telescoped ammunition (CTA) didn't burn completely during the combustion process, the microcellular combustible objects were foamed with numerous cells in the micron order to improve the combustion performance by the supercritical carbon dioxide (SCeCO2) foaming technology. As the cell structure determined the combustion properties of microcellular combustible objects, the solubility of SCeCO2 dissolved into the combustible objects was obtained from the gravimetric method, and scanning electron microscope (SEM) was applied to characterize the cell structure under various process conditions of solubility, foaming temperature and foaming time. SEM images indicate that the cell diameter of microcellular combustible objects is in the level of 1 mm and the cell density is about 1011 cell,cm^-3. The microcellular combustible objects fabricated by the SCeCO2 foaming technology are smooth and uniform, and the high specific surface area of cell structure can lead to the significant combustion performance of microcellular combustible object for CTA in the future.展开更多
A fractal pore structure model of combustible cartridge cases was established by virtue of the fractal geometry. Pore structure information, such as backbone fractal dimension and pore fractal dimension, of four kinds...A fractal pore structure model of combustible cartridge cases was established by virtue of the fractal geometry. Pore structure information, such as backbone fractal dimension and pore fractal dimension, of four kinds of combustible cartridge case were obtained by mercury intrusion porosimetry (MIP) . The formation mechanism of fractal pore structure of combustible cartridge was studied. The results show that the backbone fractal dimension consists of the component and influenced by the component number and size of components; the pore percolation fractal dimension reflects the pore structures of components; and the fractal dimension of pore structure is positively relative to the tensile strength of combustible cartridge case.展开更多
A two-dimensional multi-material code was indigenously developed to investigate the effects of duct boundary conditions and ignition positions on the propagation law of explosion wave for hydrogen and methane-based co...A two-dimensional multi-material code was indigenously developed to investigate the effects of duct boundary conditions and ignition positions on the propagation law of explosion wave for hydrogen and methane-based combustible mixture gas. In the code,Young's technique was employed to track the interface between the explosion products and air,and combustible function model was adopted to simulate ignition process. The code was employed to study explosion flow field inside and outside the duct and to obtain peak pressures in different boundary conditions and ignition positions. Numerical results suggest that during the propagation in a duct,for point initiation,the curvature of spherical wave front gradually decreases and evolves into plane wave. Due to the multiple reflections on the duct wall,multi-peak values appear on pressure-time curve,and peak pressure strongly relies on the duct boundary conditions and ignition position. When explosive wave reaches the exit of the duct,explosion products expand outward and forms shock wave in air. Multiple rarefaction waves also occur and propagate upstream along the duct to decrease the pressure in the duct. The results are in agreement with one-dimensional isentropic gas flow theory of the explosion products,and indicate that the ignition model and multi-material interface treatment method are feasible.展开更多
One kind of combustible gas alarms based on industrial Ethernet was designed to prevent the gas leakage in industrial production sites, The alarm adopted the high performance microprocessor LPC2214 as the main chip. T...One kind of combustible gas alarms based on industrial Ethernet was designed to prevent the gas leakage in industrial production sites, The alarm adopted the high performance microprocessor LPC2214 as the main chip. The embedded operating system μC/OS-Ⅱand TCP/IP protocol stack uIP running on LPC2214 constitute a development platform of application of the combustible gas alarm, The test shows that it can automatically and continuously detect combustible gas in industrial production sites in several positions;it can give out sound-light alarm and take protective measures immediately against the gas leakage; and it can send the detected data to PC through the Ethernet interface to realize the remote detection. The designed project provides a reference to design industrial devices based on industrial Ethernet展开更多
Based on a comprehensive and systematic analysis of the temporal and spatial distribution,periodic changes,and influencing factors of forest fires in Inner Mongolia,through fixed-point observations and experiments on ...Based on a comprehensive and systematic analysis of the temporal and spatial distribution,periodic changes,and influencing factors of forest fires in Inner Mongolia,through fixed-point observations and experiments on the ground,forest combustibles are divided into the ground litter layer,ground standing litter,and living plants.The combustibles are divided into various grades according to their load,dryness and combustibility.By determining the influencing factors of each combustible grade,a forecast model of the combustibility grade of combustibles is established.The forecast model has been widely used in the mid-and long-term forecast model of fire danger grade,and the accuracy rate of the fall area forecast through back-generation fitting verification is above 88.43%.展开更多
In this paper, we investigate a free boundary problem of a semilinear combustible system with higher dimension and heterogeneous environment. Such a problem is usually used as a model to describe heat propagation in a...In this paper, we investigate a free boundary problem of a semilinear combustible system with higher dimension and heterogeneous environment. Such a problem is usually used as a model to describe heat propagation in a two-component combustible mixture In which the free boundary is described by Stefan-like condition. For simplicity, we assume that the environment and solutions are radially symmetric. We use the contraction mapping theorem to prove the local existence and uniqueness of the solution. Also we study the blowup property and the long time behavior of the solution. Our results show that when pq 〉 1 blowup occurs if the initial datum is large enough and the solution is global and slow, whose decay rate is at most polynomial if the initial value is suitably large, while when p 〉 1, q 〉 1 there is a global and fast solution, which decays uniformly at an exponential rate if the initial datum is small.展开更多
