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NASA NTRSDate not supplied

CFD Model Development of a Cryogenic Storage Tank Self-Pressurization in Normal Gravity and Validation against SHIIVER Experiment

Two-phase flow and heat transfer simulations with interfacial phase change of the Structural Heat Intercept, Insulation, and Vibration Evaluation Rig (SHIIVER) self-pressurization experiment were conducted using storage tank CFD model in the framework of the ANSYS Fluent CFD code. The simulations were performed for the 70% fill level case with MLI on domes and no vapor cooling. All the phase change calculations in these simulations were generated by in-house Schrage-based evaporation-condensation model. The calculations were performed using both the Volume of Fluid (VOF) and Sharp Interface multiphase 2D axisymmetric models. A number of parametric and sensitivity studies were performed to check the various aspects of the CFD model. These studies helped to understand the effects of varying several parameters on the tank pressure and temperature during self-pressurization. Turbulence modeling; turbulence damping at the interface; and using constant vs. temperature dependent fluid properties were shown to have the most profound influence on predicted tank pressures and temperatures. Current study indicates that including phase change at the interface into the computational model is crucial for accurate prediction of the tank self-pressurization process. The effect of accommodation coefficient was also studied. Tank pressure values predicted by the VOF, and Sharp Interface models are within 4% of the experimental ones.

Computational Fluid Dynamics↗

NASA NTRS1997

Transport Phenomena During Equiaxed Solidification of Alloys

Recent progress in modeling of transport phenomena during dendritic alloy solidification is reviewed. Starting from the basic theorems of volume averaging, a general multiphase modeling framework is outlined. This framework allows for the incorporation of a variety of microscale phenomena in the macroscopic transport equations. For the case of diffusion dominated solidification, a simplified set of model equations is examined in detail and validated through comparisons with numerous experimental data for both columnar and equiaxed dendritic growth. This provides a critical assessment of the various model assumptions. Models that include melt flow and solid phase transport are also discussed, although their validation is still at an early stage. Several numerical results are presented that illustrate some of the profound effects of convective transport on the final compositional and structural characteristics of a solidified part. Important issues that deserve continuing attention are identified.

Beckermann, C.↗

NASA NTRS2000

Volatile Removal Assembly Flight Experiment and KC-135 Packed Bed Experiment: Results and Lessons Learned

The Volatile Removal Assembly (VRA) is a high temperature catalytic oxidation process that will be used as the final treatment for recycled water aboard the International Space Station (ISS). The multiphase nature of the process had raised concerns as to the performance of the VRA in a microgravity environment. To address these concerns, two experiments were designed. The VRA Flight Experiment (VRAFE) was designed to test a full size VRA under controlled conditions in microgravity aboard the SPACEHAB module and in a 1 -g environment and compare the performance results. The second experiment relied on visualization of two-phase flow through small column packed beds and was designed to fly aboard NASA's microgravity test bed plane (KC-135). The objective of the KC-135 experiment was to understand the two-phase fluid flow distribution in a packed bed in microgravity. On Space Transportation System (STS) flight 96 (May 1999), the VRA FE was successfully operated and in June 1999 the KC-135 packed bed testing was completed. This paper provides an overview of the experiments and a summary of the results and findings.

Holder, Donald W.↗

NASA NTRSDate not supplied

Overview of Extractive and Optical PM Measurements from the NASA SE-5 High Pressure Flame Diagnostics Laboratory

Soot emissions measurements of multiphase non-premixed flames are sparse in the literature due to the complexities of sampling in such environments. We present an overview from on-going work at the NASA SE-5 High Pressure Flame Diagnostics laboratory focusing on soot and gaseous emissions at elevated pressures. SE-5 is a gaseous and liquid fueled high pressure flame tube facility capable of operating at pressures up to 880 psia, cooling capacity of 4,000,000 BTU/hr, liquid fuel flow rates up to 2 GPH, and an equivalence ratio range of 0.2 (fuel lean) to 4 (fuel rich). SE-5 provides optical access via four UV-grade fused silica optical windows of the primary reaction zone enabling non-intrusive optical diagnostics of the flame.

