Some Aspects of the Glow Discharge Between Coaxial Cylinders in the Presence of a Non-Homogeneous Axial Magnetic Field

1948 ◽  
Vol 1 (4) ◽  
pp. 400
Author(s):  
JM Somerville ◽  
KSW Champion ◽  
EK Bigg
Keyword(s):  
Magnetic Field ◽  
Glow Discharge ◽  
Axial Magnetic Field ◽  
Outer Cylinder ◽  
Negative Resistance ◽  
Coaxial Cylinders ◽  
Maximum Magnetic Field

The characteristics of the glow discharge in air between coaxial cylindrical electrodes in the presence of a non-homogeneous axial magnetic field are described. With the outer cylinder as cathode the discharge is narrow and takes place near the position of maximum magnetic field. If the cathode is cut transversely into halves dividing the discharge there may be a negative incremental resistance between these halves. This negative resistance may be used as the basis of an oscillator working with an efficiency of about 70 per cent. up to frequencies of about 100 kilocycles per second.

scholarly journals DC Glow Discharge in Axial Magnetic Field at Low Pressures

2017 ◽  
Vol 2017 ◽  
pp. 1-8 ◽  
Author(s):  
Shen Gao ◽  
Shixiu Chen ◽  
Zengchao Ji ◽  
Wei Tian ◽  
Jun Chen
Keyword(s):  
Magnetic Field ◽  
Glow Discharge ◽  
Differential Equations ◽  
Axial Magnetic Field ◽  
Glow Discharge Plasma ◽  
Dc Glow Discharge ◽  
Fluid Approximation ◽  
Low Pressures ◽  
Physical Quantities ◽  
The Magnetic Field

On the basis of fluid approximation, an improved version of the model for the description of dc glow discharge plasma in the axial magnetic field was successfully developed. The model has yielded a set of analytic formulas for the physical quantities concerned from the electron and ion fluids equations and Poisson equation. The calculated results satisfy the practical boundary conditions. Results obtained from the model reveal that although the differential equations under the condition of axial magnetic field are consistent with the differential equations without considering the magnetic field, the solution of the equations is not completely consistent. The results show that the stronger the magnetic field, the greater the plasma density.

Numerical Study of Magnetic Field Influence on Three-Dimensional Flow Regime and Combined-Convection Heat Exchange Within Concentric and Eccentric Rotating Cylinders

2020 ◽  
Vol 142 (11) ◽  
Author(s):  
Javad Sodagar-Abardeh ◽  
Payam Nasery ◽  
Ahmad Arabkoohsar ◽  
Mahmood Farzaneh-Gord
Keyword(s):  
Magnetic Field ◽  
Heat Exchange ◽  
Flow Regime ◽  
Axial Magnetic Field ◽  
Numerical Study ◽  
Outer Cylinder ◽  
Three Dimensional ◽  
Convection Heat ◽  
Combined Convection ◽  
Number Variation

Abstract The forced and natural flows of fluid within an annulus caused by the rotation of cylinders and temperature differences of the inner and outer walls are observed in various engineering applications. In this research, the laminar flow regime and mixed convection inside a ring-shaped horizontal concentric and eccentric space for an incompressible fluid are studied in the existence of an axial magnetic field. The present work is the first effort to investigate the influence of a magnetic field on flow and combined-convection heat exchange characteristics within an annulus with a cold outer cylinder and an inner hot cylinder. Here, the properties of the flow and heat transfer characteristics are studied using the finite volume method. Numerical procedures are mainly investigated for recognizing the influence of Hartmann number (in the range of 0 ≤ Ha ≤ 100), as the representative of the magnetic force, on velocity components, Nusselt number, streamlines, and isothermal lines. One of the notable effects is that when Ha number increases, it will reduce the vorticity of the fluid and buoyancy forces. As a result, streamlines and isothermal lines can be seen more constant as regular concentric circles. A rise in Ha number decreases the range of local Nu number variation for both cylinders. The average Nu number for the outer and inner cylinders has different trends when Ha number increases. Taking concentric cylinders as an example, this parameter for the inner and the outer cylinders increases and decreases by about 1.2 and 1.6, respectively.

scholarly journals Measurement of Some Argon Plasma Parameters Glow Discharge Under Axial Magnetic Field

