MHD Generator Research Articles

Novel intrinsic helical cores and MHD dynamo flux pumping evidence in DIII-D

Novel intrinsic helical cores and MHD dynamo flux pumping evidence in DIII-D

A computational study on square and helical magnetohydrodynamic generators including applications to a combined power cycle

A computational study on square and helical magnetohydrodynamic generators including applications to a combined power cycle

Numerical analysis of hydrothermal performance and entropy generation in an active cooling system: A case study with NEPCM, double-diffusive mixed-convection and MHD

Magnetohydrodynamic and entropy generation of double-diffusive mixed convection in a curvilinear cavity filled with nano-enhanced phase change material and a rotating cylinder has been studied in this paper. Three heat sources have been considered and a range of different variables such as Reynolds number (10 ≤ Re ≤ 100), Richardson number (0.1≤ Ri ≤ 10), Hartmann number (0≤ Ha ≤50) Lewis number (0.1≤ Le ≤ 0.9), bouncy ratio (1≤ Nz ≤ 5), fusion temperature (0.1≤ θf ≤0.9) and Stephan number (0.1≤ Ste ≤0.9). These variables have been numerically solved by applying the Finite Element Method. The main results indicated that heat transfer, mass transfer and heat capacity are hugely increased with the increase of the Re, Ri and volume concentration while decreasing with the increase of the Ha number and entropy generation. Furthermore, the melting/solidification region is hugely influenced by the fusion temperature while this variable has a negligible influence on streams, heat transfer and mass transfer. Furthermore, the value of the average Nusselt number and average Sherwood number has increased by 328 % and 258 % respectively by increasing the Reynolds number from 10 to 100. Also, these two numbers have decreased by 61 % and 54 % respectively by increasing the Hartmann number from 0 to 20.

Thermodynamic and mass analysis of a novel two-phase liquid metal MHD enhanced energy conversion system for space nuclear power source

The higher-efficiency and more lightweight space nuclear power source is one of the most important prerequisites for future deep space exploration. Magnetohydrodynamic (MHD) power generation is the potential technical route to achieve significant improvement in energy conversion performance, but technology is not yet mature. By combining the characteristics of MHD and closed Brayton cycle (CBC) power generation systems, a novel quasi-Ericsson cycle with performance advantages is proposed in this study. The estimation method for the MHD power generator is refined and the thermodynamic and mass analysis models for the novel system are established. Comparative studies between the LMMHD-CBC cycle and the traditional CBC cycle are conducted under various boundary conditions and internal parameters. The results indicate that the LMMHD-CBC cycle increases the electricity generation per unit mass flow rate of working fluid under the same temperature conditions, thereby achieving a reduction in the specific mass of the power generation system. The LMMHD-CBC system is more suitable in lower reactor temperatures and higher radiator temperature conditions. Within the parameters range considered in this study, the relative reduction in specific mass compared to traditional CBC systems reaches up to 30.84 %.

Computational analysis of nanoparticles and waste discharge concentration past a rotating sphere with Lorentz forces

Abstract As industries rely more and more on magnetohydrodynamic (MHD) systems for different uses in power, production, and management of the environment, it becomes essential to optimize these operations. The study seeks to improve the effectiveness and productivity of cooling structures, chemical reaction reactors, and contaminant control methods by investigating these intricate interconnections. Because of this, the work scrutinizes the endothermic/exothermic (EN/EX) chemical processes, convective boundary conditions, and pollutant concentration impacts on MHD nanofluid circulation around a rotating sphere. The governing equations based on the above assumptions are reduced into a system of ordinary differential equations and solved numerically with Runge–Kutta Fehlberg’s fourth- and fifth- order schemes. The obtained numerical outcomes from the numerical scheme are presented with the aid of graphs, and the results show that the rate of mass transfer decreases with an increase in the external pollutant local source and solid volume percentage. For changes in the values of the activation energy parameter and solid fraction, the rate of thermal dispersion drops for the EN case and upsurges for the EX case. The concentration profile shows increment with the addition of the external pollutant source variation parameter and local pollutant external source parameter. The outcomes of the present work can be helpful in cooling equipment, developing advanced methods for controlling pollution, environmental management, MHD generators, and various industrial contexts.