Soot↗

NASA NTRS2005

The nakhlite meteorites: Augite-rich igneous rocks from Mars

The seven nakhlite meteorites are augite-rich igneous rocks that formed in flows or shallow intrusions of basaltic magma on Mars. They consist of euhedral to subhedral crystals of augite and olivine (to 1 cm long) in fine-grained mesostases. The augite crystals have homogeneous cores of Mg' = 63% and rims that are normally zoned to iron enrichment. The core-rim zoning is cut by iron-enriched zones along fractures and is replaced locally by ferroan low-Ca pyroxene. The core compositions of the olivines vary inversely with the steepness of their rim zoning - sharp rim zoning goes with the most magnesian cores (Mg' = 42%), homogeneous olivines are the most ferroan. The olivine and augite crystals contain multiphase inclusions representing trapped magma. Among the olivine and augite crystals is mesostasis, composed principally of plagioclase and/or glass, with euhedra of titanomagnetite and many minor minerals. Olivine and mesostasis glass are partially replaced by veinlets and patches of iddingsite, a mixture of smectite clays, iron oxy-hydroxides and carbonate minerals. In the mesostasis are rare patches of a salt alteration assemblage: halite, siderite, and anhydrite/ gypsum. The nakhlites are little shocked, but have been affected chemically and biologically by their residence on Earth. Differences among the chemical compositions of the nakhlites can be ascribed mostly to different proportions of augite, olivine, and mesostasis. Compared to common basalts, they are rich in Ca, strongly depleted in Al, and enriched in magmaphile (incompatible) elements, including the LREE. Nakhlites contain little pre-terrestrial organic matter. Oxygen isotope ratios are not terrestrial, and are different in anhydrous silicates and in iddingsite. The alteration assemblages all have heavy oxygen and heavy carbon, while D/H values are extreme and scattered. Igneous sulfur had a solar-system isotopic ratio, but in most minerals was altered to higher and lower values. High precision analyses show mass-independent fractionations of S isotopes. Nitrogen and noble gases are complex and represent three components: two mantle sources (Chas-E and Chas-S), and fractionated Martian atmosphere. The nakhlites are igneous cumulate rocks, formed from basaltic magma at approx.1.3 Ga, containing excess crystals over what would form from pure magma. After accumulation of their augite and olivine crystals, they were affected (to various degrees) by crystallization of the magma, element diffusion among minerals and magma, chemical reactions among minerals and magma, magma movement among the crystals, and post-igneous chemical equilibration. The extent of these modifications varies, from least to greatest, in the order: MIL03346, NWA817, Y000593, Nakhla = Governador Valadares, Lafayette, and NWA998. Chemical, isotopic, and chronologic data confirm that the nakhlites formed on Mars, most likely in thick lava flows or shallow intrusions. Their crystallization ages, referenced to crater count chronologies for Mars, suggest that the nakhlites formed on the large volcanic constructs of Tharsis, Elysium, or Syrtis Major. The nakhlites were suffused with liquid water, probably at approx.620 ma. This water dissolved olivine and mesostasis glass, and deposited iddingsite and salt minerals in their places. The nakhlites were ejected from Mars at approx.10.75Ma by an asteroid impact and fell to Earth within the last 10,000 years. Although the nakhlites are enriched in incompatible elements, their source mantle was strongly depleted. This depletion event was ancient, as the nakhlites source mantle was fractionated while short-lived radionuclides (e.g., t(sub 1/2 = 9 my) were still active. This differentiation event may have been core formation coupled with a magma ocean, as is inferred for the moon.

Treiman, Allan H.↗

NASA NTRS1989

High-temperature ordered intermetallic alloys III; Proceedings of the Third Symposium, Boston, MA, Nov. 29-Dec. 1, 1988

The present conference on high-temperature ordered intermetallic alloys discusses alloy theory and phase stability, defects and microstructures, mechanical behavior, alloy design and material processing, multiphase and composite materials, nickel aluminides, titanium aluminides, and other ordered intermetallics. Attention is given to compositional effects on processing and properties of nickel aluminides, dynamic compaction and hot-isostatic-pressing of nickel aluminides, improvement of elevated-temperature material properties in Ni3Al, the effect of microalloying B on the high-temperature mechanical properties of Ti3Al, the effects of structure on creep of Ti-53.4 mol pct Al intermetallics, the deformation microstructure in Ni3Si polycrystals strained over the range of temperature of flow stress anomaly, and the microstructure and mechanical properties of dual phase alloys consisting of the intermetallic phases.

