The current work includes a numerical investigation of the effect of biodiesel blends with different aluminum oxide nanoparticle concentrations on the combustion process in the cylinder of a diesel engine.IC Engine Fl...The current work includes a numerical investigation of the effect of biodiesel blends with different aluminum oxide nanoparticle concentrations on the combustion process in the cylinder of a diesel engine.IC Engine Fluent,a specialist computational tool in the ANSYS software,was used to simulate internal combustion engine dynamics and combustion processes.Numerical analysis was carried out using biodiesel blends with three Al_(2)O_(3) nanoparticles in 50,100,and 150 ppm concentrations.The tested samples are called D100,B20,B20A50,B20A100,and B20A150 accordingly.The modeling runs were carried out at various engine loads of 0,100,and 200 Nm at a rated speed of 1800 rpm.The combustion characteristics are improved due to the catalytic effect and higher surface area of nano additives.The results showed the improvements in the combustion process as the result of nanoparticle addition,which led to the higher peak cylinder pressure.The increases in the peak cylinder pressures for B20A50,B20A100,and B20A150 about B20 were 3%,5%,and 8%,respectively,at load 200 Nm.The simulation found that the maximum temperature for biodiesel blends diesel was higher than pure diesel;this was due to higher hydrocarbon values of B20.Also,nano-additives caused a decrease in temperatures in the combustion of biofuels.展开更多
To investigate the differences in combustion and energy release characteristics of metastable intermolecular composite materials composed of aluminum alloys and polyvinylidene fluoride(PVDF)with different compositions...To investigate the differences in combustion and energy release characteristics of metastable intermolecular composite materials composed of aluminum alloys and polyvinylidene fluoride(PVDF)with different compositions,two types of alloys were selected:Al-Mg and Al-Si.Pure aluminum powder of the same size was also chosen for comparison.The PVDF-coated metal particle composites and the mixtures of PVDF with metal particles were prepared using electrospray(ES)and physical blending methods(PM),respectively.A systematic study was conducted on the morphology,compositional structure,combustion performance,energy release characteristics,and thermal reactivity of the fabricated composites and their combustion products through scanning electron microscopy(SEM),energy-dispersive X-ray spectroscopy(EDS),X-ray diffraction(XRD),combustion performance experiments,closed vessel pressure tests,and simultaneous thermogravimetric-differential scanning calorimetry(TG-DSC).The experimental results indicated that the PVDF-coated metal particles prepared by the electrospray method exhibited a distinct core-shell structure,with the metal particles in close contact with the PVDF matrix.Compared to the PM blended materials,the ES composites demonstrated superior combustion performance and energy release characteristics during combustion.Analysis of different metal fuel systems under identical preparation conditions revealed that Al-Mg and Al-Si fuels modulate the combustion and energy release properties of aluminum alloy-PVDF MICs through two distinct pathways.展开更多
This paper describes an experimental study investigating the effects of sinusoidal pulsed injection on the combustion mode transition in a dual-mode supersonic combustor.The results are obtained under inflow condition...This paper describes an experimental study investigating the effects of sinusoidal pulsed injection on the combustion mode transition in a dual-mode supersonic combustor.The results are obtained under inflow conditions of 2.9 MPa stagnation pressure,1900 K stagnation temperature,and Mach number of 3.0.It has been observed that,at the same equivalence ratio,the combustion mode and flow field structure undergo irreversible changes from a weak combustion state to a strong combustion state at a specific pulsed jet frequency compared to steady jet.For steady jet,the combustion mode is dual-mode.As the frequency of the unsteady jet changes,the combustion mode also changes:it becomes a transition mode at frequencies of 171 Hz and 260 Hz,and a ramjet mode at 216 Hz.Combustion instability under steady jet manifests as a transition in flame stabilization mode.In contrast,under pulsed jet,combustion instability appears either as a transition in flame stabilization mode or as flame blow-off and flashback.The flow field oscillation frequency in the non-reacting flow is 171 Hz,which may resonate with the 171 Hz pulsed jet frequency,making the combustion oscillations most pronounced at this frequency.When the jet frequency is increased to 216 Hz,the combustion intensity significantly increases,and the combustion mode transfers to the ramjet mode.However,further increasing the frequency to 260 Hz results in a decrease in combustion intensity,returning to the transition mode.The frequency of the flow field oscillations varies with the coupling of the pulsed injection frequency,shock wave,and flame,and if the system reaches an unstable state,that is,pre-combustion shock train moves far upstream of the isolator during the pulsed jet period,strong combustion state can be achieved,and this process is irreversible.展开更多
Combustion dynamics are a critical factor in determining the performance and reliabilityof a chemical propulsion engine.The underlying processes include liquid atomization,evaporation,mixing,and chemical reactions.Thi...Combustion dynamics are a critical factor in determining the performance and reliabilityof a chemical propulsion engine.The underlying processes include liquid atomization,evaporation,mixing,and chemical reactions.This paper presents a high-fidelity numerical study of liquidatomization and spray combustion under high-pressure conditions,emphasizing the effects of pres-sure oscillations on the flow evolution and combustion dynamics.The theoretical framework isbased on the three-dimensional conservation equations for multiphase flows and turbulent combus-tion.The numerical solution is achieved using a coupling method of volume-of-fluid and Lagran-gian particle tracking.The Zhuang-Kadota-Sutton(ZKS)high-pressure evaporation model andthe eddy breakup-Arrhenius combustion model are employed.Simulations are conducted for amodel combustion chamber with impinging-jet injectors using liquid oxygen and kerosene as pro-pellants.Both conditions with and without inlet and outlet pressure oscillations are considered.Thefindings reveal that pressure oscillations amplify flow fluctuations and can be characterized usingkey physical parameters such as droplet evaporation,chemical reaction,and chamber pressure.The spectral analysis uncovers the axial variations of the dominant and secondary frequenciesand their amplitudes in terms of the characteristic physical quantities.This research helps establisha methodology for exploring the coupling effect of liquid atomization and spray combustion.It alsoprovides practical insights into their responses to pressure oscillations during the occurrence ofcombustion instability.This information can be used to enhance the design and operation ofliquid-fueled propulsion engines.展开更多
The kerosene-fueled Scramjet with multi-cavity combustor has the potential to serve aspropulsion system for hypersonic flight.However,the impact of injection positions on combustionperformance and mechanism at high Ma...The kerosene-fueled Scramjet with multi-cavity combustor has the potential to serve aspropulsion system for hypersonic flight.However,the impact of injection positions on combustionperformance and mechanism at high Mach numbers remains uncertain.Therefore,a comparativestudy was conducted using numerical methods to explore multi-cavity Scramjet combustor perfor-mance at a flight Mach number 7.0 with different injection positions.The combustor is equippedwith 6 cavities arranged in three groups along the flow direction,each consisting of two cavities per-pendicular to the flow.It is shown that the injection location significantly influences combustionperformance:Front-injection yields higher combustion efficiency than post-injection,but post-injection is advantageous for the intake start.Additionally,regardless of injection positions,themainstream flow state near the cavities behind the injection can be categorized as supersonic flow,supersonic-subsonic coexistence flow,and subsonic flow.The optimal length from the downstreamto the trailing edge of the cavities behind the injection for achieving maximum combustion effi-ciency is determined.Further extension beyond this optimal length does not significantly increasethe combustion efficiency.In addition,the optimal length varies with different injection positions-specifically,it is about 60%longer with post-injection conditions than with front-injection con-ditions in this investigation.Moreover,significant secondary combustion within the cavities leadingto improved efficiency only occurs when mainstream flow state is either supersonic flow orsupersonic-subsonic coexistence flow.Also,with a well-optimized design,the kerosene-fueledmulti-cavity Scramjet can achieve enhanced combustion efficiency,which shows relatively smallvariation across a wide range of equivalence ratios.This might be caused by the effects of interac-tion among these multiple cavities.Therefore,these research findings can provide valuable insightsfor designing and optimizing the kerosene-fueled multi-cavity combustor in Scramjet at high Machnumbers.展开更多
