Search

In this article, the circuit model and the dynamic model of railgun launching process are established by analyzing the Lorentz force, air resistance, and friction force of the armature in the gun bore. Based on the armature dynamic model, a muzzle velocity model of armature can be simulated by utilizing MATLAB, which takes the launching current and loading force of railgun as the main input parameters. Through those two input parameters, the variation curve of armature velocity is measured and calculated by using the armature muzzle velocity model. Moreover, we can read the armature muzzle velocity from the armature variation curve. The influencing factors of the muzzle velocity of armature in this model are also calculated and analyzed, respectively. Comparing with the armature muzzle velocity measured by net target and B-probe, the result shows that the armature muzzle velocity model can accurately estimate the armature muzzle velocity, and can be used to calculate the muzzle velocity in the railgun launching experiment. This method provides reference for the performance optimization design of railgun. [ABSTRACT FROM AUTHOR]

The revolving armature can effectively improve the firing accuracy of the railgun, which rotates at high speed under the action of electromagnetic force during the movement in the bore. However, the research on the influence of the armature structural parameters on the startup contact state between the armature and the rail is rarely involved. In this article, for a 15-mm caliber railgun, the finite-element calculation model of the revolving armature assembly process of interference is established, and the interference fit of the traditional revolving armature with different structural parameters such as crack length C_L and width C_w, interference amount $d_{1}$ , tail thickness $t$ , and length $L_{1}$ is calculated, and the influence law of the structural parameters of the rotating armature on the initial contact states–contact area, contact force, maximum equivalent stress, and plastic volume is obtained. Second, on the basis of the traditional revolving armature, an armature structure with interference at both ends leading edge and trailing edge is proposed, and the influence law of interference at the leading edge and the middle turning position on the contact ratio at both ends of the new armature is obtained. Finally, the startup contact states of the new armature, the traditional long-arm armature (tail length 18 mm), and the short-arm armature (tail length 14 mm) are compared. The results show that the new armature can significantly reduce the equivalent stress and plastic volume of the armature. [ABSTRACT FROM AUTHOR]

Multi-stage synchronous induction coilgun is one of the important research aspects of the electromagnetic launch. Researchers mainly focus on the optimization of the geometrical dimension and parameters for the multi-stage launcher, pulsed power supply, armature, and so on, in order to achieve the best matching between parameters. Based on the basic principle of multi-stage induction coilgun, the acceleration mechanism is investigated in terms of the magnetic field arrangement. First, a field-circuit coupled model for a 15-stage coilgun is built. Through analyzing the velocity profile and the distribution of current density vector on the armature, it is considered that the armature is affected by the magnetic field generated by frontal stages and current stage during the launching process, so the braking force and pushing force both act on the armature. Therefore, the system conversion efficiency is affected. In order to reduce the braking force and increase the variation of the magnetic field, the direction of the magnetic field is changed. The distribution of the current density vector on the armature and transition process for the variation of the magnetic field is analyzed. The simulation results show that the muzzle velocity can be increased significantly by changing the direction of the magnetic field. The acceleration mechanism of the inconsistent direction of the magnetic field is different from that of a consistent direction. The current density on the armature is increased dramatically in the transition area, which is beneficial to increase the magnetic pushing force. A previously built 15-stage coilgun was used to validate the method. The launching experiments are carried out under the condition of the consistent direction and inconsistent direction of the magnetic field. The experiment results show that the system conversion efficiency is improved significantly for the inconsistent direction of the magnetic field. It provides a valuable reference for multi-stage induction coilgun design. [ABSTRACT FROM AUTHOR]

The driving coil, as a key element of synchronous induction coilgun, endures not only the radial expansionary force because of the magnetic flux compression but also the axial force due to the compressive force and counterforce of the armature. Dielectric breakdown and mechanical structure damage occurs frequently. Meanwhile, the driving coil should have high energy conversion efficiency as a pusher to accelerate the armature. Therefore, it is important to choose the appropriate structure and parameters in order to achieve a high launching performance. In this paper, the factors that influence the system efficiency are analyzed first. Different structure designs of the driving coil with the same inductance are evaluated. The effect of different calibers on the system efficiency is analyzed. The simulation result shows that the structure of the driving coil should be chosen according to the practical launching requirement while the magnetic coupling should be increased. Second, the electromagnetic force applied on the coil is calculated and the stress is analyzed. The thickness and displacement of the containment are calculated on the condition of unyielding. In order to validate the accuracy of the theoretical analysis, an electromagnetic-mechanical coupling finite element model is built. Comparing two calculation results, the error is small. Therefore, the method can be used to guide the design of the driving coil. Finally, a driving coil is fabricated according to the calculation results and experimented through static and dynamic tests. The experimental results show that the driving coil performs well and have high conversion efficiency. It provides a theoretical and experimental basis for the future design of multistage induction coilgun. [ABSTRACT FROM AUTHOR]

