MHD Generator Research Articles

A Computational Study of Magneto-Convective Heat Transfer Over Inclined Surfaces With Thermodiffusion

In this article, the ocean energy generator system is analysed. The need for sustainable renewable energy systems is continually growing, given the situation of the world’s energy supplies. Numerous similar systems, including photovoltaic solar collectors, biomass, and wind turbines are used for energy generation. The ocean energy generator system uses the magnetohydrodynamics transformation concept to convert kinetic energy to electrical energy. Similar to conventional generators, an ocean generator requires an applied magnetic field to generate current, making it a critical component of the system. To optimize the performance and efficiency of ocean generators, various devices utilizing superconducting magnets have been developed, including Hall current generators, rotating channels, rotating disc magnetohydrodynamics generators, and helicoid generators. However, these systems also involve complex heat, momentum, and mass transfer, which can be better understood through mathematical modeling. The similarity transformation are introduced to transform the mathematical model from partial differential equation system to ordinary differential equation system. By adopting this approach, the numerical solution is significantly simplified while still preserving numerous crucial physical aspects of the studied heat and material transport phenomena. The physical characteristics of sea waves are governed by the three variables of seawater: temperature, salinity, and pressure. Small dispersed particles also affect the generation of hydroelectric power from surface water. The behaviour of velocity, temperature, and salinity profile is observed for the variations of different parameters such as magnetic, Grashof number and heat source. The system is converted into an optimization problem and solved by a neural network procedure. The solutions are compared with reference solutions for validation. The errors, performance, testing and training data are also presented graphically. The data is typically visualized using histograms, line graphs, and other visual aids. This allows for easier comprehension and analysis of the data.

Hybrid Nanofluid Flow and Heat Transfer Past a Vertical Cylinder in the Presence of MHD and Heat Generation

The basic objective of this work is to investigate the effects of Lorentz force and internal heat generation on the unsteady flow of a hybrid nanofluid and the heat transfer caused by a moving semi-infinite vertical cylinder. The governing partial differential equations are solved numerically using a robust implicit finite difference approach with proper boundary conditions. The current work is corroborated by existing literature on the subject of special situations of the problem. The effects of the magnetic parameter, the Grashof number, and the heat generation parameter on the Nusselt number, the skin friction coefficient, as well as the velocity and temperature fields, have been investigated and graphed. The results obtained can be applied to a variety of engineering devices, such as chemical reactors, heat exchangers, and solar collectors.

Optimal Design of an Inductive MHD Electric Generator

In this paper, the problem of optimizing the design of an inductive Magneto-Hydro-Dynamic (MHD) electric generator is formalized as a multi-objective optimization problem where the conflicting objectives consist of maximizing the output power while minimizing the hydraulic losses and the mass of the apparatus. In the proposal, the working fluid is ionized with periodical pulsed discharges and the resulting neutral plasma is unbalanced by means of an intense DC electrical field. The gas is thus split into two charged streams, which induce an electromotive force into a magnetically coupled coil. The resulting generator layout does not require the use of superconducting coils and allows you to manage the issues related to the conductivity of the gas and the corrosion of the electrodes, which are typical limits of the MHD generators. A tailored multi-objective optimization algorithm, based on the Tabu Search meta-heuristics, has been implemented, which returns a set of Pareto optimal solutions from which it is possible to choose the optimal solution according to further applicative or performance constraints.

Influence of the Asymmetric Geometry of Inflow Ducts on the Performance of Nonequilibrium Disk-Shaped Magnetohydrodynamic Generators

To examine the influence of the asymmetric geometry of inflow ducts on the performance of nonequilibrium disk-shaped magnetohydrodynamic (MHD) generators, we conducted MHD numerical simulations of a nonequilibrium disk-shaped MHD generator with an asymmetric, one-sided inflow duct and that with a symmetric, two-sided inflow duct. In our design concept, the two MHD generators have the same thermal input, applied magnetic field, and channel shape of the power extraction part. Numerical results show that the MHD generator with the one-sided inflow duct induces asymmetric distributions of plasma-fluid properties around the bent channel to connect the inflow duct with the channel of the MHD generator. However, the asymmetric distributions progressively disappear and transit to almost symmetric distributions before the plasma enters the power extraction part. Furthermore, the distributions of plasma-fluid properties in the power extraction part are almost identical to those in the MHD generator with the two-sided inflow duct. Consequently, the MHD generator with the one-sided inflow duct can obtain the same enthalpy extraction ratio (E.E.R.) as that with the two-sided inflow duct. Moreover, the numerical results indicate that the one-sided inflow duct is better for realizing high isentropic efficiency (I.E.) under the design concept used here than the two-sided inflow duct.