2019 ◽  
Vol 7 (4) ◽  
pp. 158-166
Author(s):  
Pshtiwan M.A. Karim ◽  
Diyar S. Mayi ◽  
Shamo Kh. Al-Hakary
Keyword(s):  
Magnetic Field ◽  
Electrical Conductivity ◽  
Glow Discharge ◽  
Electron Temperature ◽  
Breakdown Voltage ◽  
Axial Magnetic Field ◽  
Argon Plasma ◽  
Emission Lines ◽  
Plasma Parameters ◽  
Gas Pressures

This paper investigates the characteristics some of argon plasma parameters of glow discharge under axial magnetic field. The DC power supply of range (0-6000) V is used as a breakdown voltage to obtain the discharge of argon gas. The discharge voltage-current (V-I) characteristic curves and Paschen’s curves as well as the electrical conductivity were studied with the presents of magnetic field confinement at different gas pressures. The magnetic field up to 25 mT was obtained using four coils of radius 6 cm and 320 turn by passing A.C current up to 5 Amperes. Spectroscopic measurements are employed for purpose of estimating two main plasma parameters electron temperature (Te) and electron density (ne). Emission spectra from positive column (PC) zone of the discharge have been studies at different values of magnetic field and pressures at constant discharge currents of 1.5 mA. Electron temperature (Te) and its density are calculated from the ratio of the intensity of two emission lines of the same lower energy levels. Experimental results show the abnormal glow region characteristics (positive resistance). Breakdown voltage versus pressure curves near the curves of paschen and decrease as magnetic field increases due to magnetic field confinement of plasma charged particles. Also the electrical conductivity increases due to enhancing magnetic field at different gas pressures. Both temperature density of electron and the intensities of two selected emission lines decrease with increasing pressure due decreasing of mean free path of electron. Electron density increase according to enhancing magnetic field, while the intensity of emitting lines tends to decrease.

DC radial glow discharge in axial magnetic field at low pressures

2019 ◽  
Vol 88 (3) ◽  
pp. 30801
Author(s):  
Shen Gao ◽  
Jianyuan Feng ◽  
Wenqi Li ◽  
Jihe Cai
Keyword(s):  
Magnetic Field ◽  
Glow Discharge ◽  
Plasma Density ◽  
High Intensity ◽  
Axial Magnetic Field ◽  
Spatial Density ◽  
Glow Plasma ◽  
Low Pressures ◽  
Moving Path ◽  
Intensity Magnetic Field

The influence of magnetic field on DC radial glow plasma was studied by self-designed coaxial glow discharge device, and the influence of magnetic field on the spatial distribution of plasma density is studied. The experimental results show that the spatial density distribution of plasma from cathode to anode increases gradually in the high-intensity magnetic field, and decreases gradually in the absence of magnetic field. Theoretical analysis of the above results show that the high-intensity magnetic field increases the moving path of the electrons, enhances the collision efficiency between the electrons and the neutral atoms, and makes the discharge plasma density remarkably enhanced.

Stability of hydromagnetic dissipative Couette flow with non-axisymmetric disturbance

1998 ◽  
Vol 366 ◽  
pp. 135-158 ◽  
Author(s):  
CHA'O-KUANG CHEN ◽  
MIN HSING CHANG
Keyword(s):  
Magnetic Field ◽  
Couette Flow ◽  
Hartmann Number ◽  
Axial Magnetic Field ◽  
Outer Cylinder ◽  
Numerical Procedure ◽  
Stationary Mode ◽  
Instability Modes ◽  
Wide Range ◽  
Axisymmetric Instability

