Purpose:This article aims to determine the percentage of"Sparking"articles among the work of this year’s Nobel Prize winners in medicine,physics,and chemistry.Design/methodology/approach:We focus on under-c...Purpose:This article aims to determine the percentage of"Sparking"articles among the work of this year’s Nobel Prize winners in medicine,physics,and chemistry.Design/methodology/approach:We focus on under-cited influential research among the key publications as mentioned by the Nobel Prize Committee for the 2020 Noble Prize laureates.Specifically,we extracted data from the Web of Science,and calculated the Sparking Indices using the formulas as proposed by Hu and Rousseau in 2016 and 2017.In addition,we identified another type of igniting articles based on the notion in 2017.Findings:In the fields of medicine and physics,the proportions of articles with sparking characteristics share 78.571%and 68.75%respectively,yet,in chemistry 90%articles characterized by"igniting".Moreover,the two types of articles share more than 93%in the work of the Nobel Prize included in this study.Research limitations:Our research did not cover the impact of topic,socio-political,and author’s reputation on the Sparking Indices.Practical implications:Our study shows that the Sparking Indices truly reflect influence of the best research work,so it can be used to detect under-cited influential articles,as well as identifying fundamental work.Originality/value:Our findings suggest that the Sparking Indices have good applicability for research evaluation.展开更多
Exploding foil initiator(EFI)is a kind of advanced device for initiating explosives,but its function is unstable when it comes to directly igniting pyrotechnics.To solve the problem,this research aims to reveal the ig...Exploding foil initiator(EFI)is a kind of advanced device for initiating explosives,but its function is unstable when it comes to directly igniting pyrotechnics.To solve the problem,this research aims to reveal the ignition mechanism of EFIs directly igniting pyrotechnics.An oscilloscope,a photon Doppler velocimetry,and a plasma spectrum measurement system were employed to obtain information of electric characteristics,impact pressure,and plasma temperature.The results of the electric characteristics and the impact pressure were inconsistent with ignition results.The only thing that the ignition success tests had in common was that their plasma all had a relatively long period of high-temperature duration(HTD).It eventually concludes that the ignition mechanism in this research is the microconvection heat transfer rather than the shock initiation,which differs from that of exploding foil initiators detonating explosives.Furthermore,the methods for evaluating the ignition success of semiconductor bridge initiators are not entirely applicable to the tests mentioned in this paper.The HTD is the critical parameter for judging the ignition success,and it is influenced by two factors:the late time discharge and the energy of the electric explosion.The longer time of the late time discharge and the more energy of the electric explosion,the easier it is to expand the HTD,which improves the probability of the ignition success.展开更多
How to directly fabricate metallic functional parts with selective laser sintering (SLS) process is a potential technique that scientists are researching. Existent problems during directly fabricating metal part by us...How to directly fabricate metallic functional parts with selective laser sintering (SLS) process is a potential technique that scientists are researching. Existent problems during directly fabricating metal part by use of SLS are analyzed. For the sake of solving the problems, a new idea of adding self-propagating high-temperature synthesis (SHS) material into metallic powder material to form new type of SLS metallic powder material is put forward. This powder material can release controllable amount of heat during its interaction with the laser beam energy to reduce the requirement to laser power during directly sintering metallic part, to prolong the time of metallic liquid phase existing, and to improve the intensity and accuracy of SLS part. For this reason, SHS material′s interaction with the CO2 laser beam energy is researched, which proves that CO2 laser beam energy may instantly ignite SHS reaction. On the basis of the above-mentioned researches, the effect of sintering the metal powder material mixing SHS material with CO2 laser is also researched, which shows: there is an optimal blending ratio of various material in the new metallic powder material. Under the optimal blending ratio and SLS process parameters, this new metallic powder material can indeed release amount of heat and SHS reaction may be controlled within the laser sintering. This research result makes it possible that the metallic part is directly sintered with small CO2 laser (less than 50W), which may greatly reduce the volume, cost and running expenditure of SLS machine, be propitious to application.展开更多
Ten million times more compact energy than from burning carbon can be obtained from nuclear fusion reactions corresponding to equilibrium temperature reactions in the range above 100 million degrees.Following the ener...Ten million times more compact energy than from burning carbon can be obtained from nuclear fusion reactions corresponding to equilibrium temperature reactions in the range above 100 million degrees.Following the energy gain in stars,one has to gain nuclear energy from slamming very light nuclei where however the extremely high temperatures above 100 million degrees are needed for the sufficient pressures at thermal equilibrium ignition.A radically new option works with non-thermal pressures of picosecond laser pulses at ultrahigh optical powers by nonlinear forces of ponderomotion.The nuclear fusion of hydrogen with the isotope 11 of boron produces primarily harmless helium and has no problems with dangerous radioactive waste and excludes any catastrophic melt-down as fission reactors,it has the potential to be of low costs and can supply the Earth for more than 10,000 years with electricity.展开更多
The transition from a student to a professional is an important juncture in the path of life.This not only means a change in the environment,but also a complete upgrade of the mental model.Based on real workplace scen...The transition from a student to a professional is an important juncture in the path of life.This not only means a change in the environment,but also a complete upgrade of the mental model.Based on real workplace scenarios and the author’s years of experience,this book extracts the"core rules"to help newcomers complete role transformation:role adjustment,ability improvement,and mentality building.Through specific cases and practical tools,this book depicts how to fight your first battle in the workplace and find your own career development path.展开更多
