No abstract available

No abstract available

[en] The present invention is directed to a method for determining, by a condensation method, the vapor pressure of a material with a known vapor pressure versus temperature characteristic, in a flow system particularly in a mercury isotope enrichment process. 2 figures

[en] A staircase electrode-wall configuration for a mhd generator which uses fluid dynamic means to protect the electrodes from substantial damage due to arcing and chemical attack. The electrode walls of a mhd generator duct have periodic conductor/insulator elements where channel divergence or convergence is accomplished in a stepwise fashion. The electrode is situated within the insulator of each element to be backwardfacing so as not to be directly exposed to the hot gas flow. The turbulence which exists at the backward-facing electrode moves the arc spot about the surface to prevent severe local damage. Chemical attack is inhibited by a laminated electrode surface of a low corrosive material and the turbulence which aids in cooling the electrode face. Additional cooling may be obtained by a purge jet at the electrode face

[en] The anode sheath of a medium density discharge from plane electrodes is formulated. The plasma is assumed to be describable by the steady, one-dimensional species continuity and Poisson equations under constant properties. A single, highly non-linear equation for the electric field at the sheath is obtained. This equation is studied in terms of a testing function which is an educated guess for the electric field distribution. Testing functions meet the conditions of the problem only to a limited extent. Their importance lies in the fact that they afford quick, largely non-numerical solutions of some validity. The particular testing function proposed yields a set of electron and ion distributions which in turn determine the charge species generation at the sheath. The numbers are worked out for nitrogen and reasonable results are obtained with a monotonically decreasing profile as the E-field moves away from the anode. The resulting electron and ion profiles are also reasonable and the reactivity in the sheath is then found. It turns out that for sufficiently low currents and for two body recombination, the nitrogen results are realistic. It is anticipated that such testing function analysis will help establish criteria for conditions under which anode constriction takes place

[en] This paper reports that solutions to the anode sheath problem have been studied for the case where the electron and plasma temperature is constant and equal. The planar geometry description of steady, low-temperature collisional plasmas permits certain simplifications to the species continuity equations whereby a single, highly nonlinear equation is obtained for the entire region disturbed by the electrode. This equation is given in terms of the electric field and a variable representing the currents. The authors' formulation includes charged-particle production with a net current flow. Solutions are generated with a nontrivial analytic expression for the electric field of the form: E(y) = E_∞ exp {A/(y + a)²}, where a, A and E_∞ are shape factors. Defects in the approximation can be minimized by identifying the coefficients for the net production of charges a posteriori, thereby yielding largely non-numerical solutions of some validity

[en] Inherent in any lasing process involving three or more energy levels is the release of heat. The heat is the inefficiency implied in the definition of laser quantum efficiency. In supersonic flow the heat release causes compression waves and a wake, thereby perturbing the gas density. Gas density variations within the laser cavity degrade the beam quality. A comprehensive analysis was made using an extension of the Tsien-Beilock linearized solution for heat addition. A computer program has been developed which incorporates multiple wall reflections, arbitrary beam cross section, and finite kinetics for the transition from the lower laser level to the ground state. Several examples are discussed

[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] Anodes display either a glow mode or a constricted mode in plasmas of interest for MHD generator applications. The purpose of this paper is to outline the conditions underlying the existence of anode constrictions or anode spots in conjunction with criteria governing the anode glow. A steady current flowing through velocity and thermal boundary layers is investigated. The sheath and the ambipolar region are considered from an approximation theory viewpoint, and then the nonexistence of a one-dimensional Cartesian or diffuse mode for a nonreacting anode region is shown using the continuum equations for electrostatic probes

[en] Voltage drops associated with the collisional sheath of nonemitting, MHD electrodes are investigated. The problem is described by a set of coupled nonlinear partial differential equations which are solved by finite differencing in a computer. The sheath and ambipolar regions form in a self-consistent way obviating the need to match boundaries. A two-dimensional model with periodic active sites on a flat plate is used. The current constricts at these sites in order to satisfy the controlling equations for frozen charge flow. The effects of a magnetic field as well as of Joule heating are included in the model; convection can be shown to be negligible in the sheath. Joule heating is assumed to have no effect on the bulk temperature of the gas. Changes in the current-voltage characteristics due to Joule heating are small since the effect is extremely localized; the presence of a magnetic field has a slight influence on the size of the sheath but alters noticeably the current-voltage characteristics