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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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Prediction of strain, inter-layer interaction and critical current in CORC ® wires under axial strain by T-A modeling

Superconducting conductors on round core (CORC ® ) cables and wires can meet the needs of large high-field magnets, such as particle accelerators and compact nuclear fusion machines, due to their simple cabling process, high current-carrying capacity and reliable operation under high mechanical stresses. Many high-field magnets require CORC ® cables to carry a current of thousands of amperes in a background magnetic field exceeding 20 T. As a result, the large electromagnetic forces will deform the cable in the axial direction due to hoop stress and in the transverse direction by compressive stress. Therefore, it is essential to determine the irreversible deformation limit of the CORC ® cable under axial tensile load and optimize the cabling parameters to potentially extend this limit. Analytical and numerical methods are developed to assess the performance degradation of CORC ® wires under axial tensile load. The strain level, interlayer contact pressure and friction and their impact on the critical current are calculated by combining the mechanical response and the T-A method. Analyzing the results shows that the winding angle of the tape and the Poisson’s ratio of the inner core are key factors affecting the irreversible tensile strain limit of CORC ® wires. The smaller the winding angle and the higher the Poisson’s ratio of the inner core, the higher the irreversible tensile strain limit. For multi-layer CORC ® wires, the initial contact pressure caused by the cabling process must also be considered. The inter-layer interaction is coupled with the tape strain of each layer. The results of this research can serve as a basis for optimizing and designing CORC ® wires with extended irreversible strain limits.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS2011

Two-Dimensional Analysis of Conical Pulsed Inductive Plasma Thruster Performance

A model of the maximum achievable exhaust velocity of a conical theta pinch pulsed inductive thruster is presented. A semi-empirical formula relating coil inductance to both axial and radial current sheet location is developed and incorporated into a circuit model coupled to a momentum equation to evaluate the effect of coil geometry on the axial directed kinetic energy of the exhaust. Inductance measurements as a function of the axial and radial displacement of simulated current sheets from four coils of different geometries are t to a two-dimensional expression to allow the calculation of the Lorentz force at any relevant averaged current sheet location. This relation for two-dimensional inductance, along with an estimate of the maximum possible change in gas-dynamic pressure as the current sheet accelerates into downstream propellant, enables the expansion of a one-dimensional circuit model to two dimensions. The results of this two-dimensional model indicate that radial current sheet motion acts to rapidly decouple the current sheet from the driving coil, leading to losses in axial kinetic energy 10-50 times larger than estimations of the maximum available energy in the compressed propellant. The decreased available energy in the compressed propellant as compared to that of other inductive plasma propulsion concepts suggests that a recovery in the directed axial kinetic energy of the exhaust is unlikely, and that radial compression of the current sheet leads to a loss in exhaust velocity for the operating conditions considered here.

Hallock, A. K.↗
NASA NTRS1998

Wave Augmented Diffusers for Centrifugal Compressors

A conceptual device is introduced which would utilize unsteady wave motion to slow and turn flows in the diffuser section of a centrifugal compressor. The envisioned device would substantially reduce the size of conventional centrifugal diffusers by eliminating the relatively large ninety degree bend needed to turn the flow from the radial/tangential to the axial direction. The bend would be replaced by a wall and the flow would instead exit through a series of rotating ports located on a disk, adjacent to the diffuser hub, and fixed to the impeller shaft. The ports would generate both expansion and compression waves which would rapidly transition from the hub/shroud (axial) direction to the radial/tangential direction. The waves would in turn induce radial/tangential and axial flow. This paper presents a detailed description of the device. Simplified cycle analysis and performance results are presented which were obtained using a time accurate, quasi-one-dimensional CFD code with models for turning, port flow conditions, and losses due to wall shear stress. The results indicate that a periodic wave system can be established which yields diffuser performance comparable to a conventional diffuser. Discussion concerning feasibility, accuracy, and integration follow.