Conventional ignition methods are proving to be ineffective for low-sensitivity energetic materials,highlighting the need to investigate alternative ignition systems,such as laser-based techniques.Over the past decade...Conventional ignition methods are proving to be ineffective for low-sensitivity energetic materials,highlighting the need to investigate alternative ignition systems,such as laser-based techniques.Over the past decade,lasers have emerged as a promising solution,providing focused energy beams for controllable,efficient,and reliable ignition in the field of energetic materials.This study presents a comparative analysis of two state-of-the-art ignition approaches:direct laser ignition and laser-driven flyer ignition.Experiments were performed using a Neodymium-doped Yttrium Aluminum Garnet(Nd:YAG)laser at different energy beam levels to systematically evaluate ignition onset.In the direct laser ignition test setup,the laser beam was applied directly to the energetic tested material,while laserdriven flyer ignition utilized 40 and 100μm aluminum foils,propelled at velocities ranging from 300 to 1250 m/s.Comparative analysis with the Lawrence and Trott model substantiated the velocity data and provided insight into the ignition mechanisms.Experimental results indicate that the ignition time for the laser-driven flyer method was significantly shorter,with the pyrotechnic composition achieving complete combustion faster compared to direct laser ignition.Moreover,precise ignition thresholds were determined for both methods,providing critical parameters for optimizing ignition systems in energetic materials.This work elucidates the advantages and limitations of each technique while advancing next-generation ignition technology,enhancing the reliability and safety of propulsion systems.展开更多
Based on the characteristics of laser-induced surface ignition,energetic photosensitive films show promising potential to meet the ignition requirements of various energetic materials(EMs).In this study,DATNBI/ferric ...Based on the characteristics of laser-induced surface ignition,energetic photosensitive films show promising potential to meet the ignition requirements of various energetic materials(EMs).In this study,DATNBI/ferric alginate(DI/FeA),DI/cobalt alginate(DI/CoA),and DI/nickel alginate(DI/Ni A)films are fabricated by employing sodium alginate(SA)with a three-dimensional network structure as the film matrix,via ionic cross-linking of SA with Fe^(3+),Co^(2+),and Ni^(2+)ions.The study demonstrates that the ionic cross-linking enhances the hydrophobic performance of the films,with the water contact angle increasing from 82.1° to 123.5°.Concurrently,the films'near-infrared(NIR)light absorption improved.Furthermore,transition metal ions facilitate accelerated electron transfer,thereby catalyzing the thermal decomposition of DATNBI.Under 1064 nm laser irradiation,the DI/Fe A film exhibits exceptional combustion performance,with an ignition delay time as low as 76 ms.It successfully acts as an NIR laser ignition medium to initiate the self-sustained combustion of CL-20.This study demonstrates the synergistic realization of enhanced hydrophobicity,improved photosensitivity,and promoted catalytic decomposition through microstructural design of the material,providing new insights for the design of additive-free EMs in laser ignition applications.展开更多
Boron has attracted increasing attention in the field of high-energy explosives and propellants due to its high volume calorific value and mass calorific value.However,the complicated combustion process and low combus...Boron has attracted increasing attention in the field of high-energy explosives and propellants due to its high volume calorific value and mass calorific value.However,the complicated combustion process and low combustion efficiency hinder its wide application.To tackle this challenge,bioinspired polydopamine(PDA)interface reinforced boron-Viton composites,with high structure stability and excellent energy releasing efficiency,are designed and prepared,combining the interface regulation of PDA biomimetic materials and combustion promotion of fluoropolymers.Firstly,the stronger adsorption energy of PDA with boron compared to Viton is demonstrated by molecular dynamics simulations.Next,B@PDA@Viton is prepared by the combination of in-situ dopamine polymerization and solvent/nonsolvent method,and the double-layer core-shell structure is confirmed by XPS,FTIR,and TEM characterizations.TG-DSC analysis shows that B@PDA@Viton possesses superior thermal properties,with a 55.48%increase in oxidation heat compared to raw B.Furthermore,ignition and combustion performance tests indicate that B@PDA@Viton reduces ignition delay by 57.56%and increases heat of combustion by 68.63%relative to raw B.These findings elucidate the ignition and combustion mechanisms of B@PDA@Viton.This work not only developed high-performance boron-based composite fuels but also provided insights into the development of boron-based fuels.展开更多
Underwater gas-liquid two-phase propulsion technology is an emerging propulsion method that offers high efficiency and unrestricted navigation speed.The integration of this technology into water ramjet engines can sig...Underwater gas-liquid two-phase propulsion technology is an emerging propulsion method that offers high efficiency and unrestricted navigation speed.The integration of this technology into water ramjet engines can significantly enhance propulsion efficiency and holds substantial potential for broad applications.However,forming a gas-liquid two-phase flow within the nozzle requires introducing a large amount of rammed seawater.At this time,there is a complex phase transition problem of combustion products in the combustion chamber,which makes the thermodynamic calculation for gas-liquid two-phase water ramjet engines particularly challenging.This paper proposes a thermodynamic calculation method for gas-liquid two-phase water ramjet engines,based on the energy equation for gas-liquid two-phase flow and traditional thermodynamic principles,enabling thermodynamic calculations under conditions of ultra-high water-fuel ratios.Additionally,ground ignition tests of the gas-liquid two-phase engine were conducted,yielding critical engine test parameters.The results demonstrate that the gas-liquid two-phase water ramjet engine achieves a high specific impulse,with a theoretical maximum specific impulse of up to 7000(N s)/kg.The multiphase flow effects significantly impact engine performance,with specific impulse losses reaching up to 25.86%.The error between the thrust and specific impulse in the ground test and the theoretical values is within 10%,validating the proposed thermodynamic calculation method as a reliable reference for further research on gas-liquid two-phase water ramjet engines.展开更多
