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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Impedance Emulation Control of Wave Energy Converters

Modeling and control of wave energy conversion (WEC) systems for maximum power extraction is challenging due to complex multiphysics that include fluids, mechanics, and machine drives. To uncover an intuitive model that clearly depicts WEC system operation, we utilize a force-current equivalent circuit framework which then enables us to design an impedance emulation control strategy. To provide context for our framework, we focus on a standard reference model-3 (RM3) point absorber device coupled to a permanent magnet synchronous generator. After the proposed extremum seeking controller is computed, we experimentally validate its performance on a platform that consists of two back-to-back connected inverters that emulate the WEC system.

wave energy conversion, impedance emulation, machi↗
DOE OSTI2022

In situ temperature measurements in sooting methane/air flames using synchrotron x-ray fluorescence of seeded krypton atoms

Synchrotron x-ray fluorescence has been used to measure temperatures in optically dense gases where traditional methods would fail. These data provide a benchmark for stringent tests of computational fluid dynamics models for complex systems where physical and chemical processes are intimately linked. The experiments measured krypton number densities in a sooting, atmospheric pressure, nonpremixed coflow flame that is widely used in combustion research. The experiments not only form targets for the models, but the simulations also identify potential sources of uncertainties in the measurements, allowing for future improvements.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Using Low-Field Nuclear Magnetic Resonance and X-Ray Computed Microtomography Imaging to Explore Potential of Microbially-Induced Calcium Carbonate Precipitation Treatment to Seal Shale Fractures

Microbially-induced calcium carbonate precipitation (MICP) is a biological process in which microbially produced urease enzymes convert urea and calcium into solid calcium carbonate (CaCO 3 ) deposits. Studies have shown that MICP can be used to seal fractures in shale, raising the possibility of applying this technology to restimulate fracking wells by plugging underperforming fractures. For this and other applications to become a reality, non-invasive tools are needed to determine how effectively MICP seals shale fractures under subsurface conditions. In this study, a 2.54 cm wide and 5.08 cm long Marcellus shale core with a single, ~1 mm wide fracture held open by sand "proppant" underwent MICP-treatment at 60°C until reaching three orders of magnitude permeability reduction. Low-field nuclear magnetic resonance (LF-NMR) and X-Ray computed microtomography (μ-CT) techniques were used to assess the extent of biomineralization within the fracture. These tools revealed that while CaCO 3 precipitation occurred throughout the fracture, there was preferential precipitation around proppant, and the core sealed at the effluent end before filling most of the fracture. Both tools were able to independently calculate of the amount of solid biomineral formed inside the fracture. Furthermore, this study found that the distribution of proppant within the shale fracture was an important parameter controlling the degree of biomineralization.

clastic rock↗
NASA NTRS1975

Dynamo generation in Mercury

Models of the interior and thermal evolution of Mercury calculated by Siegfried and Solomon (1974) using Lewis' (1972) cosmochemical calculations to constrain the composition are tested for four necessary conditions for MHD dynamo generation. It is shown that dynamo generation requires at least a partially fluid interior, an energy source that drives a flow of core fluid relative to the rigidly rotating planet, a magnetic-field diffusion time in excess of the characteristic fluid-flow time scale, and a fluid flow of sufficient complexity to satisfy Cowling's (1934) theorem. It is concluded that a literal interpretation of Lewis' calculations implies that dynamo generation in Mercury is improbable. Generation would be possible only if the metallic core were contaminated with substantial amounts of radioactive material.

Stevenson, D. J.↗
NASA NTRS1986

Separated flow

A brief overview of flow separation phenomena is provided. Langley has many active research programs in flow separation related areas. Three cases are presented which describe specific examples of flow separation research. In each example, a description of the fundamental fluid physics and the complexity of the flow field is presented along with a method of either reducing or controlling the extent of separation. The following examples are discussed: flow over a smooth surface with an adverse pressure gradient; flow over a surface with a geometric discontinuity; and flow with shock-boundary layer interactions. These results will show that improvements are being made in the understanding of flow separation and its control.

