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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Mass and Momentum Turbulent Transport Experiments

The downstream mixing of coaxial jets discharging in an expanded duct was studied to improve turbulent transport models which are used in computational procedures throughout the propulsion community for combustor flow modeling. Laser velocimeter (LV) and laser induced fluorescence (LIF) techniques were used to measure velocities and concentration and flow visualization techniques to determine the time dependent characteristics of the flow and the scale of the turbulent structure.

Johnson, B. V.↗
NASA NTRS1982

Scanning delay generator for measurement of kinetic decays using laser-induced fluorescence techniques

An electronic device is described which generates a delayed pulse, where the delay is increased in a step-like manner. This device finds application in the measurement of kinetic decays, particularly when laser-induced fluorescent (LIF) detection of the decaying species is used. The circuit uses 15 low-power Schottky TTL chips and is contained within a dual width NIM module.

Halpern, J. B.↗
NASA NTRS1983

Statistical characteristics of velocity, concentration, mass transport, and momentum transport for coaxial jet mixing in a confined duct

An experimental study of mixing downstream of coaxial jets discharging into an expanded circular duct was conducted to obtain data for the evaluation and improvement of turbulent transport models currently used for combustor flow modeling. A combination of turbulent momentum transport rate and two velocity component data was obtained from simultaneous measurements with a two-color LV system. A combination of turbulent mass transport rate, concentration and velocity data was obtained from simultaneous measurements with laser velocimeter (LV) and laser induced fluorescence (LIF) systems. These measurements were used to obtain mean, second central moment, skewness and kurtosis values for three velocity components and the concentration. These measurements showed the existence of countergradient turbulent axial mass transport where the annular jet fluid was accelerating the inner jet fluid. Results from the study are related to the assumptions employed in the current mass and momentum turbulent transport models.

Johnson, B. V.↗
NASA NTRS1983

Feasibility of airborne detection of laser-induced fluorescence emissions from green terrestrial plants

The present investigation provides a demonstration of the feasibility of the airborne detection of the laser-induced fluorescence spectral emissions from living terrestrial grasses, shrubs, and trees using existing levels of lidar technology. Airborne studies were performed to ascertain system requirements necessary to detect laser-induced fluorescence from living terrestrial plants, to assess the practical acquisition of useful single-shot laser-induced fluorescence (LIF) waveforms over vegetative canopies, and to determine the comparative suitability of laser system, airborne platform, and terrestrial environmental parameters. The field experiment was conducted on May 3, 1982, over the northern portion of Wallops Island, VA. Attention is given to airborne lidar results and the description of laboratory investigations.

Hoge, F. E.↗
NASA NTRS1983

Mass and momentum turbulent transport experiments with confined swirling coaxial jets

Swirling coaxial jets mixing downstream, discharging into an expanded duct was conducted to obtain data for the evaluation and improvement of turbulent transport models currently used in a variety of computational procedures throughout the combustion community. A combination of laser velocimeter (LV) and laser induced fluorescence (LIF) techniques was employed to obtain mean and fluctuating velocity and concentration distributions which were used to derive mass and momentum turbulent transport parameters currently incorporated into various combustor flow models. Flow visualization techniques were also employed to determine qualitatively the time dependent characteristics of the flow and the scale of turbulence. The results of these measurements indicated that the largest momentum turbulent transport was in the r-z plane. Peak momentum turbulent transport rates were approximately the same as those for the nonswirling flow condition. The mass turbulent transport process for swirling flow was complicated. Mixing occurred in several steps of axial and radial mass transport and was coupled with a large radial mean convective flux. Mixing for swirling flow was completed in one-third the length required for nonswirling flow.

Roback, R.↗
NASA NTRS1984

Interaction of atomic oxygen with solid surfaces at orbital altitudes (A0114)

The basic approach to this experiment is to expose a wide variety of material surfaces to the atomic flux in orbit. The experiment is passive and depends on preflight and postflight measurements of the test surfaces in the laboratory. The experiment will also include a reflectometer device to measure atomic beam reflection angles and thus momentum accommodations, and a unique passive spacecraft attitude sensor. Samples consisting of solid disks or thin film coatings on substrate disks will be mounted in a panel. The face of this panel will be flown on Long Duration Exposure Facility normal to the incident stream of oxygen atoms. Each disk will have part of its front surface masked so exposure to the atomic-oxygen reaction will be limited to selected areas, the shadowed areas being used as control surfaces in the measurements. A typical sample is an optically flat quartz disk overcoated with a film of the material of interest. These include Ag, Au, Pt, Nb, Ni, Al, C, Si, Ge, LiF, and a few engineering materials. Some materials for which the expected removal rate is high, such as carbon, will be solid disks rather than thin films.