In this research study,magnesium-aluminum(Mg-Al)bimetallic oxide powders are synthesized via the sol-gel auto combustion method using diethanolamine(DEA)as the fuel.In order to subsequently determine the influence of ...In this research study,magnesium-aluminum(Mg-Al)bimetallic oxide powders are synthesized via the sol-gel auto combustion method using diethanolamine(DEA)as the fuel.In order to subsequently determine the influence of calcination temperatures upon the structure,chemical bonding,morphology,optical properties,and fluorescence properties of the as-synthesized and calcined Mg-Al bimetallic oxide powders,the researcher employed X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),scanning electron microscopy(SEM),transmission electron microscopy(TEM),UV–visible diffuse reflectance spectroscopy(UV-DRS),and photoluminescence spectroscopy(PL),respectively.It was apparent on the basis of the XRD and FT-IR analyses that those powders undergoing calcination at temperatures of 500℃,700℃,and 900℃contained the major phase magnesium aluminate(Mg Al_(2)O_(4))spinel with trace magnesium oxide(Mg O)and hydrotalcite(Mg_(6)Al_(2)(CO_(3))(OH)_(16)).When the calcination temperature rose to 1100℃,this resulted in a single phase MgAl_(2)O_(4)while MgO and(Mg_(6)Al_(2)(CO_(3))(OH)_(16))were no longer observed.UV-DRS analysis revealed that in optimized conditions,calcination resulted in better sample absorption and reflection levels when compared to the ultraviolet,visible,and infrared spectra observed in the case of the as-synthesized sample.The bandgap energy(E_(g))for calcined samples was in the range of 2.65 e V to 5.85 e V,in contrast to the value of 4.10 e V for the as-synthesized sample.Analysis of photoluminescence showed that for the as-synthesized samples and those calcined at low temperatures,visible light was emitted only in the violet,blue,and green regions with low intensity,while for samples calcined at higher temperatures,the emissions showed greater intensity and extended to the yellow and orange regions.Multiple defect centers were found in the bandgap which can explain these findings.展开更多
Spontaneous combustion of lignite is closely related to the inherent minerals it contains, and the iron component has a remarkable influence on the combustion property of lignite. It is very important to study the inf...Spontaneous combustion of lignite is closely related to the inherent minerals it contains, and the iron component has a remarkable influence on the combustion property of lignite. It is very important to study the influence of iron component on the combustion reaction property of lignite to reveal autoignition mechanism of lignite and reduce autoignition of lignite. In this research, FeCl_(3) and Fe_(2)O_(3) were doped into demineralised lignite (SL+) by impregnation to research the effects of iron salts and iron oxides on the combustion properties of lignite. Based on the above, the effects of post-treatment method of the FeCl_(3)-doped coal samples, iron-salt hydrolysis products and heat-treated temperatures on the combustion property of lignite were researched, and the microstructures of the coal samples were characterised and analysed using Fourier transform infrared spectroscopy (FTIR), Scanning electron microscope-energy dispersive spectrometer (SEM-EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results demonstrate that doping with FeCl_(3) increases the combustion performance of lignite, thereby reducing the ignition temperature of lignite by approximately 112 ℃. In contrast, doping with Fe_(2)O_(3) has a weaker combustion-promoting effect. XRD and XPS characterisation indicates that iron species in the coal samples doped with iron salts are highly dispersed and exhibit the FeOOH structure, whereas iron species in the coal samples doped with Fe_(2)O_(3) exhibit the crystal form of α-Fe_(2)O_(3). Doping of lignite with FeCl_(3) and its hydrolysis product β-FeOOH reduces the ignition temperature of the coal samples. Iron species in the FeCl_(3)-doped coal samples after heat treatment at 300–500 ℃ increase the combustion property of the coal samples, whereas iron species after heat treatment at 600–900 ℃ have a much weaker or non-existent promoting effect on the combustion performance of the coal samples. The characterisation show a change in iron species in the coal samples with the rise in the heat treatment temperature. This change progresses from highly dispersed β-FeOOH below 300 ℃ to Fe_(3)O_(4) above 400 ℃. Fe_(3)O_(4) is gradually reduced, with part of it further reduced to elementary iron at the same time as grain growth. It is believed that the gradual agglomeration of Fe_(3)O_(4) and the appearance of elementary iron are the main reasons for the weakening or disappearance of the promoting effect on coal combustion.展开更多
Aluminum-water(Al-H_(2)O)propellants represent an innovative class of solid propellants characterized by low cost and minimal signal signature.However,conventional formulations are hindered by significant aluminum(Al)...Aluminum-water(Al-H_(2)O)propellants represent an innovative class of solid propellants characterized by low cost and minimal signal signature.However,conventional formulations are hindered by significant aluminum(Al)agglomeration,leading to reduced combustion efficiency and substantial residues.This study introduces a method for modifying Al powder with Polyvinylidene Fluoride(PVDF)to enhance the performance of Al-H_(2)O propellants by mitigating agglomeration during combustion.Experimental methodologies,including thermogravimetric analysis under ambient-pressure nitrogen atmosphere and laser ignition tests,were employed to investigate the influence of varying PVDF content on the combustion characteristics of the propellants.Furthermore,the effect of PVDF on motor performance was systematically evaluated through laboratoryscale Solid Rocket Motor(SRM)tests.The results demonstrate that the addition of 7.5%PVDF significantly enhances the burning rate from 1.12 mm/s to 3.78 mm/s and reduces the mean particle size of condensed combustion products from 699μm to 527μm.Combustion efficiency rises from88.57%to 94.51%,while injection efficiency improves significantly from 30.45%to 70.45%.SRM tests further demonstrate an increase in combustion chamber pressure from 0.17 MPa to 0.58 MPa.A dynamic agglomeration model explains these improvements,attributing reduced agglomeration to enhanced aerodynamic forces and a thinner melting layer,while increased gas yield improves injection performance.This study highlights PVDF's potential in advancing Al-H_(2)O propellants by improving combustion and injection efficiency.展开更多
AP(Ammonium Perchlorate)and HMX(Octogen)are the two oxidizers most often used in Nitrate-Ester-Plasticized Polyether(NEPE)rocket propellants.How the AP–HMX ratio influences the agglomeration of NEPE propellants remai...AP(Ammonium Perchlorate)and HMX(Octogen)are the two oxidizers most often used in Nitrate-Ester-Plasticized Polyether(NEPE)rocket propellants.How the AP–HMX ratio influences the agglomeration of NEPE propellants remains unclear.We experimentally investigated the effect of the AP–HMX ratio on the combustion and agglomeration of NEPE propellants using burning rate test,quenched surface analysis,microscopic observations,and the collection of condensed combustion products.It was found that with the decrease in AP content from 40wt%to 10wt%,the burning rate decreased from 14.2 mm/s to 9.2 mm/s because the adiabatic flame temperature of NEPE propellants decreased from 3828 K to 3736 K.Pockets bounded by AP particles appeared on the surface when AP content was 40wt%;however,the accumulations grew and covered the burning surface eventually as the AP–HMX ratio decreased.The time required for the accumulation to coalesce into agglomerates increased with decreasing AP content.Even with similar agglomerate sizes,the coalescence time increased by 83%when the AP content decreased from 40wt%to 30wt%.The agglomerate size in the Condensed Combustion Products(CCPs)increased from 100μm to 200μm,and the fraction of large agglomerations increased from 6.4%to 24.7%when the AP content decreased from 40wt%to 10wt%.Overall,the high flame temperature of the AP particles enhanced the decomposition of the surrounding binder,resulting in the rapid ejection of the aluminum particles into the gas,which had a separating effect on the accumulation,thus weakening the agglomeration.展开更多
Boron-based fuels,recognized for their high energy density and potential in energetic applications,encounter challenges such as long ignition delays and incomplete combustion,which result in reduced combustion efficie...Boron-based fuels,recognized for their high energy density and potential in energetic applications,encounter challenges such as long ignition delays and incomplete combustion,which result in reduced combustion efficiency and limited performance in aerospace propulsion.In this study,boron carbide(B4C)is investigated as an alternative fuel to pristine boron due to its favorable gas-phase combustion.Both metal oxide(nickel oxide(NiO))and metal fluoride(nickel fluoride(NiF_(2)))are selected as oxidizing modifiers to enhance the reactivity of B4C.A method combining laser ignition with optical diagnostics is employed to investigate the enhancing effects of different oxidizers on the ignition and combustion characteristics of B4C.Both NiO and NiF_(2)can significantly increase the combustion radiation intensity and reduce the time to maximum intensity of B4C.Differential scanning calorimetry,in-situ X-ray diffraction,and Fourier transform infrared spectroscopy were used for simultaneous thermal analysis of the B4C composite powders.Combined thermal analysis showed that the effects of NiO and NiF_(2)on promoting B4C combustion is mainly achieved via the formation of NimBn and the release of a large number of gas products.It is reasonable to speculate that the phase separation at the B2O3/NimBn interface forms new pathways for oxygen diffusion and reaction with the B core.The difference in the combustion mechanism of B4C with NiO and NiF_(2)lies in the gas phase products,i.e.,CO_(2)and BF3,respectively,thus leading to significant differences in their reaction processes.展开更多