Coupling study of onboard power generation system of Magnetohydrodynamics enhanced Brayton Cycle

Closed cycle power generation systems offer a possible solution to meet the high electricity needs of hypersonic vehicles, but the power generation is limited by the finite cold source and cycle temperature. Introducing two-phase flow liquid metal (LM) MHD power generation based on Closed-Brayton-Cycle (CBC) is a potential solution that can enhance the thermal-electricity conversion process at the system level. However, it is difficult to reflect the complex coupling relationship between the power generation system and the vehicles propulsion system and the limitations of finite cold sources by relying only on ideal system analysis, especially the contradiction between the void fraction and the mass flow of working fluid after the introduction of LMMHD power generation. The study utilizes a multi-dimensional model to evaluate the performance of the CBC enhanced by multi-stage LMMHD generators coupled with hydrocarbon fuel scramjet. The multi-stage mixing-separation LMMHD generator is proposed to decouple the void fraction of the MHD channel and the wall cooling process, and control the void fraction by change number of stages. The calculation result indicate that the void fraction significantly affects the overall power generation performance, including output power, performance boundary, etc. Increasing the void fraction is beneficial, and the optimal void fraction is 0.65. At the same Mach number, the fuel cooling capacity available to the system increases with the fuel equivalence ratio, resulting in higher total power output. The maximum Mach number for thermal protection of the combustor walls alone may surpass 9.5. For gas void fractions of 0.35/0.5/0.65, the maximum power generation reaches 182.8/167.1/156.9 kW, respectively. The novel system is compared with other advanced thermal-electricity conversion cycles under nearly the same conditions and demonstrated clear performance advantages.

Numerical computations of magnetohydrodynamic (MHD) thermal fluid flow in a permeable cavity: A time dependent based study

This study presents a comprehensive analysis of unsteady, two-dimensional flow with the interaction between cold walls and heated cylindrical obstacles. The investigation focuses on the interplay among fluid dynamics, heat transfer, and magnetic fields. The behavior of the conducting fluid with the effect of a magnetic field present is described using the MHD equations, while the obstacles are maintained at elevated temperatures. The unsteady nature of the flow introduces additional complexities. The analysis provides insights into various flow pattern formation, boundary layers, and thermal distributions. The impact of magnetic forces on fluid dynamics and heat transfer is examined, shedding light on the overall behavior of the system. The obtained results clearly indicate that changes in the spacing distance on cylindrical obstacles will induce deformations in the isotherms, especially near the obstacles, resulting in localized variations. As the Hartmann number increases, the impact of magnetic forces becomes more pronounced. An increase in the Eckert number, tends to improve convective heat transfer efficiency. This research contributes to a better understanding of MHD-driven flow with practical implications in areas such as magnetohydrodynamic power generation, astrophysical phenomena, and controlled fusion.

Numerical study of plasma behavior in a disk‐shaped noble gas MHD generator

AbstractPlasma behavior in cesium‐seeded argon (Ar/Cs) and xenon‐seeded argon (Ar/Xe) disk‐shaped MHD generators are compared under almost the same working conditions using r‐θ two‐dimensional simulation. For both working gases, uniform plasma occurs at the optimum load resistance, and the power outputs are the same under an identical inlet ionization degree. For Ar/Cs, plasma is stable and uniform in the range of electron temperature of 4300–5800 K basically according to the linear perturbation theory. In the actual plasma in the MHD generator, however, the uniform plasma still can be maintained even at higher electron temperatures due to the low three‐body recombination coefficient of Ar. For Ar/Xe, on the other hand, uniform plasma is maintained when the characteristic time of the electron number density is longer than the residence time of the working gas where the electron temperature is around 4300–8600 K, even though unstable plasma is suggested from the linear perturbation theory.

Modeling and sensitivity analysis of a supersonic inductive Magnetohydrodynamic (MHD) generator

This study presents the supersonic inductive Magnetohydrodynamic (SIMHD) generator and simulates its model through the use of COSMOL Multiphysics. This generator, as an inductive MHD generator, is suggested to address the problems associated with the conventional MHD generator. Since the proposed generator does not require a moving part to convert thermal energy to electrical energy, it is categorized as a direct energy convertor. The SIMHD generator consists of a converging-diverging duct and is divided into two sections at the diverging part by means of a diaphragm. Both of these sections are diverging, which makes it possible to obtain a high Mach number. In this regard, the performance of the SIMHD generator is studied by its mathematical modeling and numerical simulation using the finite element method. In addition, a sensitivity analysis is carried out on the design parameters. The results indicate that the proposed SIMHD duct design will increase the speed from 160 to 1300 m⁄s, and decrease the temperature from 2100 to 1300 K. Moreover, considering a charge generation equation, the produced power for the resistive load 50 Ω equals 25.3 kW. This generator also has the potential to be used in scramjets and ramjets.

