The combustion behavior of Ti-Al-Mo-Zr-Sn-W alloy(TC25G)was studied in a high-temperature and high-speed air flow environment using the laser ignition method combined with ultra-high temperature infrared thermometer,s...The combustion behavior of Ti-Al-Mo-Zr-Sn-W alloy(TC25G)was studied in a high-temperature and high-speed air flow environment using the laser ignition method combined with ultra-high temperature infrared thermometer,scanning electron microscope,X-ray diffractometer,and transmission electron microscope.The burn-resistant performance of TC25G and TC11 alloys was compared.Meanwhile,the microstructural characteristics,crystal structure,and formation mechanism of the combustion products of TC25G alloy were analyzed in detail.The results show that the high-temperature and high-speed air flow promotes combustion within the air flow temperature range of 200–400℃and the air flow velocity range of 0–100 m/s.The combustion path advances along the direction of the air flow.The combustion of TC25G alloy mainly relies on the diffusion of the oxygen and the expansion of the combustion area caused by the movement of the melt.Based on the microstructure and composition of combustion product,it can be divided into the combustion zone,the melting zone,and the heat affected zone.During combustion,the formation of microstructures is closely correlated with the behavior of alloying elements and their selective combination with O.The major oxidation products of Ti are TiO and TiO_(2).The oxides formed by Mo and W hinder the movement of the melt during the combustion.Al and Zr tend to undergo internal oxidation.Al_(2)O_(3)precipitates on the surface of ZrO_(2),forming a protective oxide layer that inhibits the inward diffusion of O.Moreover,the element enrichment at the interface between the melting zone and the heat affected zone increases the melting point on the solid side,hindering the migration of the solid-liquid interface.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
The development of solar-driven interfacial evaporation technology is pivotal for addressing global water scarcity.However,it is hindered by the difficulty in synergizing high photothermal conversion with low water ev...The development of solar-driven interfacial evaporation technology is pivotal for addressing global water scarcity.However,it is hindered by the difficulty in synergizing high photothermal conversion with low water evaporation enthalpy into a single material.Herein,we propose an iron-aldehyde-cooperative dynamic covalent anchoring strategy,successfully constructing a covalently locked,hydroxymethyl-functionalized PEDOT-PVA integrated dual-network hydrogel(MEPH).This strategy employs Fe3+to achieve the one-step in situ oxidative polymerization of hydroxymethyl EDOT while concurrently forming a physical hybrid network with PVA,which is subsequently reinforced by covalent cross-linking using glutaraldehyde.This design endows the MEPH with exceptional broadband light absorption(>99%),efficient water transport,and regulated water state within the hydrogel matrix,leading to a reduced evaporation enthalpy of 732 J·g^(−1).The resulting evaporator achieves an ultrahigh evaporation rate of 4.95 kg·m^(−2)·h^(−1)under 1-sun illumination,corresponding to an energy conversion efficiency exceeding 95%,while maintaining stable,salt-resistant operation in high-salinity environments.Outdoor experiments validate its outstanding practicality for seawater and wastewater purification,with the produced freshwater significantly promoting plant growth,highlighting its great potential in sustainable agricultural water cycles.This iron-aldehyde-cooperative dynamic covalent anchoring strategy provides an innovative design paradigm for a new generation of high-performance and robust solar evaporators.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
In composite solid propellants with high aluminum(Al)content and low burning rate,incomplete combustion of the Al powder may occur.In this study,varying lithium(Li)content in Al-Li alloy powder was utilized instead of...In composite solid propellants with high aluminum(Al)content and low burning rate,incomplete combustion of the Al powder may occur.In this study,varying lithium(Li)content in Al-Li alloy powder was utilized instead of pure aluminum particles to mitigate agglomeration and enhance the combustion efficiency of solid propellants(Combustion efficiency herein refers to the completeness of metallic fuel oxidation,quantified as the ratio of actual-to-theoretical energy released during combustion)with high Al content and low burning rates.The impact of Al-Li alloy with different Li contents on combustion and agglomeration of solid propellant was investigated using explosion heat,combustion heat,differential thermal analysis(DTA),thermos-gravimetric analysis(TG),dynamic high-pressure combustion test,ignition experiment of small solid rocket motor(SRM)tests,condensation combustion product collection,and X-ray diffraction techniques(XRD).Compared with pure Al,Al-Li alloys exhibit higher combustion heat,which contributes to improved combustion efficiency in Al-Li alloy-containing propellants.DTA and TG analyses demonstrated higher reactivity and lower ignition temperatures for Al-Li alloys.High-pressure combustion experiments at 5 MPa showed that Al-Li alloy fuel significantly decreases combustion agglomeration.The results from theφ75 mm andφ165 mm SRM and XRD tests further support this finding.This study provides novel insights into the combustion and agglomeration behaviors of high-Al,low-burning-rate composite solid propellants and supports the potential application of Al-Li alloys in advanced propellant formulations.展开更多