Pre-chamber ignition technology can address the issue of uneven in-cylinder mixture combustion in large-bore marine engines.The impact of various pre-chamber structures on the formation of the mixture and jet flames w...Pre-chamber ignition technology can address the issue of uneven in-cylinder mixture combustion in large-bore marine engines.The impact of various pre-chamber structures on the formation of the mixture and jet flames within the pre-chamber is explored.This study performed numerical simulations on a large-bore marine ammonia/hydrogen pre-chamber engine prototype,considering pre-chamber volume,throat diameter,the distance between the hydrogen injector and the spark plug,and the hydrogen injector angle.Compared with the original engine,when the pre-chamber volume is 73.4 ml,the throat diameter is 14 mm,the distance ratio is 0.92,and the hydrogen injector angle is 80°.Moreover,the peak pressure in the pre-chamber increased by 23.1%,and that in the main chamber increased by 46.3%.The results indicate that the performance of the original engine is greatly enhanced by altering its fuel and pre-chamber structure.展开更多
Deaf-mute Jiang Xintian lights a small cauldron in the hands of wheelchairbound fencer Jin Jing at the Paralympic Flame Lighting Ceremony in Beijing’s symbolic Temple of Heaven on August 28. For nine days until Septe...Deaf-mute Jiang Xintian lights a small cauldron in the hands of wheelchairbound fencer Jin Jing at the Paralympic Flame Lighting Ceremony in Beijing’s symbolic Temple of Heaven on August 28. For nine days until September 6, when the 13th Paralympics opens in Beijing, a total of 850 torchbearers would relay the Paralympic flame along two routes through 11 Chinese provinces,展开更多
Hot molten metal droplets with high fire hazard can easily ignite combustibles. Molten metal kinetics on the surface of a combustible material directly affects the ignition likelihood. Existing research focuses on the...Hot molten metal droplets with high fire hazard can easily ignite combustibles. Molten metal kinetics on the surface of a combustible material directly affects the ignition likelihood. Existing research focuses on the behavior of droplets during collisions, rarely addressing the ignition of combustibles by hot metal droplets. Here, the mechanisms of aluminum and copper droplets impinging on and igniting extended polystyrene (EPS) foam boards at different velocities were investigated. The relationship between the critical ignition temperature and impact velocity of droplets with diameters of 6 and 8 mm was experimentally studied for aluminum droplets;the critical ignition temperature non-monotonically depended on the impact velocity. For copper droplets, the relationship between the ignition probability and the impact velocity of droplets with diameters in the 3.5–7 mm range was experimentally studied. The most obvious difference between the two droplet ignition types was that the impact of copper droplets was accompanied by intense splashing, and the fragmentation extent positively correlated with the impact velocity. It was challenging to ignite using completely broken copper droplets. Droplets with the diameter of 5 mm were the most dangerous under the experimental conditions of this study, because the foam could still be ignited at higher impact velocities. Numerical simulations suggested that the main factors explaining the critical ignition temperature of aluminum droplets were gas mixing and splat cooling. The main factor affecting the ignition of copper droplets was fragmentation, and experimental observations were explained using non-dimensional droplet fragmentation theories.展开更多
Magnesium and its alloys offer lightweight advantage and have extensive development prospects,particularly in aerospace.However,their flammability poses a significant barrier on the development of Mg alloys.The igniti...Magnesium and its alloys offer lightweight advantage and have extensive development prospects,particularly in aerospace.However,their flammability poses a significant barrier on the development of Mg alloys.The ignition resistance of these alloys often depends on the protectiveness of the oxide film formed on the surface.This paper elucidates the formation mechanism of oxide film from thermodynamics and kinetics,classifying oxide films based on their layered structure to assess their protective properties.Furthermore,it comprehensively reviews the impact of characteristics on the protective effectiveness such as compactness,continuity,thickness,and mechanical properties.The paper also introduces various characterization methods for the microstructure and properties of oxide film.The primary objective of this paper is to enhance the comprehension of oxide film concerning the ignition resistance of Mg alloys and to furnish references for future advancements and research in Mg alloys with heightened ignition resistance.展开更多
The incorporation of Y significantly improves the fire resistance of the Mg-3Nd-2Gd-0.2Zr-0.2Zn(EV32)alloy.The findings indicate a significant increase in the ignition point of the alloy upon Y addition,notably reachi...The incorporation of Y significantly improves the fire resistance of the Mg-3Nd-2Gd-0.2Zr-0.2Zn(EV32)alloy.The findings indicate a significant increase in the ignition point of the alloy upon Y addition,notably reaching 813.9℃ for the EV32–3Y(wt.%)alloy.Additionally,the calculated residual stresses of the Y_(2)O_(3) and Gd_(2)O_(3) films were 2.732 GPa and 2.569 GPa respectively,showcasing a distinct correlation between Y concentration and improved fire resistance.This enhancement can be attributed to the formation of denser oxide films,especially Y_(2)O_(3) and Gd_(2)O_(3),effectively reducing the susceptibility of the oxide film to thermal stress-induced tearing.The study elucidates the vital role of Y addition in enhancing fire resistance,thoroughly investigating the mechanisms that impact both the formation of oxide films and ignition within the alloy structure.These findings not only contribute to a deeper comprehension of magnesium alloy performance under high-temperature conditions but also offer valuable theoretical guidance for enhancing its fire resistance through alloy design and application.展开更多
