Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “phase transfer”

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 1,153 records · Page 64
All sourcesNASA NTRSDOE OSTI
NASA NTRS1999

Ignition and Combustion of Bulk Metals in a Microgravity Environment

Results of a study of heterogeneous and homogeneous combustion of metals in reduced gravity are presented. Cylindrical titanium and magnesium samples are radiatively ignited in pure-oxygen at 1 atm. Qualitative observations, propagation rates, and burning times are extracted from high-speed cinematography. Time-resolved emission spectra of gas-phase reactions are acquired with an imaging spectrograph. Lower propagation rates of the reacting mass on titanium and of ignition waves on magnesium are obtained at reduced gravity. These rates are compared to theoretical results from fire-spread analyses with a diffusion/convection controlled reaction. The close agreement found between experimental and theoretical propagation rates indicates the strong influence of natural-convection-enhanced oxygen transp6rt on burning rates. Lower oxygen flux and lack of condensed product removal appear to be responsible for longer burning times of magnesium gas-phase diffusion flames in reduced gravity. Spherically symmetric explosions in magnesium flames at reduced gravity (termed radiation-induced metal explosions, or RIME) may be driven by increased radiation heat transfer from accumulated condensed products to an evaporating metal core covered by a porous, flexible oxide coating. In titanium specimens, predominantly heterogeneous burning characterizes the initial steady propagation of the molten mass, while homogeneous gas-phase reactions are detected around particles ejected from the molten mixture. In magnesium specimens, band and line reversal of all the UV spectral systems of Mg and MgO are attributed to the interaction between small oxide particles and the principal gaseous emitters.

Branch, Melvyn C.↗
NASA NTRS1992

Mars dust and cloud opacities and scattering properties

We have recently completed an analysis of the visible emission-phase function (EPF) sequences obtained with the solar-band channel of the Infrared Thermal Mapping (IRTM) instrument onboard the two Viking Orbiters. Roughly 100 of these EPF sequences were gathered during the 1977-1980 period, in which the total broadband (.3-3.0 microns) reflectances of the atmosphere/surface above specific locations on Mars were measured versus emission angle as the spacecraft passed overhead. A multiple scattering radiative transfer program was employed to model the EPF observations in terms of the optical depths of dust/clouds, their single scattering albedos and phase functions, and the Lambert albedos and phase coefficient of the underlying surfaces. Due to the predominance of atmospheric scattering at large atmospheric pathlengths and/or large dust opacities, we were able to obtain strong constraints on the scattering properties of dust/clouds and their opacities for a wide range of latitudes, longitudes, and seasons on Mars.

Clancy, R. T.↗
NASA NTRS1993

Advanced Multi-Phase Flow CFD Model Development for Solid Rocket Motor Flowfield Analysis

It is known that the simulations of solid rocket motor internal flow field with AL-based propellants require complex multi-phase turbulent flow model. The objective of this study is to develop an advanced particulate multi-phase flow model which includes the effects of particle dynamics, chemical reaction and hot gas flow turbulence. The inclusion of particle agglomeration, particle/gas reaction and mass transfer, particle collision, coalescence and breakup mechanisms in modeling the particle dynamics will allow the proposed model to realistically simulate the flowfield inside a solid rocket motor. The Finite Difference Navier-Stokes numerical code FDNS is used to simulate the steady-state multi-phase particulate flow field for a 3-zone 2-D axisymmetric ASRM model and a 6-zone 3-D ASRM model at launch conditions. The 2-D model includes aft-end cavity and submerged nozzle. The 3-D model represents the whole ASRM geometry, including additional grain port area in the gas cavity and two inhibitors. FDNS is a pressure based finite difference Navier-Stokes flow solver with time-accurate adaptive second-order upwind schemes, standard and extended k-epsilon models with compressibility corrections, multi zone body-fitted formulations, and turbulence particle interaction model. Eulerian/Lagrangian multi-phase solution method is applied for multi-zone mesh. To simulate the chemical reaction, penalty function corrected efficient finite-rate chemistry integration method is used in FDNS. For the AL particle combustion rate, the Hermsen correlation is employed. To simulate the turbulent dispersion of particles, the Gaussian probability distribution with standard deviation equal to (2k/3)(exp 1/2) is used for the random turbulent velocity components. The computational results reveal that the flow field near the juncture of aft-end cavity and the submerged nozzle is very complex. The effects of the turbulent particles affect the flow field significantly and provide better prediction of the ASRM performance. The multi-phase flow analysis using the FDNS code in the present research can be used as a design tool for solid rocket motor applications.