Combustible agricultural waste is a potential source of energy because of its high organic content and heating value.As China’s economy develops,energy demand increases while environmental protection becomes more str...Combustible agricultural waste is a potential source of energy because of its high organic content and heating value.As China’s economy develops,energy demand increases while environmental protection becomes more stringent.These competing demands make it urgent to find environmentally acceptable ways to extract energy from agricultural wastes.In this study,a liquid catalyst flow fuel cell(FFC)directly powered by combustible agricultural waste is investigated.This type of flow fuel cell can directly convert combustible agricultural waste at atmospheric pressure to electricity at 80-150℃and it is environmentally friendly.Polyoxometalates act as catalysts and charge carriers to drive the FFC.Wheat straw and wine residues were used to represent the main components of combustible agricultural waste.Experiment results indicated that the power density reached as high as 111 mW/cm^(2),hundreds of times higher than the output of a microbial cell.展开更多
Aged municipal solid wastes(MSW)excavated from landfills and dumpsites were characterized to analyze their fraction composition,moisture content,and lower heat value(LHV).The necessity and feasibility of recycling com...Aged municipal solid wastes(MSW)excavated from landfills and dumpsites were characterized to analyze their fraction composition,moisture content,and lower heat value(LHV).The necessity and feasibility of recycling combustibles from aged MSW to improve the incineration of fresh MSW were investigated.The results showed that combustibles in aged MSW were easily separated from other components and than LHV of the separated combustibles are higher than 11000 kJ/kg.The fresh MSW are of high moisture contents with average LHV below 6500 kJ/kg,making their stable combustion difficult to maintain in MSW incinerators.For both fresh MSW and aged MSW,plastics are the main contributor to their LHV.To improve incineration of fresh MSW that are characterized with low LHV,combustibles separated from aged MSW were made into refuse derived fuel(RDF)pellets and were then added to fresh MSW by 2%wt.–5%wt.LHV variation and air supply resistance change of the MSW layer on the incinerator grate caused by the addition of RDF was checked,and no significant changes were found.No obvious difference was observed for the‘burn-out time’between RDF pellets and fresh MSW either.RDF made from aged MSW combustibles is found to be a promising auxiliary fuel to improve the incineration of fresh MSW,and aged MSW from old landfill cells and dumpsites can be finally disposed of jointly with fresh MSW by recycling combustible from the former to be coincinerated with the latter in the incineration plants.展开更多
This paper studies gas detectors, especially, gas sensors in which a thermochemical reac-tion takes place on a catalytic element. The novel catalytic sensor is fabricated using micro-electronic thick-film techniques, ...This paper studies gas detectors, especially, gas sensors in which a thermochemical reac-tion takes place on a catalytic element. The novel catalytic sensor is fabricated using micro-electronic thick-film techniques, and it is used to monitor the concentration of combustiblegases and their mixture in a flow reactor. This sensor has two identical platinum films whichare used as the heater, resistance thermometer and the surface of reaction. Catalyst of palla-dium is deposited on one of the platinum film by chemical method, while the other platinumfilm serves as a compensating element. The difference in the minimum reaction temperaturefor the catalytic oxidation of the combustible gas components of mixture by palladium sug-gests that it is possible to analyse such a gas mixture. The purpose of the study is to demon-strate that the sensor fabricated by this process has good sensing characteristics for hydrogenor carbon monoxide gas in the mixture of methane and ethane.展开更多
Electrically controlled solid propellant(ECSP)offers multiple ignition and adjustable burning rate,serving as fuel for next-generation intelligent propulsion systems.To further enhance the combustion performance of EC...Electrically controlled solid propellant(ECSP)offers multiple ignition and adjustable burning rate,serving as fuel for next-generation intelligent propulsion systems.To further enhance the combustion performance of ECSP,a method utilizing electrochemical and thermal decomposition catalysts has been proposed.In this work,we investigated the combustion characteristics of hydroxylamine nitrate(HAN)-based ECSP incorporating cerium oxide(CeO_(2))and graphene oxide(GO)by using an electrically controlled combustion test system.Electrochemical impedance spectroscopy(EIS)and linear sweep voltammetry(LSV)were used to measure the electrical conductibility and overpotential of ECSP with various additives,and Tafel curves were calculated.Thermogravimetric analysis coupled with differential scanning calorimetry(TG-DSC)was employed to investigate the thermal decomposition behavior of ECSP.While the addition of CeO_(2) and GO reduced the conductivity of ECSP,both catalysts exhibited strong electrocatalytic properties and facilitated the thermal decomposition of ECSP.Between two catalysts,GO demonstrated superior electrochemical catalytic performance but weaker thermal decomposition catalytic ability than CeO_(2).The addition of catalysts significantly enhanced the combustion performance of HAN-based ECSP.Specifically,the ignition delay time was shortened by 10%~20%.CeO_(2) raised the burning rate by approximately 20%but GO exhibited a remarkable boost of 40%in burning rate at high voltage.The combination of GO and PVA produced a flame-retardant substance that negatively impacted the ignition delay of ECSP and resulted in a smaller increase in the burning rate of ECSP at low ignition voltages.展开更多
This study investigates the performance boundaries of ramjet and scramjet engines fueled by boronbased propellant through full-scale engine modeling and three-dimensional computational fluid dynamics simulations.Resul...This study investigates the performance boundaries of ramjet and scramjet engines fueled by boronbased propellant through full-scale engine modeling and three-dimensional computational fluid dynamics simulations.Results show that the performance boundary between ramjets and scramjets occurs near Mach 7.Specifically,at Mach 6,the ramjet exhibits a 1290 m/s higher specific impulse than the scramjet;however,at Mach 7,their performance becomes comparable.The ramjet's higher static temperature promotes boron particle vaporization and B_(2)O_(2) dissociation,limiting the total temperature increase,unlike in scramjets.The boron vapor mass fraction significantly impacts this temperature difference,with ramjets exhibiting values 8.5 and 3.9 times higher than scramjets at Mach 6 and Mach 7,respectively.Despite lower total temperatures,ramjets achieve more efficient boron combustion due to the combined effects of higher pressures and longer particle residence times.These findings offer valuable insights for engine designers in selecting ramjet or scramjet configurations for boron-fueled propulsion systems.展开更多