Enhancing the ignition system performance of turbo engines is crucial,with a focus on rapidly and reliably igniting the entire combustor in low-temperature,low-pressure,high-speed inlet flow conditions.This challenge ...Enhancing the ignition system performance of turbo engines is crucial,with a focus on rapidly and reliably igniting the entire combustor in low-temperature,low-pressure,high-speed inlet flow conditions.This challenge has garnered international attention.To address the issue of reliable ignition in the combustors of advanced propulsion system,this paper proposes a Multichannel Jet Enhanced Plasma Igniter(MJEPI) and conducts comparative experimental studies with the conventional spark igniter in a component-level dual-dome swirl combustor.The ignition limit in the combustor is obtained and the ignition processes are recorded.Experimental results demonstrate that the MJEPI significantly improves the ignition performance at high altitude.Specifically,at 0 km and 6 km for ground start-up,ignition limit is extended by 36% and 29%,respectively.At 6 km and 12 km for high-altitude relight,ignition limit is extended by 32% and 21%,respectively.The maximum ignition height is increased by 2.3 km,as determined by the global equivalence ratio of 1.The primary reason for these improvements is attributed to the larger initial flame kernel with greater penetration depth generated by MJEPI,which enables it to withstand more sever conditions such as low temperature,low pressure,and poor kerosene spray quality at elevated altitudes.展开更多
In February 2024,192 lasers at the National Ignition Facility(NIF)in Livermore,CA,USA,began pouring 2.2 MJ of energy into a gold container smaller than the tip of a person’s little finger,heat-ing it to more than thr...In February 2024,192 lasers at the National Ignition Facility(NIF)in Livermore,CA,USA,began pouring 2.2 MJ of energy into a gold container smaller than the tip of a person’s little finger,heat-ing it to more than three million degrees Celsius(Fig.1)[1-4].Inside the container was a tiny fuel capsule containing tritium and deuterium that imploded at more than 400 km·s^(-1)causing atoms to combine and releasing 5.2 MJ of energy[1-4].展开更多
The reignition of aero-engine combustors at high altitudes poses significant challenges due to the low-temperature and low-pressure environment.A novel Long Pulse-Width Plasma Ignition(LPWPI)system has been developed ...The reignition of aero-engine combustors at high altitudes poses significant challenges due to the low-temperature and low-pressure environment.A novel Long Pulse-Width Plasma Ignition(LPWPI)system has been developed to enhance ignition performance.The LPWPI system can effectively prolong the discharge duration time,improve ignition efficacy,and increase the plasma penetration depth.Experimental comparisons with the traditional Spark Ignition(SI)system demonstrate that the LPWPI increased discharge duration to 2.03 ms,which is 45 times longer than that of the SI system,while also doubling the spark penetration depth to 24.1 mm.The LPWPI system achieved a discharge efficiency of 61.1%,significantly surpassing the SI system's efficiency of23.3%.These advancements facilitated an extension of the lean ignition boundary by approximately 22.7%to 39.3%.High-speed camera recordings reveal that the spark duration of the LPWPI system was extended to 2.1 ms,compared to 0.6 ms in the SI system.Ignition progress with LPWPI shows a sustained spark kernel without the flame residence stage observed in the SI system.The impressive performance of the LPWPI system suggests that it is a promising alternative for aero-engine ignition systems.展开更多
Oxide films hinder diffusion and resist external forces,which determines the flame ignition mechanism of magnesium alloys.The effects of the continuity,compactness and mechanical properties of oxide films on the ignit...Oxide films hinder diffusion and resist external forces,which determines the flame ignition mechanism of magnesium alloys.The effects of the continuity,compactness and mechanical properties of oxide films on the ignition mechanism were analyzed,by investigating the flame ignition behaviors of AZ80(ZM5),EZ30K(ZM6)and WE43 Mg alloys.The results show that the rupture of the oxide films caused by liquid gravity was the key to causing ignition.According to thermodynamic calculations,compared with Mg,Al cannot be preferentially oxidized;while Nd can be preferentially oxidized through significant enrichment,resulting in a discontinuous Nd_(2)O_(3)inner layer in the ZM6 alloy;in contrast,Y has a strong preferential oxidation ability,which gives the WE43 alloy a continuous Y_(2)O_(3)inner layer and self-healing ability.In addition,the oxide film of the ZM5 alloy is loose and has poor mechanical properties,so it cannot effec-tively hinder diffusion and resist liquid gravity.Differently,the oxide films of the ZM6 and WE43 alloys are dense and have better mechanical properties,leading to higher ignition temperatures and longer igni-tion times.In addition,a criterion was proposed to predict the ignition time based on the law of energy conservation,and it was simplified to predict the ignition temperature.The errors between the predicted and measured values are within 11%.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
Gas explosions in coal mine goafs are associated with the roof rock fracturing.An experimental system was established to investigate the potential for electrical ignition induced by sandstone fracturing.The electrical...Gas explosions in coal mine goafs are associated with the roof rock fracturing.An experimental system was established to investigate the potential for electrical ignition induced by sandstone fracturing.The electrical responses,luminescent emissions,and ignition characteristics during tensile and compressive failure of sandstones were analyzed in methane/air premixed gas environments.Results indicate that the application of mechanical loading induces the emergence of electrical signals on rock surfaces and in the surrounding atmosphere.This phenomenon is attributed to the generation,accumulation,and subsequent release of free charges during the deformation and fracture within the sandstone.Compressive failure proved to be more conducive to free charge generation than tensile failure,owing to more crack connections.Furthermore,a precipitous increase in surface and external voltages was observed during complete fracturing,a consequence of electron emission from crack tips within the rock structure.Moreover,the ionization induces luminous emissions owing to the collision of energetic electrons released from gas molecules in methane/air mixtures.A strong positive correlation(R2=0.9429)was identified between luminescence intensity and the magnitude of electrical discharge resulting from rock fracture.Notably,such discharge by rock fracturing can be capable of igniting the premixed gas,particularly when the quartz content exceeds 61%.Piezoelectric effects and crack propagation are crucial mechanisms in the causal chain of the charge generation,discharge,and ionization triggered by rock fractures.Based on the above laboratory results,electric ignition of the transient roof fracturing caused by stress mutations can serve as a new potential ignition source for gas explosions in the goaf.These results offer new insights into the prevention and control of gas explosions.展开更多