By combining the merits of radiative cooling(RC)and evaporation cooling(EC),radiative coupled evaporative cooling(REC)has attracted considerable attention for sub-ambient cooling purposes.However,for outdoor devices,t...By combining the merits of radiative cooling(RC)and evaporation cooling(EC),radiative coupled evaporative cooling(REC)has attracted considerable attention for sub-ambient cooling purposes.However,for outdoor devices,the interior heating power would increase the working temperature and fire risk,which would suppress their above-ambient heat dissipation capabilities and passive water cycle properties.In this work,we introduced a REC design based on an all-in-one photonic hydrogel for above-ambient heat dissipation and flame retardancy.Unlike conventional design RC film for heat dissipation with limited cooling power and fire risk,REC hydrogel can greatly improve the heat dissipation performance in the daytime with a high workload,indicating a 12.0℃lower temperature than the RC film under the same conditions in the outdoor experiment.In the nighttime with a low workload,RC-assisted adsorption can improve atmospheric water harvesting to ensure EC in the daytime.In addition,our REC hydrogel significantly enhanced flame retardancy by absorbing heat without a corresponding temperature rise,thus mitigating fire risks.Thus,our design shows a promising solution for the thermal management of outdoor devices,delivering outstanding performance in both heat dissipation and flame retardancy.展开更多
The evaporation residual cross sections(ERCSs)of these reactions were calculated by using^(144)Sm,^(160,164)Dy,^(165)Ho,^(166)Er,^(169)Tm,^(171,174)Yb,^(175)Lu,^(176-180)Hf,^(181)Ta,^(180,182)W and^(187)Re targets wit...The evaporation residual cross sections(ERCSs)of these reactions were calculated by using^(144)Sm,^(160,164)Dy,^(165)Ho,^(166)Er,^(169)Tm,^(171,174)Yb,^(175)Lu,^(176-180)Hf,^(181)Ta,^(180,182)W and^(187)Re targets with^(40)Ar projectiles in the theoretical framework of the dinuclear system(DNS)model.The de-excitation process of the compound nucleus was theoretically calculated using two different statistical models,namely the statistical model 1 and statistical model 2(GEMINI++model).The calculated ERCSs were also compared with the experimental data.The ERCSs of synthesizing new proton-rich nuclides were investigated based on the fusion evaporation reaction.Predictions were made for the ERCSs of new isotopes of Pu,Cm and Bk in the heavy nuclei region,while the new isotopes of Ds,Cn and Fl are predicted in the superheavy nuclei region of Z≥104.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
To address the kinetic constraints inherent in the catalytic combustion of pulverized coal injection under low heating-rate conditions within conventional air atmospheres,a drop tube furnace was utilized to simulate t...To address the kinetic constraints inherent in the catalytic combustion of pulverized coal injection under low heating-rate conditions within conventional air atmospheres,a drop tube furnace was utilized to simulate the catalytic combustion of pulverized coal(PC).The effects of gas composition,oxygen concentration,the type,and the content of catalysts on the combustion reactivity were systematically analyzed.Furthermore,the structural changes of unburned pulverized coal were also examined.Experimental results indicate that as the oxygen concentration increased from 21%to 79%,compared with the O_(2)/N_(2)condition,the increment in the burnout rate of PC under the O_(2)/CO_(2)condition increased from 3%to 23%.After the addition of catalysts,including hematite,metallurgical oil sludge,and light-burnt dolomite(LBD),under the condition of 21%oxygen concentration,the effects of the three catalysts under the O_(2)/CO_(2)condition were superior to those under the O_(2)/N_(2)condition.This trend was reversed under the conditions of 38%and 79%oxygen concentrations.In all atmospheres,the three catalysts can enhance the burnout rate of PC.Among them,LBD exhibits the most favorable effect,and there exists an optimal dosage.Mechanistic analysis through scanning electron microscopy,X-ray diffraction,and N_(2)adsorption-desorption reveals that under 21%O_(2)/79%CO_(2)conditions,high-concentration CO_(2)leads to the formation of pores,and additives accelerate the oxidation of C and the gasification of CO_(2)through oxygen transfer,thereby enhancing the burnout rate of PC.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
Temperature is one of the main causes of spontaneous coal combustion.To improve the flame retardant performance,CaCl2,ammonium polyphosphate(APP),and calcium phosphate(CaHP)were compounded to control the temperature r...Temperature is one of the main causes of spontaneous coal combustion.To improve the flame retardant performance,CaCl2,ammonium polyphosphate(APP),and calcium phosphate(CaHP)were compounded to control the temperature response of different stages of coal spontaneous combustion through physical and chemical synergy.Simultaneous thermal analysis,thermogravimetric-Fourier infrared spectroscopy(TG-FTIR),in-situ FTIR and electron paramagnetic resonance(EPR)were used to study the multitemperature stage synergistic inhibition of coal spontaneous combustion.The results show that the proposed method is effective.By obtaining the characteristics of the spontaneous combustion reaction stage of coal in advance,the method of configuring an appropriate composite inhibitor can effectively realize the intelligent control of the temperature response of coal spontaneous combustion.The ignition point of long-flame coal increased by 37.15℃.The inhibition rate of the gas phase products was more than 20%,and the inhibition rate of the functional groups was more than 30%.It has a good quenching effect on free radicals and can effectively inhibit the oxidation activity of active free radicals such as H,HO,and O.The results provide experimental and theoretical support for the study of temperature-responsive composite flame retardants for coal with different metamorphic degrees.展开更多