Controllability of Ion Out Flow Driven by Ambipolar Electric Field from Magnetic Mirror

A laminar flow is an ordered form of energy containers in plasma systems, hence tractable energy form to control or to convert to the other forms in plasmas. For this reason, plasma flows are utilized for various purposes, such as propulsion of spacecrafts, magnetohydrodynamic generators, and confinement of high-β fusion plasmas. In this study, we investigate properties of out flow of ions from a magnetic mirror in a laboratory experiment with a detailed measurement of axial profiles of plasma parameters for varied mirror ratios of the magnetic mirror. The experimental results reveal that the speed of the ion out flow is increased with the mirror ratio. This is considered to be attributed to enhancement of an ambipolar axial electric field accompanied by the increased mirror ratio. The relationship between the ambipolar potential height and the mirror ratio follows the relationship indicating a constant effective mirror ratio, which is an indication of an elimination of the mirror confinement effect by the enhanced ambipolar axial electric field. It is confirmed that the ion out flow satisfies the Bernoulli’s theorem and the continuity equation consistently. Accordingly, the ion out flow speed can be increased up to the speed corresponding to unity Mach number in the downstream of the magnetic mirror. Our work is the first detailed experimental confirmation of the Bernoulli’s theorem in a plasma flow system, which incorporates electrostatic potential variation in space. Another remarkable finding is that in the case of the mirror ratio lower than unity, the direction of the axial flow is reversed.

Diffusion phenomenon for natural convection flow of classical Hartmann problem due to a cylindrical tube by generalized Fourier’s theories: A Fractional analysis

The classical Hartmann flow problem is still interesting and novel due to its applications in MHD generators, plasma physics, power systems, etc. Owing to such importance in mind, this investigation explores the natural convection flow of viscous fluid following the Hartmann flow phenomenon due to a cylindrical tube. The heat transfer characteristics with diffusion phenomenon have been taken into consideration. The classical problem is further extended by countering the magnetic force impact. The fractional framework based on the Atangana–Baleanu (AB) and Caputo–Fabrizio (CF) is performed. The closed-form solutions are attained with Laplace as well as finite Hankel transforms. Further, the obtained results are stated as a combination of G-functions of Lorenzo and Hartley. The particular cases for the obtained simulations have been performed. The role of flow parameters governing the flow is graphically attributed.

Performance analysis of thermoacoustic plasma MHD generation

We develop a quasi-one-dimensional theoretical model describing the oscillatory plasma MHD conversion in a channel with parallel electrodes. Based on the model, a thermoacoustic plasma MHD generation system with a looped configuration is proposed and the characteristics of the operation of the system are investigated. Our results show that, for efficient oscillatory MHD generation, the channel dimension of the MHD duct should be much larger than the penetration depth (a proper Womersley number is above 100), otherwise the thermoacoustic effect will play a major role and consume considerable energy. Further, the electromagnetic induction parameter should be larger than 100S⋅T2/m, so that a majority of the kinetic energy of the oscillatory plasma can be harnessed for energy conversion. Moreover, a load ratio between 0.6 to 0.8 is suggested for the presented system, with which an efficiency above 20% can be achieved when the electromagnetic induction parameter is 500S⋅T2/m. In the optimal case, an efficiency of 24% can be obtained, with the corresponding output electricity of 1644 W. These results shed light on the feasibility of the closed-cycle MHD generation without any moving part, which endows the system with advantages of high reliability and long lifetime.

