Magnetohydrodynamic Energy Conversion Research Articles

Influence of Hall current & Lorentz force with nonlinear thermal radiation in an inclined slip flow of couple stress fluid over a Riga plate

Partially ionised fluids subject to an external magnetic field results in a completely different dynamical behaviour. Very few studies are conducted to explore the fascinating properties of Hall current and Ion slip in fluid flows. Flow over a Riga plate with MHD Ion and Hall currents, nonlinear thermal radiation is still rare. We aim to analyse the inclined stagnation point slip flow of Couple Stress fluid over a stretched horizontal Riga plate to close this gap. The flow problem is modelled using Navier stokes theory along with energy conservation and then principal partial differential equations are converted into ordinary differential equations. The governed system is solved mathematically by numerical technique RK Fehlberg method. The behaviour of fluid is described through graphs including fluid’s motion and energy. Local surface skin friction coefficients and local heat and mass flux at surface are the concerned physical magnitudes which are described through graphs and tables and are highly recommended in practical solicitations in numerous production plants and manufacturing workshops. Thermally radiative MHD flow with Ion Hall currents are broadly used in thermal controlling systems, spectro scopy, microchip technology, Magnetohydrodynamic energy conversion campaigns, exploration and expansion for high & low efficiency release, power-driven & power generation structures, MHD accelerations & thrusters, and drift regulator in hypersonic and automobiles.

Quasi-Two-Dimensional Numerical Analysis of Influence of Taylor Vortex and Eddy Current on Generation Characteristics of Co-axial MHD Energy Conversion Device under Laminar Flow

Quasi-two-dimensional magnetohydrodynamic (MHD) numerical simulation was conducted to clarify the power generation characteristics of a co-axial MHD energy conversion device under laminar flow. The numerical results were compared with one-dimensional theoretical results in the radial direction. For a fixed load resistance, the dependence of output power and efficiency on Hartmann number, which is proportional to the magnetic flux density, was investigated. We found the decrease in mean velocity and the increase in viscous wall shear stress owing to upper and lower walls, the increase in viscous wall shear stress owing to Taylor vortex cells, and the increase in Joule heating owing to eddy current in the MHD numerical simulation compared to those in the one-dimensional theoretical analysis.

High-temperature inert gas plasma magnetohydrodynamic energy conversion by using linear-shaped Faraday-type channel

We describe high-density magnetohydrodynamic (MHD) energy conversion in a high-temperature seed-free argon plasma, for which a compact linear-shaped Faraday-type MHD electrical power generator is used. Short-time-duration single-pulse shock-tunnel-based experiments demonstrate the MHD energy conversion with varying total inflow temperature up to 9000 K and applied magnetic-flux density up to 4.0 T. The high-temperature plasma is transformed from the thermal-equilibrium state at the entrance to the weak-nonequilibrium state in the supersonic MHD channel. The discharge structure is reasonably homogeneous without suffering from serious streamer development. The power generation performance is monotonically improved by increasing total inflow temperature and strength of magnetic field. The enthalpy extraction efficiency of 13.1% and overall power density of 0.16 GW/m3 are attained. The local power density at the middle of the channel reaches 0.24 GW/m3.

Magnetohydrodynamic energy conversion by using convexly divergent channel

We describe a magnetohydrodynamic (MHD) electrical power generator equipped with a convexly divergent channel, as determined through shock-tunnel-based experiments. The quality of MHD power-generating plasma and the energy conversion efficiency in the convexly divergent channel are compared with those from previous linearly divergent channel. The divergence enhancement in the channel upstream is effective for suppressing an excessive increase in static pressure, whereby notably high isentropic efficiency is achieved.

Simulation and demonstration of magnetohydrodynamic energy conversion in a high-temperature inert gas

The present paper describes high-density magnetohydrodynamic (MHD) energy conversion in a high-temperature seed-free argon plasma, for which a quasi-three-dimensional numerical simulation and a single-pulse shock-tunnel-based demonstration are conducted. The numerical model simulates the two-dimensional profiles of both the electron and the heavy-particle system of the supersonic argon plasma flow, of which the total inflow temperature is 8000 K. The MHD power-generating experiment clarifies the relationship between the plasma quality and the energy conversion efficiency as functions of the total inflow temperature (7600–9600 K) and the applied magnetic flux density (up to 4.0 T). The increase in the total inflow temperature from 7600 to 9400 K and the application of magnetic flux with density of 0.5–1.2 T change the plasma state; unstable behavior accompanied by an inhomogeneous structure is transformed to a homogeneous and stable state, which results in the significant improvement of the power generation performance. Even in low-density magnetic flux, the attained generator performance is comparable or superior to previous results obtained using a conventional low-temperature seeded gas.

