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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

FY-24 Progress on Computational Modeling of the Water Based NSTF

This report summarizes the computational modeling of the Natural Convection Shutdown Heat Removal Test Facility (NSTF) completed in FY24. This year’s modeling campaign focuses on the continual testing of the RELAP5 model against experimental data. Several fault cases were simulated with the RELAP5 model in FY23 to study the accuracy of the model under complex flow conditions. Similarly, in FY24, a case is simulated where the chimney outlet is throttled with a valve while the flow is undergoing two-phase oscillations. The purpose of this case is to study the effects of increasing pressure drop in the two-phase region on the system behavior. Even though the model is able to capture the experimental data qualitatively, it overpredicts the pressure drops experienced by the flow in the two-phase regime. Nevertheless, the model and the experiment show that oscillations are stabilized with increased pressure drop in the two-phase region.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
NASA NTRS1995

ASSIST user manual

Semi-Markov models can be used to analyze the reliability of virtually any fault-tolerant system. However, the process of delineating all the states and transitions in a complex system model can be devastatingly tedious and error prone. The Abstract Semi-Markov Specification Interface to the SURE Tool (ASSIST) computer program allows the user to describe the semi-Markov model in a high-level language. Instead of listing the individual model states, the user specifies the rules governing the behavior of the system, and these are used to generate the model automatically. A few statements in the abstract language can describe a very large, complex model. Because no assumptions are made about the system being modeled, ASSIST can be used to generate models describing the behavior of any system. The ASSIST program and its input language are described and illustrated by examples.

Johnson, Sally C.↗
NASA NTRS2010

Combining Model-Based and Feature-Driven Diagnosis Approaches - A Case Study on Electromechanical Actuators

Model-based diagnosis typically uses analytical redundancy to compare predictions from a model against observations from the system being diagnosed. However this approach does not work very well when it is not feasible to create analytic relations describing all the observed data, e.g., for vibration data which is usually sampled at very high rates and requires very detailed finite element models to describe its behavior. In such cases, features (in time and frequency domains) that contain diagnostic information are extracted from the data. Since this is a computationally intensive process, it is not efficient to extract all the features all the time. In this paper we present an approach that combines the analytic model-based and feature-driven diagnosis approaches. The analytic approach is used to reduce the set of possible faults and then features are chosen to best distinguish among the remaining faults. We describe an implementation of this approach on the Flyable Electro-mechanical Actuator (FLEA) test bed.

Narasimhan, Sriram↗
NASA NTRS2018

Advanced Stirling Convertor Control Unit Testing at NASA Glenn Research Center in the Radioisotope Power Systems System Integration Laboratory

Future NASA missions could include long-duration flyby, orbital, lander, or rover applications where generating power from sunlight may be limited. Radioisotope power systems (RPSs) provide a dependable power source for missions where inadequate sunlight or operational requirements make other power systems impractical. Over the past 16 years, NASA Glenn Research Center has been supporting the development of RPSs. The advanced Stirling radioisotope generator (ASRG) utilized a pair of advanced Stirling convertors (ASCs). Although flight development of the ASRG has been canceled, much of the technology and hardware continued development and testing to guide future activities. Specifically, a controller for the convertor(s) is an integral part of a Stirling-based RPS. For the ASRG design, the controller maintains stable operation of the convertors, regulates the alternating current produced by the linear alternator of the convertor, provides a specified direct-current output voltage for the spacecraft, and synchronizes the piston motion of the two convertors to minimize vibration as well as manage and maintain operation with a stable piston amplitude and hot-end temperature. It not only provides power to the spacecraft but also must regulate convertor operation to avoid damage to internal components and maintain safe thermal conditions after fueling. Lockheed Martin Coherent Technologies, Inc., has designed, developed, and tested an ASC control unit engineering development unit (ACU EDU) to support this effort. GRC used the ACU EDU as part of its nonnuclear representation of a RPS that also consists of a Dual advanced Stirling convertor simulator (DASCS), and associated support equipment to perform a test in the Radioisotope Power Systems System Integration Laboratory (RSIL). The RSIL was designed and built with flexibility to evaluate hardware utilizing RPS technology. The RSIL provides insight into the electrical interactions between as many as three radioisotope power generators, associated control strategies, and typical electric system loads. The first phase of testing included a DASCS that was developed by Johns Hopkins University Applied Physics Laboratory and simulates the operation and electrical behavior of a pair of ASCs in real time via a combination of hardware and software. Testing included the following spacecraft electrical energy storage configurations: capacitor, battery, and supercapacitor. Testing of the DASCS and ACU in each energy storage configuration included simulation of a typical mission profile and transient voltage and current data during load turnon and turnoff. Testing for these devices also included the initiation of several system faults such as short circuits, electrical bus overvoltage, undervoltage, and a "dead bus" recovery to restore normal power operations. The goal of this testing was to verify operation of the ACU(s) when connected to a spacecraft electrical bus. The results of these tests are presented here.