基金the National Natural Science Foundation of China Grant numbers:71974167 and 71573225。
文摘Purpose:This article aims to determine the percentage of"Sparking"articles among the work of this year’s Nobel Prize winners in medicine,physics,and chemistry.Design/methodology/approach:We focus on under-cited influential research among the key publications as mentioned by the Nobel Prize Committee for the 2020 Noble Prize laureates.Specifically,we extracted data from the Web of Science,and calculated the Sparking Indices using the formulas as proposed by Hu and Rousseau in 2016 and 2017.In addition,we identified another type of igniting articles based on the notion in 2017.Findings:In the fields of medicine and physics,the proportions of articles with sparking characteristics share 78.571%and 68.75%respectively,yet,in chemistry 90%articles characterized by"igniting".Moreover,the two types of articles share more than 93%in the work of the Nobel Prize included in this study.Research limitations:Our research did not cover the impact of topic,socio-political,and author’s reputation on the Sparking Indices.Practical implications:Our study shows that the Sparking Indices truly reflect influence of the best research work,so it can be used to detect under-cited influential articles,as well as identifying fundamental work.Originality/value:Our findings suggest that the Sparking Indices have good applicability for research evaluation.
文摘Exploding foil initiator(EFI)is a kind of advanced device for initiating explosives,but its function is unstable when it comes to directly igniting pyrotechnics.To solve the problem,this research aims to reveal the ignition mechanism of EFIs directly igniting pyrotechnics.An oscilloscope,a photon Doppler velocimetry,and a plasma spectrum measurement system were employed to obtain information of electric characteristics,impact pressure,and plasma temperature.The results of the electric characteristics and the impact pressure were inconsistent with ignition results.The only thing that the ignition success tests had in common was that their plasma all had a relatively long period of high-temperature duration(HTD).It eventually concludes that the ignition mechanism in this research is the microconvection heat transfer rather than the shock initiation,which differs from that of exploding foil initiators detonating explosives.Furthermore,the methods for evaluating the ignition success of semiconductor bridge initiators are not entirely applicable to the tests mentioned in this paper.The HTD is the critical parameter for judging the ignition success,and it is influenced by two factors:the late time discharge and the energy of the electric explosion.The longer time of the late time discharge and the more energy of the electric explosion,the easier it is to expand the HTD,which improves the probability of the ignition success.
文摘How to directly fabricate metallic functional parts with selective laser sintering (SLS) process is a potential technique that scientists are researching. Existent problems during directly fabricating metal part by use of SLS are analyzed. For the sake of solving the problems, a new idea of adding self-propagating high-temperature synthesis (SHS) material into metallic powder material to form new type of SLS metallic powder material is put forward. This powder material can release controllable amount of heat during its interaction with the laser beam energy to reduce the requirement to laser power during directly sintering metallic part, to prolong the time of metallic liquid phase existing, and to improve the intensity and accuracy of SLS part. For this reason, SHS material′s interaction with the CO2 laser beam energy is researched, which proves that CO2 laser beam energy may instantly ignite SHS reaction. On the basis of the above-mentioned researches, the effect of sintering the metal powder material mixing SHS material with CO2 laser is also researched, which shows: there is an optimal blending ratio of various material in the new metallic powder material. Under the optimal blending ratio and SLS process parameters, this new metallic powder material can indeed release amount of heat and SHS reaction may be controlled within the laser sintering. This research result makes it possible that the metallic part is directly sintered with small CO2 laser (less than 50W), which may greatly reduce the volume, cost and running expenditure of SLS machine, be propitious to application.
文摘Ten million times more compact energy than from burning carbon can be obtained from nuclear fusion reactions corresponding to equilibrium temperature reactions in the range above 100 million degrees.Following the energy gain in stars,one has to gain nuclear energy from slamming very light nuclei where however the extremely high temperatures above 100 million degrees are needed for the sufficient pressures at thermal equilibrium ignition.A radically new option works with non-thermal pressures of picosecond laser pulses at ultrahigh optical powers by nonlinear forces of ponderomotion.The nuclear fusion of hydrogen with the isotope 11 of boron produces primarily harmless helium and has no problems with dangerous radioactive waste and excludes any catastrophic melt-down as fission reactors,it has the potential to be of low costs and can supply the Earth for more than 10,000 years with electricity.
文摘The transition from a student to a professional is an important juncture in the path of life.This not only means a change in the environment,but also a complete upgrade of the mental model.Based on real workplace scenarios and the author’s years of experience,this book extracts the"core rules"to help newcomers complete role transformation:role adjustment,ability improvement,and mentality building.Through specific cases and practical tools,this book depicts how to fight your first battle in the workplace and find your own career development path.