MHD turbulence: a biased review

This review of scaling theories of magnetohydrodynamic (MHD) turbulence aims to put the developments of the last few years in the context of the canonical time line (from Kolmogorov to Iroshnikov–Kraichnan to Goldreich–Sridhar to Boldyrev). It is argued that Beresnyak's (valid) objection that Boldyrev's alignment theory, at least in its original form, violates the Reduced-MHD rescaling symmetry can be reconciled with alignment if the latter is understood as an intermittency effect. Boldyrev's scalings, a version of which is recovered in this interpretation, and the concept of dynamic alignment (equivalently, local 3D anisotropy) are thus an example of a physical theory of intermittency in a turbulent system. The emergence of aligned structures naturally brings into play reconnection physics and thus the theory of MHD turbulence becomes intertwined with the physics of tearing, current-sheet disruption and plasmoid formation. Recent work on these subjects by Loureiro, Malletet al.is reviewed and it is argued that we may, as a result, finally have a reasonably complete picture of the MHD turbulent cascade (forced, balanced, and in the presence of a strong mean field) all the way to the dissipation scale. This picture appears to reconcile Beresnyak's advocacy of the Kolmogorov scaling of the dissipation cutoff (as$\mathrm {Re}^{3/4}$) with Boldyrev's aligned cascade. It turns out also that these ideas open the door to some progress in understanding MHD turbulence without a mean field – MHD dynamo – whose saturated state is argued to be controlled by reconnection and to contain, at small scales, a tearing-mediated cascade similar to its strong-mean-field counterpart (this is a new result). On the margins of this core narrative, standard weak-MHD-turbulence theory is argued to require some adjustment – and a new scheme for such an adjustment is proposed – to take account of the determining part that a spontaneously emergent 2D condensate plays in mediating the Alfvén-wave cascade from a weakly interacting state to a strongly turbulent (critically balanced) one. This completes the picture of the MHD cascade at large scales. A number of outstanding issues are surveyed: imbalanced turbulence (for which a new, tentative theory is proposed), residual energy, MHD turbulence at subviscous scales, and decaying MHD turbulence (where there has been dramatic progress recently, and reconnection again turned out to feature prominently). Finally, it is argued that the natural direction of research is now away from the fluid MHD theory and into kinetic territory – and then, possibly, back again. The review lays no claim to objectivity or completeness, focusing on topics and views that the author finds most appealing at the present moment.

Finite element analysis on the thermo-convective non-isothermal nanofluid flow in MHD Hall generator system with Soret and Dufour effects

Theoretical work for Cattaneo–Christov impacts on the non-isothermal flow of micropolar nanofluids with the application of a Hall magnetohydrodynamic (MHD) generator across a non-linearly enlarging sheet is discussed in this study. Fluid flow focuses on the impacts of Joule and viscous dispersion. A substantial electromagnetic field is utilized orthogonally to the fluid flow. The physical and geometric aspects of the study are capable of generating some findings of practical importance for thermally efficient devices. The momenta (for bulk flow and micromotion), heat transport, and concentration phenomena are formulated in the form of partial differential equations (PDEs) with the determination of conditions on the bounding wall of the sheet. The set of partial differential equations is transmuted with the help of similarity vectors. Then the finite element method (FEM) yields a viable solution. The validation of the FEM code in the Matlab script is assured when compared with the previous findings for some particular cases. The effects of various parameters on the varying characteristics of primary and secondary flow velocities, micro-motion, temperature, and nanoparticle concentration are observed, including the Hall current parameter (n), the micropolar parameter (G), the magnetic parameter (M), the thermophoretic parameter (Nt), the Cattaneo–Christov thermal relaxation parameter (γT), the Brownian motion parameter (Nb), and the non-linear wall stretching factor (m) is observed. The progressing inputs of (M) impeded the primary flow and micromotion, but it enhanced the secondary flow and temperature. It is observed that the temperature and velocity profiles are reduced while microrotation and secondary flow velocity are intensified with an increasing variety of the Hall current parameter. The findings are tabulated and graphed in detail.

Establishment of Impulsive and Accelerated Motions of Casson Fluid in an Inclined Plate in the Proximity of MHD and Heat Generation

This article is committed to examine the unsteady MHD Casson liquid flow in an inclined infinite vertical plate in the proximity of heat generation and thermal radiation. The governing energy and momentum partial differential equations are ascertained. The momentum equation is established for two distinct types of conditions when the magnetic domain is relevant to the liquid and the magnetic domain is relevant to the moving plate. Analytical expressions for liquid temperature and motion are acquired by applying Laplace transform technique. The effects of physical parameters are accounted for two distinct types of motions namely impulsive motion and accelerated motion. The numerical values of liquid motion and temperature are displayed graphically for various values of pertinent flow parameters. A particular case of our development shows an excellent compromise with the previous consequences in the literature.

