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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Investigation of the tip clearance flow inside and at the exit of a compressor rotor passage. II - Turbulence properties

The flow in the tip clearance region of a compressor rotor is highly turbulent due to the strong interaction of the leakage flow with the annulus wall boundary layer. This paper deals with the turbulence properties of the flow in the tip clearance region of a moderately loaded compressor rotor. The experimental results reported in this paper were obtained using a two-sensor hot-wire probe in combination with an ensemble averaging technique. Blade-to-blade distribution of the axial and tangential turbulence intensities at various radial locations and ten axial locations (four inside the blade passage and the remaining six outside the passage) were derived from this data. Isointensity contours in the clearance region at various radial locations were also obtained from the experimental data. A region of very high turbulence intensities was indicated at the half-chord location from these results. The turbulence intensity profiles also indicated that the leakage flow travels toward the midpassage before rolling up. The turbulence is almost isotropic beyond three-quarter chord downstream of the trailing edge.

Pandya, A.↗
NASA NTRS1983

Analysis of coolant entrance boundary shape of porous region to control cooling along exit boundary

A cooled porous region has a plane surface exposed to a specified spatially varying heat flux. The coolant leaves the region through this surface, and it is desired to control the flow distribution to maintain a specified uniform surface temperature. This is accomplished by having the coolant entrance surface shaped to provide in the region the necessary variation of path length and, hence, flow resistance. The surface shape at the coolant entrance is found by solving a Cauchy boundary value problem. An exact solution is obtained that will deal with a wide variety of heating distributions for both two- and three-dimensional shapes.

Siegel, R.↗
NASA NTRS1984

Shape of porous region to control cooling along curved exit boundary

A cooled porous insert in a curved wall has a specified spatially varying heat flux applied to one side. It is desired to control the distribution of coolant flow out through this curved surface so that the surface will be kept at a desired uniform temperature. The flow regulation is accomplished by shaping the surface through which the coolant enters the region to obtain the required variation of flow resistance within the region. The proper surface shape is found by solving a Cauchy boundary value problem. Analytical solutions are given in two dimensions for various shapes of the heated boundary subjected to different heating distributions.

Siegel, R.↗
NASA NTRS1987

Directional thermal infrared exitance distributions of a deciduous forest in summer

Directional measurements of effective radiant temperatures (ERT) were made from a rotating mount suspended above an Oak-Hickory canopy. A directional ERT distribution is presented showing fairly weak trends with view angle. Additional data are presented to illustrate the character of spatial variations of ERT as a function of view and sun angle.

Balick, Lee K.↗
NASA NTRS1988

Non-intrusive Space Shuttle Main Engine nozzle exit diagnostics

The results of a conceptual design study on the feasibility of nonintrusive optical diagnostics have shown that UV laser-excited Raman scattering can furnish reliable and accurate temperature and multiple-species data for the Space Shuttle Main Engine's exhaust flow. Enhanced OH flow tagging by UV photodissociation of H2O was used in velocity measurements; a time-delayed pulsed dye laser beam at 308 nm excites fluorescence from OH, and the location of the convected enhanced OH zone is measured with an optical multichannel detector.

Shirley, John A.↗
NASA NTRS1990

Ground impingement of supersonic jets from nozzles with various exit geometries

Aerodynamc and acoustic measurements of single and twin free and impinging jets were made for circular convergent and CD nozzles, rectangular CD nozzles, and D-shaped convergent nozzles. Measured shock cell lengths and screech tone frequencies compare well with existing theory. Noise due to jet impingement correlates on the basis of the nozzle-to-ground distance relative to the free jet shock structure, with the highest sound pressure levels generally due to jet impingement tones. All nozzle types experienced near-field OASPL of 160 dB at some nozzle-to-ground distances, including the CD nozzles operating at their design pressure. The effect of the second jet was to sometimes increase levels due to twin jet resonance and at other times reduce levels due either to suppression of the screech/impingement feedback process or more simply by acoustic interference of the noise produced by the two jets.