Algebraic quantification of the contribution of active regions to the Sun’s dipole moment: applications to century-scale polar field estimates and solar cycle forecasting

ABSTRACT The solar cycle is generated by a magnetohydrodynamic dynamo mechanism which involves the induction and recycling of the toroidal and poloidal components of the Sun’s magnetic field. Recent observations indicate that the Babcock–Leighton (BL) mechanism – mediated via the emergence and evolution of tilted bipolar active regions – is the primary contributor to the Sun’s large-scale dipolar field. Surface flux transport models and dynamo models have been employed to simulate this mechanism, which also allows for physics-based solar cycle forecasts. Recently, an alternative analytic method has been proposed to quantify the contribution of individual active regions to the Sun’s dipole moment (DM). Utilizing solar cycle observations spanning a century, here, we test the efficacy of this algebraic approach. Our results demonstrate that the algebraic quantification approach is reasonably successful in estimating DMs at solar minima over the past century – providing a verification of the BL mechanism as the primary contributor to the Sun’s dipole field variations. We highlight that this algebraic methodology serves as an independent approach for estimating DMs at the minima of solar cycles, relying on characteristics of bipolar solar active regions. We also show how this method may be utilized for solar cycle predictions; our estimate of the Sun’s dipole field at the end of cycle 24 using this approach indicates that solar cycle 25 would be a moderately weak cycle, ranging between solar cycle 20 and cycle 24.

On the Uniqueness of the Solution to the Inverse Problem of Determining the Diffusion Coefficient of the Magnetic Field Necessary for Constructing Analytical Models of the Magnetic Field of Mercury

This paper considers the problem of the uniqueness of the solution to the coefficient inverse problem for the system of equations of magneto-hydrodynamics, the solution to which allows more accurately describing the processes of generating the magnetic field of planets with a magneto-hydrodynamic dynamo. The conditions under which it is possible to determine three components of the magnetic induction vector and the magnetic field diffusion coefficient are determined.

Multi-Objective Optimization of Vortex Magnetohydrodynamics (MHD) Generator using Response Surface Methodology

The introduction of electromagnetic fields in fluid dynamics in magnetohydrodynamics (MHD), particularly when those fields are vector and non-uniform, complicates its application in vortex geometry. The imperative to optimize MHD generators arises from the inherent trade-off between voltage and pressure drop in energy conversion systems, to maximize voltage output while minimizing associated pressure drop. This study focuses on optimizing vortex MHD generators by applying Response Surface Methodology (RSM), which is based on mathematical models that capture the complex relationships between factor and response variables. This method offers a comprehensive approach to obtaining the optimum solution to the objectives, voltage and pressure drop, based on fluid velocity and magnetic field strength input parameters. Numerical optimization RSM generates 11 solutions. The optimum solutions obtained are a velocity of 1.415 m/s, and magnetic field strength of 0.43 T, and the corresponding optimum output voltage and pressure drop will be 4.264 mV and 4.254 psi, respectively, with a desirability level of the selected solution is 0.770. This study suggests the RSM method shows a good measurement of R2 and RSME. Our findings contribute to the understanding of optimizing vortex MHD generators and offer insights into achieving efficient energy conversion systems of a set of optimum generator operating parameters.

How well does surface magnetism represent deep Sun-like star dynamo action?

Context. For Sun-like stars, the generation of toroidal magnetic field from poloidal magnetic field is an essential piece of the dynamo mechanism powering their magnetism. Previous authors have estimated the net toroidal flux generated in each hemisphere of the Sun by exploiting its conservative nature. This only requires observations of the photospheric magnetic field and surface differential rotation. Aims. We explore this approach using a 3D magnetohydrodynamic dynamo simulation of a cool star, for which the magnetic field and its generation are precisely known throughout the entire star. Methods. Changes to the net toroidal flux in each hemisphere were evaluated using a closed line integral bounding the cross-sectional area of each hemisphere, following the application of Stokes theorem to the induction equation; the individual line segments correspond to the stellar surface, base, equator, and rotation axis. We evaluated the influence of the large-scale flows, the fluctuating flows, and magnetic diffusion on each of the line segments, along with their depth-dependence. Results. In the simulation, changes to the net toroidal flux via the surface line segment typically dominate the total line integral surrounding each hemisphere, with smaller contributions from the equator and rotation axis. The surface line integral is governed primarily by the large-scale flows, and the diffusive current; the latter acting like a flux emergence term due to the use of an impenetrable upper boundary in the simulation. The bulk of the toroidal flux is generated deep inside the convection zone, with the surface observables capturing this due to the conservative nature of the net flux. Conclusions. Surface magnetism and rotation can be used to produce an estimate of the net toroidal flux generated in each hemisphere, allowing us to constrain the reservoir of magnetic flux for the next magnetic cycle. However, this methodology cannot identify the physical origin or the location of the toroidal flux generation. In addition, not all dynamo mechanisms depend on the net toroidal field produced in each hemisphere, meaning this method may not be able to characterise every magnetic cycle.