Liu, C. T.↗

NASA NTRS1986

Shock waves and shock tubes; Proceedings of the Fifteenth International Symposium, Berkeley, CA, July 28-August 2, 1985

A detailed survey is presented of shock tube experiments, theoretical developments, and applications being carried out worldwide. The discussions explore shock tube physics and the related chemical, physical and biological science and technology. Extensive attention is devoted to shock wave phenomena in dusty gases and other multiphase and heterogeneous systems, including chemically reactive mixtures. Consideration is given to techniques for measuring, visualizing and theoretically modeling flowfield, shock wave and rarefaction wave characteristics. Numerical modeling is explored in terms of the application of computational fluid dynamics techniques to describing flowfields in shock tubes. Shock interactions and propagation, in both solids, fluids, gases and mixed media are investigated, along with the behavior of shocks in condensed matter. Finally, chemical reactions that are initiated as the result of passage of a shock wave are discussed, together with methods of controlling the evolution of laminar separated flows at concave corners on advanced reentry vehicles.

Bershader, D.↗

NASA NTRS2017

Synthetic Absorption Lines for a Clumpy Medium: A Spectral Signature for Cloud Acceleration in AGN?

There is increasing evidence that the highly ionized multiphase components of AGN disc winds may be due to thermal instability. The ions responsible for forming the observed X-ray absorption lines may only exist in relatively cool clumps that can be identified with the so-called warm absorbers. Here we calculate synthetic absorption lines for such warm absorbers from first principles by combining 2D hydrodynamic solutions of a two-phase medium with a dense grid of photoionization models to determine the detailed ionization structure of the gas. Our calculations reveal that cloud disruption, which leads to a highly complicated velocity field (i.e. a clumpy flow), will only mildly affect line shapes and strengths when the warm gas becomes highly mixed but not depleted. Prior to complete disruption, clouds that are optically thin to the driving UV resonance lines will cause absorption at an increasingly blueshifted line-of-sight velocity as they are accelerated. This behavior will imprint an identifiable signature on the line profile if warm absorbers are enshrouded in an even broader absorption line produced by a high column of intercloud gas. Interestingly, we show that it is possible to develop a spectral diagnostic for cloud acceleration by differencing the absorption components of a doublet line, a result that can be qualitatively understood using a simple partial covering model. Our calculations also permit us to comment on the spectral differences between cloud disruption and ionization changes driven by flux variability. Notably, cloud disruption offers another possibility for explaining absorption line variability.

line: formation â€“ galaxies: nuclei â€“ quasars: ↗

NASA NTRS1997

Evidence for a Multiphase ISM in Early Type Galaxies and Elliptical Galaxies with Strong Radio Continuum

We have observed NGC 1316 (Fornax A) with the ROSAT HRI. In this paper, we present the results of these observations and we complement them with the spectral analysis of the archival PSPC data. The spectral properties suggest the presence of a significant component of thermal X-ray emission (greater than 60%), amounting to approx. 10(exp 9) solar mass of hot ISM. Within 3 feet from the nucleus of NGC 1316, the HRI X-ray surface brightness falls as r(exp -2) following the stellar light. In the inner approx. 30 inch., however, the X-ray surface brightness is significantly elongated, contrary to the distribution of stellar light, which is significantly rounder within 10 inch. This again argues for a non-stellar origin of the X-ray emission. This flattened X-ray feature is suggestive of either the disk-like geometry of a rotating cooling flow and/or the presence of extended, elongated dark matter. By comparing the morphology of the X-ray emission with the distribution of optical dust patches, we find that the X-ray emission is significantly reduced at the locations where the dust patches are more pronounced, indicating that at least some of the X-ray photons are absorbed by the cold ISM. We also compare the distribution of the hot and cold ISM with that of the ionized gas, using recently obtained H(sub alpha) CCD data. We find that the ionized gas is distributed roughly along the dust patches and follows the large scale X-ray distribution at r greater than 1 foot from the nucleus. However, there is no one-to-one correspondence between ionized gas and hot gas. Both morphological relations and kinematics suggest different origins for hot and cold ISM. The radio jets in projection appear to pass perpendicularly through the central X-ray ellipsoid. Comparison of thermal and radio pressures suggests that the radio jets are confined by the surrounding hot gaseous medium.