文摘Conventional ignition methods are proving to be ineffective for low-sensitivity energetic materials,highlighting the need to investigate alternative ignition systems,such as laser-based techniques.Over the past decade,lasers have emerged as a promising solution,providing focused energy beams for controllable,efficient,and reliable ignition in the field of energetic materials.This study presents a comparative analysis of two state-of-the-art ignition approaches:direct laser ignition and laser-driven flyer ignition.Experiments were performed using a Neodymium-doped Yttrium Aluminum Garnet(Nd:YAG)laser at different energy beam levels to systematically evaluate ignition onset.In the direct laser ignition test setup,the laser beam was applied directly to the energetic tested material,while laserdriven flyer ignition utilized 40 and 100μm aluminum foils,propelled at velocities ranging from 300 to 1250 m/s.Comparative analysis with the Lawrence and Trott model substantiated the velocity data and provided insight into the ignition mechanisms.Experimental results indicate that the ignition time for the laser-driven flyer method was significantly shorter,with the pyrotechnic composition achieving complete combustion faster compared to direct laser ignition.Moreover,precise ignition thresholds were determined for both methods,providing critical parameters for optimizing ignition systems in energetic materials.This work elucidates the advantages and limitations of each technique while advancing next-generation ignition technology,enhancing the reliability and safety of propulsion systems.
基金supported by Research Fund of SWUST for PhD(Grant No.22zx7175)Sichuan Science and Technology Program(Grant No.2024NSFSC1097)。
文摘Based on the characteristics of laser-induced surface ignition,energetic photosensitive films show promising potential to meet the ignition requirements of various energetic materials(EMs).In this study,DATNBI/ferric alginate(DI/FeA),DI/cobalt alginate(DI/CoA),and DI/nickel alginate(DI/Ni A)films are fabricated by employing sodium alginate(SA)with a three-dimensional network structure as the film matrix,via ionic cross-linking of SA with Fe^(3+),Co^(2+),and Ni^(2+)ions.The study demonstrates that the ionic cross-linking enhances the hydrophobic performance of the films,with the water contact angle increasing from 82.1° to 123.5°.Concurrently,the films'near-infrared(NIR)light absorption improved.Furthermore,transition metal ions facilitate accelerated electron transfer,thereby catalyzing the thermal decomposition of DATNBI.Under 1064 nm laser irradiation,the DI/Fe A film exhibits exceptional combustion performance,with an ignition delay time as low as 76 ms.It successfully acts as an NIR laser ignition medium to initiate the self-sustained combustion of CL-20.This study demonstrates the synergistic realization of enhanced hydrophobicity,improved photosensitivity,and promoted catalytic decomposition through microstructural design of the material,providing new insights for the design of additive-free EMs in laser ignition applications.
基金funded by the National Natural Science Foundation of China,Grant No.22405208。
文摘Boron has attracted increasing attention in the field of high-energy explosives and propellants due to its high volume calorific value and mass calorific value.However,the complicated combustion process and low combustion efficiency hinder its wide application.To tackle this challenge,bioinspired polydopamine(PDA)interface reinforced boron-Viton composites,with high structure stability and excellent energy releasing efficiency,are designed and prepared,combining the interface regulation of PDA biomimetic materials and combustion promotion of fluoropolymers.Firstly,the stronger adsorption energy of PDA with boron compared to Viton is demonstrated by molecular dynamics simulations.Next,B@PDA@Viton is prepared by the combination of in-situ dopamine polymerization and solvent/nonsolvent method,and the double-layer core-shell structure is confirmed by XPS,FTIR,and TEM characterizations.TG-DSC analysis shows that B@PDA@Viton possesses superior thermal properties,with a 55.48%increase in oxidation heat compared to raw B.Furthermore,ignition and combustion performance tests indicate that B@PDA@Viton reduces ignition delay by 57.56%and increases heat of combustion by 68.63%relative to raw B.These findings elucidate the ignition and combustion mechanisms of B@PDA@Viton.This work not only developed high-performance boron-based composite fuels but also provided insights into the development of boron-based fuels.
基金supported by the Stable Support Fund forBasic Disciplines,China(No.3072024WD0201)。
文摘Underwater gas-liquid two-phase propulsion technology is an emerging propulsion method that offers high efficiency and unrestricted navigation speed.The integration of this technology into water ramjet engines can significantly enhance propulsion efficiency and holds substantial potential for broad applications.However,forming a gas-liquid two-phase flow within the nozzle requires introducing a large amount of rammed seawater.At this time,there is a complex phase transition problem of combustion products in the combustion chamber,which makes the thermodynamic calculation for gas-liquid two-phase water ramjet engines particularly challenging.This paper proposes a thermodynamic calculation method for gas-liquid two-phase water ramjet engines,based on the energy equation for gas-liquid two-phase flow and traditional thermodynamic principles,enabling thermodynamic calculations under conditions of ultra-high water-fuel ratios.Additionally,ground ignition tests of the gas-liquid two-phase engine were conducted,yielding critical engine test parameters.The results demonstrate that the gas-liquid two-phase water ramjet engine achieves a high specific impulse,with a theoretical maximum specific impulse of up to 7000(N s)/kg.The multiphase flow effects significantly impact engine performance,with specific impulse losses reaching up to 25.86%.The error between the thrust and specific impulse in the ground test and the theoretical values is within 10%,validating the proposed thermodynamic calculation method as a reliable reference for further research on gas-liquid two-phase water ramjet engines.