Liaw, Paul↗
NASA NTRS2026

Incremental Learning for Passive Microwave Precipitation Retrievals using Advanced Technology Microwave Sounder

Spaceborne passive microwave (PMW) radiometry is central to global precipitation monitoring, yet retrieval uncertainties remain substantial, particularly for cross-track sounders whose variable footprints and channel configurations are optimized for atmospheric temperature and moisture profiling rather than precipitation. Consequently, existing operational products often exhibit angular-dependent biases, limited effective swath utilization, unrealistic rainfall probability distributions, and systematic misclassification of precipitation phase. These limitations are further compounded by the scarcity of globally accurate and representative precipitation observations, as training data from the Dual-frequency Precipitation Radar (DPR) and the Cloud Profiling Radar (CPR) are spatially sparse, lack uniform global coverage, and exhibit heterogeneous error characteristics across precipitation regimes. To address these challenges, this study presents a supervised retrieval algorithm that incrementally trains an ensemble of extreme gradient-boosted decision trees by augmenting base learners with pre-training on reanalysis data and post-training on coincident DPR and CPR observations matched with the Advanced Technology Microwave Sounder (ATMS). By transferring prior information from reanalysis to posterior constraints from radar observations and adopting a sequential detection–estimation strategy for precipitation phase and rate retrieval, the proposed approach yields retrievals across the full ATMS swath that are largely free from persistent deficiencies in current Global Precipitation Measurement (GPM) passive microwave operational products. In particular, the method resolves bimodal artifacts in rainfall retrievals and mitigates systematic high-latitude snowfall biases, including overestimation across the Arctic and underestimation across the Antarctic. Validation against independent Multi-Radar Multi-Sensor (MRMS) data over the Contiguous United States (CONUS) further demonstrates improved performance in precipitation phase detection and rate estimation relative to both reanalysis and current GPM PMW products.

Mahyar Garshasbi↗
NASA NTRS1992

Remote sensing of Earth terrain

Research findings are summarized for projects dealing with the following: application of theoretical models to active and passive remote sensing of saline ice; radiative transfer theory for polarimetric remote sensing of pine forest; scattering of electromagnetic waves from a dense medium consisting of correlated Mie scatterers with size distribution and applications to dry snow; variance of phase fluctuations of waves propagating through a random medium; theoretical modeling for passive microwave remote sensing of earth terrain; polarimetric signatures of a canopy of dielectric cylinders based on first and second order vector radiative transfer theory; branching model for vegetation; polarimetric passive remote sensing of periodic surfaces; composite volume and surface scattering model; and radar image classification.

Kong, J. A.↗
NASA NTRS2007

Thermal Modeling of the Mars Reconnaissance Orbiter's Solar Panel and Instruments during Aerobraking

The Mars Reconnaissance Orbiter (MRO) launched on August 12, 2005 and started aerobraking at Mars in March 2006. During the spacecraft s design phase, thermal models of the solar panels and instruments were developed to determine which components would be the most limiting thermally during aerobraking. Having determined the most limiting components, thermal limits in terms of heat rate were established. Advanced thermal modeling techniques were developed utilizing Thermal Desktop and Patran Thermal. Heat transfer coefficients were calculated using a Direct Simulation Monte Carlo technique. Analysis established that the solar panels were the most limiting components during the aerobraking phase of the mission.

Dec, John A.↗
NASA NTRS1982

User interface design of software tool system as a technology transfer vehicle

Design considerations of an on going research project for developing an effective and easy to use tool system that supports entire maintenance phases are introduced. The primary focus is the design of an intelligent user interface mechanism. By analyzing why existing tools and tool systems are not used very effectively, we can define user requirements for the user interface mechanisms, specify design criteria of user interface functions, and introduce some features of the implementation. Because this project is still in process, intermediate evaluation and expected effectiveness are discussed.

Miyamoto, I.↗
NASA NTRS1983

Flight evaluation results for a digital electronic engine control in an F-15 airplane

A digital electronic engine control (DEEC) system on an F100 engine in an F-15 airplane was evaluated in flight. Thirty flights were flown in a four-phase program from June 1981 to February 1983. Significant improvements in the operability and performance of the F100 engine were developed as a result of the flight evaluation: the augmentor envelope was increased by 15,000 ft, the airstart envelope was improved by 75 knots, and the need to periodically trim the engine was eliminated. The hydromechanical backup control performance was evaluated and was found to be satisfactory. Two system failures were encountered in the test program; both were detected and accommodated successfully. No transfers to the backup control system were required, and no automatic transfers occurred. As a result of the successful DEEC flight evaluation, the DEEC system has entered the full-scale development phase.

