In the double-cone ignition schemes(DCIS), the deuterium–tritium target shell is ablated and compressed by a highpower nanosecond laser in Au-cones to generate plasmas. Under the actions of spherically symmetric compression and acceleration along the Au cone, they will be ejected out of the cone mouth and collide with each other. The plasmas experience conversion from kinetic energy to internal energy at the vertex of the geometric center of two Au cones that are symmetric to each other, because of which high-density fusion plasmas are preheated. This key physical process has undergone experimental verification on the Shenguang-II upgraded facility in China. Apparently, the improvement and optimization of the velocity of plasmas in hypersonic jet flow at the cone mouth are crucial for the success of the DCIS. In the DCIR7 experiment of the Shenguang-II upgraded facility, a velocity yield of approximately 130–260 km/s was achieved for the plasmas at the cone mouth, with a result of nearly 300 km/s based on numerical simulation. In this paper, theoretical analysis is performed as regards the process, in which target shells are ablated and compressed by laser to generate highvelocity plasmas ejected through jet flow. Based on this analysis, the formula for the velocity of plasmas in supersonic jet flow at the cone mouth is proposed. This study also provides measures that are more effective for improving the kinetic energy of plasmas and optimizing energy conversion efficiency, which can serve as theoretical references for the adjustment and optimization of processes in subsequent experiments.
Field emission electric propulsion(FEEP) thrusters possess excellent characteristics, such as high specific impulse, low power requirements, compact size and precise pointing capabilities,making them ideal propulsion devices for micro-nano satellites. However, the detection of certain aspects, such as the evolution process of the liquid cone and the physical quantities at the cone apex, proves challenging due to the minute size of the needle tip and the vacuum environment in which they operate. Consequently, this paper introduces a computational fluid dynamics(CFD) model to gain insight into the formation process of the liquid cone on the tip apex of indium FEEP. The CFD model is based on electrohydrodynamic(EHD) equations and the volume of fluid(VOF) method. The entire cone formation process can be divided into three stages, and the time-dependent characteristics of the physical quantities at the cone apex are investigated. The influences of film thickness, apex radius size and applied voltage are compared.The results indicate a gradual increase in the values of electrostatic stress and surface tension stress at the cone apex over an initial period, followed by a rapid escalation within a short duration.Apex configurations featuring a small radius, thick film and high voltage exhibit a propensity for liquid cone formation, and the cone growth time decreases as the film thickness increases.Moreover, some unstable behavior is observed during the cone formation process.
Cone-disk systems find frequent use such as conical diffusers,medical devices,various rheometric,and viscosimetry applications.In this study,we investigate the three-dimensional flow of a water-based Ag-Mg O hybrid nanofluid in a static cone-disk system while considering temperature-dependent fluid properties.How the variable fluid properties affect the dynamics and heat transfer features is studied by Reynolds's linearized model for variable viscosity and Chiam's model for variable thermal conductivity.The single-phase nanofluid model is utilized to describe convective heat transfer in hybrid nanofluids,incorporating the experimental data.This model is developed as a coupled system of convective-diffusion equations,encompassing the conservation of momentum and the conservation of thermal energy,in conjunction with an incompressibility condition.A self-similar model is developed by the Lie-group scaling transformations,and the subsequent self-similar equations are then solved numerically.The influence of variable fluid parameters on both swirling and non-swirling flow cases is analyzed.Additionally,the Nusselt number for the disk surface is calculated.It is found that an increase in the temperature-dependent viscosity parameter enhances heat transfer characteristics in the static cone-disk system,while the thermal conductivity parameter has the opposite effect.