基金Supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions under Grant No.014000319/2018-00391.
文摘Pre-chamber ignition technology can address the issue of uneven in-cylinder mixture combustion in large-bore marine engines.The impact of various pre-chamber structures on the formation of the mixture and jet flames within the pre-chamber is explored.This study performed numerical simulations on a large-bore marine ammonia/hydrogen pre-chamber engine prototype,considering pre-chamber volume,throat diameter,the distance between the hydrogen injector and the spark plug,and the hydrogen injector angle.Compared with the original engine,when the pre-chamber volume is 73.4 ml,the throat diameter is 14 mm,the distance ratio is 0.92,and the hydrogen injector angle is 80°.Moreover,the peak pressure in the pre-chamber increased by 23.1%,and that in the main chamber increased by 46.3%.The results indicate that the performance of the original engine is greatly enhanced by altering its fuel and pre-chamber structure.
文摘Deaf-mute Jiang Xintian lights a small cauldron in the hands of wheelchairbound fencer Jin Jing at the Paralympic Flame Lighting Ceremony in Beijing’s symbolic Temple of Heaven on August 28. For nine days until September 6, when the 13th Paralympics opens in Beijing, a total of 850 torchbearers would relay the Paralympic flame along two routes through 11 Chinese provinces,
基金This research was supported by the National Natural Science Foundation of China(Grant No.:U2033206)China Postdoctoral Science Foundation(Grant No.2021M691705).
文摘Hot molten metal droplets with high fire hazard can easily ignite combustibles. Molten metal kinetics on the surface of a combustible material directly affects the ignition likelihood. Existing research focuses on the behavior of droplets during collisions, rarely addressing the ignition of combustibles by hot metal droplets. Here, the mechanisms of aluminum and copper droplets impinging on and igniting extended polystyrene (EPS) foam boards at different velocities were investigated. The relationship between the critical ignition temperature and impact velocity of droplets with diameters of 6 and 8 mm was experimentally studied for aluminum droplets;the critical ignition temperature non-monotonically depended on the impact velocity. For copper droplets, the relationship between the ignition probability and the impact velocity of droplets with diameters in the 3.5–7 mm range was experimentally studied. The most obvious difference between the two droplet ignition types was that the impact of copper droplets was accompanied by intense splashing, and the fragmentation extent positively correlated with the impact velocity. It was challenging to ignite using completely broken copper droplets. Droplets with the diameter of 5 mm were the most dangerous under the experimental conditions of this study, because the foam could still be ignited at higher impact velocities. Numerical simulations suggested that the main factors explaining the critical ignition temperature of aluminum droplets were gas mixing and splat cooling. The main factor affecting the ignition of copper droplets was fragmentation, and experimental observations were explained using non-dimensional droplet fragmentation theories.
基金supported by the National Key Research and Development Program of China(Grant No.2021YFB3501002)the National Natural Science Foundation of China(Grant No.52301059,No.52271009)the Shanghai Post-doctoral Excellence Program(Grant No.2023372).
文摘Magnesium and its alloys offer lightweight advantage and have extensive development prospects,particularly in aerospace.However,their flammability poses a significant barrier on the development of Mg alloys.The ignition resistance of these alloys often depends on the protectiveness of the oxide film formed on the surface.This paper elucidates the formation mechanism of oxide film from thermodynamics and kinetics,classifying oxide films based on their layered structure to assess their protective properties.Furthermore,it comprehensively reviews the impact of characteristics on the protective effectiveness such as compactness,continuity,thickness,and mechanical properties.The paper also introduces various characterization methods for the microstructure and properties of oxide film.The primary objective of this paper is to enhance the comprehension of oxide film concerning the ignition resistance of Mg alloys and to furnish references for future advancements and research in Mg alloys with heightened ignition resistance.
基金supported by the National Key Laboratory for Precision Hot Processing of Metals(Nos.6142909220102).
文摘The incorporation of Y significantly improves the fire resistance of the Mg-3Nd-2Gd-0.2Zr-0.2Zn(EV32)alloy.The findings indicate a significant increase in the ignition point of the alloy upon Y addition,notably reaching 813.9℃ for the EV32–3Y(wt.%)alloy.Additionally,the calculated residual stresses of the Y_(2)O_(3) and Gd_(2)O_(3) films were 2.732 GPa and 2.569 GPa respectively,showcasing a distinct correlation between Y concentration and improved fire resistance.This enhancement can be attributed to the formation of denser oxide films,especially Y_(2)O_(3) and Gd_(2)O_(3),effectively reducing the susceptibility of the oxide film to thermal stress-induced tearing.The study elucidates the vital role of Y addition in enhancing fire resistance,thoroughly investigating the mechanisms that impact both the formation of oxide films and ignition within the alloy structure.These findings not only contribute to a deeper comprehension of magnesium alloy performance under high-temperature conditions but also offer valuable theoretical guidance for enhancing its fire resistance through alloy design and application.
基金supported by the Science Center for Gas Turbine Project, China (No. P2022-B-Ⅱ-018-001)。
文摘Enhancing the ignition system performance of turbo engines is crucial,with a focus on rapidly and reliably igniting the entire combustor in low-temperature,low-pressure,high-speed inlet flow conditions.This challenge has garnered international attention.To address the issue of reliable ignition in the combustors of advanced propulsion system,this paper proposes a Multichannel Jet Enhanced Plasma Igniter(MJEPI) and conducts comparative experimental studies with the conventional spark igniter in a component-level dual-dome swirl combustor.The ignition limit in the combustor is obtained and the ignition processes are recorded.Experimental results demonstrate that the MJEPI significantly improves the ignition performance at high altitude.Specifically,at 0 km and 6 km for ground start-up,ignition limit is extended by 36% and 29%,respectively.At 6 km and 12 km for high-altitude relight,ignition limit is extended by 32% and 21%,respectively.The maximum ignition height is increased by 2.3 km,as determined by the global equivalence ratio of 1.The primary reason for these improvements is attributed to the larger initial flame kernel with greater penetration depth generated by MJEPI,which enables it to withstand more sever conditions such as low temperature,low pressure,and poor kerosene spray quality at elevated altitudes.