The operational demands of a wide range significantly exacerbate combustion instability issues within ramjet combustor.To suppress combustion oscillations,an open-loop control system utilizing Linear Genetic Programmi...The operational demands of a wide range significantly exacerbate combustion instability issues within ramjet combustor.To suppress combustion oscillations,an open-loop control system utilizing Linear Genetic Programming(LGP)has been developed for a full-scale annular ramjet combustor.The LGP is used to generate control laws that include multi-frequency forcing.These laws are then transformed into square waves to actuate the solenoid valve,which modulates the kerosene supply for open-loop control.The results show that the duty cycle has little effect on instability amplitude,whereas an increase in frequency leads to a remarked reduction in combustion amplitude.After five generations evolvements,the pressure amplitude is reduced by 40.6% under the optimal control law generated by LGP.Furthermore,the machine learning process is depicted using a proximity map of control law similarity,with the search pathway visualized by the steepest descent.All individuals go forward to the upper left corner of the map with the evolution process,terminating at the optimal individual of the fifth generation.展开更多
Understanding the relative contributions of transpiration(T)and evaporation(E)to evapotranspiration(ET)is critical for evaluating water use efficiency,ecosystem productivity,and soil–plant–atmosphere interactions in...Understanding the relative contributions of transpiration(T)and evaporation(E)to evapotranspiration(ET)is critical for evaluating water use efficiency,ecosystem productivity,and soil–plant–atmosphere interactions in a changing environment.However,such partitioning and its responses to dry,normal,and wet conditions,as well as the controlling factors at multiple temporal scales,remain poorly understood in China's boreal forests,characterized by synchronization of water supply and energy demand.In this study,we used 8 years of ET data from the growing season(GS;May–September)collected via the eddy-covariance system and applied the underlying water use efficiency(uWUE)method to estimate T and E in a boreal larch forest in China.Our results revealed that E was the dominant component of ET.Specifically,T accounted for 0.44 of ET(T/ET),whereas E contributed to 0.56 of ET(E/ET)over the study period.The response of T/ET to dry conditions during the leaf defoliation stage(LDS)was more pronounced than during the leaf expansion stage(LES).Despite an increase in T/ET(reaching 0.49)during the dry season compared to the normal season(0.42),E was still the dominant contributor to ET.Furthermore,E/ET was significantly controlled by vapor pressure deficit(VPD)across daily to GS scales.Interestingly,soil water content(SWC)was not a controlling factor for regulating E/ET,indicating that atmospheric forces strongly constrained the variability of E/ET in this boreal forest.These findings highlight that E should be given greater attention in boreal forests than before.Our study suggests that effective management strategies for improving water use efficiency in such forest ecosystems are urgently needed.展开更多
Powder-Fueled Water Ramjet Engine(PFWRE)is the most promising powerplant in underwater high-speed propulsion.However,the effect of powder injection mode on its performance and the mechanism of this effect are not well...Powder-Fueled Water Ramjet Engine(PFWRE)is the most promising powerplant in underwater high-speed propulsion.However,the effect of powder injection mode on its performance and the mechanism of this effect are not well understood.In this paper,a computational framework for multiphase combustion flow is developed and validated.Further,the effects of different injection schemes on flow combustion characteristics and engine performance are evaluated via simulation.Our findings indicate that the dominant recirculation zone in front of the primary water inlet delivers water vapor to the combustor head,providing the necessary oxidant for the ignition and combustion of Al particles.Changing the injection parameters directly affects the flame zone distribution and the ability of the recirculation zone to deliver water vapor,leading to variations in particle ignition delay.The engine combustion efficiency and specific impulse efficiency exhibit a negative correlation with injection height,peaking before declining with increased injection angle.It is shown that particle mixing degree and particle dispersion degree are closely related to engine performance.Enhanced particle mixing in front of the primary water inlet and particle dispersion behind the secondary water inlet are considered favorable approaches to improve engine performance,which promotes the particle combustion process and improves the heat-work conversion efficiency.展开更多
This study aims to reveal the influence of Local Momentum Ratio(LMR)on the combustion efficiency of an LOX/GCH4 pintle injector from the perspective of spray characteristics.Hot fire tests were conducted to establish ...This study aims to reveal the influence of Local Momentum Ratio(LMR)on the combustion efficiency of an LOX/GCH4 pintle injector from the perspective of spray characteristics.Hot fire tests were conducted to establish the relationship between combustion efficiency and LMR.The spray characteristics for different LMRs were simulated by the validated volume of fluid-to-discrete phase model method,taking into account the combustion chamber wall confinement.Subsequently,the difference in combustion efficiency was analyzed by comparing the spray simulation results of backpressure conditions similar to hot fire tests.The results indicate that combustion efficiency increased initially(LMR=1.12-1.64)and then decreased(LMR>1.64).Quantitative analysis revealed a linear correlation(R^(2)=0.95)between LMR and combustion efficiency within 1.12<LMR<1.64.As the LMR