Sellers, W. L., III↗
NASA NTRS1990

Quantitative computer representation of propellant processing

With the technology currently available for the manufacture of propellants, it is possible to control the variance of the total specific impulse obtained from the rocket boosters to within approximately five percent. Though at first inspection this may appear to be a reasonable amount of control, when it is considered that any uncertainty in the total kinetic energy delivered to the spacecraft translates into a design with less total usable payload, even this degree of uncertainty becomes unacceptable. There is strong motivation to control the variance in the specific impulse of the shuttle's solid boosters. Any small gains in the predictability and reliability of the booster would lead to a very substantial payoff in earth-to-orbit payload. The purpose of this study is to examine one aspect of the manufacture of solid propellants, namely, the mixing process. The traditional approach of computational fluid mechanics is notoriously complex and time consuming. Certain simplifications are made, yet certain fundamental aspects of the mixing process are investigated as a whole. It is possible to consider a mixing process in a mathematical sense as an operator, F, which maps a domain back upon itself. An operator which demonstrates good mixing should be able to spread any subset of the domain completely and evenly throughout the whole domain by successive applications of the mixing operator, F. Two and three dimensional models are developed and graphical visualization two and three dimensional mixing processes are presented.

Hicks, M. D.↗
NASA NTRS1993

A Fine-Grid Model for the ASRM Aft Segment with Gimballed Nozzle

Results from computational fluid dynamic analyses for complex three-dimensional internal flows in the Advanced Solid Rocket Motor (ASRM) are presented. In particular, flow visualization and tabulated results from a fine-grid model consisting of 1.5 M grid points for the ASRM Aft Segment at the l9-second burn time with an 8-degree nozzle gimbal angle are shown. The results from this model will enable characterization of various aspects of the ASRM internal environment, and in particular will allow an assessment of the heat transfer and stresses exerted on the submerged nozzle, casing insulation, and nozzle case joint.

Reske, Edward J.↗
NASA NTRS1999

Effects of Buoyancy in Hydrogen Jet Diffusion Flames

This project was carried out to understand the effects of heat release and buoyancy on the flame structure of diffusion flames. Experiments were conducted at atmospheric pressure in both normal gravity and microgravity conditions in the NASA LeRC 2.2 s drop tower. Experiments were also conducted in a variable pressure combustion facility in normal gravity to scale buoyancy and thus, to supplement the drop tower experiments. Pure H2 or H2 mixed with He was used as the jet fluid to avoid the complexities associated with soot formation. Fuel jet burning in quiescent air was visualized and quantified by the Rainbow Schlieren Deflectometry (RSD) to obtain scalar profiles (temperature, oxygen concentration) within the flame. Burner tube diameter (d) was varied from 0.3 to 1.19 mm producing jet exit Reynolds numbers ranging from 40 to 1900, and generating flames encompassing laminar and transitional (laminar to turbulent) flow structure. Some experiments were also complemented with the CFD analysis. In a previous paper, we have presented details of the RSD technique, comparison of computed and measured scalar distributions, and effects of buoyancy on laminar and transitional H2 gas-jet diffusion flames. Results obtained from the RSD technique, variable pressure combustion chamber, and theoretical models have been published. Subsequently, we have developed a new drop rig with improved optical and image acquisition. In this set up, the schlieren images are acquired in real time and stored digitally in RAM of an onboard computer. This paper deals with laminar diffusion flames of pure H2 in normal and microgravity.

