Search NASA⌕ Search

SEARCH · Search NASA

Results for “liquid phase ratio”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2011

Robust Control Algorithm for a Two Cart System and an Inverted Pendulum

The Rectilinear Control System can be used to simulate a launch vehicle during liftoff. Several control schemes have been developed that can control different dynamic models of the rectilinear plant. A robust control algorithm was developed that can control a pendulum to maintain an inverted position. A fluid slosh tank will be attached to the pendulum in order to test robustness in the presence of unknown slosh characteristics. The rectilinear plant consists of a DC motor and three carts mounted in series. Each cart s weight can be adjusted with brass masses and the carts can be coupled with springs. The pendulum is mounted on the first cart and an adjustable air damper can be attached to the third cart if desired. Each cart and the pendulum have a quadrature encoder to determine position. Full state feedback was implemented in order to develop the control algorithm along with a state estimator to determine the velocity states of the system. A MATLAB program was used to convert the state space matrices from continuous time to discrete time. This program also used a desired phase margin and damping ratio to determine the feedback gain matrix that would be used in the LabVIEW program. This experiment will allow engineers to gain a better understanding of liquid propellant slosh dynamics, therefore enabling them to develop more robust control algorithms for launch vehicle systems

Wilson, Chris L.↗
NASA NTRS2018

(GO)2-SIM: a GCM-Oriented Ground-Observation Forward-Simulator Framework for Objective Evaluation of Cloud and Precipitation Phase

General circulation model (GCM) evaluation using ground-based observations is complicated by inconsistencies in hydrometeor and phase definitions. Here we describe (GO)2-SIM, a forward simulator designed for objective hydrometeor-phase evaluation, and assess its performance over the North Slope of Alaska using a 1-year GCM simulation. For uncertainty assessment, 18 empirical relationships are used to convert model grid-average hydrometeor (liquid and ice, cloud, and precipitation) water contents to zenith polarimetric micropulse lidar and Ka-band Doppler radar measurements, producing an ensemble of 576 forward-simulation realizations. Sensor limitations are represented in forward space to objectively remove from consideration model grid cells with undetectable hydrometeor mixing ratios, some of which may correspond to numerical noise.Phase classification in forward space is complicated by the inability of sensors to measure ice and liquid signals distinctly. However, signatures exist in lidar–radar space such that thresholds on observables can be objectively estimated and related to hydrometeor phase. The proposed phase-classification technique leads to misclassification in fewer than 8% of hydrometeor-containing grid cells. Such misclassifications arise because, while the radar is capable of detecting mixed-phase conditions, it can mistake water- for ice-dominated layers. However, applying the same classification algorithm to forward-simulated and observed fields should generate hydrometeor-phase statistics with similar uncertainty. Alternatively, choosing to disregard how sensors define hydrometeor phase leads to frequency of occurrence discrepancies of up to 40%. So, while hydrometeor-phase maps determined in forward space are very different from model "reality" they capture the information sensors can provide and thereby enable objective model evaluation.

Lamer, K.↗
NASA NTRS1994

Method for forming single phase, single crystalline 2122 BCSCO superconductor thin films by liquid phase epitaxy

A substantially single phase, single crystalline, highly epitaxial film of Bi.sub.2 CaSr.sub.2 Cu.sub.2 O.sub.8 superconductor which has a T.sub.c (zero resistance) of 83 K is provided on a lattice-matched substrate with no intergrowth. This film is produced by a Liquid Phase Epitaxy method which includes the steps of forming a dilute supercooled molten solution of a single phase superconducting mixture of oxides of Bi, Ca, Sr, and Cu having an atomic ratio of about 2:1:2:2 in a nonreactive flux such as KCl, introducing the substrate, e.g., NdGaO.sub.3, into the molten solution at 850.degree. C., cooling the solution from 850.degree. C. to 830.degree. C. to grow the film and rapidly cooling the substrate to room temperature to maintain the desired single phase, single crystalline film structure.