Thermal Analysis of a Casson Boundary Layer Flow over a Penetrable Stretching Porous Wedge

This work aims to analyze the Casson thermal boundary layer flow over an expanding wedge in a porous medium with convective boundary conditions and ohmic heating. Moreover, the effects of porosity and viscous dissipation are studied in detail and included in the analysis. The importance of this study is due to its applications in biomedical engineering where the analysis of behavior of non-Newtonian blood flow in arteries and veins is desired. Within the context of blood flow, it is also applicable to many other fields, for instance, radiative therapy, MHD generators, soil machines, melt-spinning, and insulation processes. The modeled problem is a set of PDEs, which is nondimensionalized to derive a nonlinear boundary value problem (BVP). The obtained BVP is solved using the shooting technique, endowed with the order four Runge-Kutta and Newton methods. The impact of different parameters on the momentum and temperature fields is investigated along with two important parameters of physical significance, i.e., the Nusselt number and the surface drag force. Results are validated, and an excellent agreement is seen for the parameters of interest using MATLAB built-in function bvp4c. A significant finding is that by increasing the Casson liquid parameter, the velocity decreases as the wedge expands quicker than the free stream velocity at R=2. However, the velocity increases for the case when R=0.1. A decrease in the Darcy number increases the temperature profile. Furthermore, the convective parameter accelerated the heat transmission rate, and a rise in the Prandtl number thickens the thermal boundary layer. The findings of this investigation contribute to problems in fluid dynamics and heat transfer that involve studying the behavior of a non-Newtonian fluid with Casson rheological properties near a solid porous wedge surface.

Combustion and plume-plasma characteristics of cesium-based solid propellant

The high-temperature plume of solid propellant has spawned considerable amount of highly ionized plasma, which can be used to increase the specific impulse of propellant with the external physical field, as well as serve as the charged particles for the magnetohydrodynamic (MHD) generator on the thruster. Unfortunately, the deficiency of workable deal to promote the electrical performance of the plume hinders the development of the above technologies. In this work, cesium-based composite solid propellants (CCSP) were designed and fabricated by introducing cesium-based oxidants into the AP/HTPB/Al propellant as the highly ionized seed. The propulsion properties and plume conductivity of CCSP were preliminarily calculated through theoretical method. The comprehensive combustion-plasma characteristics (plume conductivity, flame morphology and combustion temperature) of CCSP were further investigated, utilizing plume-plasma diagnostic system. Profiting from the high electron derailment capacity of cesium atom with high temperature, the density of charged particles in the plume of CCSP significantly multiplied. The conductivity of CCSP plume with a value of >1000 S/m presented several orders of magnitude enhancement compared with the plume of baseline propellant (3.9 S/m). Additionally, partially replacing AP with CN/CP contributed to the combustion adequacy of Al MPs. The investigation on the burning rate pressure-index of CCSP and baseline using the high-pressure combustion chamber indicated that 0<nbaseline<nCCSP<1, proving the application ability on SRM and the ability to regulate the burning rate over a wide pressure range for CCSP. Overall, the presented work provided a novel method for improving the plume-plasma performance of propellant, exhibiting the admirable application prospects for Rocket-MHD generator technology and enhancement technology of thrust/specific impulse by physical energy field.

Enhancing Strategy of the Small-Polaron Conductivity in LaCrO3: First-Principles Calculations and Experimental Validation.

LaCrO3 (LCO) has promising applications as a p-type conductive material in the fields of transparent conducting oxes, high-temperature sensors, and magnetohydrodynamic power generators. However, the easy volatility of the Cr element, along with the issues of low electrical conductivity caused by the small-polaron conduction mechanism and wide band gap, has hindered the widespread application of LCO. In this work, based on band engineering and defect engineering, we screened doping schemes through first-principles calculations that can reduce Cr volatility by enhancing the Cr-O bond energy. We also aimed to promote small-polaron hopping and improve the electrical conductivity by introducing impurity levels. Additionally, we conducted a thorough analysis of the small-polaron conductivity mechanism. Through the solid-state method, we successfully prepared codoped LCO with Ca and Zn. The Zn dopants effectively enhanced the Cr-O bond strength, suppressed the Cr volatility, and improved high-temperature stability. The Zn dopants introduced additional impurity energy levels within the band gap, significantly changing the mobility of small polarons. Through optimal doping concentration, the La0.7Ca0.3Cr0.95Zn0.05O3 sample demonstrated a significant enhancement in electrical conductivity compared to La0.7Ca0.3CrO3, increasing from 7 to 60 at 1000 K. Additionally, the impurity energy levels enhanced the asymmetry near the Fermi level, resulting in an increased Seebeck coefficient (S). This is beneficial for the production of high-temperature sensors. The output voltage of an LCO thermocouple module reaches up to 58 mV at 2170 K, indicating that the performance optimization strategy employed in this work has significant implications for the regulation and application of oxide electrical materials.