Norum, Thomas D.↗
NASA NTRS1991

Converged three-dimensional quantum mechanical reaction probabilities for the F + H2 reaction on a potential energy surface with realistic entrance and exit channels and comparisons to results for three other surfaces

Accurate three-dimensional quantum mechanical reaction probabilities are presented for the reaction F + H2 yields HF + H on the new global potential energy surface 5SEC for total angular momentum J = 0 over a range of translational energies from 0.15 to 4.6 kcal/mol. It is found that the v-prime = 3 HF vibrational product state has a threshold as low as for v-prime = 2.

Lynch, Gillian C.↗
NASA NTRS1991

Anisotropy of thermal infrared exitance above and within plant canopies

Any significant angular dependence of the emitted long wave radiation could result in errors in remotely estimated energy budgets or evapotranspiration. Empirical data and thermal infrared radiation models are reviewed in reference to anisotropic emissions from the plant canopy. The biometeorological aspects of linking longwave models with plant canopy energy budgets and micrometeorology are discussed. A new soil plant atmosphere model applied to anisotropic longwave emissions from a canopy is presented. Time variation of thermal infrared emission measurements is discussed.

Pawu, Kyaw Tha↗
NASA NTRS1992

Runway exit designs for capacity improvement demonstrations. Phase 2: Computer model development

The development is described of a computer simulation/optimization model to: (1) estimate the optimal locations of existing and proposed runway turnoffs; and (2) estimate the geometric design requirements associated with newly developed high speed turnoffs. The model described, named REDIM 2.0, represents a stand alone application to be used by airport planners, designers, and researchers alike to estimate optimal turnoff locations. The main procedures are described in detail which are implemented in the software package and possible applications are illustrated when using 6 major runway scenarios. The main output of the computer program is the estimation of the weighted average runway occupancy time for a user defined aircraft population. Also, the location and geometric characteristics of each turnoff are provided to the user.

Trani, A. A.↗
NASA NTRS1991

Calculating satellite umbra/penumbra entry and exit positions and times

The problem of calculating earth satellite entry/exit positions and times through the earth's umbra and penumbra for elliptical satellite orbits is solved in closed form; i.e., without iteration, by reducing the problem to that of finding the roots of a quartic polynomial in a cartesian coordinate. Typical results from an algorithm constructed from the method are shown.

Mullins, Larry D.↗
NASA NTRS1992

The effects of nozzle exit geometry on forebody vortex control using blowing

An experimental study has been undertaken to examine the influence of the blowing jet geometry on the effectiveness of the aft blowing technique for forebody vortex control. The experiments were conducted with a 3.0 tangent caliber ogive model at subsonic, laminar flow conditions. Asymmetric aft blowing was accomplished using both a single nozzle and a double nozzle configuration. Detailed surface pressure measurements on the model were obtained. The experimental results show that the height and the width of the blowing jet are important parameters that determine the effectiveness of aft blowing; a broad, lowly positioned blowing jet is found to be most effective for the forebody vortex control technique using aft blowing.

Gittner, Nathan M.↗
NASA NTRS1993

Statistical modeling of capture, association, and exit-channel dynamics in the CH3(+)/CH3CN system

The ion-molecule CH3(+) + CH3CN reaction is presently modeled by means of a master equation treatment incorporating weak collisions. The parameter required for the Rice-Ramsberger-Kassel-Markus (RRKM) treatment is derived from an ab initio investigation of the energy surface in question, and a means of including the capture rate coefficients in the RRKM approach is developed in which only the hindered dipole rotation is coupled in the reaction coordinate at large separations. Unimolecular rate coefficients for the (CH3CNCH3+)-activated complex are calculated for all product channels in the 300-600 K temperature range.

Smith, S. C.↗
NASA NTRS1993

EXITE observation of the Galactic center - A new transient?

The balloon-borne Energetic X-ray Imaging Telescope Experiment observed the Galactic center on May 9, 1989. Within the 3.4-deg (FWHM) field of view, imaged with 22-arcmin resolution at 20-250 keV, two sources were detected: the 'Einstein source' (1E1740.7-2942) and a possible second source about 40 deg West (EXS1737.9-2952). This source was detected significantly at both 20-30 keV and 83-111 keV, suggesting a double-backscattered 511 keV line source at 102 keV and a soft excess, perhaps from a black hole candidate undergoing a transient outburst.

Grindlay, J. E.↗