Pandey, Raghvendra K.↗
NASA NTRS1995

Epitaxial layers of 2122 BCSCO superconductor thin films having single crystalline structure

A substantially single phase, single crystalline, highly epitaxial film of Bi.sub.2 CaSr.sub.2 Cu.sub.2 O.sub.8 superconductor which has a T.sub.c (zero resistance) of 83K is provided on a lattice-matched substrate with no intergrowth. This film is produced by a Liquid Phase Epitaxy method which includes the steps of forming a dilute supercooled molten solution of a single phase superconducting mixture of oxides of Bi, Ca, Sr, and Cu having an atomic ratio of about 2:1:2:2 in a nonreactive flux such as KCl, introducing the substrate, e.g., NdGaO.sub.3, into the molten solution at 850.degree. C., cooling the solution from 850.degree. C. to 830.degree. C. to grow the film and rapidly cooling the substrate to room temperature to maintain the desired single phase, single crystalline film structure.

Pandey, Raghvendra K.↗
NASA NTRS2004

Structure and Dynamics of Freely Suspended Liquid Crystals

Smectic liquid crystals are phases of rod shaped molecules organized into one dimensionally (1 D) periodic arrays of layers, each layer being between one and two molecular lengths thick. In the least ordered smectic phases, the smectics A and C, each layer is a two dimensional (2D) liquid. Additionally there are a variety of more ordered smectic phases having hexatic short range translational order or 2D crystalline or quasi long range translational order within the layers. The inherent fluid-layer structure and low vapor pressure of smectic liquid crystals enables the long term stabilization of freely suspended, single component, layered fluid films as thin as 30A, a single molecular layer. The layering forces the films to be an integral number of smectic layers thick, quantizing their thickness in layer units and forcing a film of a particular number of layers to be physically homogeneous with respect to its layer structure over its entire area. Optical reflectivity enables the precise determination of the number of layers. These ultrathin freely suspended liquid crystal films are structures of fundamental interest in condensed matter and fluid physics. They are the thinnest known stable fluid structures and have the largest surface-to-volume ratio of any stable fluid preparation, making them ideal for the study of the effects of reduced dimensionality on phase behavior and on fluctuation and interface phenomena. Their low vapor pressure and quantized thickness enable the effective use of microgravity to extend the study of basic capillary phenomena to ultrathin fluid films. Freely suspended films have been a wellspring of new LC physics. They have been used to provide unique experimental conditions for the study of condensed phase transitions in two dimensions. They are the only system in which the hexatic has been unambiguously identified as a phase of matter, and the only physical system in which fluctuations of a 2D XY system and Kosterlitz Thouless phase transition has been observed and 2D XY quasi long range order verified. Smectic films have enabled the precise determination of smectic layer electron density and positional fluctuation profiles and have been used to show that the interlayer interactions in antiferroelectric tilted smectics do not extend significantly beyond nearest neighbors. Freely suspended films played a pivotal role in the recent discovery of macroscopic chiral-polar ordering in fluids of achiral molecules. The interactions which are operative in liquid crystals are generally weak in comparison to those in crystalline phases, leading to the facile manipulation of the order in liquid crystals by external agents such as applied fields and surfaces. Effects arising from weak ordering are significantly enhanced in ultrathin free films and filaments, in which the intermolecular coupling is effectively further reduced by loss of neighbors. Over the past four years this research, which we now detail, has produced a host of exciting new discoveries and unexpected results, maintaining the study of freely suspended liquid crystal structures as one of most exciting and fruitful areas of complex fluid physics. In addition, a class of experiments on the behavior of 1D interfaces in 2D films have been pursued with results that point to potentially quite interesting effects in microgravity.

Clark, Noel A.↗
NASA NTRS1993

Immiscible phase incorporation during directional solidification of hypermonotectics

Solidification processes in immiscible samples were investigated by directly observing the events taking place at the solid-liquid interface during directional solidification. Visualization of these events was made possible through the use of a transparent metal analog system and a temperature gradient stage assembly fitted to an optical microscope. The immiscible transparent analog system utilized was the succinonitrile-glycerol system. This system has been shown to exhibit the same morphological transitions as observed in metallic alloys of monotectic composition. Both monotectic and hypermonotectic composition samples were directionally solidified in order to gain an improved understanding of the manner in which the excess hypermonotectic liquid is incorporated into the solidifying structure. The processing conditions utilized prevented sedimentation of the excess hypermonotectic liquid by directionally solidifying the samples in very thin (13 microns), horizontally oriented cells. High thermal gradient to growth rate ratios (G/R) were used in an effort to prevent constitutional supercooling and the subsequent formation of L(sub 2) droplets in advance of the solidification front during the growth of fibrous composite structures. Results demonstrated that hypermonotectic composites could be produced in samples up to two weight percent off of the monotectic composition by using a G/R ratio greater than or equal to 4.6 x 10(exp 4) C(s)/mm(sup 2) to avoid constitutional supercooling. For hypermonotectic samples processed with G/R ratios below 4.6 x 10(exp 4) C(s)/mm(sup 2), constitutional supercooling occurred and resulted in slight interfacial instability. For these samples, two methods of incorporation of the hypermonotectic liquid were observed and are reported. The correlation between the phase spacing, lambda, and the growth rate, R, was examined and was found to obey a relationship generally associated with a diffusion controlled coupled growth process. For samples with compositions ranging from the monotectic composition up to 2 percent off of the monotectic composition, data indicated that the square of the phase spacing (lambda) varied linearly with the inverse of the growth rate (R).

