In order to investigate the influence of aluminum vapor on the breakdown performance of air,this paper makes a study of the dielectric breakdown characteristics of Al-air mixture in the temperature range of 300-5000 K...In order to investigate the influence of aluminum vapor on the breakdown performance of air,this paper makes a study of the dielectric breakdown characteristics of Al-air mixture in the temperature range of 300-5000 K at atmospheric pressure.A Boltzmann analysis method is used to deal with the electron energy distribution function(EEDF),the reduced ionization coefficients(α/N),the reduced attachment coefficients(η/N)and the critical reduced breakdown strength((E/N)cr)so as to explore the influence of temperature and mixing ratio on the dielectric breakdown properties.In the temperature range of 300-2000 K,the property of the mixture is mainly determined by the mixing proportion of aluminum vapor because the composition of particles remains unchanged.In the temperature range of 2000-2500 K,the decomposition of Al2O_(2)leads to the increase of aluminum oxides and NO,and a rise in the percentage of highenergy electrons as well as the increment ofα/N.Also,the joint action of O_(2)and NO makesη/N increase first and then decrease,and(E/N)crgoes down to a smaller temperature range.An increase in the proportion of aluminum vapor causes(E/N)crto decrease in the low-temperature region and to increase in the high-temperature region,which will reduce the transition between these two temperature regions.展开更多
In order to solve the problem of the original residual energy release strategy being unsuitable for high-energy and fast-firing electromagnetic rail launch,this work has explored the applicability of active arc-igniti...In order to solve the problem of the original residual energy release strategy being unsuitable for high-energy and fast-firing electromagnetic rail launch,this work has explored the applicability of active arc-ignition technology(AAT).The results obtained from the comparison of launching experiments show that AAT has no influence on the acceleration of the armature and is capable of quickly releasing the residual energy.Based on the theory of magnetohydrodynamics,this work has also made numerical simulation of the muzzle arc,analyzed the influence of AAT on the muzzle arc flow field,electromagnetic(EM)field and temperature field,and evaluated the performance of AAT according to the projectile initial disturbance,the EM impact on guidance devices and the rail ablation.The results show that AAT is now one of the most practicable strategies for residual energy release.展开更多
The electromagnetic(EM)rail launcher G10 insulator is prone to delamination damage during launch,which affects the service life of the insulator.Through the secondary development of ABAQUS®commercial finite‐elem...The electromagnetic(EM)rail launcher G10 insulator is prone to delamination damage during launch,which affects the service life of the insulator.Through the secondary development of ABAQUS®commercial finite‐element software,an EM‐structure coupling launch dynamics model considering projectile‐barrel coupling is established.The simulation indicates that the transverse swing of the projectile changes in a sine‐like law,and the time of the upper half wave corresponds to the pulse width of the impact force pulse waveform.The stress concentration occurs on the inner surface of the insulator where the contact‐impact occurs,resulting in impact damage.The midline of the insulator inner surface bears a large compressive strain under the action of pre‐tightening force,and the insulator is compressed oscillatingly under the influence of the timevarying load of the rail during launch.Under the condition of repeated launch,the launch package repeatedly impacts the insulator,and the alternating load of the rail is cyclically loaded on the insulator with impact damage,which will cause the compression fatigue of the insulator and the expansion of impact damage crack.They are the main reasons for the delamination failure of insulator,and the experimental analysis is carried out.This study provides a method to study the delamination failure mechanism of the insulator,and provides guidance for improving the life of the insulator.展开更多
Due to the large error of the traditional battery theoretical model during large-rate discharge for electromagnetic launch,the Shepherd derivative model considering the factors of the pulse cycle condition,temperature...Due to the large error of the traditional battery theoretical model during large-rate discharge for electromagnetic launch,the Shepherd derivative model considering the factors of the pulse cycle condition,temperature,and life is proposed by the Naval University of Engineering.The discharge rate of traditional lithium-ion batteries does not exceed 10C,while that for electromagnetic launch reaches 60C.The continuous pulse cycle condition of ultra-large discharging rate causes many unique electrochemical reactions inside the cells.The traditional model cannot accurately describe the discharge characteristics of the battery.The accurate battery theoretical model is an important basis for system efficiency calculation,precise discharge control,and remaining capacity prediction.To this purpose,an experimental platform for electromagnetic launch is built,and discharge characteristics of the battery under different rate,temperature,and life decay are measured.Through the experimental test and analysis,the reason that the traditional model cannot accurately characterize the large-rate discharge process is analyzed.And a novel battery theoretical model is designed with the help of genetic algorithm,which is integrated with the electromagnetic launch topology.Numerical simulation is compared with the experimental results,which verifies the modeling accuracy for the large-rate discharge.On this basis,a variety of discharge conditions are applied to test the applicability of the model,resulting in better results.Finally,with the continuous cycle-pulse condition in the electromagnetic launch system,the stability and accuracy of the model are confirmed.展开更多
基金supported in part by National Natural Science Foundation of China(Nos.51522706,51877214,and 51607187)in part by the National Basic Research Program of China(973 Program)(No.613262)。
文摘In order to investigate the influence of aluminum vapor on the breakdown performance of air,this paper makes a study of the dielectric breakdown characteristics of Al-air mixture in the temperature range of 300-5000 K at atmospheric pressure.A Boltzmann analysis method is used to deal with the electron energy distribution function(EEDF),the reduced ionization coefficients(α/N),the reduced attachment coefficients(η/N)and the critical reduced breakdown strength((E/N)cr)so as to explore the influence of temperature and mixing ratio on the dielectric breakdown properties.In the temperature range of 300-2000 K,the property of the mixture is mainly determined by the mixing proportion of aluminum vapor because the composition of particles remains unchanged.In the temperature range of 2000-2500 K,the decomposition of Al2O_(2)leads to the increase of aluminum oxides and NO,and a rise in the percentage of highenergy electrons as well as the increment ofα/N.Also,the joint action of O_(2)and NO makesη/N increase first and then decrease,and(E/N)crgoes down to a smaller temperature range.An increase in the proportion of aluminum vapor causes(E/N)crto decrease in the low-temperature region and to increase in the high-temperature region,which will reduce the transition between these two temperature regions.