Catalyzed gasoline particulate filters(cGPFs)are being developed to enable compliance with the particulate number limits for passenger cars equipped with gasoline direct injection(GDI)engines in China and Europe,It is...Catalyzed gasoline particulate filters(cGPFs)are being developed to enable compliance with the particulate number limits for passenger cars equipped with gasoline direct injection(GDI)engines in China and Europe,It is appealing to build catalysts with ceria—an irreplaceable"reducible"component in three-way converters—to help eliminate the soot particles trapped in cGPFs via O_(2)-assisted combustion.While research aiming at understanding how these recipes function has continued for more than two decades,a universal model elucidating the roles of different"active oxygen"species is yet to be realized.In this perspective,by critically assessing the reported data about gasoline soot catalytic combustion over ceria catalysts,it is suggested that ceria ignites soot through contributing its lattice oxygen,giving rise to a"hot ring"region at the periphery of soot-catalyst interface.During the"re-oxidation"semi-cycles,electrophilic superoxides and/or peroxides(O_(x)^(n-))are produced at the Ce^(3+)and oxygen vacancy sites enriched in this collar-like region,and then work as key reactive phases for soot deep oxidation.Based on this"O_(x)^(n-)assisted"Mars-van Krevelen mechanism,several guidelines for ceria catalyst designing are proposed,ending with a summary about where future opportunities and challenges may lie in developing efficient and practical cGPF catalysts.展开更多
Pd-based catalysts have been extensively studied in the catalytic oxidation of methane,but their longterm stability and water resistance are unsatisfactory as the active sites are susceptible to water toxicity.The add...Pd-based catalysts have been extensively studied in the catalytic oxidation of methane,but their longterm stability and water resistance are unsatisfactory as the active sites are susceptible to water toxicity.The addition of Pt to Pd-based catalysts is found to be the most effective and promising method.However,distinct states of existence of Pt can affect the catalytic performance to different degrees,even negatively.Therefore,the impact mechanism of Pt on Pd-based catalysts needs to be further understood.In this work,A-site defective La_(0.9)AlO_(x)perovskite was used as a support,and the state of Pt in catalysts was regulated by adjusting the introducing sequence of Pd and Pt,It is found that only when Pt is introduced preferentially,the activity and water resistance of the bimetal can be improved.Combining a series of characterization results of the fresh catalysts,reduced catalysts,and the samples after reduction and use,it is found that the higher Pt^(2+)content in the catalyst is the main reason for promoting bimetallic properties,while more Pt0has an inhibitory effect.This work provides a new understanding of the promotion effect of Pt on Pd-Pt bimetal in the catalytic oxidation reaction of methane.展开更多
Coal power plants annually generate quantities of byproducts that release environmentally hazardous heavy metals like Cd and Pb.Understanding the behavior and spatiotemporal impacts on soils of these releases is cruci...Coal power plants annually generate quantities of byproducts that release environmentally hazardous heavy metals like Cd and Pb.Understanding the behavior and spatiotemporal impacts on soils of these releases is crucial for pollution control.This study investigated the concentrations and isotope ratios of Cd/Pb in combustion byproducts,depositions and soils collected froma coal-fired power plant or its surrounding area.The pulverized fuel ash(PFA)and desulfurized gypsum(DG)exhibited heavier Cd isotopes withΔ^(114)Cd values of 0.304‰and 0.269‰,respectively,while bottom ash(BA)showed lighter Cd isotopes(Δ^(114)CdBA-coal=–0.078‰),compared to feed coal.We proposed a two-stage condensation process that governs the distribution of Cd/Pb,including accumulation on PFA and DG within electrostatic precipitators and desulfurization unit,as well as condensation onto fine particles upon release from the stack.Emissions from combustion and large-scale transport make a significant contribution to deposition,while the dispersion of Cd/Pb in deposition is primarily influenced by the prevailing wind patterns.However,the distribution of Cd/Pb in soils not only exhibit predominant wind control but is also potentially influenced by the resuspension of long-term storage byproducts.The power plant significantly contributes to soil in the NW–N–NE directions,even at a considerable distance(66%–79%),demonstrating its pervasive impact on remote regions along these orientations.Additionally,based on the vertical behavior in the profile,we have identified that Cd tends to migrate downward through leaching,while variations in Pb respond to the historical progression of dust removal.展开更多
With the rapid development of adsorbents for removal of elemental mercury (Hg0) from coal combustion flue gas,the preparation of adsorbents with superior performance,lower cost and environmental friendliness remains a...With the rapid development of adsorbents for removal of elemental mercury (Hg0) from coal combustion flue gas,the preparation of adsorbents with superior performance,lower cost and environmental friendliness remains an important challenge.An incipient wetness impregnation method followed by in-situ selenization was used to load copper selenide(CuSe) onto the surface of optimal magnetic biochar (OMBC).The results showed that CuSe significantly enhanced the Hg0removal performance of the OMBC,and CuSe loading ratio of 10%(10CuSe/OMBC) had the best Hg0removal performance.10CuSe/OMBC maintained its Hg0removal efficiency above 95% for 150 min at 30-150℃,and it had a good resistance to SO2.The equilibrium adsorption capacity of 10CuSe/OMBC could reach up to 8.73 mg/g,which was close to the theoretical value 12.99 mg/g,and the adsorption rate was up to 20.33μg/(g·min) Meanwhile,10CuSe/OMBC had strong magnetism that is not permanently magnetized,which could be separated from desulfurization gypsum and recycled many times.Characterization results demonstrated that Se22-,Cu2+and Oβplayed essential roles in the oxidation of Hg0,and Se22-and Se2-can immobilize Hg2+to HgSe.10CuSe/OMBC has important guiding significance for practical application because of its low cost,high performance and low mercury leaching characteristic to form HgSe.展开更多
The counterflow burner is a combustion device used for research on combustion.By utilizing deep convolutional models to identify the combustion state of a counter flow burner through visible flame images,it facilitate...The counterflow burner is a combustion device used for research on combustion.By utilizing deep convolutional models to identify the combustion state of a counter flow burner through visible flame images,it facilitates the optimization of the combustion process and enhances combustion efficiency.Among existing deep convolutional models,InceptionNeXt is a deep learning architecture that integrates the ideas of the Inception series and ConvNeXt.It has garnered significant attention for its computational efficiency,remarkable model accuracy,and exceptional feature extraction capabilities.However,since this model still has limitations in the combustion state recognition task,we propose a Triple-Scale Multi-Stage InceptionNeXt(TSMS-InceptionNeXt)combustion state recognitionmethod based on feature extraction optimization.First,to address the InceptionNeXt model’s limited ability to capture dynamic features in flame images,we introduce Triplet Attention,which applies attention to the width,height,and Red Green Blue(RGB)dimensions of the flame images to enhance its ability to model dynamic features.Secondly,to address the issue of key information loss in the Inception deep convolution layers,we propose a Similarity-based Feature Concentration(SimC)mechanism to enhance the model’s capability to concentrate on critical features.Next,to address the insufficient receptive field of the model,we propose a Multi-Scale Dilated Channel Parallel Integration(MDCPI)mechanism to enhance the model’s ability to extract multi-scale contextual information.Finally,to address the issue of the model’s Multi-Layer Perceptron Head(MlpHead)neglecting channel interactions,we propose a Channel Shuffle-Guided Channel-Spatial Attention(ShuffleCS)mechanism,which integrates information from different channels to further enhance the representational power of the input features.To validate the effectiveness of the method,experiments are conducted on the counterflow burner flame visible light image dataset.The experimental results show that the TSMS-InceptionNeXt model achieved an accuracy of 85.71%on the dataset,improving by 2.38%over the baseline model and outperforming the baseline model’s performance.It achieved accuracy improvements of 10.47%,4.76%,11.19%,and 9.28%compared to the Reparameterized Visual Geometry Group(RepVGG),Squeeze-erunhanced Axial Transoformer(SeaFormer),Simplified Graph Transformers(SGFormer),and VanillaNet models,respectively,effectively enhancing the recognition performance for combustion states in counterflow burners.展开更多