increased,the improvement in combustion efficiency was attributed to a wider spray distribution range and smaller droplet sizes.The area of the mantle recirculation zone that is detrimental to combustion decreased by approximately 38%,and the droplet size reduced from 37 to 16μm.This effectively enhanced both the mixing of the propellant and the evaporation process.When the LMR exceeded the critical value(1.64 in this study),the impingement of liquid oxygen on the combustion chamber wall was confirmed via overheating discoloration marks on the inner surface of combustion chamber's cylindrical section.The impingement of liquid oxygen on the combustion chamber wall increased the transport of liquid oxygen to the wall,directly reducing the mixing quality and combustion efficiency.The outcomes of this study provide the practical guidance for design and improvement in combustion efficiency of the pintle injector thrust chamber.展开更多
The electrode structures in ignition devices for Electrically Controlled Solid Propellants(ECSP) can be classified into fixed and movable types. In movable electrode structures, springs are typically used to push the ...The electrode structures in ignition devices for Electrically Controlled Solid Propellants(ECSP) can be classified into fixed and movable types. In movable electrode structures, springs are typically used to push the electrodes and the propellant. The effects of spring pressure on the ignition and combustion of propellants have not yet been studied. In this paper, a universal testing machine and an electrochemical workstation were firstly utilized to investigate the compressive mechanical property and conductivity of Hydroxylamine Nitrate(HAN)-ECSP. The maximum pressure at which the propellant undergoes elastic deformation is 65 kPa. When the spring pressure increased from 5.1 k Pa to 20.4 kPa, the propellant resistance decreased from 56.8 Ω to 36.8 Ω.Various observation methods were employed to study the process of electrical energy injection and the ignition and combustion characteristics under constant voltage. Appropriately increasing the spring pressure can accelerate the injection of electrical energy into the propellant, increase the electrification current, and thus reduce the initial ignition delay time of the propellant. When the spring pressure is 20.4 kPa, the squeezing speed of the propellant is too fast, making it difficult for the propellant to be adequately heated at the electrode interface, which is unfavorable for ignition. Excessive spring pressure also leads to the accumulation of a large amount of combustion residue on the electrode plate, hindering the mixing and diffusion of hot gases during the second ignition process, preventing the gaseous flame of the propellant. When the spring pressure is 5.1 kPa, improving the working voltage can enhance the repeated ignition characteristics of the propellant.展开更多
Engineering the pore structure of biomass-derived activated carbons is critical for optimizing their performance in adsorptionbased applications.This study demonstrates for the first time that washing hydrochars in so...Engineering the pore structure of biomass-derived activated carbons is critical for optimizing their performance in adsorptionbased applications.This study demonstrates for the first time that washing hydrochars in solvents of different polarity before activation is a simple yet powerful strategy to tailor pore size distribution.Hydrochar is produced from spent coffee grounds via hydrothermal carbonization,followed by washing in various solvents and activation in KOH.This results in carbons with a very large surface area(~2700 m^(2)/g),and washing is demonstrated to significantly increase product yield.Furthermore,washing in non-polar or mixed-polarity solvents removes long-chain carboxylic acids and esters from the hydrochar,promoting the development of narrow micropores while suppressing mesopore formation.To illustrate the impact of this structural control of porous carbons,post-combustion CO_(2)capture is investigated as a case study.Narrower pore size distribution enhances CO_(2)uptake,significantly improving capacity from 2.8 mmol/g for unwashed samples to 3.8 mmol/g for acetone-washed samples.Interestingly,moderate pore size(9-12Å)is shown to be optimal for CO_(2):N2 selectivity,while smaller pores result in lower selectivity due to stronger interactions between N2 and the pore walls.These findings highlight the potential role of solvent washing in directing pore architecture of hydrochars for adsorption-based carbon capture technologies and beyond.展开更多
Existing droplet evaporation/combustion mod- els in computational fluid dynamics （CFD） simulation of spray combustion are based on simplified 1-D models. Both these models and recently developed 3-D models of single...Existing droplet evaporation/combustion mod- els in computational fluid dynamics （CFD） simulation of spray combustion are based on simplified 1-D models. Both these models and recently developed 3-D models of single- droplet combustion do not give the conditions for the different existing droplet combustion modes. In this paper, droplet evaporation and combustion are studied both analytically and numerically. In the analytical solution, a 2-D axisymmetric flow surrounding an evaporating and combusting droplet was considered. The governing equations were solved using an integral method, similar to the Karman-Pohlhausen method for solving boundary-layer flows with pressure gradient. The results give a local evaporation rate and flame radius in agree- ment with experimental results. In numerical simulation, 3-D combusting gas flows surrounding an ethanol droplet were studied. The prediction results show three modes of droplet combustion under different relative velocities, explaining the change in the evaporation constant with an increase in relative velocity observed in experiments. This implies that different droplet combustion models should be developed in simu- lating spray combustion. The predicted local evaporation rate and flame radius by numerical simulation are in agree- ment with the analytical solution in the range of azimuthal angles 0° 〈 θ 〈 90°. The numerical results indicate that the drag force of an evaporating and combusting droplet is much smaller than that of a cold solid particle, and thus the currently used drag models should be modified.展开更多