Burcham, F. W., Jr.↗
NASA NTRS2005

An LO Phase Link Using a Commercial Geo-Stationary Satellite

This viewgraph presentation reviews an experiment to determine feasibility of achieving 1 ps level time transfer using a satellite link and make use of inexpensive Ku band transmit/receive equipment. It reviews the advantages of Two Way Satellite Time Transfer using a commercial Geo-Stationary Satellite: (1) Commercial satellites are available (2) Significant cost reduction when compared to Hydrogen Masers and (3) Large footprint- entire US (including Hawaii) with just one satellite.

two way time transfer↗
NASA NTRS2019

Investigation of Transient Gas Phase Column Density Due to Droplet Evaporation

A NASA robotic refueling mission experiment on board the International Space Station (ISS) was designed to repeatedly transfer simulated cryogenic propellant between two dewars. After each metered transfer, the cryogen was to be vented overboard via sublimation or evaporation. ISS payload providers must conduct analyses to demonstrate that any planned gaseous venting generate no more than a certain level of material that may interfere with optical measurements from other payloads that may be located nearby. This requirement is expressed in terms of a maximum column number density (CND). For the experiment under consideration, fluid droplets likely would accompany any such vapor. Earlier related studies led to development of analytical expressions for column density along general paths for a number of practical cases under steady conditions, including droplet evaporation. These expressions are not appropriate for rapid evaporation of small droplets however, since the droplets cannot sustain mass flow rates consistent with steady conditions. In this work, analytical expressions are developed for estimating column density near a rapidly evaporating droplet along general paths. The influence for instantaneous evaporation is created first as a limiting case, where it is found the peak value occurs at the time it takes a wave of vapor to reach the closest point along the optical path traveling at its most probable thermal speed. Next, the case for finite-period evaporation is evaluated for constant conditions. Compared to the instantaneous case, peak column density occurs shortly after droplet extinction, but at a lower intensity. A new mathematical function is discovered that solves the integrals associated with this case. Finally, ways to account for droplet motion and changes in evaporation rate with size and temperature are discussed in this framework.

Woronowicz, M. S.↗
NASA NTRS2002

The International Intercomparison of 3-Dimensional Radiation Codes

I3RC (International Intercomparison of 3-dimensional Radiation Codes) has as its primary goal to compare a wide variety of three-dimensional (3D) radiative transfer methods applied to Earth's atmosphere, with a few selected cloud fields as input, and a few selected radiative quantities as output. Phases 1 and 2 are now complete, and participants represented institutions in Canada, France, Germany, Russia, the United Kingdom, and the USA, who met for two workshops in Tucson, Arizona USA, and compared results from 5 cloud fields of varying complexity, beginning with simplified atmosphere and surface, and proceeding to more realistic cases. Phase 3 is now underway, focusing on improvement and sharing of 3D radiation code, aided by working groups on "Approximations" and "Open Source". The "Approximations" group has so far focused on diffusive approximate methods in an attempt to gain advantages in execution time, and also to advance the understanding of 3D radiation processes. The "Open Source" subgroup is developing a Monte Carlo radiative transfer toolkit that makes state-of-the-art techniques available to a wide range of users. Activities of both subgroups are further explained at the I3RC website http://i3rc.gsfc.nasa.gov. Participants in 13RC are forming a 3D Working Group under the auspices of the International Radiation Commission, and will meet for this and related activities at a workshop in Tucson in November 2002.

Cahalan, R. F.↗
NASA NTRSDate not supplied

Development of an Advanced Clothing Model that Considers Heat and Moisture Transport

Despite recent advancements in the development of human thermal physiology models, clothing is often considered in only a rudimentary manner, that is, as a boundary condition at the skin characterized by its bulk thermal and evaporative impedances. While such an approach may be sufficient for thermoregulation modeling of humans operating in relatively low thermal burden scenarios, e.g., within an office environment, a clothing thermal model that does not explicitly consider the layer-to-layer transport of vapor can yield incorrect results, especially under conditions corresponding to high thermal stress or extreme environments. For example, vapor diffusing through layers of clothing can reach its dew point, in which case a phase change will occur that can fundamentally affect the transport of moisture and heat within the clothing ensemble. Specifically, the evaporation and condensation of moisture within the fabric layers can affect liquid content and temperature and, ultimately, affect thermo-physiological response and thermal comfort perception. Development of an advanced clothing model that considers heat and moisture transport within the fabric layers can improve the accuracy of human thermal predictions in scenarios where clothing-based condensation and evaporation occur. This paper describes how a general heat transfer software modeling tool was modified to consider the transport of vapor, the storage of liquid, and the thermal effects of phase change within a clothing ensemble. The advanced clothing moisture model was tested by comparing its predictions to measurements derived from sweating hot plate experiments and human physiological experiments. The model was able to reproduce the thermal and moisture results from tests performed under conditions in which condensation within the clothing layers was known to occur. This study demonstrates the importance of considering layer-to-layer vapor transport in clothing models and its impact on human thermal modeling predictions.

