MHD Channel Research Articles

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.

Computational analysis of MHD channel flow of Maxwell fluid with radiation and chemical reaction effects

Computational analysis of MHD channel flow of Maxwell fluid with radiation and chemical reaction effects

Entropy generation for exact irreversibility analysis in the MHD channel flow of Williamson fluid with combined convective-radiative boundary conditions

The scrutinization of entropy optimization in the various flow mechanisms of non-Newtonian fluids with heat transfer has been incredibly enhanced. Through the investigation of irreversibility sources in the steady flow of a non-Newtonian Willaimson fluid, an analysis of entropy generation is carried out in this current work. The current study has an essential aspect of investigating the heat transfer mechanism with flow phenomenon by considering convective-radiative boundary conditions. A horizontal MHD channel is assumed with two parallel plates to develop a mathematical model for the flow phenomenon by considering the variable viscosity of the fluid. The contribution of physical impacts of thermal radiation, Joule heating, and viscous dissipation is interpolated in the constitutive energy equation. The complete flow of the current analysis is established in the form of ordinary differential equations which further take the form of the dimensionless system through the contribution of the similarity variables. A graphical scrutinization of the physical features of the flow phenomenon in relation to the pertinent parameters is proposed. This study reveals that the higher magnitude of radiation parameter and Brinkman number dominates the system's entropy. Moreover, the temperature distribution experiences an increasing mechanism with improved conduction-radiation parameter at the lower plate.

Numerical solution of MHD channel flow in a porous medium with uniform suction and injection in the presence of an inclined magnetic field

Journal of Applied Mathematics and Computational Mechanics, Prace Naukowe Instytutu Matematyki i Informatyki, Politechnika Częstochowska, Scientific Research of the Institute of Mathematics and Computer Science, Czestochowa University of Technology

Исследование процессов в генераторе плазмы импульсного МГД-генератора на комбинированном пиротехническом топливе

This paper presents the results of numerical simulation of the processes in a two-chamber plasma generator of the pulsed MHD generator running on combustion products of a combined pyrotechnic fuel with afterburning in air oxygen. A mixture of Mg powder (a fuel) and KNO3 powder (an oxidizer and a source of the easily ionized additive) is chosen as a pyrotechnic fuel. The considered plasma generator includes a gas generator and an afterburner. Multicomponent combustion products of the selected pyrotechnic fuel contain solid particles of MgO and gaseous Mg. Within the afterburner, the unburnt Mg is burned up in the presence of air oxygen, forming MgO liquid particles. The proposed mathematical model allows one to numerically investigate all the processes occurring in a plasma generator of an MHD generator with an afterburner and to obtain the required data for determining the shape of the accelerating nozzle and the relevant parameters for calculations in the MHD channel.

The operating mode of the water-cooled MHD accelerator of SMGDU with a magnetic field that changed along the channel

The work is aimed at solving the problem of creating in laboratory conditions hypersonic high-enthalpy gas flows that parameters are kept constant for 5-10 seconds. For this purpose the test section of the MHD channel with water-cooled electrodes and side walls was under investigation at the set up with a magnetohydrodynamic accelerator in TsAGI. A new series of runs was performed in which the MHD-acceleration stage was successively increased to 5 seconds. It was determined that the electrical and gas-dynamic characteristics of the MHD accelerator did not depend on the duration of the run. It was first demonstrated that the use of a magnetic field special shaped along the axis of the channel made it possible to avoid catastrophic damage to the side walls of the channel at the entrance and exit of the MHD accelerator, which increased the service life of the installation.

Oxygen and Silver Nanoparticle Aerosol Magnetohydrodynamic Power Cycle

Pressure and thermal energy of a novel hydrogen chemistry driven plasma is converted into kinetic energy using a converging-diverging nozzle, and the kinetic energy is converted to electricity in a novel highly efficient MHD cycle exploiting (i) the ability of silver to form nanoparticles at its melting point when exposed to oxygen and (ii) the ability of silver at its melting point to absorb up to 25 mole percent oxygen wherein the corresponding rates to support the cycle where experimentally confirmed. Equations for a constant pressure expansion of a constant conductivity working fluid in an MHD channel with uniform magnetic field demonstrated that as the flow decelerates the kinetic energy of the fluid is converted to MHD power in proportion to the loading factor W at a power density of 23.1 MW/liter, and the remaining fraction (1–W) of the kinetic energy is converted to fluid enthalpy that can be recovered wherein the MHD converter has no moving parts. Since the MHD efficiency may approach W=1, the electrical conversion of the power of the plasma into electricity may approach the efficiency of pressure-thermal to kinetic energy conversion wherein the corresponding nozzle efficiencies of 99% have been realized. This novel thermodynamic cycle enables closed liquid magnetohydrodynamic power conversion of a breakthrough clean hydrogen plasma power source into electrical power at a power density that is orders of magnitude higher than previously possible at an efficiency approaching unity.