基金China“Ye Qisun”Science Foundation Project of National Natural Science Foundation(U2141222)Innovation Fund(8F231527Z)。
文摘The combustion behavior of Ti-Al-Mo-Zr-Sn-W alloy(TC25G)was studied in a high-temperature and high-speed air flow environment using the laser ignition method combined with ultra-high temperature infrared thermometer,scanning electron microscope,X-ray diffractometer,and transmission electron microscope.The burn-resistant performance of TC25G and TC11 alloys was compared.Meanwhile,the microstructural characteristics,crystal structure,and formation mechanism of the combustion products of TC25G alloy were analyzed in detail.The results show that the high-temperature and high-speed air flow promotes combustion within the air flow temperature range of 200–400℃and the air flow velocity range of 0–100 m/s.The combustion path advances along the direction of the air flow.The combustion of TC25G alloy mainly relies on the diffusion of the oxygen and the expansion of the combustion area caused by the movement of the melt.Based on the microstructure and composition of combustion product,it can be divided into the combustion zone,the melting zone,and the heat affected zone.During combustion,the formation of microstructures is closely correlated with the behavior of alloying elements and their selective combination with O.The major oxidation products of Ti are TiO and TiO_(2).The oxides formed by Mo and W hinder the movement of the melt during the combustion.Al and Zr tend to undergo internal oxidation.Al_(2)O_(3)precipitates on the surface of ZrO_(2),forming a protective oxide layer that inhibits the inward diffusion of O.Moreover,the element enrichment at the interface between the melting zone and the heat affected zone increases the melting point on the solid side,hindering the migration of the solid-liquid interface.
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financially supported by the Natural Science Foundation of Jiangxi Province(No.20232ACB204002)the Jiangxi Provincial Key Laboratory of Flexible Electronics(No.20242BCC32010).
文摘The development of solar-driven interfacial evaporation technology is pivotal for addressing global water scarcity.However,it is hindered by the difficulty in synergizing high photothermal conversion with low water evaporation enthalpy into a single material.Herein,we propose an iron-aldehyde-cooperative dynamic covalent anchoring strategy,successfully constructing a covalently locked,hydroxymethyl-functionalized PEDOT-PVA integrated dual-network hydrogel(MEPH).This strategy employs Fe3+to achieve the one-step in situ oxidative polymerization of hydroxymethyl EDOT while concurrently forming a physical hybrid network with PVA,which is subsequently reinforced by covalent cross-linking using glutaraldehyde.This design endows the MEPH with exceptional broadband light absorption(>99%),efficient water transport,and regulated water state within the hydrogel matrix,leading to a reduced evaporation enthalpy of 732 J·g^(−1).The resulting evaporator achieves an ultrahigh evaporation rate of 4.95 kg·m^(−2)·h^(−1)under 1-sun illumination,corresponding to an energy conversion efficiency exceeding 95%,while maintaining stable,salt-resistant operation in high-salinity environments.Outdoor experiments validate its outstanding practicality for seawater and wastewater purification,with the produced freshwater significantly promoting plant growth,highlighting its great potential in sustainable agricultural water cycles.This iron-aldehyde-cooperative dynamic covalent anchoring strategy provides an innovative design paradigm for a new generation of high-performance and robust solar evaporators.
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the National Natural Science Foundation of China(Grant No.U2441263)for financial support of this work。
文摘In composite solid propellants with high aluminum(Al)content and low burning rate,incomplete combustion of the Al powder may occur.In this study,varying lithium(Li)content in Al-Li alloy powder was utilized instead of pure aluminum particles to mitigate agglomeration and enhance the combustion efficiency of solid propellants(Combustion efficiency herein refers to the completeness of metallic fuel oxidation,quantified as the ratio of actual-to-theoretical energy released during combustion)with high Al content and low burning rates.The impact of Al-Li alloy with different Li contents on combustion and agglomeration of solid propellant was investigated using explosion heat,combustion heat,differential thermal analysis(DTA),thermos-gravimetric analysis(TG),dynamic high-pressure combustion test,ignition experiment of small solid rocket motor(SRM)tests,condensation combustion product collection,and X-ray diffraction techniques(XRD).Compared with pure Al,Al-Li alloys exhibit higher combustion heat,which contributes to improved combustion efficiency in Al-Li alloy-containing propellants.DTA and TG analyses demonstrated higher reactivity and lower ignition temperatures for Al-Li alloys.High-pressure combustion experiments at 5 MPa showed that Al-Li alloy fuel significantly decreases combustion agglomeration.The results from theφ75 mm andφ165 mm SRM and XRD tests further support this finding.This study provides novel insights into the combustion and agglomeration behaviors of high-Al,low-burning-rate composite solid propellants and supports the potential application of Al-Li alloys in advanced propellant formulations.