Andrews, J. Barry↗
NASA NTRS1972

A two dimensional theory for two phase detonation of liquid films.

A theory for the propagation of detonations through tubes coated with a thin fuel film is developed. Vaporization is assumed as the rate limiting process dominating the detonation structure. Inclusion of the boundary layer displacement effect resulted in better agreement between computed and measured propagation speed, pressure ratio, and reaction zone length than was obtained in an earlier theory in which this effect was neglected. New film detonation data is presented covering a wide range of fuel air ratios. A general Chapman-Jouguet condition is formulated for film detonations, and use of the plane of complete film vaporization as the Chapman-Jouguet plane is justified in the case of thin films.

Rao, C. S. R.↗
NASA NTRS1960

Liquid-Phase Heat-Release Rates of the Systems Hydrazine-Nitric Acid and Unsymmetrical Dimethylhydrazine-Nitric Acid

The initial rates of heat release produced by the reactions of hydrazine and unsymmetrical dimethylhydrazine with nitric acid were determined in a bomb calorimeter under conditions of forced mixing. Fuel-oxidant weight ratio and injection velocity were varied. The rate of heat release apparently depended on the interfacial area between the propellants. Above a narrow range of injection velocities representing a critical amount of interfacial area, the rates reached a maximum and were almost constant with injection velocity. The maximum rate for hydrazine was about 70 percent greater than that for unsymmetrical dimethylhydrazine. The total heat released did not vary with mixture ratio over the range studied.

Somogyi, Dezso↗
NASA NTRS1990

Planar Laser Imaging of Sprays for Liquid Rocket Studies

A planar laser imaging technique which incorporates an optical polarization ratio technique for droplet size measurement was studied. A series of pressure atomized water sprays were studied with this technique and compared with measurements obtained using a Phase Doppler Particle Analyzer. In particular, the effects of assuming a logarithmic normal distribution function for the droplet size distribution within a spray was evaluated. Reasonable agreement between the instrument was obtained for the geometric mean diameter of the droplet distribution. However, comparisons based on the Sauter mean diameter show larger discrepancies, essentially because of uncertainties in the appropriate standard deviation to be applied for the polarization ratio technique. Comparisons were also made between single laser pulse (temporally resolved) measurements with multiple laser pulse visualizations of the spray.

Lee, W.↗
NASA NTRS1975

Experimental and analytical investigation of 0 G condensation in a mechanical refrigeration system application

Basic equations of momentum and energy are presented and discussed with respect to heat transfer and pressure drop for forced flow condensation in horizontal tubes under 1-g and 0-g conditions. Some experimental results are presented for condensing refrigerant-12 in a system of three parallel-connected quartz tubes (3-mm inside diameter, G = 1.037 to 3.456 x 105 lbm/hr-sq. ft). From high speed photographs, measurements were obtained of film thickness, phase velocities, disturbance wavelengths, and flow regimes and their transitions. Based upon these measurements various dimensionless force ratios (flow and instability parameters) were calculated. Under 0-g conditions a uniformly thick redistribution of liquid condensate about the tube walls was found to result in a lowered heat transfer coefficient as compared with 1-g conditions, based upon fundamental heat transfer theory. A model is proposed that takes into account the difference in heat transfer due to condensate distribution under 1-g and 0-g conditions.

Keshock, E. G.↗
NASA NTRS1984

Early solar system aqueous activity - Sr isotope evidence from the Orgueil CI meteorite

The Sr isotopic composition and Rb-87/Sr-86 ratio have been measured in carbonates and sulfate separated from the Orgueil meteorite in order to determine the time when liquid water may have acted on the parent body. Both of the studied phases probably precipitated from aqueous solution. The results show that carbonate deposition occurred contemporaneously with parent body formation or shortly after it, probably within 100 Myr. On the other hand, at least some of the calcium sulfate seems to have been formed recently.