Kim, Dong Woo↗

NASA NTRSDate not supplied

Parabolic Flights in Support of the Ring-Sheared Drop (RSD) Module Aboard the ISS

The Ring-Sheared Drop module was conceived as a centimeter-scale, containerless biochemical reactor to study shearing flow at gas-liquid interfaces without complications associated with solid walls. The drop is constrained by a thin, stationary contact ring in one hemisphere and sheared by the steady rotation of another ring in the other hemisphere. The original experiment considers a 2.5 cm diameter drop of human insulin solution in order to examine the formation of amyloid fibrils without wall nucleation. Shear-induced amyloidogenesis is of wide interest due to the pathogenic role amyloid proteins play in diseases such as Alzheimer's, Parkinson's, prion diseases, and type-2 diabetes. Pinning full-scale drops of native protein solutions - prior to any fibrillization - was challenging and required a collaborative effort. In this talk we report on laboratory experiments, multiphase CFD simulations, and several parabolic flights to find strategies that are effective for constraining large drops of protein in microgravity.

Amir Hirsa↗

NASA NTRS1989

Turbulence kinetic energy equation for dilute suspensions

A multiphase turbulence closure model is presented which employs one transport equation, namely the turbulence kinetic energy equation. The proposed form of this equation is different from the earlier formulations in some aspects. The power spectrum of the carrier fluid is divided into two regions, which interact in different ways and at different rates with the suspended particles as a function of the particle-eddy size ratio and density ratio. The length scale is described algebraically. A mass/time averaging procedure for the momentum and kinetic energy equations is adopted. The resulting turbulence correlations are modeled under less retrictive assumptions comparative to previous work. The closures for the momentum and kinetic energy equations are given. Comparisons of the predictions with experimental results on liquid-solid jet and gas-solid pipe flow show satisfactory agreement.

Abou-Arab, T. W.↗

NASA NTRS1995

Microgravity combustion of dust clouds: Quenching distance measurements

The current level of physical understanding of dust combustion phenomena is still in a rudimentary state compared with the understanding of gas combustion processes. The reason for such a lack of fundamental understanding is partially based on the complexity of multiphase combustion and the enormous diversity of chemical-physical properties of heterogeneous combustible mixtures but is largely due to difficulties in the experimental investigation of dust combustion. The influence of gravity on a dust suspension is the main reason. First of all, when particulates (either solid particles or liquid droplets) with a characteristic size of the order of tens of microns are suspended, they rapidly settle in the gravitational field. To maintain a particulate suspension for a time duration adequate to carry out combustion experiments invariably requires continuous convection of particulates at or in excess of the gravitational settling velocity. Of necessity, this makes the experiments turbulent in character and makes it impossible to study laminar dust flames. For particle sizes of the order of microns a stable laminar dust flow can be maintained only for relatively small dust concentrations (e.g., for low fuel equivalence ratios) at normal gravity conditions. High dust loading leads to gravitational instability of the dust cloud and to the formation of recirculation cells in a dust suspension in a confined volume, or to the rapid sedimentation of the dense dust cloud as a whole in an unconfined volume. In addition, many important solid fuels such as low volatile coal, carbon, and boron have low laminar flame speeds (of the order of several centimeters per second). Gravitational convection that occurs in combustion products due to the buoyancy forces disrupts low speed dust flames and, therefore, makes observation of such flames at normal gravity impossible. The only way to carry out 'clean' fundamental experiments in dust combustion over a wide range of dust cloud parameters is in a gravity-free environment. Access to the microgravity environment provided by the use of large-scale drop towers, parabolic flights of aircraft and rockets, and shuttle and space station orbits has permitted now to proceed with a systematic program of dust combustion microgravity research. For example, the NASA-Lewis drop tower and a Lear jet parabolic flight aircraft were used by Ross et al. and by Berlad and Tangirala for experiments with Iycopodium/air mixtures. The Japan Microgravity Center drop shaft (JAMIC) where a microgravity condition of 10(exp -4) g for 10 s is available, was recently used by Kobayashi, Niioka et al. for measuring flame propagation velocities in polymethyl methacrylate dust/air suspensions. Microgravity dust combustion experiments were started at McGill University in the early 90's under the sponsorship of the Canadian Space Agency. Several generations of dust combustion platforms permitting dust combustion microgravity experiments to be carried out on board a parabolic flight aircraft (KC-135, NASA) have been designed and tested. The experimental data and experience gained from this research allowed us to design and build in a current phase of this program the microgravity apparatus for the visual observation of freely propagating constant pressure laminar dust flames. Quenching distances in aluminum dust suspensions have been measured in a wide range of dust cloud parameters in ground-based experiments and in recent microgravity experiments (KC-135 parabolic flights, Houston, February 1995).