Coal cinder is an abundant byproduct of the extensive consumption of coal in industrial production and daily life.Making full use of the cinder is conducive to a low-carbon economy.In this study,inspired by the burnin...Coal cinder is an abundant byproduct of the extensive consumption of coal in industrial production and daily life.Making full use of the cinder is conducive to a low-carbon economy.In this study,inspired by the burning of coal,a new method for constructing a silica-based composite porous material(SiO_(2)-CPM)was developed by combusting a siloxane-modified anthracite coal gel(CSiO_(2) gel).During this process,the combustion product was directly converted into a porous material,and the calorific value of the coal remained nearly unchanged(~98%of the original calorific value was retained),demonstrating the viability of this method for energy-efficient applications.The SiO_(2)-CPM exhibited an ultra-low thermal conductivity(0.036 W/(m·K)at room temperature),outperforming conventional insulation materials(e.g.,cotton~0.05 W/(m·K)).Additionally,it showed enhanced mechanical strength(fracture stress of 41.8 kPa)compared to the powder state of the coal cinder.Experimental results indicate that the amount of siloxane,structure-directing agent,and an acidic environment were critical for mechanical enhancement.The SiO_(2)-CPM showed good dimensional stability against thermal expansion and exhibited excellent thermal insulation and fire resistance even at 900℃.Meanwhile,the SiO_(2)-CPM with complex geometry could be easily fabricated using this method owing to the excellent shaping ability of the CSiO_(2) gel.Compared to conventional methods such as sol-gel synthesis or freeze-drying,this approach for fabricating SiO_(2)-CPM is simpler and cost-effective and allows the direct utilization of coal cinder post-combustion.展开更多
Boron has attracted increasing attention in the field of high-energy explosives and propellants due to its high volume calorific value and mass calorific value.However,the complicated combustion process and low combus...Boron has attracted increasing attention in the field of high-energy explosives and propellants due to its high volume calorific value and mass calorific value.However,the complicated combustion process and low combustion efficiency hinder its wide application.To tackle this challenge,bioinspired polydopamine(PDA)interface reinforced boron-Viton composites,with high structure stability and excellent energy releasing efficiency,are designed and prepared,combining the interface regulation of PDA biomimetic materials and combustion promotion of fluoropolymers.Firstly,the stronger adsorption energy of PDA with boron compared to Viton is demonstrated by molecular dynamics simulations.Next,B@PDA@Viton is prepared by the combination of in-situ dopamine polymerization and solvent/nonsolvent method,and the double-layer core-shell structure is confirmed by XPS,FTIR,and TEM characterizations.TG-DSC analysis shows that B@PDA@Viton possesses superior thermal properties,with a 55.48%increase in oxidation heat compared to raw B.Furthermore,ignition and combustion performance tests indicate that B@PDA@Viton reduces ignition delay by 57.56%and increases heat of combustion by 68.63%relative to raw B.These findings elucidate the ignition and combustion mechanisms of B@PDA@Viton.This work not only developed high-performance boron-based composite fuels but also provided insights into the development of boron-based fuels.展开更多
Maintaining the structural integrity of parallel natural gas pipelines during leakage-induced jet fires remains a critical engineering challenge.Existing methods often fail to account for the complex interactions amon...Maintaining the structural integrity of parallel natural gas pipelines during leakage-induced jet fires remains a critical engineering challenge.Existing methods often fail to account for the complex interactions among heat transfer,material behavior,and pipeline geometry,which can lead to overly simplified and potentially unsafe assessments.To address these limitations,this study develops a multiphysics approach that integrates small-orifice leakage theory with detailed thermo-fluid-structural simulations.The proposed framework contributes to a more accurate failure analysis through three main components:(1)coupled modeling that tracks transient heat flow and stress development as fire conditions evolve;(2)risk assessment incorporating spatial layout,material property changes with temperature,and operational limits;and(3)sensitivity analysis to identify key design factors that influence structural performance under high thermal loads.Simulation results demonstrate that thermal radiation from neighboring jet fires significantly accelerates material degradation,with inter-pipeline spacing emerging as a critical determinant of structural response.Notably,increasing the spacing between pipelines reduces thermal interaction and mechanical stress transfer.As a result,systems with optimized spacing exhibit markedly lower deformation than conventional configurations.These findings provide a foundation for re-evaluating pipeline layout strategies and strengthening safety protocols,particularly in high-risk environments where fire exposure can severely compromise structural reliability.The proposed approach offers actionable guidance for engineers and policymakers seeking to enhance the resilience of pipeline infrastructure under extreme thermal conditions.展开更多
This paper investigates the reliability of internal marine combustion engines using an integrated approach that combines Fault Tree Analysis(FTA)and Bayesian Networks(BN).FTA provides a structured,top-down method for ...This paper investigates the reliability of internal marine combustion engines using an integrated approach that combines Fault Tree Analysis(FTA)and Bayesian Networks(BN).FTA provides a structured,top-down method for identifying critical failure modes and their root causes,while BN introduces flexibility in probabilistic reasoning,enabling dynamic updates based on new evidence.This dual methodology overcomes the limitations of static FTA models,offering a comprehensive framework for system reliability analysis.Critical failures,including External Leakage(ELU),Failure to Start(FTS),and Overheating(OHE),were identified as key risks.By incorporating redundancy into high-risk components such as pumps and batteries,the likelihood of these failures was significantly reduced.For instance,redundant pumps reduced the probability of ELU by 31.88%,while additional batteries decreased the occurrence of FTS by 36.45%.The results underscore the practical benefits of combining FTA and BN for enhancing system reliability,particularly in maritime applications where operational safety and efficiency are critical.This research provides valuable insights for maintenance planning and highlights the importance of redundancy in critical systems,especially as the industry transitions toward more autonomous vessels.展开更多