基金financially supported by the Science and Technology Innovation Program of Hunan Province(2024RC3003)the Central South University Innovation-Driven Research Programme(2023CXQD012)the Initiative for Sustainable Energy for its financial support。
文摘By combining the merits of radiative cooling(RC)and evaporation cooling(EC),radiative coupled evaporative cooling(REC)has attracted considerable attention for sub-ambient cooling purposes.However,for outdoor devices,the interior heating power would increase the working temperature and fire risk,which would suppress their above-ambient heat dissipation capabilities and passive water cycle properties.In this work,we introduced a REC design based on an all-in-one photonic hydrogel for above-ambient heat dissipation and flame retardancy.Unlike conventional design RC film for heat dissipation with limited cooling power and fire risk,REC hydrogel can greatly improve the heat dissipation performance in the daytime with a high workload,indicating a 12.0℃lower temperature than the RC film under the same conditions in the outdoor experiment.In the nighttime with a low workload,RC-assisted adsorption can improve atmospheric water harvesting to ensure EC in the daytime.In addition,our REC hydrogel significantly enhanced flame retardancy by absorbing heat without a corresponding temperature rise,thus mitigating fire risks.Thus,our design shows a promising solution for the thermal management of outdoor devices,delivering outstanding performance in both heat dissipation and flame retardancy.
基金supported by the National Natural Science Foundation of China(Nos.12175064 and U2167203)Hunan Outstanding Youth Science Foundation(No.2022JJ10031)。
文摘The evaporation residual cross sections(ERCSs)of these reactions were calculated by using^(144)Sm,^(160,164)Dy,^(165)Ho,^(166)Er,^(169)Tm,^(171,174)Yb,^(175)Lu,^(176-180)Hf,^(181)Ta,^(180,182)W and^(187)Re targets with^(40)Ar projectiles in the theoretical framework of the dinuclear system(DNS)model.The de-excitation process of the compound nucleus was theoretically calculated using two different statistical models,namely the statistical model 1 and statistical model 2(GEMINI++model).The calculated ERCSs were also compared with the experimental data.The ERCSs of synthesizing new proton-rich nuclides were investigated based on the fusion evaporation reaction.Predictions were made for the ERCSs of new isotopes of Pu,Cm and Bk in the heavy nuclei region,while the new isotopes of Ds,Cn and Fl are predicted in the superheavy nuclei region of Z≥104.
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the National Natural Science Foundation of China(No.52374347)Yulin Science and Technology Program Project(No.2024-SF-227)Key Research and Development Program of Shaanxi(No.2021GY-128).
文摘To address the kinetic constraints inherent in the catalytic combustion of pulverized coal injection under low heating-rate conditions within conventional air atmospheres,a drop tube furnace was utilized to simulate the catalytic combustion of pulverized coal(PC).The effects of gas composition,oxygen concentration,the type,and the content of catalysts on the combustion reactivity were systematically analyzed.Furthermore,the structural changes of unburned pulverized coal were also examined.Experimental results indicate that as the oxygen concentration increased from 21%to 79%,compared with the O_(2)/N_(2)condition,the increment in the burnout rate of PC under the O_(2)/CO_(2)condition increased from 3%to 23%.After the addition of catalysts,including hematite,metallurgical oil sludge,and light-burnt dolomite(LBD),under the condition of 21%oxygen concentration,the effects of the three catalysts under the O_(2)/CO_(2)condition were superior to those under the O_(2)/N_(2)condition.This trend was reversed under the conditions of 38%and 79%oxygen concentrations.In all atmospheres,the three catalysts can enhance the burnout rate of PC.Among them,LBD exhibits the most favorable effect,and there exists an optimal dosage.Mechanistic analysis through scanning electron microscopy,X-ray diffraction,and N_(2)adsorption-desorption reveals that under 21%O_(2)/79%CO_(2)conditions,high-concentration CO_(2)leads to the formation of pores,and additives accelerate the oxidation of C and the gasification of CO_(2)through oxygen transfer,thereby enhancing the burnout rate of PC.
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.
基金financial support from the National Natural Science Foundation of China(Nos.52174183 and 52374203).
文摘Temperature is one of the main causes of spontaneous coal combustion.To improve the flame retardant performance,CaCl2,ammonium polyphosphate(APP),and calcium phosphate(CaHP)were compounded to control the temperature response of different stages of coal spontaneous combustion through physical and chemical synergy.Simultaneous thermal analysis,thermogravimetric-Fourier infrared spectroscopy(TG-FTIR),in-situ FTIR and electron paramagnetic resonance(EPR)were used to study the multitemperature stage synergistic inhibition of coal spontaneous combustion.The results show that the proposed method is effective.By obtaining the characteristics of the spontaneous combustion reaction stage of coal in advance,the method of configuring an appropriate composite inhibitor can effectively realize the intelligent control of the temperature response of coal spontaneous combustion.The ignition point of long-flame coal increased by 37.15℃.The inhibition rate of the gas phase products was more than 20%,and the inhibition rate of the functional groups was more than 30%.It has a good quenching effect on free radicals and can effectively inhibit the oxidation activity of active free radicals such as H,HO,and O.The results provide experimental and theoretical support for the study of temperature-responsive composite flame retardants for coal with different metamorphic degrees.