基金supported in part by National Natural Science Foundation of China(Nos.51522706,51877214,51607187)in part by the National Basic Research Program of China(973 Program)(No.613262)。
文摘In order to solve the problem of the original residual energy release strategy being unsuitable for high-energy and fast-firing electromagnetic rail launch,this work has explored the applicability of active arc-ignition technology(AAT).The results obtained from the comparison of launching experiments show that AAT has no influence on the acceleration of the armature and is capable of quickly releasing the residual energy.Based on the theory of magnetohydrodynamics,this work has also made numerical simulation of the muzzle arc,analyzed the influence of AAT on the muzzle arc flow field,electromagnetic(EM)field and temperature field,and evaluated the performance of AAT according to the projectile initial disturbance,the EM impact on guidance devices and the rail ablation.The results show that AAT is now one of the most practicable strategies for residual energy release.
基金National Natural Science Foundation of China,Grant/Award Numbers:51925704,92166204,92166108。
文摘The electromagnetic(EM)rail launcher G10 insulator is prone to delamination damage during launch,which affects the service life of the insulator.Through the secondary development of ABAQUS®commercial finite‐element software,an EM‐structure coupling launch dynamics model considering projectile‐barrel coupling is established.The simulation indicates that the transverse swing of the projectile changes in a sine‐like law,and the time of the upper half wave corresponds to the pulse width of the impact force pulse waveform.The stress concentration occurs on the inner surface of the insulator where the contact‐impact occurs,resulting in impact damage.The midline of the insulator inner surface bears a large compressive strain under the action of pre‐tightening force,and the insulator is compressed oscillatingly under the influence of the timevarying load of the rail during launch.Under the condition of repeated launch,the launch package repeatedly impacts the insulator,and the alternating load of the rail is cyclically loaded on the insulator with impact damage,which will cause the compression fatigue of the insulator and the expansion of impact damage crack.They are the main reasons for the delamination failure of insulator,and the experimental analysis is carried out.This study provides a method to study the delamination failure mechanism of the insulator,and provides guidance for improving the life of the insulator.
基金This study was supported by the National Natural Science Foundation of China(Nos.51607187,51877214,51907203,51925704,and 52107235)the Hubei Provincial Natural Science Foundation of China(Nos.2019CFB371 and 2019CFB373)partially by No.12 Special Financial 349 Aid to China Postdoctoral Science Foundation(No.2019T120972).
文摘Due to the large error of the traditional battery theoretical model during large-rate discharge for electromagnetic launch,the Shepherd derivative model considering the factors of the pulse cycle condition,temperature,and life is proposed by the Naval University of Engineering.The discharge rate of traditional lithium-ion batteries does not exceed 10C,while that for electromagnetic launch reaches 60C.The continuous pulse cycle condition of ultra-large discharging rate causes many unique electrochemical reactions inside the cells.The traditional model cannot accurately describe the discharge characteristics of the battery.The accurate battery theoretical model is an important basis for system efficiency calculation,precise discharge control,and remaining capacity prediction.To this purpose,an experimental platform for electromagnetic launch is built,and discharge characteristics of the battery under different rate,temperature,and life decay are measured.Through the experimental test and analysis,the reason that the traditional model cannot accurately characterize the large-rate discharge process is analyzed.And a novel battery theoretical model is designed with the help of genetic algorithm,which is integrated with the electromagnetic launch topology.Numerical simulation is compared with the experimental results,which verifies the modeling accuracy for the large-rate discharge.On this basis,a variety of discharge conditions are applied to test the applicability of the model,resulting in better results.Finally,with the continuous cycle-pulse condition in the electromagnetic launch system,the stability and accuracy of the model are confirmed.