High-density magnetohydrodynamic energy conversion in a high-temperature inert gas

We describe high-density magnetohydrodynamic (MHD) energy conversion in a high-temperature seed-free argon plasma, for which a compact disk-shaped Hall-type radial-flow MHD electrical power generator is used. The state of the MHD power-generating plasma changes with increasing total inflow temperature from 8200to9400K; unstable behavior accompanied by the appearance of fine structures is transformed to a homogeneous and stable state. The attained enthalpy extraction efficiency is comparable to previous results using a conventional seeded gas. Furthermore, a high power output density is achieved even in relatively low-density magnetic flux.

High-performance nonequilibrium-plasma magnetohydrodynamic electrical power generator using slightly divergent channel configuration: I. Calculation

We describe quasi-three-dimensional numerical simulations of a high-performance nonequilibrium-plasma magnetohydrodynamic (MHD) electrical power generator using a slightly divergent configuration. The slightly divergent generator provides greater isentropic efficiency (IE) than a highly divergent generator when an identical enthalpy extraction ratio (EER) is obtained. The inherent feature of a small divergent geometry is clarified; MHD energy conversion is accompanied by less entropy production as well as less gas expansion. The orientation of the performance improvement on an IE–EER map is consistent with the theoretically predicted orientation, which is formulated using an algebraic method based on classical thermodynamic results for supersonic compressible fluid dynamics. The power-generating performance indicators, IE and EER, are clearly determined by modified magnetic flux density, that is, the square of magnetic flux density divided by total inflow pressure. A virtual operating condition for a practical closed-cycle MHD system is proposed considering the relationships between the applied magnetic flux density, the total inflow pressure and the total pressure gradient throughout the generator. This paper is the first part of a duology.

Rf-assisted magnetohydrodynamic power generation in a pure-argon plasma

We describe seed-free pure-argon-plasma magnetohydrodynamic (MHD) power generation assisted by an external radio-frequency electromagnetic field to enhance the nonequilibrium plasma excitation process. The rf heating induces nonequilibrium ionization under a low total argon-gas temperature at which thermal ionization is insufficient. The rf-assisted plasma, the behavior of which is rather stable, contributes to continuous MHD energy conversion.

Studies of helical magnetohydrodynamic seawater flow in fields up to twelve teslas

This article discusses analytical and experimental studies of a helical magnetohydrodynamic (MHD) seawater thruster (or pump) device using a 12-T superconducting solenoid magnet. This magnet is situated and the experiments are conducted at Francis Bitter National Magnet Laboratory of the Massachusetts Institute of Technology. Analytical models are developed to predict the performance of the helical MHD thruster in a closedloop environment. The analytical results are compared with experimental data and good agreement is obtained. A significant increase in MHD energy conversion efficiency compared to the same thruster at lower magnetic field strengths (6-8 T) is realized. A significant increase in the maximum fluid velocity, from 2.5 m/s at the 8T electromagnet, to 3.7 m/s, is also realized. For the first time in our experimental MHD thruster studies, a gross mechanical efficiency greater than 10% is observed.

MHD linear generator modelling

The performance of typical magnetohydrodynamic (MHD) linear generators are evaluated as function of the excitation magnetic field profile. Using a three dimensional (3D) lumped parameter model, able to simulate all major physical MHD energy conversion phenomena, a parametric analysis has been pointed out for various saddle shaped superconducting (SC) coils. For each type of MHD linear generator (Faraday, Hall and diagonal connected generator) the output electrical power has been correlated to the magnetic field characteristics and it has been compared with an ideal flat magnetic field profile in order to quantify the decay of the energy conversion efficiency. >

Calculation of magnetic field and electromagnetic forces in MHD superconducting magnets

A superconducting prototype magnet for MHD (magnetohydrodynamic) energy conversion is under development in Italy. The authors discuss analytical methods developed at the Department of Electrical Engineering of Padova University for calculating magnetic field and electromagnetic forces in MHD superconducting magnets and utilized in the preliminary design of the prototype. Due to the flexibility, speed, and ease of use of the corresponding computer programs, the described analytical methods for field computation proved to be useful in rapid parametric studies in the preliminary design of superconducting magnets with cylindrical or rectangular saddle coils. Some examples of application are presented concerning the choice of the number and shape of coils and the evaluation of the far field of the prototype magnet.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Assessment of the Potential of Magnetohydrodynamic Energy Conversion for Tokamak Reactors

In this paper, the feasibility of the original in situ magnetohydrodynamic (MHD) concept is studied. In this concept, a large number of MHD generators are installed in the spaces between the toroidal field (TF) coils of a tokamak fusion reactor in order to convert the fusion power into electricity. A pebble bed is needed outside the first wall around the fusion plasma, in which the neutron energy is converted into thermal energy, to act as the heat source for the MHD generators. To determine the feasibility of this concept, quasi-one-dimensional calculations of MHD generators with a mercury-cesium medium are performed. The question of whether the electron cyclotron radiation emitted by the fusion plasma can be absorbed by the medium in the MHD generator so as to be able to work with enhanced non-equilibrium ionization is studied.