Powder-Fueled Water Ramjet Engine(PFWRE)is of great attraction for high-speed and long-voyage underwater propulsion,as well as air–water trans-media navigation applications due to its high energy density and thrust a...Powder-Fueled Water Ramjet Engine(PFWRE)is of great attraction for high-speed and long-voyage underwater propulsion,as well as air–water trans-media navigation applications due to its high energy density and thrust adjustability.However,the complex multiphase combustion process in the combustor significantly affects engine performance.In this study,a detailed model for aluminum particle combustion in water vapor is developed and validated via literature data as well as the ground direct-connected test we conducted.Thereafter,the numerical study on the multiphase combustion process inside the aluminum-based PFWRE combustor is carried out within the Euler–Lagrange framework using the developed model.Results show that a reverse rotating vortex pair before the primary water injection causes particles to flow back towards the combustor head and leads to product deposition.Aluminum particles external to the powder jet have shorter preheating time than internal particles and burn out in advance.The analysis of the particle combustion process indicates that the flame structure inside the combustor consists of the particle preheating zone,the surface combustion heat release zone,the gas-phase combustion heat release zone,and the post-flame zone.In the present configuration,as the particle size increases from 10μm to 20μm,the preheating zone length increases from 35 mm to 85 mm.Meanwhile,heat release from gas-phase combustion decreases,and the average temperature of the combustor head first increases and then decreases.This study not only provides insight into the multiphase combustion characteristics of the aluminum-based PFWRE combustor but also offers guidance for the design of the combustion organization schemes and engine structure optimization.展开更多
Hydrogen doping in associated gas combustion presents a promising strategy for mitigating carbon emissions from typically flared or vented gases.To support this idea,this study employed Chemkin Pro to model the lamina...Hydrogen doping in associated gas combustion presents a promising strategy for mitigating carbon emissions from typically flared or vented gases.To support this idea,this study employed Chemkin Pro to model the laminar premixed combustion of associated gases and conducted a sensitivity analysis of key combustion factors.The results demonstrated that increasing the hydrogen-doping ratio accelerated flame propagation and reduced combustion product accumulation time,while also elevating flame instability and inducing cracks or folds on the flame front at higher ratios.Notably,flame speed exhibited a 40%increase per 10%rise in the hydrogen-doping ratio,which directly enhanced combustion efficiency.Flame temperature peaked at an equivalence ratio of 1,whereas flame speed enhancement was maximized at a ratio of 1.3.Higher premix temperatures increased flame speed,and elevated combustion pressures raised flame temperature(stabilizing above 1 atm),with flame speed peaking at 0.06 atm.Critically,hydrogen doping below 15%minimally altered flame morphology,but 30%doping caused significant flame retraction toward the nozzle,which increased the flashback risk and raised NOx emissions by nearly one third.These findings provide insights for optimizing hydrogen-doped combustion processes to balance efficiency gains while ensuring operational safety and emission control.展开更多
The mixing injection of natural gas and pulverized coal into the blast furnaces shows a promising technological approach in the context of global carbon reduction initiatives.Carrier gas and coal pass through the air ...The mixing injection of natural gas and pulverized coal into the blast furnaces shows a promising technological approach in the context of global carbon reduction initiatives.Carrier gas and coal pass through the air inlet of coal lance,and the characteristics of carrier gas affect the flow in the air inlet and the combustion efficiency of coal,so it is very important to study the change of carrier gas charac-teristics in the lower part of blast furnace.By means of numerical simulation,the influence of carrier gas characteristics(injection rate,composition,and temperature)on the mixed combustion of natural gas(NG)and pulverized coal in the tuyere raceway of Russian blast furnace was analyzed.When N_(2) is used as carrier gas,the injection rate of carrier gas is reduced from 4000 to 2000 m3/h,the average tuy-ere temperature is increased(1947.42 to 1963.30 K),the mole fractions of CO and H_(2) are increased,and the burnout rate of pulverized coal is decreased.Increasing the carrier gas temperature is helpful to improve the burnout of pulverized coal.For every 20 K increase of carrier gas temperature,the average temperature in the raceway increases by 20.6 K,which promotes the release and combustion of volat-iles,but the increase of carrier gas temperature from 373 to 393 K only leads to 1.16%burnout change.Considering the transportation characteristics of pulverized coal,it is suggested that the carrier gas temperature should be kept at about 373 K to obtain the best perform-ance.It is worth noting that when air is used as carrier gas,the burnout rate of pulverized coal is increased by 2.69%compared with N_(2).展开更多
To investigate the problem of ethylene jet mixing and combustion in the scramjet at high Mach number(Ma = 8), numerical simulations were carried out for different equivalent ratios at cold and combustion conditions, i...To investigate the problem of ethylene jet mixing and combustion in the scramjet at high Mach number(Ma = 8), numerical simulations were carried out for different equivalent ratios at cold and combustion conditions, in which three-dimensional steady compressible RANS and k-ω SST turbulence model were adopted. It demonstrates that as the equivalence ratio increases from 0.42 to 1.08, the combustion becomes more intensified, and the higher backpressure pushes flame to propagate upstream. The supersonic combustion region in the combustor decreases from 92% to 85% with the increase of equivalence ratio from 0.42 to 1.08, resulting in the transition of the combustor from scram-mode to dual-mode. Both mixing and combustion efficiencies decrease by 35% and 16% respectively when the equivalence ratio increases from 0.42 to 1.08, indicating that the high equivalence ratio is unfavorable to the mixing and combustion processes. Combustion mode analysis reveals that the flame in the cavity under the high Mach number is dominated by non-premixed flames, i.e., more than 95% behaves as non-premixed mode, and the heat release is also mainly contributed by non-premixed flame. Increasing the equivalence ratio is beneficial to the thrust performance. Although the viscous force hardly changes with equivalence ratio, the percentage of pressure force used to balance the viscous force increases gradually,which limits the engine performance.展开更多
This study calculates the combustion characteristics of various gas-generating and micro gas pyrotechnic charges,including aluminium/potassium perchlorate,boron/potassium nitrate,carbon black/potassium nitrate,and sil...This study calculates the combustion characteristics of various gas-generating and micro gas pyrotechnic charges,including aluminium/potassium perchlorate,boron/potassium nitrate,carbon black/potassium nitrate,and silicon-based delay compositions,using thermodynamic software.A multiphase flowthermal-solid coupling model was established,and the combustion process of the pyrotechnic charges within a closed bomb was simulated.The pyrotechnic shock generated by combustion was predicted.The combustion pressures and pyrotechnic shocks were measured.The simulation results demonstrated good agreement with experimental results.Additionally,the mechanism of shock generation by the combustion of pyrotechnic charges in the closed bomb was analyzed.The effects of the combustion characteristics of the pyrotechnic charges on the resulting pyrotechnic shocks were systematically investigated.Notably,the shock response spectrum of the gas-generating pyrotechnic charges is greater than that of the micro gas compositions at most frequencies,particularly in the mid-field pyrotechnic shocks(3-10 kHz).Furthermore,the pyrotechnic shocks increase approximately linearly with the impulse of the gas-generating pyrotechnic charges.展开更多
文摘The current work includes a numerical investigation of the effect of biodiesel blends with different aluminum oxide nanoparticle concentrations on the combustion process in the cylinder of a diesel engine.IC Engine Fluent,a specialist computational tool in the ANSYS software,was used to simulate internal combustion engine dynamics and combustion processes.Numerical analysis was carried out using biodiesel blends with three Al_(2)O_(3) nanoparticles in 50,100,and 150 ppm concentrations.The tested samples are called D100,B20,B20A50,B20A100,and B20A150 accordingly.The modeling runs were carried out at various engine loads of 0,100,and 200 Nm at a rated speed of 1800 rpm.The combustion characteristics are improved due to the catalytic effect and higher surface area of nano additives.The results showed the improvements in the combustion process as the result of nanoparticle addition,which led to the higher peak cylinder pressure.The increases in the peak cylinder pressures for B20A50,B20A100,and B20A150 about B20 were 3%,5%,and 8%,respectively,at load 200 Nm.The simulation found that the maximum temperature for biodiesel blends diesel was higher than pure diesel;this was due to higher hydrocarbon values of B20.Also,nano-additives caused a decrease in temperatures in the combustion of biofuels.