Al/NH_(4)CoF_(3)-Φ(Φ=0.5,1.0,1.5,2.0,and 3.0)binary composites and Al-NH_(4)CoF_(3)@P(VDF-HFP)ternary composites are fabricated via ultrasonication-assisted blending and electrostatic spraying.The effect of equivale...Al/NH_(4)CoF_(3)-Φ(Φ=0.5,1.0,1.5,2.0,and 3.0)binary composites and Al-NH_(4)CoF_(3)@P(VDF-HFP)ternary composites are fabricated via ultrasonication-assisted blending and electrostatic spraying.The effect of equivalence ratio(Φ)on the reaction properties is systematically investigated in the binary Al/NH_(4)CoF_(3)system.For ternary systems,electrostatic spraying allows both components to be efficiently encapsulated by P(VDF-HFP)and to achieve structural stabilization and enhanced reactivity through synergistic interfacial interactions.Morphological analysis using SEM/TEM revealed that P(VDF-HFP)formed a protective layer on Al and NH_(4)CoF_(3)particles,improving dispersion,hydrophobicity(water contact angle increased by 80.5%compared to physically mixed composites),and corrosion resistance.Thermal decomposition of NH_(4)CoF_(3)occurred at 265℃,releasing NH_(3)and HF,which triggered exothermic reactions with Al.The ternary composites exhibited a narrowed main reaction temperature range and concentrated heat release,attributed to improved interfacial contact and polymer decomposition.Combustion tests demonstrated that Al-NH_(4)CoF_(3)@P(VDF-HFP)achieved self-sustaining combustion.In addition,a simple validation was done by replacing the Al component in the aluminium-containing propellant,demonstrating its potential application in the propellant field.This work establishes a novel strategy for designing stable,high-energy composites with potential applications in advanced propulsion systems.展开更多
Early prevention and control of coal spontaneous combustion have emerged as a critical research area in coal mine safety.Due to their sustainability and environmental friendliness,microorganisms have gained attention....Early prevention and control of coal spontaneous combustion have emerged as a critical research area in coal mine safety.Due to their sustainability and environmental friendliness,microorganisms have gained attention.A filamentous fungus was collected in the coal mine and identified as Absidia spinosa.Results indicated that the mycelium effectively covered and repaired many coal pores.The oxygen consumption ratio of A.spinosa was higher in coal-containing environments than in coal-free conditions.The fungus significantly impacted aliphatic functional groups,disrupting bridging bonds and side chains connected to aromatic structures and reducing the relative content of C—O bonds.Additionally,A.spinosa increases the ignition temperature by 25.34℃.The total heat release was decreased by approximately 32.58%,and the activation energies were increased.The genome of Absidia spinosa revealed genes related to oxygen consumption,small molecule degradation,and secretion of metabolic products,such as those annotated under GO ID:0140657,etc.The pathways involved in the degradation of small organic molecules(e.g.,ko00626,etc.),carbon fixation,and nitrogen cycling,all linked to coal decomposition.Through oxygen consumption and the alteration of coal-active structures,A.spinosa effectively inhibits CSC,providing an experimental basis for exploring eco-friendly biological control methods in the goaf.展开更多
The presence of a surface oxide film(B_(2)O_(3))on boron(B)particles significantly compromises their combustion efficiency and kinetic performance in fuel-rich solid propellants.This study proposes an innovative conti...The presence of a surface oxide film(B_(2)O_(3))on boron(B)particles significantly compromises their combustion efficiency and kinetic performance in fuel-rich solid propellants.This study proposes an innovative continuous modification strategy combining non-thermal plasma(NTP)etching with fluorocarbon passivation.Characterization and kinetic analysis revealed that reactive plasma species—including atomic hydrogen(H),electronically excited molecular hydrogen(H_(2)^(*)),vibrationally excited molecular hydrogen(H_(2)v),and hydrogen ions(H^(+))—dominate the reduction of B_(2)O_(3)through lowering the transition energy barrier and shifting the reaction spontaneity.Subsequent argon plasma fragmentation of C_(8)F_(18)generates fluorocarbon radicals that form conformal passivation coatings(thickness:7 nm)on purified boron surfaces.The modified boron particles exhibit 37.5℃lower exothermic peak temperature and 27.2%higher heat release(14.8 kJ/g vs.11.6 kJ/g)compared to untreated counterparts.Combustion diagnostics reveal 194%increase in maximum flame height(135.10 mm vs.46.03 mm)and 134%enhancement in flame propagation rate(4.44 cm/s vs.1.90 cm/s).This NTP-based surface engineering approach establishes a scalable pathway for developing highperformance boron-based energetic composites.展开更多
Arid and semi-arid ecosystems are prone to extensive fires due to specific climatic conditions,sparse vegetation cover,and high density of fine fuels.Understanding the flammability characteristics of land covers is es...Arid and semi-arid ecosystems are prone to extensive fires due to specific climatic conditions,sparse vegetation cover,and high density of fine fuels.Understanding the flammability characteristics of land covers is essential for fire management and designing land restoration programs in arid and semi-arid ecosystems.This study provided a new approach to evaluate the flammability of shrublands and woodlands using flammability indices(FIs)including time to ignition(TI),duration of combustion(DC),and flame height(FH)of plant species and their relative frequencies in the Dalfard Basin of southeastern Iran.The results showed that there was a significant difference in FIs between land covers.Shrublands had higher flammability potential compared with woodlands.Plant moisture content had a negative relationship with TI(P<0.010)and no significant relationship with DC and FH(P>0.050).Artemisia spp.,Astragalus gossypinus Fischer,Amygdalus scoparia Spach,and Cymbopogon jwarancusa(Jones)Schult.had the highest FI.Tree species such as Rhazya stricta Decne.,and Pistacia atlantica Desf.showed greater resistance to fire.Using principal component analysis,the relationship between species and FIs was examined,and TI of wet fuel was the most important FI in relation to species.Structural equation model showed that life form(P<0.001)was the most important flammability driver.Precipitation(P<0.010)and legume species(P<0.010)were significantly related to the flammability in arid land.This study emphasizes the importance of managing high-risk species and using resistant species in vegetation restoration and shows that combining species FIs with their abundance is an effective tool for assessing fire risk and fuel management at the plant community scale.展开更多
文摘In order to solve the issue that the combustible objects for cased telescoped ammunition (CTA) didn't burn completely during the combustion process, the microcellular combustible objects were foamed with numerous cells in the micron order to improve the combustion performance by the supercritical carbon dioxide (SCeCO2) foaming technology. As the cell structure determined the combustion properties of microcellular combustible objects, the solubility of SCeCO2 dissolved into the combustible objects was obtained from the gravimetric method, and scanning electron microscope (SEM) was applied to characterize the cell structure under various process conditions of solubility, foaming temperature and foaming time. SEM images indicate that the cell diameter of microcellular combustible objects is in the level of 1 mm and the cell density is about 1011 cell,cm^-3. The microcellular combustible objects fabricated by the SCeCO2 foaming technology are smooth and uniform, and the high specific surface area of cell structure can lead to the significant combustion performance of microcellular combustible object for CTA in the future.