Magnetic-field analysis of an MHD channel in a liquid-metal circulation system of a prototype GenIV sodium fast reactor

A helical-type direct current (DC) electromagnetic pump with a developed pressure of 10 kPa and flow rate of 0.005 m3/s was analyzed at a temperature of 226 °C for an active decay heat-removal system (ADHRS) of a prototype GenIV sodium fast reactor. The rectangular-type DC electromagnetic pump, which was selected for the ADHRS, required a very large current (>1000 A). A helical-type DC electromagnetic pump was considered to provide multiple current to a pump duct to reduce the input current requirement. The magnetic flux density of a permanent magnet is one of the important factors that determine the performance of the electromagnetic pump. The magnetic field for the flow channel of the helical-type DC electromagnetic pump was analyzed in which a Sm2Co17 permanent magnet was used to generate the Lorentz force for the circulation of liquid metal. The Lorentz force, which directly affected the developed pressure of the electromagnetic pump, was increased proportional to the magnetic flux density, which led to the increase in the velocity of the liquid metal in the flow channel. The permanent magnet in the +z and −z directions and the ferromagnetic material added in the r direction increased the magnitude of the magnetic flux density, which led the magnetic flux line to the flow channel. The arrangement of the permanent magnet system showed the optimized geometry of the inner ferromagnetic material with a radius of 110 mm and outer ferromagnetic material with a thickness of 30 mm and height of 70 mm. The average value of the magnetic flux density in the liquid-metal flow channel was 0.848 T under maximum condition by considering the mechanical and spatial restrictions.

Boundary stabilization of a 2-D periodic MHD channel flow, by proportional feedbacks

Boundary stabilization of a 2-D periodic MHD channel flow, by proportional feedbacks

Влияние скачкообразного изменения магнитного поля на течение бингамовской жидкости в плоском МГД-канале

Влияние скачкообразного изменения магнитного поля на течение бингамовской жидкости в плоском МГД-канале

The CFD modeling of two-dimensional turbulent MHD channel flow

In this paper, influence of magnetic field on turbulence characteristics of twodimensional flow is investigated. The present study has been undertaken to understand the effects of a magnetic field on mean velocities and turbulence parameters in turbulent 2-D channel flow. Several cases are considered. First laminar flow in a channel and MHD laminar channel flow are analyzed in order to validate model of magnetic field influence on electrically conducting fluid flow. Main part of the paper is focused on MHD turbulence suppression for 2-D turbulent flow in a channel and around the flat plate. The simulations are performed using ANSYS CFX software. Simulations results are obtained with BSL Reynolds stress model for turbulent and MHD turbulent flow around flat plate. The nature of the flow has been examined through distribution of mean velocities, turbulent fluctuations, vorticity, Reynolds stresses and turbulent kinetic energy.

Slip Effect on the MHD Channel Flow in the Presence of the Across Mass Transfer PHenomenon

Slip Effect on the MHD Channel Flow in the Presence of the Across Mass Transfer PHenomenon

Simulation and analysis of turbulent MHD channel flow with a streamwise magnetic field

AbstractWe perform large‐eddy simulations of turbulent MHD channel flow with a streamwise magnetic field using a pseudo spectral method. The streamwise magnetic field leads to turbulent drag reduction due to the selective Joule damping of certain flow structures. Near the walls, the turbulent mean velocity profile retains the logarithmic layer but the von Karman constant decreases with increasing magnetic field strength. In the outer region, the flow is characterized by persistent streaky structures of large streamwise extent, which lead to a rather flat mean velocity profile. In addition, the streamwise velocity fluctuations develop a pronounced second peak upon increasing the magnetic induction as well as a second logarithmic layer that increases in steepness. We find that Prandtl's classical mixing‐length model with a variable Kármán constant can describe the modified logarithmic layer reasonably accurately in a wide range of Reynolds and Hartmann numbers. However, the flow modification near the center of the channel is not properly captured by this approach. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Buoyancy Effects on Unsteady MHD Flow of a Reactive Third-Grade Fluid with Asymmetric Convective Cooling

This article examines the combined effects of buoyancy force and asymmetrical convective cooling on unsteady MHD channel flow and heat transfer characteristics of an incompressible, reactive, variable viscosity and electrically conducting third grade fluid. The chemical kinetics in the flow system is exothermic and the asymmetric convective heat transfers at the channel walls follow the Newton’s law of cooling. The coupled nonlinear partial differential equations governing the problem are derived and solved numerically using a semi-implicit finite difference scheme. Graphical results are presented and physical aspects of the problem are discussed with respect to various parameters embedded in the system.