基金the National Natural Science Foundation of China(NSFC,Grant Nos.52176114 and 52306145)Natural Science Foundation of Jiangsu Province(Grant No.BK20230929)+3 种基金China Postdoctoral Science Foundation(Grant No.2023M731693)Fundamental Research Funds for the Central Universities,Grant No.30924010505Jiangsu Funding Program for Excellent Postdoctoral Talentthe Center of Analytical Facilities,Nanjing University of Science and Technology for providing technical equipment support for this article。
文摘To investigate the differences in combustion and energy release characteristics of metastable intermolecular composite materials composed of aluminum alloys and polyvinylidene fluoride(PVDF)with different compositions,two types of alloys were selected:Al-Mg and Al-Si.Pure aluminum powder of the same size was also chosen for comparison.The PVDF-coated metal particle composites and the mixtures of PVDF with metal particles were prepared using electrospray(ES)and physical blending methods(PM),respectively.A systematic study was conducted on the morphology,compositional structure,combustion performance,energy release characteristics,and thermal reactivity of the fabricated composites and their combustion products through scanning electron microscopy(SEM),energy-dispersive X-ray spectroscopy(EDS),X-ray diffraction(XRD),combustion performance experiments,closed vessel pressure tests,and simultaneous thermogravimetric-differential scanning calorimetry(TG-DSC).The experimental results indicated that the PVDF-coated metal particles prepared by the electrospray method exhibited a distinct core-shell structure,with the metal particles in close contact with the PVDF matrix.Compared to the PM blended materials,the ES composites demonstrated superior combustion performance and energy release characteristics during combustion.Analysis of different metal fuel systems under identical preparation conditions revealed that Al-Mg and Al-Si fuels modulate the combustion and energy release properties of aluminum alloy-PVDF MICs through two distinct pathways.
基金supported by the Program of Key Laboratory of Cross-Domain Flight Interdisciplinary Technology,China(No.2023-ZY0205)。
文摘This paper describes an experimental study investigating the effects of sinusoidal pulsed injection on the combustion mode transition in a dual-mode supersonic combustor.The results are obtained under inflow conditions of 2.9 MPa stagnation pressure,1900 K stagnation temperature,and Mach number of 3.0.It has been observed that,at the same equivalence ratio,the combustion mode and flow field structure undergo irreversible changes from a weak combustion state to a strong combustion state at a specific pulsed jet frequency compared to steady jet.For steady jet,the combustion mode is dual-mode.As the frequency of the unsteady jet changes,the combustion mode also changes:it becomes a transition mode at frequencies of 171 Hz and 260 Hz,and a ramjet mode at 216 Hz.Combustion instability under steady jet manifests as a transition in flame stabilization mode.In contrast,under pulsed jet,combustion instability appears either as a transition in flame stabilization mode or as flame blow-off and flashback.The flow field oscillation frequency in the non-reacting flow is 171 Hz,which may resonate with the 171 Hz pulsed jet frequency,making the combustion oscillations most pronounced at this frequency.When the jet frequency is increased to 216 Hz,the combustion intensity significantly increases,and the combustion mode transfers to the ramjet mode.However,further increasing the frequency to 260 Hz results in a decrease in combustion intensity,returning to the transition mode.The frequency of the flow field oscillations varies with the coupling of the pulsed injection frequency,shock wave,and flame,and if the system reaches an unstable state,that is,pre-combustion shock train moves far upstream of the isolator during the pulsed jet period,strong combustion state can be achieved,and this process is irreversible.
基金supported by the National Natural Science Foundation of China(Nos.U23B6009 and 12272050)。
文摘Combustion dynamics are a critical factor in determining the performance and reliabilityof a chemical propulsion engine.The underlying processes include liquid atomization,evaporation,mixing,and chemical reactions.This paper presents a high-fidelity numerical study of liquidatomization and spray combustion under high-pressure conditions,emphasizing the effects of pres-sure oscillations on the flow evolution and combustion dynamics.The theoretical framework isbased on the three-dimensional conservation equations for multiphase flows and turbulent combus-tion.The numerical solution is achieved using a coupling method of volume-of-fluid and Lagran-gian particle tracking.The Zhuang-Kadota-Sutton(ZKS)high-pressure evaporation model andthe eddy breakup-Arrhenius combustion model are employed.Simulations are conducted for amodel combustion chamber with impinging-jet injectors using liquid oxygen and kerosene as pro-pellants.Both conditions with and without inlet and outlet pressure oscillations are considered.Thefindings reveal that pressure oscillations amplify flow fluctuations and can be characterized usingkey physical parameters such as droplet evaporation,chemical reaction,and chamber pressure.The spectral analysis uncovers the axial variations of the dominant and secondary frequenciesand their amplitudes in terms of the characteristic physical quantities.This research helps establisha methodology for exploring the coupling effect of liquid atomization and spray combustion.It alsoprovides practical insights into their responses to pressure oscillations during the occurrence ofcombustion instability.This information can be used to enhance the design and operation ofliquid-fueled propulsion engines.
基金financially supported by the National Key Laboratory of Ramjet,China(No.2022-020-003)the Fundamental Research Funds for the Central Universities,China(No.501QYZX2023146001)。
文摘The kerosene-fueled Scramjet with multi-cavity combustor has the potential to serve aspropulsion system for hypersonic flight.However,the impact of injection positions on combustionperformance and mechanism at high Mach numbers remains uncertain.Therefore,a comparativestudy was conducted using numerical methods to explore multi-cavity Scramjet combustor perfor-mance at a flight Mach number 7.0 with different injection positions.The combustor is equippedwith 6 cavities arranged in three groups along the flow direction,each consisting of two cavities per-pendicular to the flow.It is shown that the injection location significantly influences combustionperformance:Front-injection yields higher combustion efficiency than post-injection,but post-injection is advantageous for the intake start.Additionally,regardless of injection positions,themainstream flow state near the cavities behind the injection can be categorized as supersonic flow,supersonic-subsonic coexistence flow,and subsonic flow.The optimal length from the downstreamto the trailing edge of the cavities behind the injection for achieving maximum combustion effi-ciency is determined.Further extension beyond this optimal length does not significantly increasethe combustion efficiency.In addition,the optimal length varies with different injection positions-specifically,it is about 60%longer with post-injection conditions than with front-injection con-ditions in this investigation.Moreover,significant secondary combustion within the cavities leadingto improved efficiency only occurs when mainstream flow state is either supersonic flow orsupersonic-subsonic coexistence flow.Also,with a well-optimized design,the kerosene-fueledmulti-cavity Scramjet can achieve enhanced combustion efficiency,which shows relatively smallvariation across a wide range of equivalence ratios.This might be caused by the effects of interac-tion among these multiple cavities.Therefore,these research findings can provide valuable insightsfor designing and optimizing the kerosene-fueled multi-cavity combustor in Scramjet at high Machnumbers.