A linear stability analysis has been implemented for hydromagnetic dissipative Couette flow, a viscous electrically conducting fluid between rotating concentric cylinders in the presence of a uniform axial magnetic field. The small-gap equations with respect to non-axisymmetric disturbances are derived and solved by a direct numerical procedure. Both types of boundary conditions, conducting and non-conducting walls, are considered. A parametric study covering wide ranges of μ, the ratio of angular velocity of the outer cylinder to that of inner cylinder, and Q, the Hartmann number which represents the strength of axial magnetic field, is conducted. Results show that the stability characteristics depend on the conductivity of the cylinders. For the case of non-conducting walls, it is found that the critical disturbance is a non-axisymmetric mode as the value of μ is sufficiently negative and the domain of Q where non-axisymmetric instability modes prevail is limited. Similar results are obtained for conducting walls at low Hartmann number. In addition, the transition of the onset of instability from non-axisymmetric modes to axisymmetric modes for the case μ=−1 with increasing strength of magnetic field are discussed in detail. For high values of the Hartmann number, the critical disturbance is always the axisymmetric stationary mode for non-conducting walls but not for conducting walls. For −1[les ]μ<1, it is demonstrated that non-axisymmetric instability modes prevail in a wide range of Q for conducting walls and axisymmetric oscillatory modes may, in fact, become more critical than both of the non-axisymmetric and axisymmetric stationary modes at higher values of the Hartmann number.

Stability effect of an axial magnetic field on fluid flow bifurcation between coaxial cylinders

2021 ◽  
pp. 2150023
Author(s):  
Hamza Benhacine ◽  
Brahim Mahfoud ◽  
Mohamed Salmi
Keyword(s):  
Magnetic Field ◽  
Vortex Breakdown ◽  
Swirling Flow ◽  
Axial Magnetic Field ◽  
Fluid Layer ◽  
Navier Stokes ◽  
Coaxial Cylinders ◽  
Viscous Forces ◽  
Fluid Layers ◽  
Number Formula

Numerical simulations aim to investigate the bifurcation caused by swirling flow between two coaxial vertical cylinders, and the fluid layers produced by the thermal gradient. The stability of both bifurcation and fluid layers by an axial magnetic field is analyzed. The finite-volume method is used to solve the governing Navier–Stokes, temperature and potential equations. A conducting viscous fluid characterized by a small Prandtl number [Formula: see text] is placed in the gap between two coaxial cylinders. The combination of aspect ratio, [Formula: see text] and Reynolds number, [Formula: see text] for three annular gaps ([Formula: see text] and [Formula: see text]) is compared in terms of flow stability, and heat transfer rates. Without a magnetic field, the vortex breakdown takes place near the inner cylinder due to the increased pumping action of the Ekman boundary layer. Fluid layered structures are developed by the competition between buoyancy and viscous forces. The increase in the magnitude of the magnetic field retarders the onset of the oscillatory instability caused by the disappearance of the vortex breakdown and reduces the number of fluid layers. The limits in which a vortex breakdown bubble manifests and the limits of transition from the multiple fluid layers to the single fluid layer are established.

Combined Effects of Magnetic Field and Thermal Radiation on Fluid Flow and Heat Transfer of Mixed Convection in a Vertical Cylindrical Annulus

2016 ◽  
Vol 138 (6) ◽  
Author(s):  
Ben-Wen Li ◽  
Wei Wang ◽  
Jing-Kui Zhang
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Fluid Flow ◽  
Mixed Convection ◽  
Axial Magnetic Field ◽  
Outer Cylinder ◽  
Mhd Equations ◽  
Temperature Fields ◽  
Flow And Heat Transfer ◽  
Cylindrical Annulus

Magnetohydrodynamic (MHD, also for magnetohydrodynamics) mixed convection of electrically conducting and radiative participating fluid is studied in a differentially heated vertical annulus. The outer cylinder is stationary, and the inner cylinder is rotating at a constant angular speed around its axis. The temperature difference between the two cylindrical walls creates buoyancy force, due to the density variation. A constant axial magnetic field is also imposed to resist the fluid motion. The nonlinear integro-differential equation, which characterizes the radiation transfer, is solved by the discrete ordinates method (DOM). The MHD equations, which describe the magnetic and transport phenomena, are solved by the collocation spectral method (CSM). Detailed numerical results of heat transfer rate, velocity, and temperature fields are presented for 0≤Ha≤100, 0.1≤τL≤10, 0≤ω≤1, and 0.2≤εW≤1. The computational results reveal that the fluid flow and heat transfer are effectively suppressed by the magnetic field as expected. Substantial changes occur in flow patterns as well as in isotherms, when the optical thickness and emissivity of the walls vary in the specified ranges. However, the flow structure and the temperature distribution change slightly when the scattering albedo increases from 0 to 0.5, but a substantial change is observed when it increases to 1.

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