Ion Slip Research Articles

Magnetohydrodynamic Power Extraction from Cold Hypersonic Airflows with External Ionizers

A novel concept of hypersonic cold-air magnetohydrodynamics (MHD) power generators with ionization by electron beams is analyzed. Electron beams are shown to allow control and stable operation of MHD channels in cold high-speed flows. To avoid excessive energy cost of ionization and damage to beam-injection foils, electron beam current densities should be restricted to a few milliamperes per square centimeter. This reduces the conductivity in electron beam sustained MHD channels compared with that in conventional MHD generators, restricting performance and calling for very strong magnetic fields and high Hall parameters. The high Hall parameters cause ion slip and near-anode phenomena to become first-order issues. Example one-dimensional calculations of hypersonic power generator performance appear to be promising. Possible problems that could be caused by hypersonic boundary layers and electrode sheaths, including anode sheath instability and ways to avoid it, are also discussed.

Transient Hartmann Flow with Heat Transfer Considering the Ion Slip

The transient Hartmann flow of an electrically conducting, viscous, incompressible fluid bounded by two parallel nonconducting porous plates is studied with heat transfer taking the ion slip into consideration. An external uniform magnetic field and a uniform suction and injection are applied perpendicular to the plates while the fluid motion is subjected to a constant pressure gradient. The two plates are kept at different but constant temperatures while the Joule and viscous dissipations are included in the energy equation. The effect of the ion slip and the uniform suction and injection on both the velocity and temperature distributions is examined.

Effects of Hall and ion–slip currents on magneto–micropolar fluid and heat transfer over a non–isothermal stretching sheet with suction and blowing

In this work, the effects of Hall and ionslip currents on the steady magnetomicropolar of a viscous incompressible and electrically conducting fluid is analysed using the theory of micropolar fluid...

Theoretical study of the structurally nonrigid ions LiP 2 + , HP 2 + , and H3P 2 +

Theoretical study of the structurally nonrigid ions LiP 2 + , HP 2 + , and H3P 2 +

Effects of non-uniformities on electrical conduction in weakly ionized plasmas

The effect of non-uniformities on the flow of electric current in weakly ionized plasmas is investigated by taking into account the ion slip as well as the Hall current. An Ohm's law for a non-uniform plasma is derived, from which the formula previously obtained by Numano, i.e. an extension of Rosa's equation, is obtainable as a special case. Making use of this new Ohm's law, the effective electrical conductivity and the effective Hall parameter are determined for isotropically turbulent plasmas. It is found that when the ion-slip effect is absent they are in good agreement with the results obtained previously.

Instabilizing-stabilizing effects of MHD anisotropic currents

We prove that in anisotropc MHD, ion slip currents can have instabilizing as well as stabilizing effects, with respect to Hall currents, on the linear stability of the thermodiffusive equilibrium of a fluid in a plane layer.

Two-dimensional model of the plasma thruster

Given the condition that the flow generated by a self-induced magnetic field is two-dimensional and steady, a model for the arc region of the plasma thruster is formulated based on magnetohydrod ynamic (MHD) descriptions. Use is made of a generalized Ohm's law that includes the Hall and ion slip terms. Characteristics of the arc region are investigated as functions of system parameters. The study shows that the Hall effect causes the current to concentrate severely at the trailing edge of the anode, and it is suggested that if the plasma thruster is a coaxial type, it is better to have the cathode inside.

Numerical Analysis of MPD Arcs for Plasma Acceleration

The characteristics of the arc region of the plasma thruster are investigated from the numerical solutions of coupled MHD equations. In this model the flow is assumed to be two-dimensional but all other realistic effects are included. They are the Hall effect, ion slip term, and other dissipations such as viscosity, thermal conductivity, and electrical resistivity. The results show that the current concentrates at the trailing edge of the anode and that the temperature of the area is raised. Also, the Hall current causes harmful effects by lowering the thrust efficiency and eroding the electrodes. The thermal diffusion is a beneficial effect in that it raises the thrust efficiency and prevents the erosion of the electrodes.