基金support from the National Natural Science Foundation of China(No.12002372)the Young Elite Scientists Sponsorship Program by China Association for Science and Technology(No.2022QNRC001)the Natural Science Foundation of Hunan Province,China(No.2021JJ40674)。
文摘The operational demands of a wide range significantly exacerbate combustion instability issues within ramjet combustor.To suppress combustion oscillations,an open-loop control system utilizing Linear Genetic Programming(LGP)has been developed for a full-scale annular ramjet combustor.The LGP is used to generate control laws that include multi-frequency forcing.These laws are then transformed into square waves to actuate the solenoid valve,which modulates the kerosene supply for open-loop control.The results show that the duty cycle has little effect on instability amplitude,whereas an increase in frequency leads to a remarked reduction in combustion amplitude.After five generations evolvements,the pressure amplitude is reduced by 40.6% under the optimal control law generated by LGP.Furthermore,the machine learning process is depicted using a proximity map of control law similarity,with the search pathway visualized by the steepest descent.All individuals go forward to the upper left corner of the map with the evolution process,terminating at the optimal individual of the fifth generation.
基金supported by the National Natural Science Foundation of China(No.32501743)the Postdoctoral Fellowship Program of CPSF(No.GZB20250475)+3 种基金the China Postdoctoral Science Foundation(No.2024M760387)the Heilongjiang Postdoctoral Financial Assistance(No.LBH-Z24062)the Key Research and Development Program(Innovation Hub)of Heilongjiang Province(No.JD24C002)the National Key Research and Development Program of China(No.2021YFD2200405)。
文摘Understanding the relative contributions of transpiration(T)and evaporation(E)to evapotranspiration(ET)is critical for evaluating water use efficiency,ecosystem productivity,and soil–plant–atmosphere interactions in a changing environment.However,such partitioning and its responses to dry,normal,and wet conditions,as well as the controlling factors at multiple temporal scales,remain poorly understood in China's boreal forests,characterized by synchronization of water supply and energy demand.In this study,we used 8 years of ET data from the growing season(GS;May–September)collected via the eddy-covariance system and applied the underlying water use efficiency(uWUE)method to estimate T and E in a boreal larch forest in China.Our results revealed that E was the dominant component of ET.Specifically,T accounted for 0.44 of ET(T/ET),whereas E contributed to 0.56 of ET(E/ET)over the study period.The response of T/ET to dry conditions during the leaf defoliation stage(LDS)was more pronounced than during the leaf expansion stage(LES).Despite an increase in T/ET(reaching 0.49)during the dry season compared to the normal season(0.42),E was still the dominant contributor to ET.Furthermore,E/ET was significantly controlled by vapor pressure deficit(VPD)across daily to GS scales.Interestingly,soil water content(SWC)was not a controlling factor for regulating E/ET,indicating that atmospheric forces strongly constrained the variability of E/ET in this boreal forest.These findings highlight that E should be given greater attention in boreal forests than before.Our study suggests that effective management strategies for improving water use efficiency in such forest ecosystems are urgently needed.
基金supported by the National Natural Science Foundation of China(No.22305053)the Fundamental Research Funds for the Central Universities,China(No.3072024WD0201)。
文摘Powder-Fueled Water Ramjet Engine(PFWRE)is the most promising powerplant in underwater high-speed propulsion.However,the effect of powder injection mode on its performance and the mechanism of this effect are not well understood.In this paper,a computational framework for multiphase combustion flow is developed and validated.Further,the effects of different injection schemes on flow combustion characteristics and engine performance are evaluated via simulation.Our findings indicate that the dominant recirculation zone in front of the primary water inlet delivers water vapor to the combustor head,providing the necessary oxidant for the ignition and combustion of Al particles.Changing the injection parameters directly affects the flame zone distribution and the ability of the recirculation zone to deliver water vapor,leading to variations in particle ignition delay.The engine combustion efficiency and specific impulse efficiency exhibit a negative correlation with injection height,peaking before declining with increased injection angle.It is shown that particle mixing degree and particle dispersion degree are closely related to engine performance.Enhanced particle mixing in front of the primary water inlet and particle dispersion behind the secondary water inlet are considered favorable approaches to improve engine performance,which promotes the particle combustion process and improves the heat-work conversion efficiency.
基金co-supported by the National Science Foundation Project,China(No.2019-JCJQ-ZQ-019)the National Natural Science Foundation of China(Nos.52476141 and T2221002)。
文摘This study aims to reveal the influence of Local Momentum Ratio(LMR)on the combustion efficiency of an LOX/GCH4 pintle injector from the perspective of spray characteristics.Hot fire tests were conducted to establish the relationship between combustion efficiency and LMR.The spray characteristics for different LMRs were simulated by the validated volume of fluid-to-discrete phase model method,taking into account the combustion chamber wall confinement.Subsequently,the difference in combustion efficiency was analyzed by comparing the spray simulation results of backpressure conditions similar to hot fire tests.The results indicate that combustion efficiency increased initially(LMR=1.12-1.64)and then decreased(LMR>1.64).Quantitative analysis revealed a linear correlation(R^(2)=0.95)between LMR and combustion efficiency within 1.12<LMR<1.64.As the LMR increased,the improvement in combustion efficiency was attributed to a wider spray distribution range and smaller droplet sizes.The area of the mantle recirculation zone that is detrimental to combustion decreased by approximately 38%,and the droplet size reduced from 37 to 16μm.This effectively enhanced both the mixing of the propellant and the evaporation process.When the LMR exceeded the critical value(1.64 in this study),the impingement of liquid oxygen on the combustion chamber wall was confirmed via overheating discoloration marks on the inner surface of combustion chamber's cylindrical section.The impingement of liquid oxygen on the combustion chamber wall increased the transport of liquid oxygen to the wall,directly reducing the mixing quality and combustion efficiency.The outcomes of this study provide the practical guidance for design and improvement in combustion efficiency of the pintle injector thrust chamber.