Goroshin, S.↗

NASA NTRS2018

Columbus IFHX Ammonia Leak Analysis

After the Columbus Moderate Temperature Loop (MTL) InterFace Heat eXchanger (IFHX) low temperature event of GMT 345-2013, NASA investigated relevant transient scenarios involving IFHX rupture after water freezing and subsequent thawing. NASA recommended development of a Fault Detection Isolation and Recovery (FDIR) plan that would, in the event of a heat exchanger freeze event, close the Water On/Off Valves (WOOVs) to isolate the heat exchanger and prevent ammonia from the external flow loops from spreading into the cabin. NASA performed a preliminary simplified analysis for the reference case of IFHX rupture, but for a deeper understanding TAS developed detailed SINDA-FLUINT models of the Columbus ITCS that were built and run through the SINAPS GUI. This allowed simulation of the ammonia leakage physics including the variation of environmental parameters, thus providing more accurate and specific input to the FDIR under development. The result was finalization of the IFHX WOOVs closure sequence and wait times to contain the ammonia propagation to Columbus and allow identification of the leaking IFHX. In addition, the analysis results provided reference pressure profiles to be used on console and by the Engineering as support for the telemetry data assessment in case of failure.This paper gives an overview on the issue and focuses on the analytical aspects of the multiphase fluid dynamics involved.

Tilloca, A.↗

NASA NTRS1986

Description of a 20 kilohertz power distribution system

A single phase, 440 VRMS, 20 kHz power distribution system with a regulated sinusoidal wave form is discussed. A single phase power system minimizes the wiring, sensing, and control complexities required in a multi-sourced redundantly distributed power system. The single phase addresses only the distribution links multiphase lower frequency inputs and outputs accommodation techniques are described. While the 440 V operating potential was initially selected for aircraft operating below 50,000 ft, this potential also appears suitable for space power systems. This voltage choice recognizes a reasonable upper limit for semiconductor ratings, yet will direct synthesis of 220 V, 3 power. A 20 kHz operating frequency was selected to be above the range of audibility, minimize the weight of reactive components, yet allow the construction of single power stages of 25 to 30 kW. The regulated sinusoidal distribution system has several advantages. With a regulated voltage, most ac/dc conversions involve rather simple transformer rectifier applications. A sinusoidal distribution system, when used in conjunction with zero crossing switching, represents a minimal source of EMI. The present state of 20 kHz power technology includes computer controls of voltage and/or frequency, low inductance cable, current limiting circuit protection, bi-directional power flow, and motor/generator operating using standard induction machines. A status update and description of each of these items and their significance is presented.