Generalized Ohm’s law for plasma including neutral particles

A simplified derivation is presented for the so-called ‘‘ion slip,’’ i.e., for the relative motion of ions with respect to the fluid center-of-mass motion, which gives rise to an extra term in the generalized Ohm’s law for partially ionized gases. In the usual formulation, this term is shown to be proportional to j⊥, the current density perpendicular to B. This turns out to be valid when the slip is not strongly affected by a pressure gradient of the neutral component. In the opposite limit, i.e., when ■pn dominates the relative motion perpendicular to B, the ion-slip term takes on a simple form again, provided inertial effects are small, i.e., under quasistatic conditions: (ΔE)slip=ηsD (j⊥−jD), where sD≡Ωe Ωimnnn/ (mnnn+mini) (νei+νen) νin is the modified ion-slip coefficient, while jD≡cB×∇(pi+ pe)/B2 denotes the diamagnetic current.

Inverse solution of Maxwell’s equations in plasmas

Maxwell’s equations, which govern the magnetic, current density, and electric field vector distributions throughout a plasma have been formulated and solved in an inverse manner. The methodology allows the geometrical configuration of those components which bound the plasma to be determined in physical space, given the magnitude of the relevant field vectors on their surfaces (boundaries of the computation region in a transformed plane). To accommodate the required mathematical structure of the analysis, a uniform plasma flow at low magnetic Reynolds number is considered in which ion slip and electron pressure/temperature gradient diffusion effects are negligible.

Applications of equivalent circuit method to three-dimensional analysis of open-cycle diagonal type MHD generator

For analysis of an open-cycle diagonal type generator, a numerical method using a new three-dimensional equivalent circuit is proposed, in which the leakage resistance of the channel insulator surface, the boundary layer, the ion slip, the effect of the finite electrode segmentation, etc. are considered. Next, through the relation between the Hall voltage and the load current obtained by use of the equivalent circuit method, a suitable number of the space elements is determined. Further, when channel wall temperature is high, an insulating sidewall (ISW) generator is superior to a diagonal conducting sidewall (DCW) one, and inversely, when the temperature is low, the latter is superior to the former. When the values of the diagonal angle and the load factor are suitably selected, the ISW generator can give high performance characteristics comparing favorably with the Faraday type one, and moreover, the DCW one can give superior characteristics to the ISW and Faraday type ones when the wall temperature is low.

Heat transfer in a MHD channel with uniform wall heat flux — effects of Hall and ion slip currents

The effects of the Hall and the ion slip currents on forced convective heat transfer in the thermal entrance region of a magnetohydrodynamic channel have been analysed by solving the energy equation as an eigenvalue problem. Both the generator and the accelerator modes are discussed. It is found that the heat transfer rates are reduced due to these currents.

Forced convective heat transfer in a magnetohydrodynamic channel with Hall and ion slip currents

The present analysis is made to investigate the effects of the ion slip currents on steady state heat transfer in a MHD channel whose walls are kept at an uniform temperature. The problem is solved analytically. The numerical values of heat transfer coefficients are presented for different values of the parameters for the generator mode, the accelerator mode and the open circuit conditions. It is found that the influence of ion slip currents on heat transfer coefficients increases for the accelerator mode.

Effect of hall and ion slip currents on heat transfer with uniform wall heat flux in the developing flow region

Effect of hall and ion slip currents on heat transfer with uniform wall heat flux in the developing flow region

Heating of dense interstellar clouds by magnetic ion slip - A constraint on cloud field strengths