Macdougall, J. D.↗
NASA NTRS2024

ECI Final Report: Closing of Critical Technology Gaps for Rotating Detonation Rocket Engines

NASA has successfully fired several configurations of a dual regenerative 10K lbf class Rotating Detonation Rocket Engines using cryogenic liquid methane, liquid hydrogen, and RP-1 as fuel and liquid or gaseous oxygen as the oxidizer. In addition, 3 hot fire test phases were conducted to evaluate parametrically varying combustor geometries using a subscale 500-1K lbf class thruster RDRE. Several studies were successfully completed to evaluate the impacts of contraction ratio, annulus L’, heat transfer through calorimetry, and varying injector designs. Laser powder bed fusion GRCop-42, GRX-810, and C-103 alloys were used for the outer bodies, inner bodies, nozzles, and injector variations. The development of RDRE technology is only now possible with additive manufacturing techniques and these specialized alloys. Critical design parameters, design rules of thumb, and operability limitations have been identified. Major lessons learned in the development of critical components have also been documented. All critical technology gaps have been demonstrated at one scale or another and closed. A major finding of this work is that the combustion efficiency of the RDRE is far superior to that of the traditional liquid rocket engine requiring an order of magnitude lower chamber volume and residence time to react. Because of this, the design trade space opens up significantly. More compact chamber geometries are now possible with potential mass savings and significant length savings possible to flight geometries. In addition, the ceiling for the technology, in terms of Isp, has not yet been reached. It is likely that an additional ~10% better Isp over equivalent state-of-the-art combustion devices may be achieved over the next decade should the technology continue to be developed. This technology has been shown to be viable for near term infusion (2-5 years) into space missions and enable cost effective space access for US industry. This final report documents all major findings from this early career initiative (ECI) project and lays out what is needed post ECI.

Thomas Teasley↗
NASA NTRS1981

Two-component Fermi-liquid theory - Equilibrium properties of liquid metallic hydrogen

It is reported that the transition of condensed hydrogen from an insulating molecular crystal phase to a metallic liquid phase, at zero temperature and high pressure, appears possible. Liquid metallic hydrogen (LMH), comprising interpenetrating proton and electron fluids, would constitute a two-component Fermi liquid with both a very high component-mass ratio and long-range, species-dependent bare interactions. The low-temperature equilibrium properties of LMH are examined by means of a generalization to the case of two components of the phenomenological Landau Fermi-liquid theory, and the low-temperature specific heat, compressibility, thermal expansion coefficient and spin susceptibility are given. It is found that the specific heat and the thermal expansion coefficient are vastly greater in the liquid than in the corresponding solid, due to the presence of proton quasiparticle excitations in the liquid.

Oliva, J.↗
NASA NTRS2003

A Comparison between Growth Morphology of "Eutectic" Cells/Dendrites and Single-Phase Cells/Dendrites

Directionally solidified (DS) intermetallic and ceramic-based eutectic alloys with an in-situ composite microstructure containing finely distributed, long aspect ratio, fiber, or plate reinforcements are being seriously examined for several advanced aero-propulsion applications. In designing these alloys, additional solutes need to be added to the base eutectic composition in order to improve heir high-temperature strength, and provide for adequate toughness and resistance to environmental degradation. Solute addition, however, promotes instability at the planar liquid-solid interface resulting in the formation of two-phase eutectic "colonies." Because morphology of eutectic colonies is very similar to the single-phase cells and dendrites, the stability analysis of Mullins and Sekerka has been extended to describe their formation. Onset of their formation shows a good agreement with this approach; however, unlike the single-phase cells and dendrites, there is limited examination of their growth speed dependence of spacing, morphology, and spatial distribution. The purpose of this study is to compare the growth speed dependence of the morphology, spacing, and spatial distribution of eutectic cells and dendrites with that for the single-phase cells and dendrites.

Tewari, S. N.↗
NASA NTRS2020

Ag isotopic and chalcophile element evolution of the terrestrial and martian mantles during accretion: new constraints from Bi, Pd, and Ag metal-silicate partitioning.