Paxson, Daniel E.↗
NASA NTRS1950

Application of radial-equilibrium condition to axial-flow compressor and turbine design

Basic general equations governing the three-dimensional compressible flow of gas through a compressor or turbine are given in terms of total enthalpy, entropy, and velocity components of the gas. Two methods of solution are obtained for the simplified, steady axially symmetric flow; one involves the use of a number of successive planes normal to the axis of the machine and short distances apart, and the other involves only three stations for a stage in which an appropriate radial-flow path is used. Methods of calculation for the limiting cases of zero and infinite blade aspect ratios and an approximate method of calculation for finite blade aspect ratio are also given. In these methods, the blade loading and the shape of the annular passage wall may be arbitrarily specified.

Wu, Chung-Hua↗
DOE OSTI2022

An overview of magneto-inertial fusion on the Z Machine at Sandia National Laboratories

We present an overview of the magneto-inertial fusion (MIF) concept MagLIF (Magnetized Liner Inertial Fusion) pursued at Sandia National Laboratories and review some of the most prominent results since the initial experiments in 2013. In MagLIF, a centimeter-scale beryllium tube or "liner" is filled with a fusion fuel, axially pre-magnetized, laser pre-heated, and finally imploded using up to 20 MA from the Z machine. All of these elements are necessary to generate a thermonuclear plasma: laser preheating raises the initial temperature of the fuel, the electrical current implodes the liner and quasi-adiabatically compresses the fuel via the Lorentz force, and the axial magnetic field limits thermal conduction from the hot plasma to the cold liner walls during the implosion. MagLIF is the first MIF concept to demonstrate fusion relevant temperatures, significant fusion production (>10^13 primary DD neutron yield), and magnetic trapping of charged fusion particles. On a 60 MA next-generation pulsed-power machine, two-dimensional simulations suggest that MagLIF has the potential to generate multi-MJ yields with significant self-heating, a long-term goal of the US Stockpile Stewardship Program. At currents exceeding 65 MA, the high gains required for fusion energy could be achievable.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

On the turbulent flow in piston engines: Coupling of statistical theory quantities and instantaneous turbulence

Planar particle image velocimetry (PIV) and tomographic PIV (TPIV) measurements are utilized to analyze turbulent statistical theory quantities and the instantaneous turbulence within a single-cylinder optical engine. Measurements are performed during the intake and mid-compression stroke at 800 and 1500 RPM. TPIV facilitates the evaluation of spatially resolved Reynolds stress tensor (RST) distributions, anisotropic Reynolds stress invariants, and instantaneous turbulent vortical structures. The RST analysis describes distributions of individual velocity fluctuation components that arise from unsteady turbulent flow behavior as well as cycle-to-cycle variability (CCV). A conditional analysis, for which instantaneous PIV images are sampled by their tumble center location, reveals that CCV and turbulence have similar contributions to RST distributions at the mean tumble center, but turbulence is dominant in regions peripheral to the tumble center. Analysis of the anisotropic Reynolds stress invariants reveals the spatial distribution of axisymmetric expansion, axisymmetric contraction, and 3D isotropy within the cylinder. Findings indicate that the mid-compression flow exhibits a higher tendency toward 3D isotropy than the intake flow. A novel post-processing algorithm is utilized to classify the geometry of instantaneous turbulent vortical structures and evaluate their frequency of occurrence within the cylinder. Findings are coupled with statistical theory quantities to provide a comprehensive understanding of the distribution of turbulent velocity components, the distribution of anisotropic states of turbulence, and compare the turbulent vortical flow distribution that is theoretically expected to what is experimentally observed. The analyses reveal requisites of important turbulent flow quantities and discern their sensitivity to the local flow topography and engine operation.