基金financial supported from the Thailand Research Fund,Office of the Higher Education Commission(Grant number MRG6280220)。
文摘In this research study,magnesium-aluminum(Mg-Al)bimetallic oxide powders are synthesized via the sol-gel auto combustion method using diethanolamine(DEA)as the fuel.In order to subsequently determine the influence of calcination temperatures upon the structure,chemical bonding,morphology,optical properties,and fluorescence properties of the as-synthesized and calcined Mg-Al bimetallic oxide powders,the researcher employed X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),scanning electron microscopy(SEM),transmission electron microscopy(TEM),UV–visible diffuse reflectance spectroscopy(UV-DRS),and photoluminescence spectroscopy(PL),respectively.It was apparent on the basis of the XRD and FT-IR analyses that those powders undergoing calcination at temperatures of 500℃,700℃,and 900℃contained the major phase magnesium aluminate(Mg Al_(2)O_(4))spinel with trace magnesium oxide(Mg O)and hydrotalcite(Mg_(6)Al_(2)(CO_(3))(OH)_(16)).When the calcination temperature rose to 1100℃,this resulted in a single phase MgAl_(2)O_(4)while MgO and(Mg_(6)Al_(2)(CO_(3))(OH)_(16))were no longer observed.UV-DRS analysis revealed that in optimized conditions,calcination resulted in better sample absorption and reflection levels when compared to the ultraviolet,visible,and infrared spectra observed in the case of the as-synthesized sample.The bandgap energy(E_(g))for calcined samples was in the range of 2.65 e V to 5.85 e V,in contrast to the value of 4.10 e V for the as-synthesized sample.Analysis of photoluminescence showed that for the as-synthesized samples and those calcined at low temperatures,visible light was emitted only in the violet,blue,and green regions with low intensity,while for samples calcined at higher temperatures,the emissions showed greater intensity and extended to the yellow and orange regions.Multiple defect centers were found in the bandgap which can explain these findings.
基金support from the National Natural Science Foundation of China(22368038,21968021,22308048)Science and Technology Plan Project of Inner Mongolia(2020GG0289)+1 种基金Natural Science Foundation of Inner Mongolia(2019MS02025)Science Fund for Distinguished Young Scholars of Inner Mongolia(2022JQ04).
文摘Spontaneous combustion of lignite is closely related to the inherent minerals it contains, and the iron component has a remarkable influence on the combustion property of lignite. It is very important to study the influence of iron component on the combustion reaction property of lignite to reveal autoignition mechanism of lignite and reduce autoignition of lignite. In this research, FeCl_(3) and Fe_(2)O_(3) were doped into demineralised lignite (SL+) by impregnation to research the effects of iron salts and iron oxides on the combustion properties of lignite. Based on the above, the effects of post-treatment method of the FeCl_(3)-doped coal samples, iron-salt hydrolysis products and heat-treated temperatures on the combustion property of lignite were researched, and the microstructures of the coal samples were characterised and analysed using Fourier transform infrared spectroscopy (FTIR), Scanning electron microscope-energy dispersive spectrometer (SEM-EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results demonstrate that doping with FeCl_(3) increases the combustion performance of lignite, thereby reducing the ignition temperature of lignite by approximately 112 ℃. In contrast, doping with Fe_(2)O_(3) has a weaker combustion-promoting effect. XRD and XPS characterisation indicates that iron species in the coal samples doped with iron salts are highly dispersed and exhibit the FeOOH structure, whereas iron species in the coal samples doped with Fe_(2)O_(3) exhibit the crystal form of α-Fe_(2)O_(3). Doping of lignite with FeCl_(3) and its hydrolysis product β-FeOOH reduces the ignition temperature of the coal samples. Iron species in the FeCl_(3)-doped coal samples after heat treatment at 300–500 ℃ increase the combustion property of the coal samples, whereas iron species after heat treatment at 600–900 ℃ have a much weaker or non-existent promoting effect on the combustion performance of the coal samples. The characterisation show a change in iron species in the coal samples with the rise in the heat treatment temperature. This change progresses from highly dispersed β-FeOOH below 300 ℃ to Fe_(3)O_(4) above 400 ℃. Fe_(3)O_(4) is gradually reduced, with part of it further reduced to elementary iron at the same time as grain growth. It is believed that the gradual agglomeration of Fe_(3)O_(4) and the appearance of elementary iron are the main reasons for the weakening or disappearance of the promoting effect on coal combustion.
基金supported by the National Natural Science Foundation of China(Nos.U2441284 and 22375164)the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University,China(No.CX2024042)。
文摘Aluminum-water(Al-H_(2)O)propellants represent an innovative class of solid propellants characterized by low cost and minimal signal signature.However,conventional formulations are hindered by significant aluminum(Al)agglomeration,leading to reduced combustion efficiency and substantial residues.This study introduces a method for modifying Al powder with Polyvinylidene Fluoride(PVDF)to enhance the performance of Al-H_(2)O propellants by mitigating agglomeration during combustion.Experimental methodologies,including thermogravimetric analysis under ambient-pressure nitrogen atmosphere and laser ignition tests,were employed to investigate the influence of varying PVDF content on the combustion characteristics of the propellants.Furthermore,the effect of PVDF on motor performance was systematically evaluated through laboratoryscale Solid Rocket Motor(SRM)tests.The results demonstrate that the addition of 7.5%PVDF significantly enhances the burning rate from 1.12 mm/s to 3.78 mm/s and reduces the mean particle size of condensed combustion products from 699μm to 527μm.Combustion efficiency rises from88.57%to 94.51%,while injection efficiency improves significantly from 30.45%to 70.45%.SRM tests further demonstrate an increase in combustion chamber pressure from 0.17 MPa to 0.58 MPa.A dynamic agglomeration model explains these improvements,attributing reduced agglomeration to enhanced aerodynamic forces and a thinner melting layer,while increased gas yield improves injection performance.This study highlights PVDF's potential in advancing Al-H_(2)O propellants by improving combustion and injection efficiency.
基金supported by the National Natural Science Foundation of China(Nos.U2241250 and U2441284)。
文摘AP(Ammonium Perchlorate)and HMX(Octogen)are the two oxidizers most often used in Nitrate-Ester-Plasticized Polyether(NEPE)rocket propellants.How the AP–HMX ratio influences the agglomeration of NEPE propellants remains unclear.We experimentally investigated the effect of the AP–HMX ratio on the combustion and agglomeration of NEPE propellants using burning rate test,quenched surface analysis,microscopic observations,and the collection of condensed combustion products.It was found that with the decrease in AP content from 40wt%to 10wt%,the burning rate decreased from 14.2 mm/s to 9.2 mm/s because the adiabatic flame temperature of NEPE propellants decreased from 3828 K to 3736 K.Pockets bounded by AP particles appeared on the surface when AP content was 40wt%;however,the accumulations grew and covered the burning surface eventually as the AP–HMX ratio decreased.The time required for the accumulation to coalesce into agglomerates increased with decreasing AP content.Even with similar agglomerate sizes,the coalescence time increased by 83%when the AP content decreased from 40wt%to 30wt%.The agglomerate size in the Condensed Combustion Products(CCPs)increased from 100μm to 200μm,and the fraction of large agglomerations increased from 6.4%to 24.7%when the AP content decreased from 40wt%to 10wt%.Overall,the high flame temperature of the AP particles enhanced the decomposition of the surrounding binder,resulting in the rapid ejection of the aluminum particles into the gas,which had a separating effect on the accumulation,thus weakening the agglomeration.