基金supported by the National Natural Science Foundation of China(Nos.T222100,22205258,52302485 and 2024JJ5404).
文摘The electrode structures in ignition devices for Electrically Controlled Solid Propellants(ECSP) can be classified into fixed and movable types. In movable electrode structures, springs are typically used to push the electrodes and the propellant. The effects of spring pressure on the ignition and combustion of propellants have not yet been studied. In this paper, a universal testing machine and an electrochemical workstation were firstly utilized to investigate the compressive mechanical property and conductivity of Hydroxylamine Nitrate(HAN)-ECSP. The maximum pressure at which the propellant undergoes elastic deformation is 65 kPa. When the spring pressure increased from 5.1 k Pa to 20.4 kPa, the propellant resistance decreased from 56.8 Ω to 36.8 Ω.Various observation methods were employed to study the process of electrical energy injection and the ignition and combustion characteristics under constant voltage. Appropriately increasing the spring pressure can accelerate the injection of electrical energy into the propellant, increase the electrification current, and thus reduce the initial ignition delay time of the propellant. When the spring pressure is 20.4 kPa, the squeezing speed of the propellant is too fast, making it difficult for the propellant to be adequately heated at the electrode interface, which is unfavorable for ignition. Excessive spring pressure also leads to the accumulation of a large amount of combustion residue on the electrode plate, hindering the mixing and diffusion of hot gases during the second ignition process, preventing the gaseous flame of the propellant. When the spring pressure is 5.1 kPa, improving the working voltage can enhance the repeated ignition characteristics of the propellant.
基金supported by JST,grant number JPMJFS2132JST SPRING,grant number JPMJSP2136by an external research grant from Mitsubishi Fuso Truck&Bus Corporation。
文摘Engineering the pore structure of biomass-derived activated carbons is critical for optimizing their performance in adsorptionbased applications.This study demonstrates for the first time that washing hydrochars in solvents of different polarity before activation is a simple yet powerful strategy to tailor pore size distribution.Hydrochar is produced from spent coffee grounds via hydrothermal carbonization,followed by washing in various solvents and activation in KOH.This results in carbons with a very large surface area(~2700 m^(2)/g),and washing is demonstrated to significantly increase product yield.Furthermore,washing in non-polar or mixed-polarity solvents removes long-chain carboxylic acids and esters from the hydrochar,promoting the development of narrow micropores while suppressing mesopore formation.To illustrate the impact of this structural control of porous carbons,post-combustion CO_(2)capture is investigated as a case study.Narrower pore size distribution enhances CO_(2)uptake,significantly improving capacity from 2.8 mmol/g for unwashed samples to 3.8 mmol/g for acetone-washed samples.Interestingly,moderate pore size(9-12Å)is shown to be optimal for CO_(2):N2 selectivity,while smaller pores result in lower selectivity due to stronger interactions between N2 and the pore walls.These findings highlight the potential role of solvent washing in directing pore architecture of hydrochars for adsorption-based carbon capture technologies and beyond.
基金supported by the National Natural Science Foundation of China(Grants 51390493 and 51266008)
文摘Existing droplet evaporation/combustion mod- els in computational fluid dynamics （CFD） simulation of spray combustion are based on simplified 1-D models. Both these models and recently developed 3-D models of single- droplet combustion do not give the conditions for the different existing droplet combustion modes. In this paper, droplet evaporation and combustion are studied both analytically and numerically. In the analytical solution, a 2-D axisymmetric flow surrounding an evaporating and combusting droplet was considered. The governing equations were solved using an integral method, similar to the Karman-Pohlhausen method for solving boundary-layer flows with pressure gradient. The results give a local evaporation rate and flame radius in agree- ment with experimental results. In numerical simulation, 3-D combusting gas flows surrounding an ethanol droplet were studied. The prediction results show three modes of droplet combustion under different relative velocities, explaining the change in the evaporation constant with an increase in relative velocity observed in experiments. This implies that different droplet combustion models should be developed in simu- lating spray combustion. The predicted local evaporation rate and flame radius by numerical simulation are in agree- ment with the analytical solution in the range of azimuthal angles 0° 〈 θ 〈 90°. The numerical results indicate that the drag force of an evaporating and combusting droplet is much smaller than that of a cold solid particle, and thus the currently used drag models should be modified.