Fundamental Experiment and Numerical Simulation of Ne/Xe Plasma Magnetohydrodynamic Electrical Power Generation

We conducted experiments in a shock-tube facility to test magnetohydrodynamic (MHD) electrical power generation with Xe-seeded Ne plasma. The performance and plasma behavior of the experimental generator were examined using time-dependent r-θ two-dimensional numerical simulations. In the experiment, an enthalpy extraction ratio of about 5.0% was obtained using a disk-shaped MHD generator with radio frequency pre-ionization. The numerical simulations show that the enthalpy extraction ratio is improved by adding small amounts of Xe to Ne, but also that adding excessive amounts of Xe deteriorates the generator performance. When an appropriate inlet electron temperature is assumed in the simulations, 5900–6450 K (inlet ionization degree of 0.25×10−4–0.72×10−4) for a seed fraction (mole % of Xe) of 0.1%, 6050–6280 K (1.08×10−4–1.70×10−4) for a seed fraction of 1.0%, and 5750–5950 K (1.27×10−4–1.97×10−4) for a seed fraction of 5.0%, the plasma structure almost becomes similar to the nonuniform plasma structure observed in the experiment, as too does the enthalpy extraction ratio. The simulations suggest that achieving an inlet ionization degree above 5–6×10−4 when using Ne/Xe with a seed fraction of 0.1–1.0% as the working gas should enable an enthalpy extraction ratio above 20%, which is expected to surpass that for pure Ar.

A novel magnetohydrodynamic power generation system using low-temperature liquid metal coupled with a rectangular single-phase natural circulation loop

A novel magnetohydrodynamic power generation system using low-temperature liquid metal coupled with a rectangular single-phase natural circulation loop

Thermodynamic properties of Casson-Sutterby-micropolar fluid flow over exponential stretching curved sheet with impact of MHD and heat generation

The study focuses on the dynamic properties of models describing the flow of couples' micropolar-Casson-Sutterby fluids over an exponentially curved sheet. The study takes into account a low Reynolds number, magnetic field effects, and chemical reactions. By employing boundary layer approximations, the governing general equations are reduced to partial differential equations. Subsequent appropriate transformations simplify the motion, micropolar, and energy equations into a set of coupled nonlinear ordinary differential equations, which can be numerically elucidated using the bvp4c function in MATLAB. The study reveals that as the material constants approach zero, the flow of micropolar fluids becomes Newtonian fluids. The fluid velocity gradually increases due to the enhancement in the Sutterby fluid factor, leading to heightened fluid shear thinning and increased fluid velocity. The results can be analyzed numerically and graphically and are accompanied by a physical explanation of various parameters. The velocity exhibited a declining trend due to an increase in the Casson fluid factor. This was caused by the enrichment of fluid viscosity with higher values of the custom fluid factor, ultimately resulting in a reduction in the fluid velocity. Increasing the values of the micropolar fluid factor resulted in diminishing velocity curves.

The Effects of an Aligned Magnetic Field on Nanofluid Flow with Newtonian Heating

Magnetic field involvement can influence heat absorption in electrically conducting fluid flow, which is useful in the control of features of final products in industries such as radiation therapy, aeronautics, and MHD generators. Consequently, this study investigates the effect of an aligned magnetic field on nanofluid flow over a stretching sheet with the boundary condition of Newtonian heating. Steady nanofluid flow with copper as chosen nanoparticles and water as conventional base fluid is considered. The problem is governed by a system of nonlinear boundary layer equations with appropriate boundary conditions which are then transformed into non-dimensionless equations using an appropriate similarity transformation. A numerical approach known as Keller-Box method is used to solve the transformed governing equations. The numerical solutions obtained are presented graphically in the form of velocity and temperature profiles for different values of aligned angle of magnetic field, Newtonian heating parameter, Prandtl number and nanoparticles volume fraction. A significant increase in aligned angle results in a decrease in fluid velocity, but an increase in temperature profile of nanofluid flow. The increment in the Newtonian heating parameter as well as the nanoparticle volume fraction also causes the temperature to increase.