42 ENGINEERING↗
DOE OSTI2016

SOFT X-RAY EXCESS FROM SHOCKED ACCRETING PLASMA IN ACTIVE GALACTIC NUCLEI

We propose a novel theoretical model to describe the physical identity of the soft X-ray excess that is ubiquitously detected in many Seyfert galaxies, by considering a steady-state, axisymmetric plasma accretion within the innermost stable circular orbit around a black hole (BH) accretion disk. We extend our earlier theoretical investigations on general relativistic magnetohydrodynamic accretion, which implied that the accreting plasma can develop into a standing shock under suitable physical conditions, causing the downstream flow to be sufficiently hot due to shock compression. We perform numerical calculations to examine, for sets of fiducial plasma parameters, the physical nature of fast magnetohydrodynamic shocks under strong gravity for different BH spins. We show that thermal seed photons from the standard accretion disk can be effectively Compton up-scattered by the energized sub-relativistic electrons in the hot downstream plasma to produce the soft excess feature in X-rays. As a case study, we construct a three-parameter Comptonization model of inclination angle θ {sub obs}, disk photon temperature kT {sub in}, and downstream electron energy kT {sub e}to calculate the predicted spectra in comparison with a 60 ks XMM-Newton /EPIC-pn spectrum of a typical radio-quiet Seyfert 1 active galactic nucleus, Ark 120. Our χ {sup 2}-analyses demonstrate that the model is plausible for successfully describing data for both non-spinning and spinning BHs with derived ranges of 61.3 keV ≲ kT {sub e}≲ 144.3 keV, 21.6 eV ≲ kT {sub in} ≲ 34.0 eV, and 17.°5 ≲ θ {sub obs} ≲ 42.°6, indicating a compact Comptonizing region of three to four gravitational radii that resembles the putative X-ray coronae.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Helium release during shale deformation: Experimental validation

This paper describes initial experimental results of helium tracer release monitoring during deformation of shale. Naturally occurring radiogenic 4 He is present in high concentration in most shales. During rock deformation, accumulated helium could be released as fractures are created and new transport pathways are created. We present the results of an experimental study in which confined reservoir shale samples, cored parallel and perpendicular to bedding, which were initially saturated with helium to simulate reservoir conditions, are subjected to triaxial compressive deformation. During the deformation experiment, differential stress, axial, and radial strains are systematically tracked. Release of helium is dynamically measured using a helium mass spectrometer leak detector. Helium released during deformation is observable at the laboratory scale and the release is tightly coupled to the shale deformation. These first measurements of dynamic helium release from rocks undergoing deformation show that helium provides information on the evolution of microstructure as a function of changes in stress and strain.

58 GEOSCIENCES↗
DOE OSTI2022

Graphene nanoplatelets reinforced cement as a solution to leaky wellbores reinforcing weak points in hydrated Portland cement with graphene nanoparticles improves mechanical and chemical durability of wellbore cements

In this work, to improve the performance of wellbore cement under subsurface environments, graphene nanoplatelets (GNPs) were added in various percentages to Class-H cement slurry. Microstructural characterization of cement slurries cured at 90 °C and 95% RH indicates that GNP modifies the microstructure of hydrated cement by reinforcing pore spaces. As a result, the mechanical properties, such as Young's modulus and axial peak stress, obtained from high temperature triaxial compression tests are significantly improved based on different percentages of added GNPs. Furthermore, the hydrated 1 × 2 inch GNP- Portland cement cores tested under simulated deep wellbore conditions of high-temperature and high pressure (HTHP), appear to have a ductile-like behavior, when compared to a typical brittle nature of Portland cement pastes. From our observations and published data on graphene resistance to fracture, GNP addition to cement is evidently enhancing the flexibility of cement. These improvements would reduce the risks associated with wellbore cement deterioration and a consequent leakage in fossil fuel production, geothermal energy production, CO 2 storage as well as long-term sealing materials in plugging and abandonment of all wellbores at the end of their service life.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Pressure-induced pseudoatom bonding collapse and isosymmetric phase transition in Zr{sub 2}Cu: First-principles predictions

The structural evolution of tetragonal Zr{sub 2}Cu has been investigated under high pressures up to 70 GPa by means of density functional theory. Our calculations predict a pressure-induced isosymmetric transition where the tetragonal symmetry (I4/mmm) is retained during the entire compression as well as decompression process while its axial ratio (c/a) undergoes a transition from ∼3.5 to ∼4.2 at around 35 GPa with a hysteresis width of about 4 GPa accompanied by an obvious volume collapse of 1.8% and anomalous elastic properties such as weak mechanical stability, dramatically high elastic anisotropy, and low Young's modulus. Crystallographically, the tetragonal axial ratio shift renders this transition analogous to a simple bcc-to-fcc structural transition, which implies it might be densification-driven. Electronically, the ambient Zr{sub 2}Cu is uncovered with an intriguing pseudo BaFe{sub 2}As{sub 2}-type structure, which upon the phase transition undergoes an electron density topological change and collapses to an atomic-sandwich-like structure. The pseudo BaFe{sub 2}As{sub 2}-type structure is demonstrated to be shaped by hybridized dxz + yz electronic states below Fermi level, while the high pressure straight Zr-Zr bonding is accommodated by electronic states near Fermi level with dx{sup 2} − y{sup 2} dominant features.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

