The dual transmitter implements the equivalent anti-magnetic flux transient electromagnetic method, which can effectively reduce the scope of the transient electromagnetic detection blind area. However, this method is...The dual transmitter implements the equivalent anti-magnetic flux transient electromagnetic method, which can effectively reduce the scope of the transient electromagnetic detection blind area. However, this method is rarely reported in the detection of pipelines in urban geophysical exploration and the application of coal mines. Based on this, this paper realizes the equivalent anti-magnetic flux transient electromagnetic method based on the dual launcher. The suppression effect of this method on the blind area is analyzed by physical simulation. And the detection experiment of underground pipelines is carried out outdoors. The results show that the dual launcher can significantly reduce the turn-off time, thereby effectively reducing the impact of the blind area on the detection results, and the pipeline detection results verify the device’s effectiveness. Finally, based on the ground experimental results, the application prospect of mine advanced detection is discussed. Compared with other detection fields, the formation of blind areas is mainly caused by the equipment. If the dual launcher can be used to reduce the blind area, the accuracy of advanced detection can be improved more effectively. The above research results are of great significance for improving the detection accuracy of the underground transient electromagnetic method.展开更多
An improved method for analyzing the radiation characteristic of the quasi-optical launcher is presented. The launcher is decomposed into an open-ended waveguide and a helical cut according to the proposed method. The...An improved method for analyzing the radiation characteristic of the quasi-optical launcher is presented. The launcher is decomposed into an open-ended waveguide and a helical cut according to the proposed method. The radiation from the open-ended waveguide is obtained by using the Stratton-Chu formulation. The helical cut＇s radiation is calculated based on its current distribution, gained by several iterative computations, which helps to improve the calculation accuracy since the diffraction effect introduced by the helical cut is considered during the calculation. The proposed method is used to study different launches, and the results are compared with the existing results. Good agreement is achieved between the results obtained from our proposed method and the reported results. The present results provide an alternative for analysis and synthesis of the optical-mode converter.展开更多
Fluctuations in outer space's temperature would affect the spacecraft's regular operation.This paper aims to study the temperature influences of the aluminum honeycomb buffer in the tether-net launcher.Firstly...Fluctuations in outer space's temperature would affect the spacecraft's regular operation.This paper aims to study the temperature influences of the aluminum honeycomb buffer in the tether-net launcher.Firstly,a buffer structure was designed to attenuate the pyroshock generated by the pyrotechnic device.Secondly,the mechanical properties of aluminum honeycomb at different temperatures were obtained through quasi-static compression experiments.Then,the internal ballistic responses of the launcher were gained by the closed bomb tests and the equivalent classical interior ballistic model.Finally,the recoil performance of the launcher with aluminum honeycomb buffer at different temperatures was studied.It is revealed that the aluminum honeycomb crushing force gradually decreases with the temperature increases.The peak pressure,burning rate coefficient and velocity increase while the peak time decreases with the temperature increase for the interior ballistics.For the launcher recoil responses,the average launch recoil decreases if the aluminum honeycomb doesn't enter the dense stage.The impact acceleration,projectile velocity and displacement increase as the temperature increase.The paper spotlights the temperature's influence on the recoil characteristics of the aluminum honeycomb buffer,which provides a new idea for buffering technology of pyrotechnic devices in a complex space environment.展开更多
The research on a 30 mm electrothermal-chemical (ETC) gun including theoretical simulation and experimental results is presented in this paper. The predictions of the theoretical model which is composed of three parts...The research on a 30 mm electrothermal-chemical (ETC) gun including theoretical simulation and experimental results is presented in this paper. The predictions of the theoretical model which is composed of three parts (i.e., pulse forming network, plasma generator and interior ballistics) are in good agreement with the experiments. In addition, we have performed some liquid propellant and solid propellant experiments, respectively. Among the solid propellant experiments, we have investigated the ignition modes of propellant and high velocity launchers. As a result, the 25 : 75 mixture of octane and hydrogen peroxide has a better effect than other liquid propellants. When the propellants are ignited nearby the bottom of projectile in chamber by using an ullage tube connected with the plasma generator, the kinetic energy of projectile will increase, while the chamber pressure will decrease. With a total input electrical energy of 180 kJ, the exit velocity of projectile is up to 2.1 km/s or so.展开更多
Brushless DC linear motors have considerable advantages of simpler structure,higher efficiency,higher thrust density and so on.They are well suited for many domains such as electromagnetic launch and launch-assist,but...Brushless DC linear motors have considerable advantages of simpler structure,higher efficiency,higher thrust density and so on.They are well suited for many domains such as electromagnetic launch and launch-assist,but it is inevitable that there exist longitudinal end effects in the mover of the motor caused by longitudinal discontinuities.The serious trouble caused by longitudinal end effects is the thrust ripple.Firstly,by using the method of finite element simulation,this paper studies the distribution of magnetic field and energy in the end region when the mover is in different positions in the range of a polar pitch and discusses the effective methods of reducing the longitudinal end effects.Then the law of the influence of different mover length on the longitudinal end effects has been studied by using analytic methods,and the influences of the mover length and its end geometry shape on the longitudinal end effects have been verified for the test model by using the method of finite element simulation.展开更多
文摘The dual transmitter implements the equivalent anti-magnetic flux transient electromagnetic method, which can effectively reduce the scope of the transient electromagnetic detection blind area. However, this method is rarely reported in the detection of pipelines in urban geophysical exploration and the application of coal mines. Based on this, this paper realizes the equivalent anti-magnetic flux transient electromagnetic method based on the dual launcher. The suppression effect of this method on the blind area is analyzed by physical simulation. And the detection experiment of underground pipelines is carried out outdoors. The results show that the dual launcher can significantly reduce the turn-off time, thereby effectively reducing the impact of the blind area on the detection results, and the pipeline detection results verify the device’s effectiveness. Finally, based on the ground experimental results, the application prospect of mine advanced detection is discussed. Compared with other detection fields, the formation of blind areas is mainly caused by the equipment. If the dual launcher can be used to reduce the blind area, the accuracy of advanced detection can be improved more effectively. The above research results are of great significance for improving the detection accuracy of the underground transient electromagnetic method.