Microwave heating of flowing slightly-ionized gases in a compact fusion advanced rankine (CFAR) cycle

A compact fusion advanced closed-Rankine cycle (CFAR) based on the less expensive “in-situ” nonequilibrium MHD (magnetohydrodynamic) conversion with assistance from synchrotron radiation superheat in the “microwave” tokamak using synchrotron radiation both for MHD energy conversion and current drive is studied for the improvement of tokamak fusion reactor economy. In this CFAR concept, superheat of flowing slightly-ionized gases by synchrotron radiation energy plays a very important role in the system cycle efficiency, using solely MHD electrical power generation. This paper describes a two-dimensional microwave superheat model and examines the above envisaged concept, which is a key issue in the CFAR cycle.

BETWEEN THE BOOKENDS

MAGNETOHYDRODYNAMIC ENERGY CONVERSION, by Richard J. RosaHANDBOOK OF RADIATIVE HEAT TRANSFER IN HIGH TEMPERATURE GASES, Ed. by R.I. Soloukhin and Robert GoulardHEAT TRANSFER IN GAS‐COOLED ANNULAR CHANNELS, by J. Vilemas, B. Cesna, V. Survila

Authors

Authors

The development of MHD energy conversion methods in the USSR

The development of magnetohydrodynamic (MHD) power conversion systems has evolved to the point where it is possible to commercially introduce MHD power plants into industry. Even at the present level of technology, the sharp increase of thermal efficiency of these plants by as much as 50–60% results in fuel economies of 20–35% and reduction of generation costs by 6–7%.

Efficiency of the induction interaction of a blob of conducting gas with an electrical circuit in which an external electromotive force is included

The possibility of increasing the efficiency of a magnetohydrodynamic energy conversion by including an external emf source in the operating winding is investigated. Values of the average electrical efficiency which can be obtained with the used operating winding are calculated. The possibility and the limits of regulating the efficiency by varying the magnitude of the external emf, the angle of the phase shift of the external emf relative to the currents in the ionized gas, and the magnitude of the excitation magnetic field for the known nature of the flow and the parameters of the gas are determined.

Magnetohydrodynamic Electrical Power Generation (Report on the Fifth International Conference, Munich, Federal Republic of Germany 19-23 April 1971)

In the three years that have elapsed since the last Symposium on Magnetohydrodynamic (MHD) Electrical Power Generation, held in Warsaw, substantial progress has been made in the research and development of plasma and liquid-metal closed-cycle MHD systems. Both of these systems have relevance to the potential application of advanced, high-temperature nuclear power reactors as heat sources for MHD energy conversion. For fossil-fuelled open-cycle systems, engineering development has advanced to the prototype stage. Such were the conclusions made at the Fifth International MHD Conference, which was held in Munich from 19 to 23 April 1971 and attended by over 250 participants from 25 countries. At this conference, which brought together experts from all the major MHD development programs in the world, notably those in the USSR, USA, F.R. of Germany and Japan, 115 papers were presented.

Electrochimie des oxydes semi-conducteurs mixtes electroniques-ioniques. Systeme zircone-oxyde-de-cerium

Defect oxides are at once electronic and ionic semi-conductors. Electrochemical methods developed for aqueous solutions and molten salts can be used to determine the characteristics of these materials.Thermodynamic and electrochemical concepts can be used to interpret the phenomena observed during the passage of electric current through oxides when they are in contact with purely electronic conductors.The experimental study of binary mixtures of zirconium and cerium oxides, which are at once ionic and electronic conductors, has interest from the point of view of electrodes for magnetohydrodynamic energy conversion

Recombination, Ionization, and Nonequilibrium Electrical Conductivity in Seeded Plasmas

New data are presented which provide direct experimental confirmation of the validity of a physical model which has been widely employed to predict the electrical conductivity of dense, two-temperature, seeded plasmas. Experimental measurements of electron temperature, and ionization and recombination rates are presented for partially ionized plasmas of potassium-seeded argon. Experimental conditions were chosen to cover those ranges of interest in connection with proposed magnetohydrodynamic energy conversion devices for which nonequilibrium electrical conductivity measurements have been previously reported, e.g., translational atom temperatures of about 2000°K, total atom densities near 1018/cm3, potassium densities of about 1016/cm3, electron densities from 1013/cm3 to 1015/cm3, and electron temperatures from 2200 to 3500°K. Measured values of electron-electron-ion recombination coefficients for potassium show good agreement with theoretical values based upon the Gryzinski classical inelastic-collision cross-section expressions. Observed ionization rates and relaxation characteristics appear to be adequately explained by a similar formulation for the ionization process.