The current density and electromagnetic force distribution of the armature directly affect the performance of electromagnetic railgun. In this paper, the electromagnetic thrust, electromagnetic pressure, and current density of the C-shaped armature and H-shaped armature are calculated, respectively, by the finite-element method under different Armature–rail contact modes (different contact areas and positions), and the calculation results under different contact modes are compared. The calculation results show that the maximum current density of the armature head is independent of the contact mode, and the position of the maximum current density of the armature tail moves with the advance of the contact position. The separation of the rear part of the armature tail and rail will result in a sharp decrease in electromagnetic pressure, so the armature tail and rail need to maintain contact to ensure a stable current transfer. At the same time, only the head and the rear part of the armature tail are in contact with the rail, the electrical performance of the armature in complete contact with the rail can be achieved. Therefore, the armature adopts the structural design scheme of interference at both ends, which is more conducive to electromagnetic emission and greatly reduces the difficulty of the armature structural design. [ABSTRACT FROM AUTHOR]

Driving ability of the armature is one of the important launching characteristics on rail gun. To push heavier load effectively with less mass is an important goal to pursue for the armature design. The armature used to be launched or push load is mainly designed in C shape. Whether the C-shaped armature is the best choice for the electromagnetic rail gun launching or not? Based on the above question, this paper proposes a novel concave armature. Similar to the principle of arch bridge, the concave shape is used to design the armature arm in order to withstand the electromagnetic force. The concave arm structure can transfer the electromagnetic force to the force that pushes the load and the pressure that the armature applies to rails, so that the concave arm avoids fracture due to the large electromagnetic force, and the driving ability for the armature is improved. This paper focuses on the comparison of driving ability between the concave armature and C-shaped armature. The C-shaped armature and concave armature, with the same mass and similar structure, also with the same load mass, are designed. Electromagnetic and mechanical coupled calculation under the same condition is conducted. Through analyzing the stress and deformation, a primary conclusion is drawn that the concave armature can push a heavy load and has small deformation. An experimental research is carried out to verify the driving ability of pushing heavy load for two armatures. It provides valuable reference for engineering design. [ABSTRACT FROM PUBLISHER]

To obtain high velocity and high energy conversion efficiency on a synchronous induction coilgun, the armature capture effect which is the inherent characteristic for the synchronous induction coilgun needs to be analyzed. The reason for the armature capture effect is first deduced and analyzed using the lumped element circuit model and then quantificational result is obtained based on the field-circuit coupled model. According to the analytical result, the method to minimize the armature capture effect is proposed from the viewpoint of the magnetic coupling between the driving coil and the armature. Several ways are analyzed through the finite-element simulation. The simulation results show that adjusting the power parameters, such as increasing the capacitance or initial voltage, and decreasing the crowbar resistance, and adjusting the armature parameters, such as decreasing the mass or adopting the solenoid armature, can minimize the armature capture effect and increase the conversion efficiency. These methods are validated through a four-stage induction coilgun. We compare the simulation results with the experimental results and show that by adjusting the armature parameters, we can minimize the armature capture effect. It provides valuable reference for synchronous induction coilgun design. [ABSTRACT FROM PUBLISHER]

Driving coils in a multistage induction coilgun are stacked end to end forming a barrel. During launching, the pulsed current flows through the driving coil, and the electromagnetic force propels the projectile ahead. The driving coil endures not only the radial expansionary force because of the magnetic flux compression, but also the axial force due to the compressive force and counterforce of the projectile. In the process of coil design, both the mechanical strength and the electrical insulation must be considered. Due to the nonlinearity of insulation materials, the theoretical calculation cannot reflect the true state for the driving coil. The conventional static-state test method is analyzed and verified through experiments. The experimental results show that this method is ineffective for the multistage launching, because it neglects the axial counterforce and does not reflect the true state of launching. An improved method for evaluating the coil strength is proposed based on the analysis of the basic principle. The projectile is accelerated by the former stages, and the testing coil accelerates the projectile with an initial speed. Equipment for testing single coil is designed and installed in the muzzle of the existing multistage coilgun. The experimental results show that this method can test the coil’s mechanical strength and electrical insulation more effectively than the conventional method. The dynamic-state method can be used to approximately evaluate the performance of different types of the coil. The structure of the driving coil can be improved through testing and evaluating, which provides experimental reference for the multistage induction coilgun design. [ABSTRACT FROM PUBLISHER]

Based on understanding the characteristics of the impulse force generated by pulsed current of the armature, it is valuable to explore effective ways to improve the armature structure to enhance the stability and prevent from the transition and erosion during launching. This paper first lists a series of conversional armature and the characteristics of these armatures are illuminated. A C-shaped armature is simulated based on the electrical–magnetic–mechanical coupled analysis method. The simulation shows that the stress is mainly distributed in the area between the cross member and arm, it may lead to local deformation. A novel concave armature is proposed and the simulation results indicate that the stress is mainly distributed in the inner side of arm and the front of armature. It is beneficial to push heavy load and avoid deformation and fracture. A device is built to validate the feasibility of armature. The armature is staying still to simulate pushing the infinite heavy load. The experimental results show that the concave armature endures higher current and has the stronger capability of pushing load compared with the C-shaped armature. This type of armature provides a valuable reference for future armature design. [ABSTRACT FROM PUBLISHER]