基金The National Natural Science Foundation of China(Grant Nos.523B2063 and 52376089)。
文摘Boron-based fuels,recognized for their high energy density and potential in energetic applications,encounter challenges such as long ignition delays and incomplete combustion,which result in reduced combustion efficiency and limited performance in aerospace propulsion.In this study,boron carbide(B4C)is investigated as an alternative fuel to pristine boron due to its favorable gas-phase combustion.Both metal oxide(nickel oxide(NiO))and metal fluoride(nickel fluoride(NiF_(2)))are selected as oxidizing modifiers to enhance the reactivity of B4C.A method combining laser ignition with optical diagnostics is employed to investigate the enhancing effects of different oxidizers on the ignition and combustion characteristics of B4C.Both NiO and NiF_(2)can significantly increase the combustion radiation intensity and reduce the time to maximum intensity of B4C.Differential scanning calorimetry,in-situ X-ray diffraction,and Fourier transform infrared spectroscopy were used for simultaneous thermal analysis of the B4C composite powders.Combined thermal analysis showed that the effects of NiO and NiF_(2)on promoting B4C combustion is mainly achieved via the formation of NimBn and the release of a large number of gas products.It is reasonable to speculate that the phase separation at the B2O3/NimBn interface forms new pathways for oxygen diffusion and reaction with the B core.The difference in the combustion mechanism of B4C with NiO and NiF_(2)lies in the gas phase products,i.e.,CO_(2)and BF3,respectively,thus leading to significant differences in their reaction processes.
基金supported by the National Natural Science Foundation of China(22076176,22276106)the Natural Science Foundation of Shandong Province(ZR2021YQ14)+3 种基金the Innovation Ability Improvement Project for Technology-based Small-and Medium-sized Enterprises of Shandong Province(2022TSGC1345)Jiangsu Province Science and Technology Plan Special Fund(BZ2022053)Key Research and Development Program of Anhui Province(202104g01020006)the Fundamental Research Funds for the Central Universities(202141008)。
文摘Catalyzed gasoline particulate filters(cGPFs)are being developed to enable compliance with the particulate number limits for passenger cars equipped with gasoline direct injection(GDI)engines in China and Europe,It is appealing to build catalysts with ceria—an irreplaceable"reducible"component in three-way converters—to help eliminate the soot particles trapped in cGPFs via O_(2)-assisted combustion.While research aiming at understanding how these recipes function has continued for more than two decades,a universal model elucidating the roles of different"active oxygen"species is yet to be realized.In this perspective,by critically assessing the reported data about gasoline soot catalytic combustion over ceria catalysts,it is suggested that ceria ignites soot through contributing its lattice oxygen,giving rise to a"hot ring"region at the periphery of soot-catalyst interface.During the"re-oxidation"semi-cycles,electrophilic superoxides and/or peroxides(O_(x)^(n-))are produced at the Ce^(3+)and oxygen vacancy sites enriched in this collar-like region,and then work as key reactive phases for soot deep oxidation.Based on this"O_(x)^(n-)assisted"Mars-van Krevelen mechanism,several guidelines for ceria catalyst designing are proposed,ending with a summary about where future opportunities and challenges may lie in developing efficient and practical cGPF catalysts.
基金Project supported by the National Key Research and Development Program(2022YFB3504200)National Natrual Science Foundation of China(22376061,21922602,22076047,U21A20326)+1 种基金Shanghai Science and Technology Innovation Action Plan(20dz1204200)Fundamental Re search Funds for the Central Universities。
文摘Pd-based catalysts have been extensively studied in the catalytic oxidation of methane,but their longterm stability and water resistance are unsatisfactory as the active sites are susceptible to water toxicity.The addition of Pt to Pd-based catalysts is found to be the most effective and promising method.However,distinct states of existence of Pt can affect the catalytic performance to different degrees,even negatively.Therefore,the impact mechanism of Pt on Pd-based catalysts needs to be further understood.In this work,A-site defective La_(0.9)AlO_(x)perovskite was used as a support,and the state of Pt in catalysts was regulated by adjusting the introducing sequence of Pd and Pt,It is found that only when Pt is introduced preferentially,the activity and water resistance of the bimetal can be improved.Combining a series of characterization results of the fresh catalysts,reduced catalysts,and the samples after reduction and use,it is found that the higher Pt^(2+)content in the catalyst is the main reason for promoting bimetallic properties,while more Pt0has an inhibitory effect.This work provides a new understanding of the promotion effect of Pt on Pd-Pt bimetal in the catalytic oxidation reaction of methane.
基金supported by the National Natural Science Foundation of China(No.42025705)the Construction Project of Modern Agricultural Science and Technology Innovation Alliance of Guangdong Province,China(No.2023KJ112)+1 种基金the National Natural Science Foundation of China(Nos.41977291 and 42177242)the GDAS’Project of Science and Technology Development,China(No.2019GDASYL-0103048).
文摘Coal power plants annually generate quantities of byproducts that release environmentally hazardous heavy metals like Cd and Pb.Understanding the behavior and spatiotemporal impacts on soils of these releases is crucial for pollution control.This study investigated the concentrations and isotope ratios of Cd/Pb in combustion byproducts,depositions and soils collected froma coal-fired power plant or its surrounding area.The pulverized fuel ash(PFA)and desulfurized gypsum(DG)exhibited heavier Cd isotopes withΔ^(114)Cd values of 0.304‰and 0.269‰,respectively,while bottom ash(BA)showed lighter Cd isotopes(Δ^(114)CdBA-coal=–0.078‰),compared to feed coal.We proposed a two-stage condensation process that governs the distribution of Cd/Pb,including accumulation on PFA and DG within electrostatic precipitators and desulfurization unit,as well as condensation onto fine particles upon release from the stack.Emissions from combustion and large-scale transport make a significant contribution to deposition,while the dispersion of Cd/Pb in deposition is primarily influenced by the prevailing wind patterns.However,the distribution of Cd/Pb in soils not only exhibit predominant wind control but is also potentially influenced by the resuspension of long-term storage byproducts.The power plant significantly contributes to soil in the NW–N–NE directions,even at a considerable distance(66%–79%),demonstrating its pervasive impact on remote regions along these orientations.Additionally,based on the vertical behavior in the profile,we have identified that Cd tends to migrate downward through leaching,while variations in Pb respond to the historical progression of dust removal.
基金supported by the Basic Research Business Fund Grant Program for University of Science and Technology Beijing(No.06500227)the Fundamental Research Funds for the Central Universities(No.FRF-TP-22-091A1)+1 种基金National Natural Science Foundation of China(No.52200121),Chinese Universities Scientific Fund(No.00007713)the Guide special project(No.40103322).
文摘With the rapid development of adsorbents for removal of elemental mercury (Hg0) from coal combustion flue gas,the preparation of adsorbents with superior performance,lower cost and environmental friendliness remains an important challenge.An incipient wetness impregnation method followed by in-situ selenization was used to load copper selenide(CuSe) onto the surface of optimal magnetic biochar (OMBC).The results showed that CuSe significantly enhanced the Hg0removal performance of the OMBC,and CuSe loading ratio of 10%(10CuSe/OMBC) had the best Hg0removal performance.10CuSe/OMBC maintained its Hg0removal efficiency above 95% for 150 min at 30-150℃,and it had a good resistance to SO2.The equilibrium adsorption capacity of 10CuSe/OMBC could reach up to 8.73 mg/g,which was close to the theoretical value 12.99 mg/g,and the adsorption rate was up to 20.33μg/(g·min) Meanwhile,10CuSe/OMBC had strong magnetism that is not permanently magnetized,which could be separated from desulfurization gypsum and recycled many times.Characterization results demonstrated that Se22-,Cu2+and Oβplayed essential roles in the oxidation of Hg0,and Se22-and Se2-can immobilize Hg2+to HgSe.10CuSe/OMBC has important guiding significance for practical application because of its low cost,high performance and low mercury leaching characteristic to form HgSe.