Hansen, I. G.↗

NASA NTRSDate not supplied

Comprehensive Digital Twin of a Macro-fluidic Electrochemical Reactor to Optimize the Electrochemical-based Recovery of O2 from Metabolic CO2

Future long-duration missions will require a sustainable and efficient system capable of yielding a minimum of 75% O 2 recovery from metabolic CO 2 to achieve self-sufficiency for long space missions beyond Earth's low orbit. A Macro-fluidic Electrochemical Reactor (MFECR) development effort to electrochemically recover O 2 from CO 2 is underway at NASA Marshall Space Flight Center (MSFC) to increase current O 2 recovery efficiency and reduce air revitalization (AR) system complexity at the International Space Station (ISS) habitat and future long missions. The authors have developed and deployed a digital twin of an actual single cell of the MFECR via a comprehensive 3D multiphysics model that thoroughly replicates the exact configuration and fluid/material domains of the MFECR. This model's electrochemical physics consists of multicomponent-multiphase electrochemical-driven reactions leading to CO 2 conversion to C 2 H 4 and CO along with the formation of H 2 on the cathode in parallel with the generation of O 2 and H 2 O on the anode. This electrochemical model is coupled with all the physics phenomena involved in the process, including but not limited to fluid and non-ideal mass transfer of reactant and product species in free and porous media, convective/conduction/radiative heat transfer, and conduction of DC electrical current with Joule heating generation. The digital twin has proved to be an essential tool for performing different qualitative studies, including the effect of reducing the height (increasing the respect ratio) of the serpentine walls, leading to a further redesign of the EDU (the newly redesigned MFECR EDU has been fabricated and is expected to be used in future tests), the evaluation of setting different MFECRs connected in series, and the assessment of feeding air directly to the MFECR skipping the preceding metabolic CO 2 separation from air. The MFECR's test stand is fully automated and equipped with several inline measurements (flow, pressure, temperature, pH, component concentration) systems on all six MFECR's IO streams, allowing reliable experimental validation of the model, parametric determination of all electrochemical reactions, and process optimization.

Jesus A Dominguez↗

NASA NTRSDate not supplied

A CFD Framework for Film Boiling and Quenching in Cryogenic Chilldown

Tests of cryogenic chilldown in a vertical stainless steel tube are simulated using computational fluid dynamics (CFD). Subcooled liquid nitrogen enters the room-temperature tube at one end, resulting in film boiling and eventual quenching of the tube walls. A CFD-based modeling framework employing the mixture multiphase model has been developed to simulate this chilldown process and applied to validate it against experimental data. Extensive sensitivity studies have been performed to create a consistent modeling framework, and a two test conditions are simulated to test the modeling capability. The importance of the rewetting temperature and its relation to the foam limit temperature is discussed and is considered in the CFD model. The presented results demonstrate a qualitatively consistent representation of the film boiling and quenching regime. However, the quantitative accuracy of the simulations varies with the test conditions. Simulated vapor volume fraction distributions are also presented, although the current lack of experimental volume fraction data does not permit a comparison.

Computational Fluid Dynamics↗

NASA NTRSDate not supplied

A CFD Framework for Film Boiling and Quenching in Cryogenic Chilldown

Tests of cryogenic chilldown in a vertical stainless-steel tube are simulated using computational fluid dynamics (CFD). Subcooled liquid nitrogen enters a room-temperature tube at one end, resulting in film boiling and eventual quenching of the tube walls. A CFDbased modeling framework employing the mixture multiphase model was developed to simulate this chilldown process and was applied to validate it against experimental data. Extensive sensitivity studies have been performed to create a consistent modeling framework, and a range of test conditions are simulated to assess the modeling capability. The importance of the rewetting temperature and its relation to the foam limit temperature is discussed and considered in the CFD framework. The presented results demonstrate a qualitatively consistent representation of the film boiling and quenching regime. However, the quantitative accuracy of the simulations varies with the test conditions. In addition, simulated distributions of the vapor volume fraction are presented, but the current lack of experimental volume fraction data prevents comparisons.

Computational Fluid Dynamics↗

NASA NTRSDate not supplied

A CFD Framework for Film Boiling and Quenching in Cryogenic Chilldown

Computational Fluid Dynamics↗