Performance assessment of a magnetohydrodynamic power generation system: Division of the exergy destruction rate into its sub-portions

Sustainable and environmental friendly energy extraction and utilization is the foremost priority of the energy sector to meet the present and near future energy demands. The need of the day is to have efficient and eco-friendly energy conversion technologies either through the enhancement of the existing technologies or the development of some all-new technology. The present study investigates a standalone open-cycle Magnetohydrodynamic (MHD) power generation system using the advanced exergy analysis analytically. The effects of distributing the exergy destruction into endogenous/exogenous and avoidable/unavoidable on the improvement possibilities and the mutual interlinkages among the different units of the MHD system have been studied. The results showed that the MHD system has a higher possibility of its further development due to low unavoidable (36.82%) and high avoidable (63.18%) exergy desolation rates. The interlinkages among various units of the MHD system were found to be reasonably stronger due to the higher rate of exergy destruction of the endogenous type as compared to the exogenous portion. In the present study, the combustion chamber is found to have the highest possibility of upgradation as it possesses the largest value of avoidable exergy destruction rate together with the maximum rate of avoidable endogenous portion of the exergy destruction.

Hydromagnetic CuO-H2O nanofluid transportation through irreversibility analysis

The current investigation aimed for the exploration of steady-state, incompressible flow and energy transportation of water-based copper oxide nanofluid past a linear stretching sheet through suction/injection possessions. Furthermore, the impact of magnetohydrodynamic, radiation, and entropy generation are taken in the problem development. The nonlinear equations are reframed into single independent variable equations by the implication of appropriate similarity transformations. The Fehlberg scheme is developed for the numerical computations of re-structured non-linear expressions. The variations of influential constraints on the dimensionless physical quantities are investigated and reported in detail. The prominent features of the investigation include the higher velocity and weaker temperature is achieved against the incrementing stretching constraint values. The irreversibility ratio is reduced against the emerging stretching strength constraint. The Bejan number is decaying against the higher magnetic constraint. The blowing and suction have opposite impacts on the skin-friction factors.

Potassium carbonate decomposition modeling within rotating detonation engines for direct power extraction applications

Recently, there has been a significant interest in detonation-based combustion systems, such as rotating detonation engines (RDE), due to potential performance advantages in propulsion and energy applications. This includes improvements in thermodynamic efficiency, inherently high gas velocities, and the possibility of achieving an increase in total pressure (i.e. pressure gain) through the combustion process. Due to approximating a constant volume combustion process, these devices also tend to exhibit extremely high local gas temperatures relative to a comparable constant pressure combustor. These advantages overlap well with desirable performance characteristics of direct power extraction (DPE) technologies, such as a magnetohydrodynamic (MHD) generator. Typically, in DPE systems hot combustion products are seeded with an easily ionizable material such as potassium carbonate (K2CO3) in order to boost the electrical conductivity. However, due to the short gas residence times within an RDE, it was unclear whether forming an electrically conductive combustion plasma would be feasible for integration with a downstream MHD generator. A model is presented which describes the heating, decomposition, and ionization of solid K2CO3 particles and aqueous solutions of K2CO3 in water, for a given initial particle diameter. This model was combined with available computational fluid dynamics (CFD) data for an oxygen-methane RDE in a one-way coupled Eulerian-Lagrangian framework to predict particle trajectories and the corresponding heating, decomposition, and ionization histories. Electrical conductivities were computed using a previously developed model, and a method was proposed to determine an equivalent average electrical conductivity. Results show that particle sizes below ∼30 µm are able to fully decompose before reaching the exit of the RDE. While the one-way coupled nature of the simulations precluded rigorous evaluation of the effects of seed material on detonability, a substantial temperature reduction is expected at the detonation wave front due to heating and decomposition. A preliminary comparison is presented between the RDE and an equivalent constant pressure adiabatic combustor, showing a potential performance advantage for the RDE.

