In response to the research demand for the armature-rail contact characteristics of a new aluminum alloy material in the series-enhanced electromagnetic rail launch test, an analytical formula for ...the armature-rail contact resistance to eliminate the influence of the induced electromotive force is derived. Based on the electromagnetic and kinematic analysis of the electromagnetic launch process, a numerical calculation model for the contact voltage and contact resistance of the armature-rail of an enhanced electromagnetic rail gun was established. The model reveals the correlation between the contact resistance of the armature-rail and physical parameters, such as muzzle voltage, muzzle-induced voltage, rail current, rail mutual inductance gradient, armature speed, and armature displacement. The experiment obtained multiple parameters, such as muzzle voltage, rail current, and armature velocity in the electromagnetic rail launch test, and achieved quantitative calculation of the armature-rail contact voltage and the sliding contact resistance of the series-enhanced electromagnetic rail gun. Based on the summary and research of the waveform change law and test phenomenon of the armature-rail contact resistance data obtained from multiple launches, the contact state between the armature and rail during the actual launch process is analyzed, which provides a necessary means to evaluate the sliding electrical contact characteristics of the electromagnetic rail gun and plays a positive role in guiding the research and design of armature-rail matching optimization mechanism.
The friction and wear characteristics of a C-shaped solid armature surface are the important factors affecting the electric contact of the armature-rail during electromagnetic rail launch. In order ...to judge whether the electrical contact state of the armature-rail is good and whether there is a transition during the launch process, this article proposes a theoretical analysis model of the armature-rail contact force considering the stiffness change of the armature arm after wear, and the nodal force and nodal temperature are extracted through finite element multiphysics coupling and mapped to the structural field with Johnson-Cook material damage failure for dynamic calculation of armature arm wear and armature-rail contact force. The simulation results show that the wear state of the armature arm, the change rule of armature wear mass, the velocity of armature after wear, and the change of armature-rail contact force after wear are consistent with the launch experimental phenomenon and the measured data, which verifies the accuracy of the finite element model for calculating the wear amount and armature-rail contact force. On this basis, the effects of different armature arm tail interference and different peak-to-average current waveforms on armature arm wear and armature-rail contact characteristics are considered. The simulation results show that the contact force curve of the armature-rail after considering wear is above the contact force curve required by the "10 N/kA" principle, and it can be considered that the armature-rail contact state is good. The calculation model of armature arm wear and armature-rail contact force established in this article can be used in the subsequent optimization design of C-shaped solid armature.
In this article, a kind of electromagnetic coil catapult for life-saving projectile (LSP) is designed and developed for water rescue. We adopted the single-stage coil launcher scheme to save costs ...and improve reliability. Two launch modes, armature-load integrated launch (ALIL) and armature-load separated launch (ALSL), are compared by simulation. In the ALIL mode, LSP and armature are integrated together. The LSP will be decelerated due to the armature drag effect after being launched to the maximum speed. In the ALSL mode, the armature will separate from the LSP after reaching the maximum speed due to the electromagnetic drag force. The LSP will fly out of the catapult at peak speed due to inertia, which will improve the muzzle speed of the LSP compared with the ALIL. Further analysis shows that in the ALSL mode, reducing the initial power supply voltage, reducing the armature-load mass ratio, and increasing the number of coil turns are beneficial to the armature recovery. The armature recovery method can make the armature reusable. A set of electromagnetic catapult devices for LSP is developed. Finally, armature launch and LSP launch tests are carried out. It is proven that the simulation and test results are consistent. Under the full voltage state, the catapult can make the LSP obtain a muzzle speed of 52 m/s, and the throw distance exceeds 180 m. The armature can be recovered and reused. Experiments verify the feasibility of the electromagnetic catapult for LSP, which has good application value.
Rice husk, as a cellulose-rich by-product in agriculture, has been considered as a low-cost substrate for the production of bioethanol and chemicals. In this study, rice husk was pretreated with an ...alkali, followed by cellulose and β-glucosidase hydrolysis optimized by an orthogonal experiment and response surface methodology (RSM), respectively. Under the optimal treatment conditions, a hydrolysate containing a high reducing sugar yield (77.85%) was obtained from the rice husk. Then, the hydrolysate was used as a carbon substrate for butyric acid production through Clostridium tyrobutyricum Δpta fermentation. Compared to free-cell fermentation, higher concentrations of butyric acid (50.01 g/L vs. 40.8 g/L and 49.03 g/L vs. 27.49 g/L) were observed in immobilized-cell fermentation for the carbon source of glucose and hydrolysate, respectively. A final butyric acid concentration of 16.91 g/L, a yield of 0.31 g/g, and an overall productivity of 0.35 g/L/h from rice husk hydrolysate were obtained in the repeated-fed-batch mode. Taken together, rice husk hydrolysate can be effectively utilized for the bioproduction of butyrate with immobilized-cell fermentation.
This article establishes a simulation model and a measurement experimental platform for static armature-rail interface contact resistance. By comparing simulation and experimental measurement results ...of different magnitudes of interference, the applicability of the Cooper-Mikic-Yovanovich (CMY) contact resistance calculation method in the assembly phase of railguns is validated. Subsequently, the relationship between the magnitude of interference and contact resistance is investigated. The results suggest that a moderate increase in the magnitude of interference leads to a decrease in contact resistance and an increase in robustness to assembly variations. The analysis of the components of contact resistance is conducted, which reveals that contact spots and uneven contact pressures jointly contribute to the increase/decrease of contact resistance. The current concentrating at the edges of the spots at the microscopic level leads to contact resistance. Additionally, at the macroscopic level, the current concentrating in regions with higher contact pressure results in contact resistance. According to the research, the increase in magnitude of interference can reduce the amount of both sources of contact resistance.