基金Sponsored by Young Fund Programs of Explosives&Propellants ( HYZ08010202-4)
文摘A fractal pore structure model of combustible cartridge cases was established by virtue of the fractal geometry. Pore structure information, such as backbone fractal dimension and pore fractal dimension, of four kinds of combustible cartridge case were obtained by mercury intrusion porosimetry (MIP) . The formation mechanism of fractal pore structure of combustible cartridge was studied. The results show that the backbone fractal dimension consists of the component and influenced by the component number and size of components; the pore percolation fractal dimension reflects the pore structures of components; and the fractal dimension of pore structure is positively relative to the tensile strength of combustible cartridge case.
基金Project(10572026) supported by the National Natural Science Foundation of China
文摘A two-dimensional multi-material code was indigenously developed to investigate the effects of duct boundary conditions and ignition positions on the propagation law of explosion wave for hydrogen and methane-based combustible mixture gas. In the code,Young's technique was employed to track the interface between the explosion products and air,and combustible function model was adopted to simulate ignition process. The code was employed to study explosion flow field inside and outside the duct and to obtain peak pressures in different boundary conditions and ignition positions. Numerical results suggest that during the propagation in a duct,for point initiation,the curvature of spherical wave front gradually decreases and evolves into plane wave. Due to the multiple reflections on the duct wall,multi-peak values appear on pressure-time curve,and peak pressure strongly relies on the duct boundary conditions and ignition position. When explosive wave reaches the exit of the duct,explosion products expand outward and forms shock wave in air. Multiple rarefaction waves also occur and propagate upstream along the duct to decrease the pressure in the duct. The results are in agreement with one-dimensional isentropic gas flow theory of the explosion products,and indicate that the ignition model and multi-material interface treatment method are feasible.
基金the National High Technology Research and Development Program of China (863 Program)(Grant No.2006AA040601)
文摘One kind of combustible gas alarms based on industrial Ethernet was designed to prevent the gas leakage in industrial production sites, The alarm adopted the high performance microprocessor LPC2214 as the main chip. The embedded operating system μC/OS-Ⅱand TCP/IP protocol stack uIP running on LPC2214 constitute a development platform of application of the combustible gas alarm, The test shows that it can automatically and continuously detect combustible gas in industrial production sites in several positions;it can give out sound-light alarm and take protective measures immediately against the gas leakage; and it can send the detected data to PC through the Ethernet interface to realize the remote detection. The designed project provides a reference to design industrial devices based on industrial Ethernet
基金Supported by Scientific and Technological Project of Inner Mongolia Autonomous Region(2020GG0016).
文摘Based on a comprehensive and systematic analysis of the temporal and spatial distribution,periodic changes,and influencing factors of forest fires in Inner Mongolia,through fixed-point observations and experiments on the ground,forest combustibles are divided into the ground litter layer,ground standing litter,and living plants.The combustibles are divided into various grades according to their load,dryness and combustibility.By determining the influencing factors of each combustible grade,a forecast model of the combustibility grade of combustibles is established.The forecast model has been widely used in the mid-and long-term forecast model of fire danger grade,and the accuracy rate of the fall area forecast through back-generation fitting verification is above 88.43%.
文摘In this paper, we investigate a free boundary problem of a semilinear combustible system with higher dimension and heterogeneous environment. Such a problem is usually used as a model to describe heat propagation in a two-component combustible mixture In which the free boundary is described by Stefan-like condition. For simplicity, we assume that the environment and solutions are radially symmetric. We use the contraction mapping theorem to prove the local existence and uniqueness of the solution. Also we study the blowup property and the long time behavior of the solution. Our results show that when pq 〉 1 blowup occurs if the initial datum is large enough and the solution is global and slow, whose decay rate is at most polynomial if the initial value is suitably large, while when p 〉 1, q 〉 1 there is a global and fast solution, which decays uniformly at an exponential rate if the initial datum is small.
