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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2010

Coaxial Propellant Injectors With Faceplate Annulus Control

An improved design concept for coaxial propellant injectors for a rocket engine (or perhaps for a non-rocket combustion chamber) offers advantages of greater robustness, less complexity, fewer parts, lower cost, and less bulk, relative to prior injectors of equivalent functionality. This design concept is particularly well suited to small, tight-tolerance injectors, for which prior designs are not suitable because the practical implementation of those designs entails very high costs and difficulty in adhering to the tolerances.

Horn, Mark D.↗
NASA NTRS2006

Method and apparatus for a substantially coaxial injector element

A system to provide a two piece robust fluid injector. According to various embodiments, the fluid injector is a fuel injector for a combustion engine. The injector includes two coaxially formed annuluses. One annulus is formed in a face plate and the second annulus or hole is defined by a tube extending through the face plate. The tube extends through the face plate in a portion of a through bore which also is used to define the second annulus. The second annulus is formed using a throughbore through which the tube extends. This allows the second annulus to always be formed inherently and precisely substantially coaxial with the first annulus. Moreover, the second annulus can be formed with a much greater tolerance than if other independent components needed to be added.

Horn, Mark D.↗
NASA NTRS2003

An evaluation of the use of new Doppler methods for detecting longitudinal function abnormalities in a pacing-induced heart failure model

BACKGROUND: Doppler tissue echocardiography and color M-mode Doppler flow propagation velocity have proven useful in evaluating cross-sections of patients with left ventricular (LV) dysfunction, but experience with serial changes is limited. Purpose and methods: We tested their use by evaluating the temporal changes of LV function in a pacing-induced congestive heart failure model. Rapid ventricular pacing was initiated and maintained in 20 dogs for 4 weeks. Echocardiography was performed at baseline and weekly during brief pacing cessation. RESULTS: With rapid pacing, LV volume significantly increased and ejection fraction (57%-28%), stroke volume (37-18 mL), and mitral annulus systolic velocity (16.1-6.6 cm/s) by Doppler tissue echocardiography significantly decreased, with ejection fraction and mitral annulus systolic velocity closely correlated (r = 0.706, P <.0001). In contrast to the mitral inflow velocities, mitral annulus early diastolic velocity decreased steadily (12.3-7.3 cm/s) resulting in a dramatic decrease in mitral annulus early/late (1.22-0.57) diastolic velocity with no tendency toward pseudonormalization. The color M-mode Doppler flow propagation velocity also showed significant steady decrease (57-24 cm/s) throughout the pacing period. Multiple regression analysis chose mitral annulus systolic velocity (r = 0.895, P <.0001) and propagation velocity (r = 0.782, P <.0001) for the most important factor predicting LV systolic and diastolic function, respectively. CONCLUSIONS: Doppler tissue echocardiography and color M-mode Doppler flow could evaluate the serial deterioration in LV dysfunction throughout the pacing period. These were more useful in quantifying progressive LV dysfunction than conventional ehocardiographic techniques, and were probably relatively independent of preload. These techniques could be suitable for longitudinal evaluation in addition to the cross-sectional study.

Evaluation Studies↗
NASA NTRS1988

Duct flow nonuniformities: Effect of struts in SSME HGM II(+)

A numerical study, using the INS3D flow solver, of laminar and turbulent flow around a two dimensional strut, and three dimensional flow around a strut in an annulus is presented. A multi-block procedure was used to calculate two dimensional laminar flow around two struts in parallel, with each strut represented by one computational block. Single block calculations were performed for turbulent flow around a two dimensional strut, using a Baldwin-Lomax turbulence model to parameterize the turbulent shear stresses. A modified Baldwin-Lomax model was applied to the case of a three dimensional strut in an annulus. The results displayed the essential features of wing-body flows, including the presence of a horseshoe vortex system at the junction of the strut and the lower annulus surface. A similar system was observed at the upper annulus surface. The test geometries discussed were useful in developing the capability to perform multiblock calculations, and to simulate turbulent flow around obstructions located between curved walls. Both of these skills will be necessary to model the three dimensional flow in the strut assembly of the SSME. Work is now in progress on performing a three dimensional two block turbulent calculation of the flow in the turnaround duct (TAD) and strut/fuel bowl juncture region.

Burke, Roger↗
NASA NTRS1991

GEOSIM: A numerical model for geophysical fluid flow simulation

A numerical model which simulates geophysical fluid flow in a wide range of problems is described in detail, and comparisons of some of the model's results are made with previous experimental and numerical studies. The model is based upon the Boussinesq Navier-Stokes equations in spherical coordinates, which can be reduced to a cylindrical system when latitudinal walls are used near the pole and the ratio of latitudinal length to the radius of the sphere is small. The equations are approximated by finite differences in the meridional plane and spectral decomposition in the azimuthal direction. The user can specify a variety of boundary and initial conditions, and there are five different spectral truncation options. The results of five validation cases are presented: (1) the transition between axisymmetric flow and baroclinic wave flow in the side heated annulus; (2) the steady baroclinic wave of the side heated annulus; (3) the wave amplitude vacillation of the side heated annulus; (4) transition to baroclinic wave flow in a bottom heated annulus; and (5) the Spacelab Geophysical Fluid Flow Cell (spherical) experiment.

