Isothermal Representation Research Articles

Experimental and Computational Study of Hybrid Diffusers for Gas Turbine Combustors

The increasing radial depth of modern combustors poses a particularly difficult aerodynamic challenge for the pre-diffuser. Conventional diffuser systems have a finite limit to the diffusion that can be achieved in a given length and it is, therefore, necessary for designers to consider more radical and unconventional diffuser configurations. This paper will report on one such unconventional diffuser; the hybrid diffuser which, under the action of bleed, has been shown to achieve high rates of diffusion in relatively short lengths. However, previous studies have not been conducted under representative conditions and have failed to provide a complete description of the relevant flow mechanisms making optimization difficult. Utilizing an isothermal representation of a modern gas turbine combustor an experimental investigation was undertaken to study the performance of a hybrid diffuser compared to that of a conventional, single-passage, dump diffuser system. The hybrid diffuser achieved a 53% increase in area ratio within the same axial length generating a 13% increase in the pre-diffuser static pressure recovery coefficient which, in turn, produced a 25% reduction in the combustor feed annulus total pressure loss coefficient. A computational investigation was also undertaken in order to investigate the governing flow mechanisms. A detailed examination of the flow field, including an analysis of the terms within the momentum equation, demonstrated that the controlling flow mechanisms were not simply a boundary layer bleed but involve a more complex interaction between the accelerating bleed flow and the diffusing mainstream flow. A greater understanding of these mechanisms enabled a more practical design of hybrid diffuser to be developed that not only simplified the geometry but also improved the quality of the bleed air making it more attractive for use in component cooling.

Uptake of Elemental Mercury Vapors by Activated Carbons.

The adsorptive capacities of virgin and sulfur-impregnated activated carbons (GAC) for gas-phase mercury were evaluated as a function of temperature and influent mercury concentration. The virgin activated carbon showed little adsorptive capacity, especially at temperatures above 90 °C. The isothermal representation of the adsorptive capacity for virgin GAC exhibited a semi-logarithmic relationship at 50 °C, 90 °C, and 140 °C. The pronounced effect of temperature on the adsorptive capacity evidences a physical adsorption mechanism between the mercury and virgin GAC. Sulfur-impregnated activated carbons exhibited enhanced mercury removal efficiency over the non-impregnated varieties, due to formation of mercuric sulfide on the carbon surface. This chemisorption process is enhanced by increased temperatures between 25 °C and 90 °C, yielding increased removal efficiency of elemental mercury. However, at 140 °C a decrease in adsorptive capacity occurs, indicating reduced formation of mercuric sulfide. The method used for impregnating GAC with sulfur had a pronounced effect on mercury removal capacity. The chemical bonding of sulfur at 600 °C provides a more uniform distribution of sulfur throughout the GAC pore structure than is achieved by conventional condensation techniques, yielding improved performance.

Stability Fields in the System MnMoO and Thermochemical Data of Mn2Mo3O8 and MnMoO4

AbstractThe decomposition of MnMoO4 and Mn2Mo3O8 has been investigated by modified TG measurements in a controlled oxygen atmosphere. From the results the μ‐x phase diagram of the system MnMoO in an isothermal representation has been obtained. The following thermochemical data have been evaluated: .

Surfaces with Isothermal Representation of Their Lines of Curvature as Envelopes of Rolling

Surfaces with Isothermal Representation of Their Lines of Curvature as Envelopes of Rolling

Surfaces with Isothermal Representation of their Lines of Curvature and their Transformations: (Second Memoir)

Surfaces with Isothermal Representation of their Lines of Curvature and their Transformations: (Second Memoir)

Surfaces with isothermal representation of their lines of curvature and their transformations. II

Surfaces with isothermal representation of their lines of curvature and their transformations. II

Surfaces with Isothermal Representation of Their Lines of Curvature and Their Transformations

Surfaces with Isothermal Representation of Their Lines of Curvature and Their Transformations

Surfaces with isothermal representation of their lines of curvature and their transformations

IN a former lnemoir with the same title t we established a transformation of surfaces with isothermal spherical representation of their lines of curvature into surfaces of the same kind, the transformation being such that lines of curvature on a surface and on a transform correspond, and the two surfaces constitute the envelope of a two-parameter family of spheres. This transformation was established by means of a theorem of MOUTARD, concerning partial differential equations of the LAPLACE type with equal invariants, q and with the aid of a transformation o£ minimal stlrfaces discovered by THYBAUT. § In our discussioll we did not take the equations of the transformation in the form given by THY:}JAUT, but in the form used by BIANCE[I,II in which case the parametric curves on the lninimal surfaces are the asymptotic lines. Such a tninimal surfaca and its THYBAUT transform are the focal sheets of a W-congruence, that is, a corlgruence upon whose focal sheets the asylnptotic lines correspond. The present paper deals with the same transformations obtained by a very diSerent method as a result of which the analysis is much simpler. In §1 it is shown that when the lines of a W-congruence are subjected to the LIE line-sphere transformatioll, the congruence of spheres envelope two surfaces upon which the lines of curvature correspond. If S and S1 denote these two surfaces and E and EI the two focal sheets of the original F-congrtlence the transformatiq frotn E; to E1 carries with it a transformation from S to S1 without quadrature. In §1 is determined the characteristic property which E must have ill order that the lines of curvature on aS may have isothermal spherical representation and the equations of the surfaces are given in simple form. Ill § 2 the determination of