Gregory, J. C.↗
NASA NTRS1985

An approach of reducing the background induced by neutrons

The background induced by interactions of neutrons with detector material (and shield material) is difficult to be rejected. It is one of the most important factors to affect the sensitivity of a balloon-borne gamma-ray astronomical telescope. The main component of neutron flux at the major detector of the telescope is incident neutrons, that consists of atmospheric neutrons and neutrons locally produced in the balloon platform. Therefore, shielding the detector from incident neutrons is a possible way to reduce the background. NaI (T1) crystal is very widely used in gamma-ray astronomical telescopes. Through balloon-borne experiment it is shown that up 6 LiF shield is effective to reduce the background in NaI crystal.

Shen, C.↗
NASA NTRS1984

Mass and momentum turbulent transport experiments with confined coaxial jets

An experimental study of mixing downstream of coaxial jets discharging into an expanded circular duct was conducted to obtain data for the evaluation and improvement of turbulent transport models. A combination of turbulent momentum transport rate and two components of velocity data were obtained from simultaneous measurements with a two-color LV system. A combination of turbulent mass transport rate, concentration and velocity data were obtained from simultaneous measurements with laser velocimeter (LV) and laser induced fluorescence (LIF) systems.

Johnson, B. V.↗
NASA NTRS1985

Role of hydroxide impurities in the thermoluminescent behavior of lithium fluoride

The influence of OH ion impurities on thermoluminescent sensitivity and supralinearity in LiF:Mg, Ti is analyzed. Available evidence is shown to be consistant with the presence of Ti-OH and Mg-OH complexes. The track interaction model is used to explain the data, with competing centers decreasing sensitivity and supralinearity at high concentrations.

Stoebe, T. G.↗
NASA NTRS1986

Characterization of the tribological coating composition 77 wt % CaF2 - 23 wt % Li F fused to IN-750 alloy

A coating composed of 77 wt % CaF2 - 23 wt % LiF fused on IN-750 nickel-based alloy was studied using SEM, XRD, EDX, and optical microscopic methods. The surfaces examined were the as-fused coating with no subsequent treatment, the coating after ultrasonic cleaning in water, and the uncoated polished and etched metal. It was found that the coating reacts during fusion with Ti and Nb rich inclusions in the alloy. Numerous small rectangular crystallites of Ca(Ti,Nb) oxide are formed beneath an overlay of fused fluoride composition. These crystallines are stubby and appear to be embedded in the metal substrate surface. It is known from previous studies that this coating-alloy system has good tribological properties in extreme conditions, such as liquid fluorine. It has been concluded from the present study that the short firmly embedded crystalline protuberances contribute to the coating adherence and thereby to enhanced coating wear life.

Deadmore, D. L.↗
NASA NTRS1986

Estimated heats of fusion of fluoride salt mixtures suitable for thermal energy storage applications

The heats of fusion of several fluoride salt mixtures with melting points greater than 973 K were estimated from a coupled analysis of the available thermodynamic data and phase diagrams. Simple binary eutectic systems with and without terminal solid solutions, binary eutectics with congruent melting intermediate phases, and ternary eutectic systems were considered. Several combinations of salts were identified, most notable the eutectics LiF-22CaF2 and NaF-60MgF2 which melt at 1039 and 1273 K respectively which posses relatively high heats of fusion/gm (greater than 0.7 kJ/g). Such systems would seemingly be ideal candidates for the light weight, high energy storage media required by the thermal energy storage unit in advanced solar dynamic power systems envisioned for the future space missions.

Misra, A. K.↗
NASA NTRS1985

An airborne lidar instrument for detection of OH using the technique of laser-induced fluorescence

Under suitable laboratory conditions, it has been demonstrated that the laser-induced fluorescence (LIF) measurement technique is sensitive enough to detect single atoms and molecules. This potential sensitivity has provided motivation for the development of this technique for ambient OH measurements. The present paper is concerned with an airborne lidar instrument for measuring OH concentration as used for the NASA GTE/CITE (Global Tropospheric Experiment/Chemical Instrumentation Test and Evaluation) intercomparison experiments during the fall of 1983 and the spring of 1984. A description is given of a working airborne instrument for measurements of OH in ambient air. The detection sensitivity demonstrated in the experiments should be sufficient for routine measurements in areas in which the OH concentration is in the range of high 1,000,000 molecule per cu cm or higher.

Davis, L. I., Jr.↗
NASA NTRS1986

Temperature dependent electronic quenching of OH(A 2 Sigma +, v-prime = 0) between 230 and 310 K

The present study is concerned with the electronic quenching of OH(A 2 Sigma +, v-prime = 0) at and below room temperature, taking into account the use of laser-induced fluorescence (LIF) in a low pressure flow cell for H2, CO2, O2, and N2 colliders. The reasons for the selection of the temperature range and the collision partners are related to the quantitative calibration of OH detection techniques in the troposphere, and to considerations of electronic quenching dynamics. Attention is given to production and rotational distribution, temperature measurements, and temperature dependent quenching rate constants.