A Review of the Research and Development of Brayton Cycle Technology in Nuclear Power Applications with a Focus on Compressor Technology

This study reviews the integration of Brayton Cycle (BC) systems in nuclear power generation, emphasizing their potential to enhance thermal efficiency and operational flexibility over traditional Rankine Cycle (RC) systems. Key working fluids, such as helium (He), supercritical carbon dioxide (sCO 2 ), nitrogen (N 2 ), and air, are evaluated for their performance, efficiency, and compatibility with nuclear systems. He is recognized for its high thermal conductivity and inertness at elevated temperatures, while sCO 2 demonstrates advantages in compactness and efficiency in midrange temperatures. This article also highlights the importance of compressor designs in optimizing BC performance and reviews, available compressor technologies. Axial and centrifugal compressor designs enable efficient gas compression while managing the thermal and mechanical stresses associated with high-pressure operations in nuclear systems. Combined with variable geometry components and advanced materials, these technologies address the challenges posed by varying load conditions. Despite the promising features of BC systems, several challenges persist, including high leakage rates and material degradation under extreme conditions, which necessitate robust sealing technologies and thorough testing. The insights gained from operational experiences at facilities, such as the Oberhausen II plant and the High-Temperature He Test Facility (HHV), underscore the complexities involved in designing high-temperature gas turbines for nuclear applications. This review concludes that as the nuclear industry evolves, BC systems hold significant promise for contributing to a sustainable energy future, particularly in the context of small modular reactors (SMRs) and microreactors. Further exploration of combined cycle configurations that combine BCs with RCs may enhance overall efficiency and flexibility in power generation.

22 - GENERAL STUDIES OF NUCLEAR REACTORS↗
NASA NTRS1979

A careful numerical study of flowfields about external conical corners. I - Symmetric configurations

A numerical study of the flowfield about symmetrical external axial corners formed by the juncture of swept compressive wedges is presented. The geometrical configuration under investigation allows a unified treatment of external corners typical of delta wings and of rectangular inlets. Comparisons are made with other numerical results. For the delta wing configuration, the occurrence of an anomalous shock behavior predicted by Gonor is discussed. A parametric study shows the singular behavior of the pressure at the corner as a function of the external corner angle, and a second parametric study shows the effect of finite corner radius on the location of the crossflow stagnation point. Previous theoretical predictions of certain flow features typical of corner flows agree well with present numerical results.

Salas, M. D.↗
NASA NTRS1980

Careful numerical study of flowfields about asymmetric external conical corners

A numerical study of the flowfield about asymmetrical external axial corners formed by the juncture of swept compressive wedges is presented. The geometrical configuration allows a unified treatment of external corners typical of delta wings and rectangular inlets. The study investigates how the flow transitions from a symmetrical flowfield with a cross-flow stagnation point at the corner to an asymmetrical flowfield for which the flow spills over the corner. The effects of leading-edge sweep, wedge compression, and corner radius are investigated.

Salas, M. D.↗
NASA NTRS1983

Actively suspended counter-rotating machine

A counter-rotating machine, such as a positive displacement pump having a pair of meshed, non-contacting helical screws (10,12), subjects its rotating members to axial and radial thrust forces when used for such purposes as compression of liquid or gaseous phase fluids while transporting them through a pump cavity (11,13). Each helical screw (10,12) has a shaft (17,17') which is actively suspended at opposite ends (11a,11b) of the pump cavity by a servo-controlled magnetic bearing assembly (19) and a servo-controlled rotary drive motor (20). Both bearing assemblies and drive motors are mounted on the outside of the pump cavity (11,13). Opto-electric angular position sensors (250) provide synchronization between radial orientation of the drive motors. The bearing assemblies and drive motors conjugately provide axial stabilization and radial centering of the helical screws during volumetric compression of aspirated liquid or gaseous phase fluids.

