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  • 1
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    Observations of 13.5 micron rotation-vibration lines of SiS in IRC +10216 (1994)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: We report the first observations of the 13.5 micron fundamental band of SiS in the spectrum of the heavily obscured carbon star IRC +10216. The lines are formed in the inner region of the circumstellar envelope where the gas is accerlerating and where the temperature ranges from 800-500 K. We have carried out a detailed model of the observed line profiles. Our observations are best fit by a gradient in the abundance of SiS. We derive an abundance relative to molecular hydrogen of x(SiS) = 4.3 x 10(exp -6) at a distance of twelve stellar radii from the central star rising to x(SiS) = 4.3 x 10(exp -5) at a few stellar radii from the surface of the star.
    Keywords: ASTRONOMY
    Type: The Astrophysical Journal, Part 1 (ISSN 0004-637X); 420; 2; p. 863-868
    Format: text
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  • 2
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    PREDICTING TURBINE STAGE PERFORMANCE (1994)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: This program was developed to predict turbine stage performance taking into account the effects of complex passage geometries. The method uses a quasi-3D inviscid-flow analysis iteratively coupled to calculated losses so that changes in losses result in changes in the flow distribution. In this manner the effects of both the geometry on the flow distribution and the flow distribution on losses are accounted for. The flow may be subsonic or shock-free transonic. The blade row may be fixed or rotating, and the blades may be twisted and leaned. This program has been applied to axial and radial turbines, and is helpful in the analysis of mixed flow machines. This program is a combination of the flow analysis programs MERIDL and TSONIC coupled to the boundary layer program BLAYER. The subsonic flow solution is obtained by a finite difference, stream function analysis. Transonic blade-to-blade solutions are obtained using information from the finite difference, stream function solution with a reduced flow factor. Upstream and downstream flow variables may vary from hub to shroud and provision is made to correct for loss of stagnation pressure. Boundary layer analyses are made to determine profile and end-wall friction losses. Empirical loss models are used to account for incidence, secondary flow, disc windage, and clearance losses. The total losses are then used to calculate stator, rotor, and stage efficiency. This program is written in FORTRAN IV for batch execution and has been implemented on an IBM 370/3033 under TSS with a central memory requirement of approximately 4.5 Megs of 8 bit bytes. This program was developed in 1985.
    Keywords: AERODYNAMICS
    Type: LEW-14218
    Format: text
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  • 3
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    Three-dimensional Navier-Stokes heat transfer predictions for turbine blade rows (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Results are shown for a three-dimensional Navier-Stokes analysis of both the flow and the surface heat transfer for turbine applications. Heat transfer comparisons are made with the experimental shock-tunnel data of Dunn and Kim, and with the data of Blair for the rotor of the large scale rotating turbine. The analysis was done using the steady-state, three-dimensional, thin-layer Navier-Stokes code developed by Chima, which uses a multistage Runge-Kutta scheme with implicit residual smoothing. An algebraic mixing length turbulence model is used to calculate turbulent eddy viscosity. The variation in heat transfer due to variations in grid parameters is examined. The effects of rotation, tip clearance, and inlet boundary layer thickness variation on the predicted blade and endwall heat transfer are examined.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 92-3068
    Format: text
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  • 4
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    Analytic investigation of effect of end-wall contouring on stator performance (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Calculations show improved stator performance when the tip end wall was contoured so that the inlet area was greater than the exit area. Comparisons are made with previously published experimental data. The results of a parametric analysis of the effect contour geometry on the efficiency of a highly loaded axial stator are given. The maximum stator efficiency gain is about 0.8 percentage point, and this represents a 22 percent reduction in stator losses. The degree to which endwall contouring reduces the forces driving secondary flows was also examined. The driving forces for both cross channel and radial secondary flow were reduced.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1943 , E-719