文摘Combustible agricultural waste is a potential source of energy because of its high organic content and heating value.As China’s economy develops,energy demand increases while environmental protection becomes more stringent.These competing demands make it urgent to find environmentally acceptable ways to extract energy from agricultural wastes.In this study,a liquid catalyst flow fuel cell(FFC)directly powered by combustible agricultural waste is investigated.This type of flow fuel cell can directly convert combustible agricultural waste at atmospheric pressure to electricity at 80-150℃and it is environmentally friendly.Polyoxometalates act as catalysts and charge carriers to drive the FFC.Wheat straw and wine residues were used to represent the main components of combustible agricultural waste.Experiment results indicated that the power density reached as high as 111 mW/cm^(2),hundreds of times higher than the output of a microbial cell.
基金the Asian Regional Research Program on Environmental Technology“Sustainable Solid Waste Landfill Management in Asia”funded from Sweden International Development Agency(Sida)and key project in China National Sciences&Technology Pillar Program during the Eleventh Five Year Plan period(Grant No.2008BAC46B06).
文摘Aged municipal solid wastes(MSW)excavated from landfills and dumpsites were characterized to analyze their fraction composition,moisture content,and lower heat value(LHV).The necessity and feasibility of recycling combustibles from aged MSW to improve the incineration of fresh MSW were investigated.The results showed that combustibles in aged MSW were easily separated from other components and than LHV of the separated combustibles are higher than 11000 kJ/kg.The fresh MSW are of high moisture contents with average LHV below 6500 kJ/kg,making their stable combustion difficult to maintain in MSW incinerators.For both fresh MSW and aged MSW,plastics are the main contributor to their LHV.To improve incineration of fresh MSW that are characterized with low LHV,combustibles separated from aged MSW were made into refuse derived fuel(RDF)pellets and were then added to fresh MSW by 2%wt.–5%wt.LHV variation and air supply resistance change of the MSW layer on the incinerator grate caused by the addition of RDF was checked,and no significant changes were found.No obvious difference was observed for the‘burn-out time’between RDF pellets and fresh MSW either.RDF made from aged MSW combustibles is found to be a promising auxiliary fuel to improve the incineration of fresh MSW,and aged MSW from old landfill cells and dumpsites can be finally disposed of jointly with fresh MSW by recycling combustible from the former to be coincinerated with the latter in the incineration plants.
基金Project supported by the National Natural Science Foundation of China and the Edison Sensor Tech. Center, Dept of Development of the State of Ohio, USA.
文摘This paper studies gas detectors, especially, gas sensors in which a thermochemical reac-tion takes place on a catalytic element. The novel catalytic sensor is fabricated using micro-electronic thick-film techniques, and it is used to monitor the concentration of combustiblegases and their mixture in a flow reactor. This sensor has two identical platinum films whichare used as the heater, resistance thermometer and the surface of reaction. Catalyst of palla-dium is deposited on one of the platinum film by chemical method, while the other platinumfilm serves as a compensating element. The difference in the minimum reaction temperaturefor the catalytic oxidation of the combustible gas components of mixture by palladium sug-gests that it is possible to analyse such a gas mixture. The purpose of the study is to demon-strate that the sensor fabricated by this process has good sensing characteristics for hydrogenor carbon monoxide gas in the mixture of methane and ethane.
基金supported by the National Natural Science Foundation of China(Grant No.12074187).
文摘Electrically controlled solid propellant(ECSP)offers multiple ignition and adjustable burning rate,serving as fuel for next-generation intelligent propulsion systems.To further enhance the combustion performance of ECSP,a method utilizing electrochemical and thermal decomposition catalysts has been proposed.In this work,we investigated the combustion characteristics of hydroxylamine nitrate(HAN)-based ECSP incorporating cerium oxide(CeO_(2))and graphene oxide(GO)by using an electrically controlled combustion test system.Electrochemical impedance spectroscopy(EIS)and linear sweep voltammetry(LSV)were used to measure the electrical conductibility and overpotential of ECSP with various additives,and Tafel curves were calculated.Thermogravimetric analysis coupled with differential scanning calorimetry(TG-DSC)was employed to investigate the thermal decomposition behavior of ECSP.While the addition of CeO_(2) and GO reduced the conductivity of ECSP,both catalysts exhibited strong electrocatalytic properties and facilitated the thermal decomposition of ECSP.Between two catalysts,GO demonstrated superior electrochemical catalytic performance but weaker thermal decomposition catalytic ability than CeO_(2).The addition of catalysts significantly enhanced the combustion performance of HAN-based ECSP.Specifically,the ignition delay time was shortened by 10%~20%.CeO_(2) raised the burning rate by approximately 20%but GO exhibited a remarkable boost of 40%in burning rate at high voltage.The combination of GO and PVA produced a flame-retardant substance that negatively impacted the ignition delay of ECSP and resulted in a smaller increase in the burning rate of ECSP at low ignition voltages.
基金funded by the National Natural Science Foundation of China(Grant No.U21B2086)。
文摘This study investigates the performance boundaries of ramjet and scramjet engines fueled by boronbased propellant through full-scale engine modeling and three-dimensional computational fluid dynamics simulations.Results show that the performance boundary between ramjets and scramjets occurs near Mach 7.Specifically,at Mach 6,the ramjet exhibits a 1290 m/s higher specific impulse than the scramjet;however,at Mach 7,their performance becomes comparable.The ramjet's higher static temperature promotes boron particle vaporization and B_(2)O_(2) dissociation,limiting the total temperature increase,unlike in scramjets.The boron vapor mass fraction significantly impacts this temperature difference,with ramjets exhibiting values 8.5 and 3.9 times higher than scramjets at Mach 6 and Mach 7,respectively.Despite lower total temperatures,ramjets achieve more efficient boron combustion due to the combined effects of higher pressures and longer particle residence times.These findings offer valuable insights for engine designers in selecting ramjet or scramjet configurations for boron-fueled propulsion systems.
