Replaceable blade turbine and stationary specimen corrosion testing facility

A facility was constructed to provide relatively low cost testing of hot section turbine blade and vane materials under hot corrosion conditions more akin to service environments. The facility consists of a small combustor whose pressurized gas flow can be directed to either a test section consisting of three small cascaded specimens or to a partial admittance single-stage axial flow turbine. The turbine rotor contains 28 replaceable turbine blades. The combustion gases resulting from the burning of Jet A-l fuel can be seeded with measured amounts of alkali salts. This facility is described here along with preliminary corrosion test results obtained during the final checkout of the facility

Material response from Mach 0.3 burner rig combustion of a coal-oil mixture

Wedge shaped specimens were exposed to the combustion gases of a Mach 0.3 burner rig fueled with a mixture of 40 weight percent micron size coal particles dispersed in No. 2 fuel oil. Exposure temperature was about 900 C and the test duration was about 44 one hour cycles. The alloys tested were the nickel base superalloys, IN-100, U-700 and IN-792, and the cobalt base superalloy, Mar-M509. The deposits on the specimens were analyzed and the extent of corrosion/erosion was measured. The chemical compositions of the deposits were compared with the predictions from an equilibrium thermodynamic analysis. The experimental results were in very good agreement with the predictions

Enamel fluorosis in rat’s incisor: S.E.M. and T.E.M. investigation

Findings on the alterations taking place in the enamel have demonstrated that they are generally caused by a daily use of highly fluoritic drinking waters.According to that, the Authors have carried out an ultrastructural study on lower incisors of albino rats after administering for 60 days water with a fluorine concentration five times the normal one.The samples, studied under the S.E.M., showed a general slowing of both the deposition and the maturation phase as well as the presence of some hypomineralized areas even after eruption.All this suggested the possibility that the damages observed were not due to the direct effect of fluorine on the enamel, but to the interaction between fluorine and ameloblasts.The Authors have then carried out an ultrastructural study on the enamel organ using the S.E.M.The results showed the presence of a well-evident endoplasmic reticulum, the lack in dense granules during the secretion phase, the lack in ruffle ended webs during the modulation phase, and the mitochondrial damage in the ameloblast.All this could justify the slowing of the enamel mineralization caused by fluorine effect on the ameloblasts.Il a été démontré que des altérations de l’émail sont généralement dues à l’absorption quotidienne d’eaux de boissons riches en fluor.Les auteurs ont entrepris une étude ultrastructurale des incisives inférieures du rat ayant reçu pendant 60 jours de l’eau dont la concentration en fluor est 5 fois supérieure à la normale.Les échantillons étudiés en microscopie électronique à balayage ont montré un ralentissement global de la déposition et de la phase de maturation ainsi que la présence de territoires hypominéralisés même après l’éruption.Toutes ces constatations suggèrent la possibilité que les dommages observés ne sont pas dus à l’effet direct du fluor sur l’émail, mais aux interactions entre le fluor et les améloblastes.Les auteurs ont mené une étude ultrastructurale de l’émail en utilisant le microscope électronique à balayage.Les résultats ont montré la présence d’un réticulum endoplasmique bien apparent, l’absence de grains denses au cours de la phase secrétoire, l’absence d’extrémités membranaires rugueuses au cours de la phase de modulation, et des altérations des mitochondries dans les améloblastes.Toutes ces constatations pourraient expliquer le ralentissement de la minéralisation de l’émail causé par les effets du fluor sur les améloblastes

The outer filament of Centaurus A as seen by MUSE

We investigate signatures of a jet-interstellar medium (ISM) interaction using optical integral-field observations of the so-called outer filament near Centaurus A, expanding on previous results obtained on a more limited area. Using the Multi Unit Spectroscopic Explorer (MUSE) on the VLT during science verification, we observed a significant fraction of the brighter emitting gas across the outer filament. The ionized gas shows complex morphology with compact blobs, arc-like structures and diffuse emission. Based on the kinematics, we identified three main components. The more collimated component is oriented along the direction of the radio jet. The other two components exhibit diffuse morphology together with arc-like structures also oriented along the radio jet direction. Furthermore, the ionization level of the gas is found to decrease from the more collimated component to the more diffuse components. The morphology and velocities of the more collimated component confirm our earlier results that the outer filament and the nearby HI cloud are likely partially shaped by the lateral expansion of the jet. The arc-like structures embedded within the two remaining components are the clearest evidence of a smooth jet-ISM interaction along the jet direction. This suggests that, although poorly collimated, the radio jet is still active and has an impact on the surrounding gas. This result indicates that the effect on the ISM of even low-power radio jets should be considered when studying the influence Active Galactic Nuclei can have on their host galaxy.Comment: 5 pages, 3 figures, Accepted for publication by A&

Static friction on the fly: velocity depinning transitions of lubricants in motion

The dragging velocity of a model solid lubricant confined between sliding periodic substrates exhibits a phase transition between two regimes, respectively with quantized and with continuous lubricant center-of-mass velocity. The transition, occurring for increasing external driving force F_ext acting on the lubricant, displays a large hysteresis, and has the features of depinning transitions in static friction, only taking place on the fly. Although different in nature, this phenomenon appears isomorphic to a static Aubry depinning transition in a Frenkel-Kontorova model, the role of particles now taken by the moving kinks of the lubricant-substrate interface. We suggest a possible realization in 2D optical lattice experiments.Comment: 5 pages, 4 figures, revtex, in print in Phys. Rev. Let

The effects of trace impurities in coal-derived liquid fuels on deposition and accelerated high temperature corrosion of cast superalloys

The effects of trace metal impurities in coal-derived liquids on deposition, high temperature corrosion and fouling were examined. Alloys were burner rig tested from 800 to 1100 C and corrosion was evaluated as a function of potential impurities. Actual and doped fuel test were used to define an empirical life prediction equation. An evaluation of inhibitors to reduce or eliminate accelerated corrosion was made. Barium and strontium were found to limit attack. Intermittent application of the inhibitors or silicon additions were found to be effective techniques for controlling deposition without losing the inhibitor benefits. A computer program was used to predict the dew points and compositions of deposits. These predictions were confirmed in deposition test. The potential for such deposits to plug cooling holes of turbine airfoils was evaluated. Tests indicated that, while a potential problem exists, it strongly depended on minor impurity variations

Theoretical and experimental studies of the deposition of Na2So4 from seeded combustion gases

Flames in a Mach 0.3 atmospheric pressure laboratory burner rig were doped with sea salt, NaS04, and NaCl, respectively, in an effort to validate theoretical dew point predictions made by a local thermochemical equilibrium (LTCE) method of predicting condensation temperatures of sodium sulfate in flame environments. Deposits were collected on cylindrical platinum targets placed in the combustion products, and the deposition was studied as a function of collector temperature. Experimental deposition onset temperatures checked within experimental error with LTCE-predicted temperatures. A multicomponent mass transfer equation was developed to predict the rate of deposition of Na2SO4(c) via vapor transport at temperatures below the deposition onset temperature. Agreement between maximum deposition rates predicted by this chemically frozen boundary layer (CFBL) theory and those obtained in the seeded laboratory burner experiments is good