Copeland, R. A.↗
NASA NTRS1987

Fluoride salts and container materials for thermal energy storage applications in the temperature range 973 to 1400 K

Multicomponent fluoride salt mixtures were characterized for use as latent heat of fusion heat storage materials in advanced solar dynamic space power systems with operating temperatures in the range of 973 to 1400 K. The melting points and eutectic composition for many systems with published phase diagrams were verified, and several new eutectic compositions were identified. Additionally, the heats of fusion of several binary and ternary eutectics and congruently melting intermediate compounds were measured by differential scanning calorimetry. The extent of corrosion of various metals by fluoride melts was estimated from thermodynamic considerations, and equilibrium conditions inside a containment vessel were calculated as functions of the initial moisture content of the salt and free volume above the molten salt. Preliminary experimental data on the corrosion of commercial, high-temperature alloys in LiF-19.5CaF2 and NaF-27CaF2-36MgF2 melts are presented and compared to the thermodynamic predictions.

Misra, Ajay K.↗
NASA NTRS1986

On the uniqueness of the constrained space orbital variation (CSOV) technique

Several CSOV analyses are performed for the 1Sigma(+) state of NiCO, and it is shown that the importance of the CO sigma donation, Ni pi back donation, and interunit polarizations are virtually independent of the order of the CSOV steps, provided that the open-shell 3d sigma and 4s Ni orbitals are orthogonalized to the CO. This order of orthogonalization is consistent with the polarization of the Ni observed in the unconstrained SCF wavefunction. If instead the CO is orthogonalized to the open-shell Ni orbitals, the frozen orbital repulsion and entire CSOV analysis becomes unphysical. A comparison of the SCF and CAS SCF descriptions for the NiCO 1Sigma(+) state shows the importance of the s to d promotion and sd hybridization in reducing the repulsion and increasing the Ni to CO pi bonding. For LiF, CSOV analyses starting from both the neutral and ionic asymptotes show the bonding to be predominantly Li(+) - F(-). These examples show the uniqueness of the CSOV decomposition.

Bauschlicher, C. W., Jr.↗
NASA NTRS1986

Remote sensing; Proceedings of the Meeting, Orlando, FL, Apr. 3, 4, 1986

Advances in optical technology for remote sensing are discussed in reviews and reports of recent experimental investigations. Topics examined include industrial applications, laser diagnostics for combustion research, laser remote sensing for ranging and altimetry, and imaging systems for terrestrial remote sensing from space. Consideration is given to LIF in forensic diagnostics, time-resolved laser-induced-breakdown spectrometry for rapid analysis of alloys, CARS in practical combustion environments, airborne inertial surveying using laser tracking and profiling techniques, earth-resources instrumentation for the EOS polar platform of the Space Station, and the SAR for EOS.

Menzies, Robert T.↗
NASA NTRS1987

A lithium oxygen secondary battery

Some recent work on a lithium-oxygen secondary battery is reported in which stabilized zirconia oxygen vacancy conducting solid electrolytes were used for the effective separation of respective half-cell reactions. The electroactive material consisted of alloys possessing the general composition Li(x)FeSi2 immersed in a ternary molten salt comprising LiF, LiCl, and Li2O. The manufacture of the cell is described, and discharge-current voltage curves for partially charged cells are shown and discussed. A galvanostatic IR free-changing curve and an IR-free charge-discharge curve are also shown.

Semkow, Krystyna W.↗
NASA NTRS1988

Solar dynamic power system definition study

The solar dynamic power system design and analysis study compared Brayton, alkali-metal Rankine, and free-piston Stirling cycles with silicon planar and GaAs concentrator photovoltaic power systems for application to missions beyond the Phase 2 Space Station level of technology for all power systems. Conceptual designs for Brayton and Stirling power systems were developed for 35 kWe and 7 kWe power levels. All power systems were designed for 7-year end-of-life conditions in low Earth orbit. LiF was selected for thermal energy storage for the solar dynamic systems. Results indicate that the Stirling cycle systems have the highest performance (lowest weight and area) followed by the Brayton cycle, with photovoltaic systems considerably lower in performance. For example, based on the performance assumptions used, the planar silicon power system weight was 55 to 75 percent higher than for the Stirling system. A technology program was developed to address areas wherein significant performance improvements could be realized relative to the current state-of-the-art as represented by Space Station. In addition, a preliminary evaluation of hardenability potential found that solar dynamic systems can be hardened beyond the hardness inherent in the conceptual designs of this study.

Wallin, Wayne E.↗