基金supported by the National Natural Science Foundation of China(No.52573220)the National Key R&D Program of China(No.2023YFC3404201)+1 种基金the Fundamental Research Funds for the Central Universities(No.FRF-IDRY-GD24-005)the State Key Laboratory of Solid Waste Reuse for Building Materials(No.SWR-2022-009).
文摘Coal cinder is an abundant byproduct of the extensive consumption of coal in industrial production and daily life.Making full use of the cinder is conducive to a low-carbon economy.In this study,inspired by the burning of coal,a new method for constructing a silica-based composite porous material(SiO_(2)-CPM)was developed by combusting a siloxane-modified anthracite coal gel(CSiO_(2) gel).During this process,the combustion product was directly converted into a porous material,and the calorific value of the coal remained nearly unchanged(~98%of the original calorific value was retained),demonstrating the viability of this method for energy-efficient applications.The SiO_(2)-CPM exhibited an ultra-low thermal conductivity(0.036 W/(m·K)at room temperature),outperforming conventional insulation materials(e.g.,cotton~0.05 W/(m·K)).Additionally,it showed enhanced mechanical strength(fracture stress of 41.8 kPa)compared to the powder state of the coal cinder.Experimental results indicate that the amount of siloxane,structure-directing agent,and an acidic environment were critical for mechanical enhancement.The SiO_(2)-CPM showed good dimensional stability against thermal expansion and exhibited excellent thermal insulation and fire resistance even at 900℃.Meanwhile,the SiO_(2)-CPM with complex geometry could be easily fabricated using this method owing to the excellent shaping ability of the CSiO_(2) gel.Compared to conventional methods such as sol-gel synthesis or freeze-drying,this approach for fabricating SiO_(2)-CPM is simpler and cost-effective and allows the direct utilization of coal cinder post-combustion.
基金funded by the National Natural Science Foundation of China,Grant No.22405208。
文摘Boron has attracted increasing attention in the field of high-energy explosives and propellants due to its high volume calorific value and mass calorific value.However,the complicated combustion process and low combustion efficiency hinder its wide application.To tackle this challenge,bioinspired polydopamine(PDA)interface reinforced boron-Viton composites,with high structure stability and excellent energy releasing efficiency,are designed and prepared,combining the interface regulation of PDA biomimetic materials and combustion promotion of fluoropolymers.Firstly,the stronger adsorption energy of PDA with boron compared to Viton is demonstrated by molecular dynamics simulations.Next,B@PDA@Viton is prepared by the combination of in-situ dopamine polymerization and solvent/nonsolvent method,and the double-layer core-shell structure is confirmed by XPS,FTIR,and TEM characterizations.TG-DSC analysis shows that B@PDA@Viton possesses superior thermal properties,with a 55.48%increase in oxidation heat compared to raw B.Furthermore,ignition and combustion performance tests indicate that B@PDA@Viton reduces ignition delay by 57.56%and increases heat of combustion by 68.63%relative to raw B.These findings elucidate the ignition and combustion mechanisms of B@PDA@Viton.This work not only developed high-performance boron-based composite fuels but also provided insights into the development of boron-based fuels.
文摘Maintaining the structural integrity of parallel natural gas pipelines during leakage-induced jet fires remains a critical engineering challenge.Existing methods often fail to account for the complex interactions among heat transfer,material behavior,and pipeline geometry,which can lead to overly simplified and potentially unsafe assessments.To address these limitations,this study develops a multiphysics approach that integrates small-orifice leakage theory with detailed thermo-fluid-structural simulations.The proposed framework contributes to a more accurate failure analysis through three main components:(1)coupled modeling that tracks transient heat flow and stress development as fire conditions evolve;(2)risk assessment incorporating spatial layout,material property changes with temperature,and operational limits;and(3)sensitivity analysis to identify key design factors that influence structural performance under high thermal loads.Simulation results demonstrate that thermal radiation from neighboring jet fires significantly accelerates material degradation,with inter-pipeline spacing emerging as a critical determinant of structural response.Notably,increasing the spacing between pipelines reduces thermal interaction and mechanical stress transfer.As a result,systems with optimized spacing exhibit markedly lower deformation than conventional configurations.These findings provide a foundation for re-evaluating pipeline layout strategies and strengthening safety protocols,particularly in high-risk environments where fire exposure can severely compromise structural reliability.The proposed approach offers actionable guidance for engineers and policymakers seeking to enhance the resilience of pipeline infrastructure under extreme thermal conditions.
基金supported by Istanbul Technical University(Project No.45698)supported through the“Young Researchers’Career Development Project-training of doctoral students”of the Croatian Science Foundation.
文摘This paper investigates the reliability of internal marine combustion engines using an integrated approach that combines Fault Tree Analysis(FTA)and Bayesian Networks(BN).FTA provides a structured,top-down method for identifying critical failure modes and their root causes,while BN introduces flexibility in probabilistic reasoning,enabling dynamic updates based on new evidence.This dual methodology overcomes the limitations of static FTA models,offering a comprehensive framework for system reliability analysis.Critical failures,including External Leakage(ELU),Failure to Start(FTS),and Overheating(OHE),were identified as key risks.By incorporating redundancy into high-risk components such as pumps and batteries,the likelihood of these failures was significantly reduced.For instance,redundant pumps reduced the probability of ELU by 31.88%,while additional batteries decreased the occurrence of FTS by 36.45%.The results underscore the practical benefits of combining FTA and BN for enhancing system reliability,particularly in maritime applications where operational safety and efficiency are critical.This research provides valuable insights for maintenance planning and highlights the importance of redundancy in critical systems,especially as the industry transitions toward more autonomous vessels.