The Earth’s timing of accretion and acquisition of moderately volatile compounds is uncertain. Hafnium-W and Mn-Cr isotopic data can bracket the timing of early planetary differentiation and core formation. The Ag-Pd system has also been utilized but its application has been limited by a lack of high pressure and temperature metal-silicate partitioning for Pd and Ag. Be-cause Ag (and Bi) are volatile chalcophile siderophile elements, understanding their early distribution can constrain the origin of volatile elements in differentiated bodies and planets. Unfortunately, neither Ag or Bi have been studied across the wide range of pressure and temperature conditions that are relevant to accretion and core-mantle differentiation. Here, new high-pressure and temperature multi-anvil metal-silicate equilibrium experiments for Bi and Ag have been carried out at conditions relevant to planetary accretion and metal silicate differentiation that allow a more refined and complete understanding of element partitioning during core formation. The new metal-silicate partitioning data utilized to predict the distributions of Bi, Pd, and Ag at conditions of accretion for Earth and Mars and show that the Pd/Ag ratio is significantly fractionated during accretion, allowing for the production of detectable 107Ag anomalies produced while 107Pd (half life = 6.5 M.y.) was still extant. Application of the new partitioning results to Earth shows that D(Bi) and D(Ag) (D = metal/silicate concentration ratio) are lowered due to the effect of pressure and Si alloyed in the metallic liquid, resulting in higher predicted mantle Bi and Ag abundances than in the bulk silicate Earth (BSE), as well as high and variable Pd/Ag. The unradiogenic Ag isotopic composition of the BSE could have been generated by early accretion of volatile-poor (high Pd/Ag) precursors, followed by later accretion of volatile–rich (low Pd/Ag) material, in agreement with earlier studies of Pd-Ag and Mn-Cr (Schönbächler et al., 2010). However, these main accretion phases would have to be followed by segregation of a sulfide liquid (at least 1.5% of magma ocean) at high pressures (>30 GPa), to explain the PUM Bi, Pd, and Ag, as well as Au, Pt, Cu and Ni concentrations as proposed previously. If the early accreted bulk Earth was volatile depleted with high Pd/Ag ratios, portions of the mantle may contain ancient domains that developed positive 107Ag isotopic anomalies (as also argued by noble gases, Nd, W, and Os isotopes). In comparison, Bi, Pd, and Ag concentrations in the martian mantle could have been set by simple metal-silicate equilibrium. Mars accreted and differentiated relatively rapidly, while also developing a deep magma ocean with a high Pd/Ag ratio that could have evolved positive 107Ag anomalies, in contrast to Earth. Measurements on shergottites may reveal these predicted Ag isotopic anomalies.

accretion↗
NASA NTRS1995

Space concentrator solar cells based on multilayer LPE grown AlGaAs/GaAs heterostructure

The high efficiency solar cells based on multilayer AlGaAs/GaAs heterostructures, prepared by low temperature liquid phase epitaxy (LPE), were developed and tested. An investigation of the low temperature LPE process for the crystallization of AlGaAs heterostructures of as high as 24.0 to 24.7 percent under AMO conditions at concentration ratios of 20 to 100x, were reached. Developed solar cells show substantial radiation resistance to the damage induced by 3.75 MeV electrons.

Khvostikov, V. P.↗
NASA NTRS1996

An Electrothermodynamic Model with Distributed Properties for Effective Permittivities of Sea Ice

This paper presents a model to calculate the temperature dependence of effective permittivities for sea ice, a heterogeneous medium containing multiphase scatterers. With the strong permittivity fluctuation approach the model accounts for the electrodynamic scattering effect together with the quasi-static characteristics of multiple species and subspecies of inhomogeneities with distributed orientations, sizes, and shapes. Because of a preferential direction in the orientation distribution, the medium is effectively anisotropic. The size distribution is described with a probability density function in terms of normalized volumetric sizes. Scatterer shapes are nonuniform and have a general ellipsoidal form characterized by arbitrary axial ratios of correlation lengths which are related to physical geometries of the scatterers. In this formulation, sea ice consisting of solid ice, liquid brine, and gaseous inclusions is modeled to derive effective permittivities with thermodynamic phase redistribution and structural metamorphism. Theoretical results are in good agreement with experimental data at the C band frequency of 4.8 GHz for saline ice undergoing warming and cooling cycles. A competitive effect between the increase of liquid brine and the shape rounding of ellipsoidal scatterers at increasing temperatures explains the trend observed in measured data. Sensitivities of effective permittivities to structural and physical parameters characterizing sea ice are also studied.

Nghiem, S. V.↗