Agrawal, A. K.↗
NASA NTRS2004

Advanced Computational Modeling of Vapor Deposition in a High-pressure Reactor

In search of novel approaches to produce new materials for electro-optic technologies, advances have been achieved in the development of computer models for vapor deposition reactors in space. Numerical simulations are invaluable tools for costly and difficult processes, such as those experiments designed for high pressures and microgravity conditions. Indium nitride is a candidate compound for high-speed laser and photo diodes for optical communication system, as well as for semiconductor lasers operating into the blue and ultraviolet regions. But InN and other nitride compounds exhibit large thermal decomposition at its optimum growth temperature. In addition, epitaxy at lower temperatures and subatmospheric pressures incorporates indium droplets into the InN films. However, surface stabilization data indicate that InN could be grown at 900 K in high nitrogen pressures, and microgravity could provide laminar flow conditions. Numerical models for chemical vapor deposition have been developed, coupling complex chemical kinetics with fluid dynamic properties.

Cardelino, Beatriz H.↗
NASA NTRS2004

Investigation of Navier-Stokes Code Verification and Design Optimization

With rapid progress made in employing computational techniques for various complex Navier-Stokes fluid flow problems, design optimization problems traditionally based on empirical formulations and experiments are now being addressed with the aid of computational fluid dynamics (CFD). To be able to carry out an effective CFD-based optimization study, it is essential that the uncertainty and appropriate confidence limits of the CFD solutions be quantified over the chosen design space. The present dissertation investigates the issues related to code verification, surrogate model-based optimization and sensitivity evaluation. For Navier-Stokes (NS) CFD code verification a least square extrapolation (LSE) method is assessed. This method projects numerically computed NS solutions from multiple, coarser base grids onto a freer grid and improves solution accuracy by minimizing the residual of the discretized NS equations over the projected grid. In this dissertation, the finite volume (FV) formulation is focused on. The interplay between the xi concepts and the outcome of LSE, and the effects of solution gradients and singularities, nonlinear physics, and coupling of flow variables on the effectiveness of LSE are investigated. A CFD-based design optimization of a single element liquid rocket injector is conducted with surrogate models developed using response surface methodology (RSM) based on CFD solutions. The computational model consists of the NS equations, finite rate chemistry, and the k-6 turbulence closure. With the aid of these surrogate models, sensitivity and trade-off analyses are carried out for the injector design whose geometry (hydrogen flow angle, hydrogen and oxygen flow areas and oxygen post tip thickness) is optimized to attain desirable goals in performance (combustion length) and life/survivability (the maximum temperatures on the oxidizer post tip and injector face and a combustion chamber wall temperature). A preliminary multi-objective optimization study is carried out using a geometric mean approach. Following this, sensitivity analyses with the aid of variance-based non-parametric approach and partial correlation coefficients are conducted using data available from surrogate models of the objectives and the multi-objective optima to identify the contribution of the design variables to the objective variability and to analyze the variability of the design variables and the objectives. In summary the present dissertation offers insight into an improved coarse to fine grid extrapolation technique for Navier-Stokes computations and also suggests tools for a designer to conduct design optimization study and related sensitivity analyses for a given design problem.

Vaidyanathan, Rajkumar↗
NASA NTRS2004

Advanced Computational Modeling of Vapor Deposition in a High-Pressure Reactor

In search of novel approaches to produce new materials for electro-optic technologies, advances have been achieved in the development of computer models for vapor deposition reactors in space. Numerical simulations are invaluable tools for costly and difficult processes, such as those experiments designed for high pressures and microgravity conditions. Indium nitride is a candidate compound for high-speed laser and photo diodes for optical communication system, as well as for semiconductor lasers operating into the blue and ultraviolet regions. But InN and other nitride compounds exhibit large thermal decomposition at its optimum growth temperature. In addition, epitaxy at lower temperatures and subatmospheric pressures incorporates indium droplets into the InN films. However, surface stabilization data indicate that InN could be grown at 900 K in high nitrogen pressures, and microgravity could provide laminar flow conditions. Numerical models for chemical vapor deposition have been developed, coupling complex chemical kinetics with fluid dynamic properties.