基金supported by the National Natural Science Foundation of China(No.51706105)。
文摘Al/NH_(4)CoF_(3)-Φ(Φ=0.5,1.0,1.5,2.0,and 3.0)binary composites and Al-NH_(4)CoF_(3)@P(VDF-HFP)ternary composites are fabricated via ultrasonication-assisted blending and electrostatic spraying.The effect of equivalence ratio(Φ)on the reaction properties is systematically investigated in the binary Al/NH_(4)CoF_(3)system.For ternary systems,electrostatic spraying allows both components to be efficiently encapsulated by P(VDF-HFP)and to achieve structural stabilization and enhanced reactivity through synergistic interfacial interactions.Morphological analysis using SEM/TEM revealed that P(VDF-HFP)formed a protective layer on Al and NH_(4)CoF_(3)particles,improving dispersion,hydrophobicity(water contact angle increased by 80.5%compared to physically mixed composites),and corrosion resistance.Thermal decomposition of NH_(4)CoF_(3)occurred at 265℃,releasing NH_(3)and HF,which triggered exothermic reactions with Al.The ternary composites exhibited a narrowed main reaction temperature range and concentrated heat release,attributed to improved interfacial contact and polymer decomposition.Combustion tests demonstrated that Al-NH_(4)CoF_(3)@P(VDF-HFP)achieved self-sustaining combustion.In addition,a simple validation was done by replacing the Al component in the aluminium-containing propellant,demonstrating its potential application in the propellant field.This work establishes a novel strategy for designing stable,high-energy composites with potential applications in advanced propulsion systems.
基金supported by the National Natural Science Foundation of China(No.51974128)the National Key Research and Development Program of China(No.2023YFC3009105)。
文摘Early prevention and control of coal spontaneous combustion have emerged as a critical research area in coal mine safety.Due to their sustainability and environmental friendliness,microorganisms have gained attention.A filamentous fungus was collected in the coal mine and identified as Absidia spinosa.Results indicated that the mycelium effectively covered and repaired many coal pores.The oxygen consumption ratio of A.spinosa was higher in coal-containing environments than in coal-free conditions.The fungus significantly impacted aliphatic functional groups,disrupting bridging bonds and side chains connected to aromatic structures and reducing the relative content of C—O bonds.Additionally,A.spinosa increases the ignition temperature by 25.34℃.The total heat release was decreased by approximately 32.58%,and the activation energies were increased.The genome of Absidia spinosa revealed genes related to oxygen consumption,small molecule degradation,and secretion of metabolic products,such as those annotated under GO ID:0140657,etc.The pathways involved in the degradation of small organic molecules(e.g.,ko00626,etc.),carbon fixation,and nitrogen cycling,all linked to coal decomposition.Through oxygen consumption and the alteration of coal-active structures,A.spinosa effectively inhibits CSC,providing an experimental basis for exploring eco-friendly biological control methods in the goaf.
基金supported by the National Natural Science Foundation of China(Nos.U2341249,12005076,22205112)the Fundamental Research Funds for the Central Universities(No.2025201012)。
文摘The presence of a surface oxide film(B_(2)O_(3))on boron(B)particles significantly compromises their combustion efficiency and kinetic performance in fuel-rich solid propellants.This study proposes an innovative continuous modification strategy combining non-thermal plasma(NTP)etching with fluorocarbon passivation.Characterization and kinetic analysis revealed that reactive plasma species—including atomic hydrogen(H),electronically excited molecular hydrogen(H_(2)^(*)),vibrationally excited molecular hydrogen(H_(2)v),and hydrogen ions(H^(+))—dominate the reduction of B_(2)O_(3)through lowering the transition energy barrier and shifting the reaction spontaneity.Subsequent argon plasma fragmentation of C_(8)F_(18)generates fluorocarbon radicals that form conformal passivation coatings(thickness:7 nm)on purified boron surfaces.The modified boron particles exhibit 37.5℃lower exothermic peak temperature and 27.2%higher heat release(14.8 kJ/g vs.11.6 kJ/g)compared to untreated counterparts.Combustion diagnostics reveal 194%increase in maximum flame height(135.10 mm vs.46.03 mm)and 134%enhancement in flame propagation rate(4.44 cm/s vs.1.90 cm/s).This NTP-based surface engineering approach establishes a scalable pathway for developing highperformance boron-based energetic composites.
文摘Arid and semi-arid ecosystems are prone to extensive fires due to specific climatic conditions,sparse vegetation cover,and high density of fine fuels.Understanding the flammability characteristics of land covers is essential for fire management and designing land restoration programs in arid and semi-arid ecosystems.This study provided a new approach to evaluate the flammability of shrublands and woodlands using flammability indices(FIs)including time to ignition(TI),duration of combustion(DC),and flame height(FH)of plant species and their relative frequencies in the Dalfard Basin of southeastern Iran.The results showed that there was a significant difference in FIs between land covers.Shrublands had higher flammability potential compared with woodlands.Plant moisture content had a negative relationship with TI(P<0.010)and no significant relationship with DC and FH(P>0.050).Artemisia spp.,Astragalus gossypinus Fischer,Amygdalus scoparia Spach,and Cymbopogon jwarancusa(Jones)Schult.had the highest FI.Tree species such as Rhazya stricta Decne.,and Pistacia atlantica Desf.showed greater resistance to fire.Using principal component analysis,the relationship between species and FIs was examined,and TI of wet fuel was the most important FI in relation to species.Structural equation model showed that life form(P<0.001)was the most important flammability driver.Precipitation(P<0.010)and legume species(P<0.010)were significantly related to the flammability in arid land.This study emphasizes the importance of managing high-risk species and using resistant species in vegetation restoration and shows that combining species FIs with their abundance is an effective tool for assessing fire risk and fuel management at the plant community scale.