Theoretical investigation of a novel three-phase alternating current liquid metal vortex magnetohydrodynamic generator

Magnetohydrodynamic (MHD) generators are a class of devices that directly convert mechanical energy of a flowing fluid into electrical energy. However, due to the production of low magnitude voltages at low fluid velocities, they are not very useful for harvesting energy from the everyday environment at a watt scale. This work theoretically investigates a novel three-phase alternating current liquid metal vortex MHD, capable of generating power on a scale of watts and voltages on a scale of volts from a wide range of environmental energy sources. A new theoretical approach is utilized, where the induced fields and the stator fields are calculated independently which makes it easy to analyze different operational modes of the system. Two limiting approximations namely duct flow and disk flow have been analyzed and the effect of the number of poles and of the electromagnetic slip on the generated power and current is studied. The obtained analytical and numerical results are in good agreement and provide a robust foundation for the generator design and experimental characterization. The formulated approach also shows that such MHD devices can be easily scaled for various applications requiring power in a range from mW to W.

HHT-based investigation on the two-phase flow regime in the mixer for a nuclear-coupled liquid metal MHD power generation system

ABSTRACT Based on the self-designed two-phase mixer prototype, the multiphase flow model combined with a self-compiled UDF program was employed to conduct a numerical study in the present paper. The influences of the inlet velocity and temperature of the liquid metal and the inlet velocity of the low-boiling medium on the two-phase flow regime at the outlet of the mixer were discussed, by using Hilbert–HuangHuang transform. The results indicate that a relatively lower inlet velocity of the liquid metal tends to cause stratified flow, and with a gradual increase of the velocity, stratified flow transforms to mixed flow. At a constant inlet velocity of the liquid metal, raising the inlet velocity of low-boiling medium or the inlet temperature of liquid metal will result in annular flow, with a gas core composed of gaseous low-boiling medium formed in the center of the outlet. In addition, the spectrum of pressure fluctuation signal of the two-phase flow was acquired by Hilbert–Huang transform. It was noticed that as the flow regime changed from mixed to annular flow, the energy indicator k of pressure signal shifted from high-frequency band to low-frequency band.

Mathematical modeling of MHD flow and radiative heat transfer past a moving porous rotating disk with Hall effect

PurposeThe present study aims to investigate the effect of radiation on the unsteady magnetohydrodynamic (MHD) flow of a viscous, electrically conducting Newtonian fluid over rotating disk moving upward/downward immersed in a porous medium, considering the Hall effect. The study is motivated by the various applications in the context of solar power technology, electric power generation, Hall accelerators, MHDs generators and other industrial areas when the fluid flow is subjected to the previously mentioned effects such as MHD, Hall effect and thermal radiation.Design/methodology/approachSuitable similarity transformations are employed to reduce the governing nonlinear partial differential equations into the nonlinear ordinary ones. The solutions of the reduced system are numerically obtained using the boundary value problem (BVP) Midrich scheme in Maple. The results are presented graphically for vertical disk movement, magnetic parameter, Hall current, Darcy parameter, thermal radiation and Schmidt number. Skin frictions, mass and heat transfer rates are numerically tabulated.FindingsIt is revealed that the vertical motion of the disk significantly boosts the radial and annular flows. Moreover, the Hall parameter has contrasting effects on velocity profiles for the range of magnetic field but temperature field is oblivious of this behavior. It is observed that heat and mass transfer considerably enhance along vertical disk movement. Also magnetic field, temperature ratio and radiation parameter significantly enhance the temperature field, while reaction rate parameter and Schmidt number decrease the concentration profile. The current model is calibrated in its reduced form to an already published literature with good correlation to ensure the numerical scheme's validity.Originality/valueThis work is original within the best efforts of the authors.