Cardelino, Beatriz H.↗
NASA NTRS2012

Supersonic Retropropulsion Technology Development in NASA's Entry, Descent, and Landing Project

NASA's Entry, Descent, and Landing (EDL) space technology roadmap calls for new technologies to achieve human exploration of Mars in the coming decades [1]. One of those technologies, termed Supersonic Retropropulsion (SRP), involves initiation of propulsive deceleration at supersonic Mach numbers. The potential benefits afforded by SRP to improve payload mass and landing precision make the technology attractive for future EDL missions. NASA's EDL project spent two years advancing the technological maturity of SRP for Mars exploration [2-15]. This paper summarizes the technical accomplishments from the project and highlights challenges and recommendations for future SRP technology development programs. These challenges include: developing sufficiently large SRP engines for use on human-scale entry systems; testing and computationally modelling complex and unsteady SRP fluid dynamics; understanding the effects of SRP on entry vehicle stability and controllability; and demonstrating sub-scale SRP entry systems in Earth's atmosphere.

Edquist, Karl T.↗
NASA NTRS2017

Evolved Gas Analyses of Sedimentary Rocks and Eolian Sediment in Gale Crater, Mars: Results of the Curiosity Rover's Sample Analysis at Mars Instrument from Yellowknife Bay to the Namib Dune

The sample analysis at Mars instrument evolved gas analyzer (SAM-EGA) has detected evolved water, H2, SO2, H2S, NO, CO2, CO, O2, and HCl from two eolian sediments and nine sedimentary rocks from Gale Crater, Mars. These evolved gas detections indicate nitrates, organics, oxychlorine phase, and sulfates are widespread with phyllosilicates and carbonates occurring in select Gale Crater materials. Coevolved CO2 (160 +/- 248-2373 +/- 820 μgC(CO2)/g) and CO (11 +/- 3-320 +/- 130 μgC(CO)/g) suggest that organic C is present in Gale Crater materials. Five samples evolved CO2 at temperatures consistent with carbonate (0.32 +/- 0.05-0.70 +/- 0.1 wt % CO3). Evolved NO amounts to 0.002 +/- 0.007-0.06 +/- 0.03 wt % NO3. Evolution of O2 suggests that oxychlorine phases (chlorate/perchlorate) (0.05 +/- 0.025-1.05 +/- 0.44 wt % ClO4) are present, while SO2 evolution indicates the presence of crystalline and/or poorly crystalline Fe and Mg sulfate and possibly sulfide. Evolved H2O (0.9 +/- 0.3-2.5 +/- 1.6 wt % H2O) is consistent with the presence of adsorbed water, hydrated salts, interlayer/structural water from phyllosilicates, and possible inclusion water in mineral/amorphous phases. Evolved H2 and H2S suggest that reduced phases occur despite the presence of oxidized phases (nitrate, oxychlorine, sulfate, and carbonate). SAM results coupled with CheMin mineralogical and Alpha-Particle X-ray Spectrometer elemental analyses indicate that Gale Crater sedimentary rocks have experienced a complex authigenetic/diagenetic history involving fluids with varying pH, redox, and salt composition. The inferred geochemical conditions were favorable for microbial habitability and if life ever existed, there was likely sufficient organic C to support a small microbial population.

Sutter, B.↗
NASA NTRS2019

Evolved Gas Analyses of Sedimentary Rocks and Eolian Sediment in Gale Crater, Mars: Results of the Curiosity Rover's Sample Analysis at Mars Instrument.