文摘The counterflow burner is a combustion device used for research on combustion.By utilizing deep convolutional models to identify the combustion state of a counter flow burner through visible flame images,it facilitates the optimization of the combustion process and enhances combustion efficiency.Among existing deep convolutional models,InceptionNeXt is a deep learning architecture that integrates the ideas of the Inception series and ConvNeXt.It has garnered significant attention for its computational efficiency,remarkable model accuracy,and exceptional feature extraction capabilities.However,since this model still has limitations in the combustion state recognition task,we propose a Triple-Scale Multi-Stage InceptionNeXt(TSMS-InceptionNeXt)combustion state recognitionmethod based on feature extraction optimization.First,to address the InceptionNeXt model’s limited ability to capture dynamic features in flame images,we introduce Triplet Attention,which applies attention to the width,height,and Red Green Blue(RGB)dimensions of the flame images to enhance its ability to model dynamic features.Secondly,to address the issue of key information loss in the Inception deep convolution layers,we propose a Similarity-based Feature Concentration(SimC)mechanism to enhance the model’s capability to concentrate on critical features.Next,to address the insufficient receptive field of the model,we propose a Multi-Scale Dilated Channel Parallel Integration(MDCPI)mechanism to enhance the model’s ability to extract multi-scale contextual information.Finally,to address the issue of the model’s Multi-Layer Perceptron Head(MlpHead)neglecting channel interactions,we propose a Channel Shuffle-Guided Channel-Spatial Attention(ShuffleCS)mechanism,which integrates information from different channels to further enhance the representational power of the input features.To validate the effectiveness of the method,experiments are conducted on the counterflow burner flame visible light image dataset.The experimental results show that the TSMS-InceptionNeXt model achieved an accuracy of 85.71%on the dataset,improving by 2.38%over the baseline model and outperforming the baseline model’s performance.It achieved accuracy improvements of 10.47%,4.76%,11.19%,and 9.28%compared to the Reparameterized Visual Geometry Group(RepVGG),Squeeze-erunhanced Axial Transoformer(SeaFormer),Simplified Graph Transformers(SGFormer),and VanillaNet models,respectively,effectively enhancing the recognition performance for combustion states in counterflow burners.
基金supported by the National Natural Science Foundation of China(No.22305053).
文摘Powder-Fueled Water Ramjet Engine(PFWRE)is of great attraction for high-speed and long-voyage underwater propulsion,as well as air–water trans-media navigation applications due to its high energy density and thrust adjustability.However,the complex multiphase combustion process in the combustor significantly affects engine performance.In this study,a detailed model for aluminum particle combustion in water vapor is developed and validated via literature data as well as the ground direct-connected test we conducted.Thereafter,the numerical study on the multiphase combustion process inside the aluminum-based PFWRE combustor is carried out within the Euler–Lagrange framework using the developed model.Results show that a reverse rotating vortex pair before the primary water injection causes particles to flow back towards the combustor head and leads to product deposition.Aluminum particles external to the powder jet have shorter preheating time than internal particles and burn out in advance.The analysis of the particle combustion process indicates that the flame structure inside the combustor consists of the particle preheating zone,the surface combustion heat release zone,the gas-phase combustion heat release zone,and the post-flame zone.In the present configuration,as the particle size increases from 10μm to 20μm,the preheating zone length increases from 35 mm to 85 mm.Meanwhile,heat release from gas-phase combustion decreases,and the average temperature of the combustor head first increases and then decreases.This study not only provides insight into the multiphase combustion characteristics of the aluminum-based PFWRE combustor but also offers guidance for the design of the combustion organization schemes and engine structure optimization.
基金supported by the China Postdoctoral Science Foundation(Grant No.2022M723497).
文摘Hydrogen doping in associated gas combustion presents a promising strategy for mitigating carbon emissions from typically flared or vented gases.To support this idea,this study employed Chemkin Pro to model the laminar premixed combustion of associated gases and conducted a sensitivity analysis of key combustion factors.The results demonstrated that increasing the hydrogen-doping ratio accelerated flame propagation and reduced combustion product accumulation time,while also elevating flame instability and inducing cracks or folds on the flame front at higher ratios.Notably,flame speed exhibited a 40%increase per 10%rise in the hydrogen-doping ratio,which directly enhanced combustion efficiency.Flame temperature peaked at an equivalence ratio of 1,whereas flame speed enhancement was maximized at a ratio of 1.3.Higher premix temperatures increased flame speed,and elevated combustion pressures raised flame temperature(stabilizing above 1 atm),with flame speed peaking at 0.06 atm.Critically,hydrogen doping below 15%minimally altered flame morphology,but 30%doping caused significant flame retraction toward the nozzle,which increased the flashback risk and raised NOx emissions by nearly one third.These findings provide insights for optimizing hydrogen-doped combustion processes to balance efficiency gains while ensuring operational safety and emission control.
基金financially supported by the National Key R&D Program of China(No.2022YFE0208100)the Major Science and Technology Project of Xinjiang Uygur Autonomous Region,China(No.2022A01003)+1 种基金the Key Research and Development Plan of Anhui Province,China(No.202210700037)the National Natural Science Foundation of China(No.52274316).
文摘The mixing injection of natural gas and pulverized coal into the blast furnaces shows a promising technological approach in the context of global carbon reduction initiatives.Carrier gas and coal pass through the air inlet of coal lance,and the characteristics of carrier gas affect the flow in the air inlet and the combustion efficiency of coal,so it is very important to study the change of carrier gas charac-teristics in the lower part of blast furnace.By means of numerical simulation,the influence of carrier gas characteristics(injection rate,composition,and temperature)on the mixed combustion of natural gas(NG)and pulverized coal in the tuyere raceway of Russian blast furnace was analyzed.When N_(2) is used as carrier gas,the injection rate of carrier gas is reduced from 4000 to 2000 m3/h,the average tuy-ere temperature is increased(1947.42 to 1963.30 K),the mole fractions of CO and H_(2) are increased,and the burnout rate of pulverized coal is decreased.Increasing the carrier gas temperature is helpful to improve the burnout of pulverized coal.For every 20 K increase of carrier gas temperature,the average temperature in the raceway increases by 20.6 K,which promotes the release and combustion of volat-iles,but the increase of carrier gas temperature from 373 to 393 K only leads to 1.16%burnout change.Considering the transportation characteristics of pulverized coal,it is suggested that the carrier gas temperature should be kept at about 373 K to obtain the best perform-ance.It is worth noting that when air is used as carrier gas,the burnout rate of pulverized coal is increased by 2.69%compared with N_(2).
文摘To investigate the problem of ethylene jet mixing and combustion in the scramjet at high Mach number(Ma = 8), numerical simulations were carried out for different equivalent ratios at cold and combustion conditions, in which three-dimensional steady compressible RANS and k-ω SST turbulence model were adopted. It demonstrates that as the equivalence ratio increases from 0.42 to 1.08, the combustion becomes more intensified, and the higher backpressure pushes flame to propagate upstream. The supersonic combustion region in the combustor decreases from 92% to 85% with the increase of equivalence ratio from 0.42 to 1.08, resulting in the transition of the combustor from scram-mode to dual-mode. Both mixing and combustion efficiencies decrease by 35% and 16% respectively when the equivalence ratio increases from 0.42 to 1.08, indicating that the high equivalence ratio is unfavorable to the mixing and combustion processes. Combustion mode analysis reveals that the flame in the cavity under the high Mach number is dominated by non-premixed flames, i.e., more than 95% behaves as non-premixed mode, and the heat release is also mainly contributed by non-premixed flame. Increasing the equivalence ratio is beneficial to the thrust performance. Although the viscous force hardly changes with equivalence ratio, the percentage of pressure force used to balance the viscous force increases gradually,which limits the engine performance.
文摘This study calculates the combustion characteristics of various gas-generating and micro gas pyrotechnic charges,including aluminium/potassium perchlorate,boron/potassium nitrate,carbon black/potassium nitrate,and silicon-based delay compositions,using thermodynamic software.A multiphase flowthermal-solid coupling model was established,and the combustion process of the pyrotechnic charges within a closed bomb was simulated.The pyrotechnic shock generated by combustion was predicted.The combustion pressures and pyrotechnic shocks were measured.The simulation results demonstrated good agreement with experimental results.Additionally,the mechanism of shock generation by the combustion of pyrotechnic charges in the closed bomb was analyzed.The effects of the combustion characteristics of the pyrotechnic charges on the resulting pyrotechnic shocks were systematically investigated.Notably,the shock response spectrum of the gas-generating pyrotechnic charges is greater than that of the micro gas compositions at most frequencies,particularly in the mid-field pyrotechnic shocks(3-10 kHz).Furthermore,the pyrotechnic shocks increase approximately linearly with the impulse of the gas-generating pyrotechnic charges.
