[en] This paper presents an investigation of the effect of ionization instability on effective conductivity and power output of an MHD generator in the presence of velocity/temperature boundary layer. Analysis is based on a phenomenological approach. It is concluded that the ratio of power output (in the presence of ionization instability) to the power output (without ionization instability) increases with an increase in the boundary layer thickness. Effective conductivity and power output both are found to decrease with the increasing magnetic field. (author)

No abstract available

[en] Quasi three-dimensional analysis is made to estimate effects of applied current parallel to magnetic field on the characteristics of nonequilibrium Faraday MHD generator. Potassium-seeded argon plasma at 1500 K and 10 atm is assumed. Resistive power-extraction electrode is taken into account to reduce the current concentration phenomena occurring at electrode edges. The applied current parallel to magnetic field enlarges the stable region free from ionization instability. The net output power exceeds the power obtained for the case of no applied current in the limited ranges of applied current and Hall parameter. The resistive power-extraction electrode is useful to successfully prevent the applied current from short-circuiting along the electrode surface. (author)

[en] Earlier experiments on use of gas wall-jets as a means of reducing shunt current losses and liquid metal boundary layers are critically reevaluated. A number of new liquid-metal MHD (LMMHD) generator experiments, with and without gas wall injection, were performed and analyzed. Experimental visualization of air wall injection in water revealed jet behavior under different pressure gradients. A gas wall-jet can separate liquid from the walls only under positive pressure gradient conditions. The basic physical cause of the inability to prevent wetting of walls under a negative pressure gradient is absence of a force that would repulse liquid from walls, such as exist, for example, in film boiling or in electromagnetic confinement. (author)

[en] This paper presents an investigation of the effect of thermal diffusion of charge carriers on the electron density in a nonequilibrium MHD generator. The source of diffusion in the inhomogeneity in the background temperature and/or the nonuniform heating of electrons across the MHD channel cross section on account of the velocity boundary layer. The continuity equation of electrons has been solved in conjunction with the diffusion velocity equation to obtain the steady state electron density distribution in an MHD generator. As a result of diffusion, the electron density is found to increase with the distance from the channel axis, while the reverse is predicted from the assumption of local equilibrium. Further, it is seen that the increase in the values of Hall parameter, boundary layer thickness and the flow velocity enhances the effect of diffusion. Decrease in the wall temperature is also found to have a similiar effect. The diffusion of the carriers is most prominent in the segmented geometry. It is concluded that overall electron density gets enhanced if recombination and diffusion times are of the same order. (author)

[en] Simplified formulae were derived for the approximate evaluation of electrical performances of an MHD generator with nonuniform equilibrium plasma. In order to clarify the effectiveness of the properly shaped nonuniform magnetic induction of the type B varies as nsub(e), the transverse component Bsub(y) was included in the formulation of the theory. It was shown that the terminal characteristics of the generator, such as the internal resistance, the motional emf, the current and the output power could be improved significantly under the shaped Bsub(z) varies as nsub(e) type of applied magnetic induction for wide ranges of electrode- and insulator wall temperatures, channel sizes and averaged intensities of the magnetic induction. (author)

[en] MHD generator performance predictions require an accurate determination of the voltage losses in the channel; however, most techniques for determining these losses need substantial calculations and/or computer storage space. This paper proposes a simplified method for calculating the ohmic boundary layer contribution to the overall voltage losses. Voltage drop regions are discussed and a description of the turbulent boundary layer contribution is derived. Appropriate simplifying assumptions on the basic transport and MHD concepts are used to express the conductivity as a function of temperature only. Weighting functions for averaging the resistivity in turbulent boundary layers are determined and the nature of these functions is presented. The results are compared with more precise descriptions and with experimental results. (author)

[en] A dynamic power-flow simulation of an overall magnetohydrodynamic (MHD)/steam electrical power generating plant is developed. Time domain solutions to the set of system equations are given. Several control configurations are applied to the system and their effects on system dynamic response are presented. The overall combined-cycle system model utilizes an input-output characterization of the Combustor/Nozzle/Channel/Diffuser. This characterization is developed from polynomial approximations of data resulting from the solutions of energy balance, state, and continuity equations for the combustor and the quasi one-dimensional MHD equations for the nozzle, channel and diffuser. The boiler and turbine valve model has turbine valve area and power available to generate steam as inputs, and throttle pressure, power to the turbines, and boiler and stack losses as outputs. Regenerative air preheater cycling is also modeled, and the effect of cycling on plant output is given. (author)

[en] A brief description of the two-phase liquid-metal MHD power generation cycle and its advantages is provided. The importance of good interfacial liquid to gas heat transfer is discussed, and data confirming that satisfactory heat transfer is indeed achieved in an experimental generator are presented. An expression for the effect of the velocity difference between the gas and the liquid on generator performance is derived. An equivalent turbine efficiency is defined to characterize the generator as part of a heat engine and related to experimental data. (author)

[en] This paper presents an investigation of the effect of boundary layer on the ionization instability in non-equilibrium MHD plasmas: the Boltzmann transfer equation has been employed in the analysis. It is concluded that the effect of finite boundary layer thickness is to reduce the growth rate. Moreover, the growth rate is not constant across the channel cross-section: it is maximum on the axis and decreases away from the axis. These effects are more pronounced at higher Hall parameters. Further, it is shown that the effect of changing the flow velocity of the gas on the growth rate is more important than the effect of changing the wall temperature. (author)