The Sample Analysis at Mars instrument evolved gas analyzer (SAM-EGA) has detected evolved water, SO2, NO, CO2, CO, O2, and HCl from two eolian sediments and nine sedimentary rocks from Gale Crater, Mars. The SAM-EGA heats samples to 870°C and measures evolved gas releases as function of temperature. These evolved gas detections indicate nitrates, organics, oxychlorine phase, and sulfates are widespread with phyllosilicates and carbonates occurring in select Gale Crater materials. CO2 and CO evolved at similar temperatures suggesting that as much as 2373 ± 820 μgC/g may occur as organic carbon in the Gale Crater rock record while relatively higher temperature CO2 detections are consistent with carbonate (<0.70 ± 0.1 wt % CO3). Evolved NO amounts up to 0.06 ± 0.03 wt % NO3 have been detected while O2 detections suggests chlorates and/or perchlorates (0.05 to 1.05 wt % ClO4) are present. Evolution of SO2 indicated the presence of crystalline and/or poorly crystalline Fe and Mg sulfate and possibly sulfide. Evolved H2O (0.9 - 2.5 wt% H2O) was consistent with the presence of adsorbed water, hydrated salts, interlayer/structural water from phyllosilicates, and possible inclusion water in mineral/amorphous phases. Evolved H2S detections suggest that reduced phases occur despite the presence of oxidized phases (nitrate, oxychlorine, sulfate, and carbonate). SAM results coupled with CheMin mineralogical and Alpha-Particle X-ray Spectrometer elemental analyses indicate that Gale Crater sedimentary rocks have experienced a complex authigenetic/diagenetic history involving fluids with varying pH, redox, and salt composition. The inferred geochemical conditions were favorable for microbial habitability and if life ever existed, there was likely sufficient organic C to support a small microbial population.

Sutter, Brad↗
NASA NTRS2019

Unraveling the Aqueous Alteration History and Searching for Extinct Life in Gale Crater, Mars: Mineralogical and Geochemical Results from the Mars Science Laboratory, Curiosity Rover's Instrument Payload

The goal of the Mars Science Laboratory (MSL), Curiosity Rover mission is to determine if Gale Crater, Mars ever had a habitable environment and to search for evidence of extinct microbial life. Gale Crater is ~155 km wide with a layered central mound (~5 km high). The Curiosity rover has traversed ~20 km from the crater floor up 350 m to the lower slopes of the central mound for over 2200 Martian solar days (sols). Curiosity's instruments have evaluated the geochemistry and mineralogy of regolith fines, eolian sediments, and sedimentary rocks to assess Gale Crater's aqueous alteration history. Results indicate that Gale Crater surface material have experienced a complex authigenetic/diagenetic history involving fluids with varying pH, redox, and salt composition. The inferred geochemical conditions were favorable for microbial habitability and if life ever existed, there was likely sufficient organic C to support a small microbial population.

Sutter, Brad↗
NASA NTRS1990

Removing spurious reflections from CFD solutions by using the Complex Cepstrum

The Complex Cepstrum is shown to remove spurious reflections from artificial boundaries in computational fluid dynamic (CFD) solutions. First, the Complex Cepstrum theory is presented. A model time sequence consisting of a direct signal and reflections is analyzed theoretically with the Complex Cepstrum, and it is shown that the direct signal uncontaminated by reflections may be recovered in the time domain. Next, the Complex Cepstrum is applied to one- and three-dimensional CFD solutions, and spurious reflections from the boundary conditions are removed. By eliminating spurious reflections introduced by artificial boundary conditions, the applicability of CFD methods to aeroacoustic problems is greatly enhanced.

Meadows, Kristine R.↗
NASA NTRS1981

Cloud fluid compression and softening in spiral arms and the formation of giant molecular cloud complexes

With regard to the galactodynamics of the cloudy interstellar medium, the paper considers the response of such a gas to a forcing potential in the tight-winding density wave theory. The cloud fluid is treated in the hydrodynamic limit with an equation of state which softens at high densities. It is shown that in the inner regions of the galaxy, cooling of the cloud fluid in the arms can result in gravitational instability and the formation of large bound complexes of clouds which are identified with the giant molecular clouds (GMCs). Masses, dimensions, distributions, and scale heights of the GMCs are predicted by the theory. It is suggested that the interstellar gas density in the disk is regulated by the gravitational instability mechanism in the arms which siphons material into star formation. Implications for the evolution of individual GMCs and for galactic morphology are discussed.

Cowie, L. L.↗