文摘An improved method for analyzing the radiation characteristic of the quasi-optical launcher is presented. The launcher is decomposed into an open-ended waveguide and a helical cut according to the proposed method. The radiation from the open-ended waveguide is obtained by using the Stratton-Chu formulation. The helical cut＇s radiation is calculated based on its current distribution, gained by several iterative computations, which helps to improve the calculation accuracy since the diffraction effect introduced by the helical cut is considered during the calculation. The proposed method is used to study different launches, and the results are compared with the existing results. Good agreement is achieved between the results obtained from our proposed method and the reported results. The present results provide an alternative for analysis and synthesis of the optical-mode converter.
基金supported by the National Natural Science Foundation of China(Grant No.52102436)the Fundamental Research Funds for the Central Universities(Grant No.30920021109)+3 种基金Natural Science Foundation of Jiangsu Province(BK20200496)China Postdoctoral Science Foundation(Grant No.2020M681615)the project of Key Laboratory of Impact and Safety Engineering(Ningbo University),Ministry of Education(Grant No.CJ202107)the State Key Laboratory of Mechanics and Control of Mechanical Structures(Nanjing University of Aeronautics and astronautics)(Grant No.MCMS-E-0221Y01)。
文摘Fluctuations in outer space's temperature would affect the spacecraft's regular operation.This paper aims to study the temperature influences of the aluminum honeycomb buffer in the tether-net launcher.Firstly,a buffer structure was designed to attenuate the pyroshock generated by the pyrotechnic device.Secondly,the mechanical properties of aluminum honeycomb at different temperatures were obtained through quasi-static compression experiments.Then,the internal ballistic responses of the launcher were gained by the closed bomb tests and the equivalent classical interior ballistic model.Finally,the recoil performance of the launcher with aluminum honeycomb buffer at different temperatures was studied.It is revealed that the aluminum honeycomb crushing force gradually decreases with the temperature increases.The peak pressure,burning rate coefficient and velocity increase while the peak time decreases with the temperature increase for the interior ballistics.For the launcher recoil responses,the average launch recoil decreases if the aluminum honeycomb doesn't enter the dense stage.The impact acceleration,projectile velocity and displacement increase as the temperature increase.The paper spotlights the temperature's influence on the recoil characteristics of the aluminum honeycomb buffer,which provides a new idea for buffering technology of pyrotechnic devices in a complex space environment.
文摘The research on a 30 mm electrothermal-chemical (ETC) gun including theoretical simulation and experimental results is presented in this paper. The predictions of the theoretical model which is composed of three parts (i.e., pulse forming network, plasma generator and interior ballistics) are in good agreement with the experiments. In addition, we have performed some liquid propellant and solid propellant experiments, respectively. Among the solid propellant experiments, we have investigated the ignition modes of propellant and high velocity launchers. As a result, the 25 : 75 mixture of octane and hydrogen peroxide has a better effect than other liquid propellants. When the propellants are ignited nearby the bottom of projectile in chamber by using an ullage tube connected with the plasma generator, the kinetic energy of projectile will increase, while the chamber pressure will decrease. With a total input electrical energy of 180 kJ, the exit velocity of projectile is up to 2.1 km/s or so.
文摘Brushless DC linear motors have considerable advantages of simpler structure,higher efficiency,higher thrust density and so on.They are well suited for many domains such as electromagnetic launch and launch-assist,but it is inevitable that there exist longitudinal end effects in the mover of the motor caused by longitudinal discontinuities.The serious trouble caused by longitudinal end effects is the thrust ripple.Firstly,by using the method of finite element simulation,this paper studies the distribution of magnetic field and energy in the end region when the mover is in different positions in the range of a polar pitch and discusses the effective methods of reducing the longitudinal end effects.Then the law of the influence of different mover length on the longitudinal end effects has been studied by using analytic methods,and the influences of the mover length and its end geometry shape on the longitudinal end effects have been verified for the test model by using the method of finite element simulation.
