Nonequilibrium modeling study on plasma flow features in a low-power nitrogen/hydrogen arcjet thruster

A two-temperature thermal non-equilibrium model is used to simulate and compare the arc characteristics within the converging-diverging and traditional cylindrical plasma torches. The modeling results show that the presence of the constrictor within the converging-diverging torch makes the evolution characteristics of the arc significantly different from that of cylindrical torch. Compared with a cylindrical geometrical torch, a much higher plasma flow velocity and relatively longer high temperature region can be generated and maintained inside the converging-diverging torch. In the constrictor of converging-diverging torch, the normalized radius of arc column increases and the degree of thermodynamic equilibrium of the plasma is significantly improved with the increase of axial distance. The radial momentum balance analysis shows that for the cylindrical torch, the pressure gradient that drives the arc expansion and the Lorentz force that drives the arc contraction dominate the radial evolution of the arc. While at the converging and constrictor region of a converging-diverging plasma torch, the radial gas dynamic forces in arc fringes pointing toward the arc center enhance the mixing of the cold gas of boundary layer with the high temperature gas of the arc center, increasing the average gas temperature and decreasing the thickness of cold boundary layer, thereby facilitating the formation of diffusion type arc anode attachment at the diverging section of torch.

Section: Temperature and Flow Fieldsmentioning

confidence: 99%

Comparative analysis of the arc characteristics inside the converging-diverging and cylindrical plasma torches

Sun

Wang

et al. 2020

“…The governing equations consist of mass continuity, momentum, energy and species conversation equations. The electromagnetic field is closely coupled by the Lorentz force and Ohmic heating with the momentum equation and the energy equation while the chemical kinetic processes are coupled to energy equations and species continuity [49,[58][59][60][61][62][63][64].…”

Section: Governing Equationsmentioning

confidence: 99%

“…where z i =p i /p, p i denotes the partial pressure of the ith species. In this equation, b ij and b ji are the thermal diffusion coefficients which are defined in [44,61].…”

Section: Ji J Imentioning

confidence: 99%

Numerical simulation of constricted and diffusive arc–anode attachments in wall-stabilized transferred argon arcs

Zhu

Wang

Sun

et al. 2019

A numerical simulation is conducted to investigate arc-anode attachment behavior, especially the formation mechanism of the constricted arc attachment mode for the water-cooled anode of wall-stabilized transferred argon arcs. Argon molecular ions and the corresponding kinetic processes are included to the finite-rate chemistry model in order to capture the chemical nonequilibrium characteristics of the arc near the anode region. Modeling results show that constricted and diffusive arc-anode attachments can be self-consistently obtained at different arc currents while keeping other parameters unchanged. The dominant kinetic processes contributing to ionization and recombination in the arc center and fringes are presented. The results show that in arc fringes and the arc attachment region, molecular ion recombination plays an important role which leads to the rapid loss of electrons. The radial evolution of the production, loss and transport processes of electrons is further analyzed. It is found that for the constricted arc attachment mode, both the recombination and convection transport caused by the anode jet result in the loss of electrons at the arc fringes, which leads to the shrinkage of the arc column at the anode. The formation of the anode jet is due to the combined action of radial and axial Lorentz forces in the anode region.

“…Lun et al [17] developed a model for the vacuum-arc cathode-spot and plasma region to predict the performance of vacuum-arc thrusters operating roughly in the arc current range of 80-300 A. Lun et al [17] reported the conventional-based cathode-spot model with many simplifying assumptions predicted spot radius, surface temperature, electric field, current densities, plasma densities, and energy fluxes. The most recent research conducted in the area has been done by Wang and his co-workers, where the plasma flow feature [18] and species diffusion [19] in a low-power nitrogen-hydrogen arcjet and plasma characteristics of a nitrogen arc [20] were studied by simulation of non-equilibrium arcjets to better understand the arcjet physics. Shen et al [21] studied the starting-up process of arcjet thruster with arc voltage signals.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of hydrogen arcjet thruster with coupled sheath model

Akhare¹,

Nandyala²,

Jayachandran³

et al. 2022

In the present work, a complete 2D chemical and thermal non-equilibrium numerical model coupled with a relatively simple sheath model is developed for hydrogen arcjet thruster. Conduction heat transfer in the anode wall is also included in the model. The operating voltages predicted by the model are compared with those in the literature and are found to be in close agreement. Power distributions for the various operating conditions are obtained, anode radiation loss primarily determines the thruster efficiency. Higher thruster efficiency was found to be associated with longer arc length. At cathode ion diffusion contribution dominates except at low input current where thermo-field electron current is dominant.