Studer, Philip A.↗
NASA NTRS1989

Microstructural non-uniformity as related to unidirectional compression performance

The compression performance of unidirectional composite laminates (UDCLs) is related not only to intrinsic or local strength, but also to a sample's ability to resist propagaton of initial damage. This paper introduces a simple shear lag model which is applied to a compression loaded UDCL with initial damage. Among the information obtained are axial overload and matrix layer shear strain factors in the neighborhood of the damage zone. These factors indicate that propagation may occur with relatively little initial damage and emphasize the need for a more complete understanding of compression behavior than currently exists.

Majors, Patrick S.↗
DOE OSTI2022

Planar, longitudinal, compressive waves in solids: Thermodynamics and uniaxial strain restrictions

A new tri-axial pressure-based constitutive expression has been found using Cauchy's stress tensor. This stress state emphasizes pressure and shear stress. The description is a pressure plus an effective shear stress allowing for a constitutive law based on atomic solid-state phase changes in crystalline cells due to pressure plus shear-based dislocation motion commonly associated with plasticity. Pressure has a new role in the material's constitutive response as it is separated from plasticity. The thermo-mechanical system describes third-order Gibbs’ expressions without specific volume restrictions placed upon the material. Isothermally, the ratio of heat to shear work in elastic copper is shown to approach zero at a very low temperature and become larger than one as temperature approaches melting. Wave compression models investigated are elastic and plastic: in fully elastic materials, the planar wave is restricted by Poisson's effect although plastic shear changes this constraint. Plastic deformation, dominated by dissipative shear stresses in uniaxial strain, heats the material while excluding phase changes from hydrostatic pressures. The material properties per se across Hugoniot shocks are described with entropy concepts. Shock waves are exceedingly complex since the constitutive laws are linked at extreme temperatures, pressures, and shear stresses. Isothermal, isentropic, isochoric, and iso-shear conditions are used throughout with Jacobian algebra.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1989

Measurements of the stress supported by the crush zone in open hole composite laminates loaded in compression

Measurements of the stress supported by the crush zone in open hole specimens loaded in compression were carried out on two composite laminates, AS4/PEEK and IM6/HST-7, containing circular holes of three different diameters. Compression tests were conducted in a specially designed high-axial-alignment material test system machine. Results indicated that the local stress supported in the crush zone is much less than the stress required to initiate the crush, providing the reason for the finding of Guynn et al. (1987) that the Dugdale model does not accurately predict the load-damage size relationship of open hole composite specimens loaded in compression.

Guynn, E. Gail↗
DOE OSTI2018

Effect of whisker breakage on the forgeability and the tensile properties of the forged 2024Al/Al18B4O33w composite

Highlights: • The rotation and breakage of whiskers and microcracks contribute to strain softening during compression. • The whiskers with orientation angle of about 45° to the applied axial stress are serious broken. • The microcracks between the broken whiskers connecting with others result in major surface crack. • The composite forged at 450 °C and at strain rate of 0.1 s{sup − 1} shows no major surface cracks and the increase in the elongation, yield strength and tensile strength. - Abstract: The effect of the whisker breakage on the forgeability of 2024Al/Al{sub 18}B{sub 4}O{sub 33}w composite is investigated. The 2024Al/Al{sub 18}B{sub 4}O{sub 33}w composite is forged according to the forgeability at the different temperatures. The tensile properties of the as-cast and forged composites are also studied. The results shows that the rotation and breakage of the whiskers and the microcracks contribute to the strain softening during compression. The whiskers with the orientation angle of about 45° to the applied axial stress are serious broken resulting in the lower average aspect ratio of the whiskers. Due to the lower flow ability of the matrix at the lower temperature than 400 °C, the microcracks between the broken whiskers connecting with others result in the major surface crack oriented to approximately 45° with respect to the compression direction. The composite forged at the temperature of 450 °C and at the strain rate of 0.1 s{sup − 1} shows the no major surface cracks and the increase in the elongation, yield strength and tensile strength.

36 MATERIALS SCIENCE↗