Two-Dimensional Modeling of the Capillary Plasma With the Kinetic Ablation Model
A steady 2-D magnetohydrodynamic model of a capillary discharge is presented. Special attention is paid to the ablation/deposition process at the capillary wall, and the results show distinct 2-D features.
Investigation into geometric effect in capillary discharge plasma generator using an improved ablation model
The wall material and the electrode material together determine the composition of the capillary discharge plasma. In this paper, an improved ablation model considering polyethylene (PE) and copper ablation and deposition was developed. Generators with different geometric sizes were calculated and tested. The results show that the concentration distributions of copper and PE in the generator were the pair-wise opposite, and the aspect ratio (AR) had a threshold (AR = 8.67). The copper mass density distribution varied from uniform to inhomogeneous with the increase in AR, which was similar to that of its concentration distribution. The maximum copper mass density increased with the increase in AR, and the AR threshold was also 8.67. The relationship between the copper or PE ablated mass and capillary length or diameter approximately followed a power law, and the relationship between the copper or PE ablated mass and AR approximately followed a proportional law. The PE mass density distribution was not similar to that of its concentration for AR ≥ 8.67. The PE ablated mass increased with the increase in AR, and its variation was similar to that of the maximum PE mass density. When the AR(AR > 5.2) was large enough, the PE mass density distribution determined the total mass density distribution. Otherwise, the total mass density distribution was determined by the mass density distribution of PE and copper. Overall, the simulation results were in good agreement with the experiments. These can be used to select the size and material of the capillary in simulating high heat flux plasma or electrothermal chemical gun ignition.
A theoretical model for the physical processes in the confined high pressure discharges of electrothermal launchers
Different physical processes in confined high-pressure discharges are analyzed. The energy transport inside the discharge tube yields a radial temperature profile which has sharp gradients only near the tube walls. The regime at which such discharges can operate at a steady state is determined. For a given discharge ablation rate and plasma pressure, the tube length is limited. An analytical model is developed for confined high-pressure discharges operating in a quasi-steady-state in which the resulting plasma jet characteristics are steady at hydrodynamic timescales. This model allows the calculation of all the discharge parameters, such as ablation rate plasma temperature, resistivity, density and pressure as functions of the slowly varying current and the tube dimensions. The scaling laws obtained in this model are important for determining the impedance matching between the discharge and the power source and upgrading the discharge energy in electrothermal launchers to hypervelocities. Good agreement is obtained between the analytical model and experimental results at energies up to 100 kJ. >