Human thermal modeling↗
NASA NTRS1972

Modulation and detection of optical signals

A summary of information is presented which is related to the modulation and detection of information on optical carriers. It emphasizes the treatment of information transfer through an entire system. The most common configurations are considered: intensity modulation, amplitude modulation, frequency or phase modulation, and both direct and coherent detection. In assessing these configurations information capacity and message signal-to-noise ratio are used as a basis of comparison. The physical and geometric treatment of optical heterodyne (or coherent) detection is given.

Goodwin, F. E.↗
NASA NTRS1973

The moon as a high temperature condensate.

The accretion during condensation mechanism, if it occurs during the early over-luminous stage of the sun, can explain the differences in composition of the terrestrial planets and the moon. An important factor is the variation of pressure and temperature with distance from the sun, and in the case of the moon and captured satellites of other planets, with distance from the median plane. Current estimates of the temperature and pressure in the solar nebula suggest that condensation will not be complete in the vicinity of the terrestrial planets, and that depending on location, iron, magnesium silicates and the volatiles will be at least partially held in the gaseous phase and subject to separation from the dust by solar wind and magnetic effects associated with the transfer of angular momentum just before the sun joins the Main Sequence. Many of the properties of the moon, including the 'enrichment' in Ca, Al, Ti, U, Th, Ba, Sr and the REE and the 'depletion' in Fe, Rb, K, Na and other volatiles can be understood if the moon represents a high temperature condensate from the solar nebula.

Anderson, D. L.↗
NASA NTRS1976

Solid state television camera

The design, fabrication, and tests of a solid state television camera using a new charge-coupled imaging device are reported. An RCA charge-coupled device arranged in a 512 by 320 format and directly compatible with EIA format standards was the sensor selected. This is a three-phase, sealed surface-channel array that has 163,840 sensor elements, which employs a vertical frame transfer system for image readout. Included are test results of the complete camera system, circuit description and changes to such circuits as a result of integration and test, maintenance and operation section, recommendations to improve the camera system, and a complete set of electrical and mechanical drawing sketches.

Source record↗
NASA NTRS1976

Multiple scattered radiation emerging from Rayleigh and continental haze layers. I - Radiance, polarization, and neutral points

The matrix operator method was used to calculate the polarization of radiation scattered on layers of various optical thicknesses, with results compared for Rayleigh scattering and for scattering from a continental haze. In both cases, there are neutral points arising from the zeros of the polarization of single scattered photons at scattering angles of zero and 180 degrees. The angular position of these Rayleigh-like neutral points (RNP) in the sky shows appreciable variation with the optical thickness of the scattering layer for a Rayleigh phase matrix, but only a small variation for haze L phase matrix. Another type of neutral point exists for non-Rayleigh phase functions that is associated with the zeros of the polarization for single scattering which occurs between the end points of the curve. A comparison of radiances calculated from the complete theory of radiative transfer using Stokes vectors with those obtained from the scalar theory shows that differences of the order of 23% may be obtained for Rayleigh scattering, while the largest difference found for a haze L phase function was of the order of 0.1%.

Kattawar, G. W.↗
NASA NTRS1984

Solidification and crystal growth of solid solution semiconducting alloys

Problems associated with the solidification and crytal growth of solid-solution semiconducting alloy crystals in a terrestrial environment are described. A detailed description is given of the results for the growth of mercury cadmium telluride (HgCdTe) alloy crystals by directional solidification, because of their considerable technological importance. A series of HgCdTe alloy crystals are grown from pseudobinary melts by a vertical Bridgman method using a wide range of growth rates and thermal conditions. Precision measurements are performed to establish compositional profiles for the crystals. The compositional variations are related to compositional variations in the melts that can result from two-dimensional diffusion or density gradient driven flow effects ahead of the growth interface. These effects are discussed in terms of the alloy phase equilibrium properties, the recent high temperature thermophysical data for the alloys and the highly unusual heat transfer characteristics of the alloy/ampule/furnace system that may readily lead to double diffusive convective flows in a gravitational environment.

Lehoczky, S. L.↗
NASA NTRS1985

Evaluation of PHOENICS as a design analysis tool for SSME

The use of the computational fluid dynamics computer code PHOENICS was proposed as a design analysis tool for improving the Space Shuttle Main Engines (SSME). The PHOENICS is a general purpose computer code for the simulation of fluid-flow, heat-transfer and combustion processes arising in engineering, scientific research and environment. It analyzes one or two-phase flows, in one, two, or three dimensions. The application of PHOENICS to evaluate the performance of high-pressure gaseous-hydrogen filters is examined. The usefulness of the code and the ability of the code to handle successively more complex features of the device are demonstrated.

Ventrice, M. B.↗