Small-scale solar jet formation and their associated waves and instabilities

Studies on small-scale jets’ formation, propagation, evolution, and role, such as type I and II spicules, mottles, and fibrils in the lower solar atmosphere’s energetic balance, have progressed tremendously thanks to the combination of detailed observations and sophisticated mathematical modelling. This review provides a survey of the current understanding of jets, their formation in the solar lower atmosphere, and their evolution from observational, numerical, and theoretical perspectives. First, we review some results to describe the jet properties, acquired numerically, analytically and through high-spatial and temporal resolution observations. Further on, we discuss the role of hydrodynamic and magnetohydrodynamic instabilities, namely Rayleigh–Taylor and Kelvin–Helmholtz instabilities, in jet evolution and their role in the energy transport through the solar atmosphere in fully and partially ionised plasmas. Finally, we discuss several mechanisms of magnetohydrodynamic wave generation, propagation, and energy transport in the context of small-scale solar jets in detail. This review identifies several gaps in the understanding of small-scale solar jets and some misalignments between the observational studies and knowledge acquired through theoretical studies and numerical modelling. It is to be expected that these gaps will be closed with the advent of high-resolution observational instruments, such as Daniel K. Inouye Solar Telescope, Solar Orbiter, Parker Solar Probe, and Solar CubeSats for Linked Imaging Spectropolarimetry, combined with further theoretical and computational developments.

Study on the Effect of Magnetic Field on Seawater Electrolysis using a Channel Flow Cell to Simulate a Linear-type Seawater Magnetohydrodynamic Power Generator

A seawater magnetohydrodynamic (MHD) power generator is a unique system that not only transforms the kinetic energy of ocean and tidal currents directly into electric energy but also generates hydrogen gas by seawater electrolysis. In this study, we constructed experimental equipment and an electrochemical flow cell, which simulated a linear-type seawater MHD power generator, and investigated the effect of magnetic field on seawater electrolysis. Under magnetic field under solution flow conditions, we clarified that the strength of the magnetic field affected the current value of seawater electrolysis, which indicates that the MHD power generation was successfully simulated by the developed experimental equipment and electrochemical flow cell. Our electrochemical measurement results suggested that magnetic field was correctly applied to the cell and that the Lorentz force acted on the ions in the electrolyte solution, showing improvement in hydrogen evolution reaction (HER) efficiency under the MHD power generation conditions.

Numerical analysis of deflection control of a gas plasma jet based on magnetohydrodynamic staggered electrode configuration

To control the deflection of the gas plasma jet, a new analytical method is proposed based on the Magnetohydrodynamic (MHD) technique. Based on the typical MHD power generation model, the applied voltage is applied to the staggered electrodes, that is, a pair of electrodes on the same side wall are connected to generate an axial current in the channel. Under the action of the magnetic field perpendicular to the direction of the flow, the plasma is subjected to electromagnetic forces perpendicular to these two directions, and the jet is deflected. The computational model including the Navier-Stokes equations coupled with electromagnetic source terms, the electric potential equation and Ohm’s law is solved. The deflection of the gas jet under the action of an electromagnetic field is observed, and the maximum deflection angle is about 14.8°. The influences of the electric field, magnetic field, and conductivity on the jet deflection are studied. Results show that although the influences of these three factors on the deflection are similar, and the effect of increasing the electric field strength is slightly greater, priority should be given to increasing the magnetic field strength from the perspective of reducing energy consumption. The Stuart number is introduced to assess the ability of electromagnetic force to control jet deflection. When the electromagnetic parameters are constant, this solution provides better control of low-density and low-speed fluid flows. The calculation results show that using the staggered electrode method configuration is feasible in terms of controlling the deflection of a plasma jet deflection.

Research progress on the seed plasma disk magnetohydrodynamic generator

To fully and clearly understand the development status and key research problems of the seed plasma disk magnetohydrodynamic (MHD) generator, this study reviews the development process of the seed plasma disk MHD generator. The development of the disk MHD generator has experienced the stages of suppressing the ionization instability of nonequilibrium plasma, revealing the characteristics of stable nonequilibrium plasma based on the concept of seed full ionization, and proving the high performance of the disk MHD generator. At present, there are attempts to use a small area ratio disk MHD generator to obtain a high entropy efficiency at a high enthalpy extraction rate with cesium added inert gas as the working fluid. Moreover, the research progress is described from two aspects of numerical simulation and experimental research, and the key technologies and problems to be solved and the development prospects of the seed plasma disk MHD generator are analysed. It is shown that the future theoretical research still will be focused on the generation and ionization process of nonequilibrium plasma. The key technology in the future is still aimed to obtain high-quality, uniform and stable non-equilibrium plasma. Therefore, in the future, it is expected to become a high-power static power supply with a compact structure and high-power conversion efficiency. Tables 2, Figs 9, Refs 153.