    Format: application/pdf
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  • 5
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    Elusive Ethylene Detected in Saturns Northern Storm Region (2013)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: The massive eruption at 40 deg. N (planetographic latitude) on Saturn in 2010 December has produced significant and lasting effects in the northern hemisphere on temperature and species abundances. The northern storm region was observed on many occasions in 2011 by Cassini's Composite Infrared Spectrometer (CIRS). In 2011 May, temperatures in the stratosphere greater than 200 K were derived from CIRS spectra in the regions referred to as "beacons" (warm regions in the stratosphere). Ethylene has been detected in the beacon region in Saturn's northern storm region using CIRS. Ground-based observations using the high-resolution spectrometer Celeste on the McMath-Pierce Telescope on 2011 May 15 were used to confirm the detection and improve the altitude resolution in the retrieved profile. The derived ethylene profile from the CIRS data gives a C2H4 mole fraction of 5.9 +/- 4.5 x 10(exp -7) at 0.5 mbar, and from Celeste data it gives 2.7 +/- 0.45 x 10(exp -6) at 0.1 mbar. This is two orders of magnitude higher than the amount measured in the ultraviolet at other latitudes prior to the storm. It is also much higher than predicted by photochemical models, indicating that perhaps another production mechanism is required or a loss mechanism is being inhibited.
    Keywords: Lunar and Planetary Science and Exploration
    Type: GSFC-E-DAA-TN6335
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  • 6
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    An algebraic turbulence model for three-dimensional viscous flows (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: An algebraic turbulence model is proposed for use with three-dimensional Navier-Stokes analyses. It incorporates features of both the Baldwin-Lomax and Cebeci-Smith models. The Baldwin-Lomax model uses the maximum of a function f(v) to determine length and velocity scales. An analysis of the Baldwin-Lomax model shows that f(v) can have a spurious maximum close to the wall, causing numerical problems and non-physical results. The proposed model uses integral relations to determine delta(*) u(sub e) and delta used in the Cebeci-Smith mode. It eliminates a constant in the Baldwin-Lomax model and determines the two remaining constants by comparison to the Cebeci-Smith formulation. Pressure gradient effects, a new wake model, and the implementation of these features in a three-dimensional Navier-Stokes code are also described. Results are shown for a flat plate boundary layer, an annular turbine cascade, and endwall heat transfer in a linear turbine cascade. The heat transfer results agree well with experimental data which shows large variations in endwall Stanton number contours with Reynolds number.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 93-0083 , AIAA, Aerospace Sciences Meeting and Exhibit; Jan 11, 1993 - Jan 14, 1993; Reno, NV; United States|; 10 p.
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  • 7
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    Ethane's 12C/13C Ratio in Titan: Implications for Methane Replenishment (2009)
    In:  Other Sources
    Details
    Publication Date: 2019-07-19
    Description: As the .main destination of carbon in the destruction of methane in the atmosphere of Titan, ethane provides information about the carbon isotopic composition of the reservoir from which methane is replenished. If the amount of methane entering the atmosphere is presently equal to the amount converted to ethane, the 12C/13C ratio in ethane should be close to the ratio in the reservoir. We have measured the 12C/13C ratio in ethane both with Cassini CIRS(exp 1) and from the ground and find that it is very close to the telluric standard and outer planet values (89), consistent with a primordial origin for the methane reservoir. The lower 12C/13C ratio measured for methane by Huygens GCMS (82.3) can be explained if the conversion of CH4 to CH3 (and C2H6) favors 12C over 13C with a carbon kinetic isotope effect of 1.08. The time required for the atmospheric methane to reach equilibrium, i.e., for replenishment to equal destruction, is approximately 5 methane atmospheric lifetimes.
    Keywords: Lunar and Planetary Science and Exploration
    Type: 09-RC-219-AAS-DPS , 41st Annual Meeting of the AAS Division for Planetary Sciences; Oct 04, 2009 - Oct 09, 2009; Fajardo; Puerto Rico
    Format: text
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