文摘In February 2024,192 lasers at the National Ignition Facility(NIF)in Livermore,CA,USA,began pouring 2.2 MJ of energy into a gold container smaller than the tip of a person’s little finger,heat-ing it to more than three million degrees Celsius(Fig.1)[1-4].Inside the container was a tiny fuel capsule containing tritium and deuterium that imploded at more than 400 km·s^(-1)causing atoms to combine and releasing 5.2 MJ of energy[1-4].
基金co-supported by the National Natural Science Foundation of China(Nos.52376138 and 52025064)the Science Center for Gas Turbine Project,China(No.P2022B-Ⅱ-018-001)the Foundation Research Project,China(No.1002TJA22010)。
文摘The reignition of aero-engine combustors at high altitudes poses significant challenges due to the low-temperature and low-pressure environment.A novel Long Pulse-Width Plasma Ignition(LPWPI)system has been developed to enhance ignition performance.The LPWPI system can effectively prolong the discharge duration time,improve ignition efficacy,and increase the plasma penetration depth.Experimental comparisons with the traditional Spark Ignition(SI)system demonstrate that the LPWPI increased discharge duration to 2.03 ms,which is 45 times longer than that of the SI system,while also doubling the spark penetration depth to 24.1 mm.The LPWPI system achieved a discharge efficiency of 61.1%,significantly surpassing the SI system's efficiency of23.3%.These advancements facilitated an extension of the lean ignition boundary by approximately 22.7%to 39.3%.High-speed camera recordings reveal that the spark duration of the LPWPI system was extended to 2.1 ms,compared to 0.6 ms in the SI system.Ignition progress with LPWPI shows a sustained spark kernel without the flame residence stage observed in the SI system.The impressive performance of the LPWPI system suggests that it is a promising alternative for aero-engine ignition systems.
基金supported by the National Key Research and Development Program of China(No.2021YFB3501002)the National Science and Technology Major Project(No.J2019-Ⅷ-0003-0165)the National Natural Science Foundation of China(No.52301059).
文摘Oxide films hinder diffusion and resist external forces,which determines the flame ignition mechanism of magnesium alloys.The effects of the continuity,compactness and mechanical properties of oxide films on the ignition mechanism were analyzed,by investigating the flame ignition behaviors of AZ80(ZM5),EZ30K(ZM6)and WE43 Mg alloys.The results show that the rupture of the oxide films caused by liquid gravity was the key to causing ignition.According to thermodynamic calculations,compared with Mg,Al cannot be preferentially oxidized;while Nd can be preferentially oxidized through significant enrichment,resulting in a discontinuous Nd_(2)O_(3)inner layer in the ZM6 alloy;in contrast,Y has a strong preferential oxidation ability,which gives the WE43 alloy a continuous Y_(2)O_(3)inner layer and self-healing ability.In addition,the oxide film of the ZM5 alloy is loose and has poor mechanical properties,so it cannot effec-tively hinder diffusion and resist liquid gravity.Differently,the oxide films of the ZM6 and WE43 alloys are dense and have better mechanical properties,leading to higher ignition temperatures and longer igni-tion times.In addition,a criterion was proposed to predict the ignition time based on the law of energy conservation,and it was simplified to predict the ignition temperature.The errors between the predicted and measured values are within 11%.
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.52130411,52174219 and 52174220)the Natural Science Foundation of Jiangsu Province(No.BK20240104)the Fundamental Research Funds for the Central Universities(No.2024-11044).
文摘Gas explosions in coal mine goafs are associated with the roof rock fracturing.An experimental system was established to investigate the potential for electrical ignition induced by sandstone fracturing.The electrical responses,luminescent emissions,and ignition characteristics during tensile and compressive failure of sandstones were analyzed in methane/air premixed gas environments.Results indicate that the application of mechanical loading induces the emergence of electrical signals on rock surfaces and in the surrounding atmosphere.This phenomenon is attributed to the generation,accumulation,and subsequent release of free charges during the deformation and fracture within the sandstone.Compressive failure proved to be more conducive to free charge generation than tensile failure,owing to more crack connections.Furthermore,a precipitous increase in surface and external voltages was observed during complete fracturing,a consequence of electron emission from crack tips within the rock structure.Moreover,the ionization induces luminous emissions owing to the collision of energetic electrons released from gas molecules in methane/air mixtures.A strong positive correlation(R2=0.9429)was identified between luminescence intensity and the magnitude of electrical discharge resulting from rock fracture.Notably,such discharge by rock fracturing can be capable of igniting the premixed gas,particularly when the quartz content exceeds 61%.Piezoelectric effects and crack propagation are crucial mechanisms in the causal chain of the charge generation,discharge,and ionization triggered by rock fractures.Based on the above laboratory results,electric ignition of the transient roof fracturing caused by stress mutations can serve as a new potential ignition source for gas explosions in the goaf.These results offer new insights into the prevention and control of gas explosions.