The muzzle voltage is an important characteristic parameter of electromagnetic railgun. The contact resistance between the sliding armature and the copper rail surface during the launching process ...can be calculated by utilizing it to analyze the armature-rail contact characteristics. However, in the engineering experiments of augmented electromagnetic railgun, the detected muzzle voltage waveform will be disturbed by the system noise because of the existence of augmented rail, firing sequence of pulse forming network (PFN), and friction of armature-rail contact surface. Therefore, it is difficult to calculate the contact resistance accurately. This article presents a new noise suppression method variational mode decomposition (VMD) for suppressing the jagged noise in the muzzle voltage. A method for calculating the contact resistance is presented to analyze the armature-rail contact characteristics. A frame for analyzing the contact characteristics of the electromagnetic railgun is presented. The method can suppress the system noise by utilizing the signal mode decomposition in the time domain based on the frequency characteristics of VMD. Then, in order to analyze the armature-rail contact characteristics, the contact resistance can be calculated according to the formula derived from the theory. The results show that the method can suppress the muzzle voltage system noise effectively. And the calculated contact resistance wave is smooth, which is helpful to analyze the armature-rail contact characteristics. The noise component extracted from muzzle voltage contains pulse signals, and the time and amplitude of these pulse signals are related to PFN's firing sequence and the changing trend of the armature-rail contact resistance. The method proposed in this article provides a new and reliable reference for monitoring the launching state of electromagnetic railgun in engineering experiments.
In this paper, the cross-coupling phenomenon in the wound-rotor synchronous starter/generator system is studied. Due to the armature reaction, the excitation field is dragged away from the d -axis by ...the armature magnetic field and the cross-coupling inductance <inline-formula><tex-math notation="LaTeX">{L_{dq}}</tex-math></inline-formula> exists. What is more, the cross-coupling phenomenon also occurs in the excitation field, it means not only the mutual inductance <inline-formula><tex-math notation="LaTeX">{M_{df}}</tex-math></inline-formula> between the d -axis and excitation field exists, but also mutual inductance <inline-formula><tex-math notation="LaTeX">{M_{qf}}</tex-math></inline-formula> between the q -axis and excitation field exists. If this <inline-formula><tex-math notation="LaTeX">{M_{qf}}</tex-math></inline-formula> component is ignored, this will result in a torque calculated error, especially facing an intense armature reaction, the error can be more than 20%. The mathematical expressions of cross-coupling inductance <inline-formula><tex-math notation="LaTeX">{L_{dq}}</tex-math></inline-formula>, <inline-formula><tex-math notation="LaTeX">{M_{qf}}</tex-math></inline-formula> are derived. Based on these expressions, a more accurate torque equation is proposed. The validity of the proposed analysis is proved by showing the agreement with experimental results and maximum torque per ampere (MTPA) loci.
Electromagnetic rail propulsion (ERP) presents several problems, including nonuniform distribution of magnetic field and force on the armature surface, severe erosion of contact surfaces, and ...insufficient propulsive force. While current optimization methods include external devices or enhanced power supply, etc. These methods to increase thrust tend to exacerbate ablation. This article introduces an armature-rail articulated guiding electromagnetic propulsion device. The device improves propulsion efficiency, while suppresses erosion by controlling the magnetic field to increase the contact pressure on the armature-rail surface, all without altering the excitation power supply or requiring external devices. To achieve this, a multiphysics field-coupled model was constructed. The key parameters, including inclination and arrangement, were analyzed. We delve into the self-control magnetic field mechanism and determine a multifactor optimization scheme to regulate contact-surface heating. This scheme inversely co-optimizes friction and contact pressure on the armature-rail surface. With the implementation of this device, there was an 18.7% increase in propulsion effectiveness, a 2.95 reduction in uniformity, and a 10.3% reduction in ablation. These results demonstrate the device's ability to simultaneously improve propulsive force, suppress erosion, and ensure uniformity of armature's magnetic field and force, successfully mitigating the contradiction between the demands of high-speed propulsion and the need for efficient electrical contacts.
The high thrust density voice coil actuator (VCA) is a key component for the deployers to determine the CubeSats' separation velocity in orbit directly. To improve the VCA's thrust density and power ...consumption, it is essential to analyze the armature reaction under heavy current work conditions. This article proposes a dynamic splitting method of the magnetic equivalent circuit (MEC) model for analyzing the armature reaction of the VCA. This MEC model can effectively reveal the interaction mechanism between the dynamic winding field and the permanent magnet (PM) field, which provides an approach to readily and quickly analyze the armature reaction. Based on the understanding of the mechanism, we found an effective way to suppress the armature reaction and propose a new VCA with double PM flux circuits. The electromagnetic performances of the new configuration are evaluated by comparing it with the conventional one. Both the theoretical and experimental results show that the new structure achieves lower magnetic saturation, lower armature reaction, and higher thrust density. A research prototype was constructed and experimentally tested to verify the theoretical results of the armature reaction, magnetic field, thrust, separation velocity, and other performances. The new VCA realizes a wide and accurate modulation of separation velocity for the CubeSats.