Fundamental Study on a New Thin Oil-film Recovery Device Based on the MHD Method

The MHD maritime oil spill recovery method has many advantages in tackling the marine thin oil-film. The existing device, in which the MHD channel is arranged horizontally, can’t operate successfully under wave conditions and the oil and air bubbles can’t move through the MHD channel smoothly. A new method with the MHD channel arranged with a slight tilt angle is proposed to improve the effect of the thin oil-film recovery. In this paper, the hydrodynamic characteristics of the seawater and air two-phase flow under the action of electromagnetic force with the MHD channel arranged obliquely were studied numerically and the results show that the static pressure decreases gradually from the MHD channel's inlet to the outlet. The flow rate decreases slightly as the tilt angle increases. The pressure rise and the effective power increase slightly as the tilt angle increases.

数値計算によるパルスレーザー駆動MHD発電の基礎的検討

The behavior of a laser-supported detonation wave and the power generation performance in a laser-driven MHD generator which can be one of the candidates of space-based laser-to-electrical power converters are examined by a time-dependent one-dimensional numerical simulation. The electric power is generated through two modes attributed to 1) the propagation of detonation wave itself in the MHD channel and 2) the high temperature and pressure gas flow caused enough after the propagation of detonation wave. The fluid and plasma properties just behind the detonation wave are varied markedly owing to the strong Lorentz force under the applied magnetic field. The generator performance is comparable or superior to that in the conventional seeded plasma MHD generator, although the laser-driven MHD generator is supposed to be operated repetitively.

MHD Channel Flow with Skewed Applied Magnetic Induction Field

The effects of the constant applied magnetic field as a function of its angle with the channel walls is studied using finite elements. This is done for insulating channel walls and for two insulating and two conducting walls forming a short-circuited magnetohydrodynamic generator. The volumetric flow rate is kept constant by regulating the pressure gradient as a function of the applied magnetic induction angle. The necessary pressure gradient diminishes as the angle increases from 0 to 45 degrees because the electrical current flow diminishes. This paper affords a simple and quick method for solving MHD generator problems that defied solution for many years.

Computational analysis of 3D-flows in rocket produced H<SUB align="right">2/H<SUB align="right">2O plasma based MHD generators for space applications

In this paper, a study is presented in which the magnetohydrodynamic interactions have been analysed in Faraday connection generators, which show potential for space applications. The channel design of an extensively studied Sakhalin generator developed in the former USSR has been used and coupled with a cesium seeded liquid hydrogen and liquid oxygen combustion based chemical rocket. The CFD analysis of this design has been done using a program code based on multigrid algorithms for the solution of momentum and electrical equations. The code implements corrections in k-epsilon turbulence equations and for the calculations of transport properties of the plasma. The development of the secondary flows with complicated six vortex cells in the MHD channel has been analysed, which show agreement with a previous experimental study. Also, it has been shown that power output of the MHD generator could be significantly improved by changing the configuration of the MHD channel.

Entropy Generation Analysis in a Variable Viscosity MHD Channel Flow with Permeable Walls and Convective Heating

This paper examines the effects of the thermodynamic second law on steady flow of an incompressible variable viscosity electrically conducting fluid in a channel with permeable walls and convective surface boundary conditions. The nonlinear model governing equations are solved numerically using shooting quadrature. Numerical results of the velocity and temperature profiles are utilised to compute the entropy generation number and the Bejan number. The results revealed that entropy generation minimization can be achieved by appropriate combination of the regulated values of thermophysical parameters controlling the flow systems.

Acceleration Effect of Swirl Flow for Disk MHD Accelerator

The purpose of this study is to verify how the swirl vane influences the acceleration performance, namely, the radial gas velocity and the static gas pressure, for the Disk MHD accelerator. A quasi-1-dimensional (Q1D) numerical program is used for the calculations. Results of the current calculations show that the static gas pressure decreases approximately 40% when using the inlet swirl vane. It is found that the MHD compression phenomena, which generates at the closest to the MHD channel inlet due to the Joule heating, could suppress effectively. The maximum radial gas velocity of 3,380m/s is successfully achieved at the channel exit when swirl ratio was -1.0, and swirl ratio was set to be 0.0 and mass flow rate was kept the same as that for the case of swirl ratio of 1.0 and -1.0. The acceleration efficiency of 40.5% and 36.7% are calculated when the swirl ratio is -1.0, and the case of swirl ratio was set to be 0.0 and mass flow rate was kept the same as that for the case of swirl ratio of 1.0 and -1.0 respectively. The difference of efficiency is due to increase the Hall parameter in the upstream and midstream of MHD channel. This current study can show and confirm the function of inlet swirl for Disk MHD accelerator.