Butler, Karen A.↗
NASA NTRS1950

Simulated altitude performance of two annular combustors with continuous axial openings for admission of primary air

Methods of introducing and distributing air and fuel in turbojet-engine combustors were evaluated with two fuels, AN-F-32 and AN-F-58. Investigations were made with two single-annulus liners in a one-quarter sector of a 25 1/2-inch-diameter turbojet combustor. Altitude performance data for these combustors are compared with existing data for a production-model double-annulus combustor. Altitude operating limits and combustion efficiencies of both single-annulus combustors were considerably higher than those of the double-annulus combustor; combustion efficiencies were insensitive to changes in fuel-air ratio.

COMBUSTION - TURBINE ENGINES↗
NASA NTRS2008

Degradation of Victoria Crater, Mars

The $\sim$750 m diameter and $\sim$75 m deep Victoria crater in Meridiani Planum, Mars, presents evidence for significant degradation including a low, serrated, raised rim characterized by alternating alcoves and promontories, a surrounding low relief annulus, and a floor partially covered by dunes. The amount and processes of degradation responsible for the modified appearance of Victoria crater were evaluated using images obtained in situ by the Mars Exploration Rover Opportunity in concert with a digital elevation model created using orbital HiRISE images. Opportunity traversed along the north and northwest rim and annulus, but sufficiently characterized features visible in the DEM to enable detailed measurements of rim relief, ejecta thickness, and wall slopes around the entire degraded, primary impact structure. Victoria retains a 5 m raised rim consisting of 1-2 m of uplifted rocks overlain by 3 m of ejecta at the rim crest. The rim is $\sim$120 to 220 m wide and is surrounded by a dark annulus reaching an average of 590 m beyond the raised rim. Comparison between observed morphology and that expected for pristine craters 500 to 750 m across indicate the original, pristine crater was close to 600 m in diameter. Hence, the crater has been erosionally widened by approximately 150 m and infilled by about 50 m of sediments. Eolian processes are responsible for modification at Victoria, but lesser contributions from mass wasting or other processes cannot be ruled out. Erosion by prevailing winds is most significant along the exposed rim and upper walls and accounts for $\sim$50 m widening across a WNW-ESE diameter. The volume of material eroded from the crater walls and rim is $\sim$20% less than the volume of sediments partially filling the crater, indicating eolian infilling from sources outside the crater over time. The annulus formed when $\sim$1 m deflation of the ejecta created a lag of more resistant hematite spherules that trapped darker, regional basaltic sands.

Wilson, Sharon A.↗
NASA NTRS2009

Electric propulsion device for high power applications

An electric propulsion device is disclosed having an anode and a cathode. The propulsion device includes a discharge annulus having the anode adjacent an end region thereof. At least one inlet aperture is adjacent the anode, the aperture(s) having propellant gas flow therethrough into the discharge annulus. The propellant gas has an ionization potential. Opposed, dielectric walls define the annulus, with at least one of the opposed dielectric walls having pores therein, the pores having cooling gas flow therethrough into the discharge annulus and substantially adjacent the opposed dielectric wall(s). The cooling gas has an ionization potential higher than the ionization energy of the propellant gas. The cooling gas is adapted to substantially prevent at least one of secondary electron emission and sputtering of the dielectric walls.

Roy, Subrata↗
NASA NTRS1973

Observations of Mare Serenitatis from lunar orbit and their interpretation

Visual observations are investigated of color differences of Serenitatis mare materials from orbit complement photography and other remotely sensed data. The light tan gray inner fill of the Serenitatis basin is younger than the dark blue gray annulus; the latter continues into and appears to be contemporaneous with the fill of Mare Tranquillitatis. Mare ridges occur in both the inner basin fill and the dark annulus of Serenitatis. Ridges are interpreted as the result of structural deformation and up-doming after the solidification of the basaltic lavas. On the southeastern rim of the Serenitatis basin is the darkes blue gray unit within which Apollo 17 landed. Highland massifs surrounding this unit have unstable slopes which are believed to be the result of localized tectonic activity. On the southwest rim of the basin are the dark tan to brown gray mantling materials of the Sulpicius Gallus Formation. Farther west on the rim are dark blue grap patches which resemble the mare material of the Serenitatis dark annulus.

El-Baz, F.↗
NASA NTRS1975

Laser geodynamic satellite thermal/optical/vibrational analysis and testing, volume 2, book 2

The main tasks described involved an interferometric evaluation of several cubes, a prediction of their dihedral angles, a comparison of these predictions with independent measurements, a prediction and comparison of far field performance, recommendations as to revised dihedral angles and a subsequent analysis of cubes which were reworked to confirm the recommendations. A tolerance study and theoretical evaluation of several cubes was also performed to aid in understanding the results. The far field characteristics evaluated included polarization effects and treated both intensity distribution and encircled energy data. The energy in the 13.2 - 16.9 arc-sec annular region was tabulated as an indicator of performance sensitivity. The results are provided in viewgraph form, and show the average dihedral angle of an original set of test cubes to have been 1.8 arc-sec with an average far field annulus diameter of 18 arc-sec. Since the peak energy in the 13.2 - 16.9 arc-sec annulus was found to occur for a 1.35 arc-sec cube, and since cube tolerances were shown to increase the annulus diameter slightly, a nominal dihedral angle of 1.25 arc-sec was recommended.

Source record↗