Observations suggest that fragmentation into stars occurs at densities comparable to those of massive interstellar clouds. However, fragmentation cannot occur if the magnetic field strength and density are related by B=B/sub 0/n/sup y/ with y=2/3, as for isotropic contraction with a frozen-in field. A semiempirical upper limit to the parameter y is derived by considering the thermal equilibrium of a cloud heated by magnetic ion slip (ambipolar diffusion) and requiring that the theoretical temperatures do not greatly exceed observed temperatures. Cooling by rotational transitions of CO, H/sub 2/, and HD and by inelastic gas-grain collisions is included in the equilibrium calculations. It is found that a value of y as large as 2/3 would result in gas temperatures in excess of 100 K at densities greater than 10/sup 4/ cm/sup -3/ and can therefore be excluded by the observations. A value of yapproximately-less-than0.55 is required if the scale of the magnetic field gradient is of the same order as the cloud radius. The calculated value of this upper limit is sensitive to the choice of B/sub 0/. The value of y can be decreased by preferential flow of gas along field lines or by magnetic ion slip. The time scalemore » for magnetic ion slip is reexamined.« less

Combined influence of Hall effect, ion slip and temperature boundary condition of third kind on MHD channel flow heat transfer

To investigate the combined influence of Hall effect, ion slip and the temperature boundary condition of the third kind on the magnetohydrodynamic heat transfer in the thermal entrance region of a flat channel, the energy equation is solved by employing the Galerkin-Kantorowich method of variational calculus. The heat generation within the fluid is neglected. It is concluded that there can be a significant influence of Biot number and Hall parameter on the local Nusselt number. Representative results are depicted in tables.

Two‐dimensional analysis of diagonal MHD generator via equivalent circuit

A new equivalent circuit method is proposed that enables one to calculate the generation characteristics in a short time with consideration of the wall leakage current, ion slip, the electrode finite segmentation effect. This method is applicable to both Faraday and Hall type MHD generators if the electrode tilt angles, electrode connection and load connection are properly modified. The effect of electrode finite segmentation on the generation characteristics is numerically examined. The result obtained by the present method agrees well with that obtained by the conformal mapping method and two-dimensional difference method. By use of configuration of space elements, a sufficiently practical result can be obtained. The computation time by the present method is much shorter than that by the difference method. For large-sized diagonal generators, the effect of the wall leakage current, ion slip, and boundary layer thickness on the generation characteristics are numerically calculated. When R/sub W//R/sub X/ 10/sup -3/, the generation characteristics worsen in the high-..beta.. region. In the high-region, the generation characteristics worsen. The Hall type is worse in the generation characteristics than the diagonal type. (WHK)

Entrance flow in a MHD channel with Hall and ion slip currents

The problem of two-dimensional MHD flow in the entrance region of a rectangular channel is solved with generalized Ohm's law under externally applied, electric field loading conditions. The magnetic Reynolds number is assumed to be small and the induced magnetic field is neglected.

Combined influence of Hall effect, ion slip, viscous dissipation and Joule heating on MHD heat transfer in a channel

To investigate the combined influence of Hall effect, ion slip, viscous dissipation and Joule heating on the fully developed laminar MHD channel heat transfer, the exact solution of the energy equation is derived assuming a constant wall heat flux, finely segmented electrodes and a small magnetic Reynolds number. It is concluded that there can be a substantial difference, depending upon Hartmann number, electric field intensity and Brinkman number, between the Nusselt number considering the Hall effect and that neglecting it. Representative results are presented in diagrams and in tables.

Preionization in a Magnetoplasmadynamic Generator

Theme P of a seeded noble gas plasma may be necessary to efficiently operate in the nonequilibrium ionization mode. This is particularly true for closed-cycle magnetoplasmadynamic systems where the maximum temperatures are limited by material considerations. A two-dimensional analytical model with nonuniform properties in the presence of combined magnetically induced and applied electric fields has been developed to evaluate the influence of the plasma temperature, pressure, Mach number, magnetic field, seed ratio, electrode separation distance, and current on the terminal voltage of a single pair of preionization electrodes located in a constant area channel. Finite ionization and recombination rates, ion slip, electron pressure gradients, plasma velocity profiles, and electrode sheath voltage drops are included. The nonlinear coupled governing equations are solved numerically using an interative relaxation technique. Ion slip was found to be an important consideration in predicting regions of unstable operation. Plasma instabilities with Hall parameters greater than about 3 were found to have a very significant effect on the terminal voltage, however, the influence of these instabilities decrease for Hall parameters greater than about 14.