General↗
DOE OSTI2021

Improving the Power Outage Resilience of Buildings with Solar PV through the Use of Battery Systems and EV Energy Storage

Buildings with solar photovoltaic (PV) generation and a stationary battery energy storage system (BESS) may self-sustain an uninterrupted full-level electricity supply during power outages. The duration of off-grid operation is dependent on the time of the power fault and the capabilities of the home energy management system (HEMS). In this paper, building resilience is quantified by analyzing the self-sustainment duration for all possible power outages throughout an entire year. An evaluation method is proposed and exercised on a reference house in California climate zone 9 for which the detailed electricity usage is simulated using the EnergyPlus software. The influence of factors such as energy use behavioral patterns, energy storage capacity from the BESS, and an electric vehicle (EV) battery on the building resilience is evaluated. Varying combinations of energy storage and controllable loads are studied for optimally improved resilience based on user preferences. It is shown that for the target home and region with a solar PV system of 7.2 kW, a BESS with a capacity of 11 kWh, and an EV with a battery of 80 kWh permanently connected to the home, off-grid self-sustained full operation is guaranteed for at least 72 h.

14 SOLAR ENERGY↗
NASA NTRS1988

Hierarchical representation and machine learning from faulty jet engine behavioral examples to detect real time abnormal conditions

The theoretical basis and operation of LEBEX, a machine-learning system for jet-engine performance monitoring, are described. The behavior of the engine is modeled in terms of four parameters (the rotational speeds of the high- and low-speed sections and the exhaust and combustion temperatures), and parameter variations indicating malfunction are transformed into structural representations involving instances and events. LEBEX extracts descriptors from a set of training data on normal and faulty engines, represents them hierarchically in a knowledge base, and uses them to diagnose and predict faults on a real-time basis. Diagrams of the system architecture and printouts of typical results are shown.

Gupta, U. K.↗
NASA NTRS2017

Advanced Stirling Convertor Control Unit Testing at NASA Glenn Research Center in the Radioisotope Power Systems System Integration Laboratory

Future NASA missions could include establishing Lunar or Martian base camps, exploring Jupiters moons and travelling beyond where generating power from sunlight may be limited. Radioisotope Power Systems (RPS) provide a dependable power source for missions where inadequate sunlight or operational requirements make other power systems impractical. Over the past decade, NASA Glenn Research Center (GRC) has been supporting the development of RPSs. The Advanced Stirling Radioisotope Generator (ASRG) utilized a pair of Advanced Stirling Convertors (ASC). While flight development of the ASRG has been cancelled, much of the technology and hardware continued development and testing to guide future activities. Specifically, a controller for the convertor(s) is an integral part of a Stirling-based RPS. For the ASRG design, the controller maintains stable operation of the convertors, regulates the alternating current produced by the linear alternator of the convertor, provides a specified direct current output voltage for the spacecraft, synchronizes the piston motion of the two convertors in order to minimize vibration as well as manage and maintain operation with a stable piston amplitude and hot end temperature. It not only provides power to the spacecraft but also must regulate convertor operation to avoid damage to internal components and maintain safe thermal conditions after fueling. Lockheed Martin Coherent Technologies has designed, developed and tested an Engineering Development Unit (EDU) Advanced Stirling Convertor Control Unit (ACU) to support this effort. GRC used the ACU EDU as part of its non-nuclear representation of a RPS which also consists of a pair of Dual Advanced Stirling Convertor Simulator (DASCS), and associated support equipment to perform a test in the Radioisotope Power Systems System Integration Laboratory (RSIL). The RSIL was designed and built to evaluate hardware utilizing RPS technology. The RSIL provides insight into the electrical interactions between as many as 3 radioisotope power generators, associated control strategies, and typical electric system loads. The first phase of testing included a DASCS which was developed by Johns Hopkins UniversityApplied Physics Laboratory and simulates the operation and electrical behavior of a pair of ASCs in real time via a combination of hardware and software. Testing included the following spacecraft electrical energy storage configurations: capacitive, battery, and supercapacitor. Testing of the DASCS and ACU in each energy storage configuration included simulation of a typical mission profile, and transient voltage and current data during load turn-on/turn-off. Testing for these devices also included the initiation of several system faults such as short circuits, electrical bus over-voltage, under-voltage and a dead bus recovery to restore normal power operations. The goal of this testing was to verify operation of the ACU(s) when connected to a spacecraft electrical bus.

Dugala, Gina M.↗
DOE OSTI2025

A Review of Medium-Mn, Low-Density Steels for Transportation Applications

Low-density steels constitute a broad and complex alloy space (Fe–Mn–Al–C) suitable for a variety of applications. In particular, there has been growing interest in duplex (ferrite + austenite) or multiphase (+ martensite, carbides) low-density steels as a lightweight, advanced high-strength steel (AHSS) for vehicle applications, spurred by extensive decarbonization efforts. Medium-Mn (med-Mn) (3 to 12 wt pct) steels with 3.5 to 10 wt pct Al additions have decreased densities, presenting an interesting opportunity for high-specific strength, intrusion-resistant, and energy-absorbing sheet components with reduced alloying contents compared to high-Mn grades like austenitic Fe–Mn–Al–C or twinning-induced plasticity steels. Compared to leaner med-Mn steels, the physical metallurgy of med-Mn, low-density steels (MMLS) is complex and distinguished by increased δ-ferrite fractions and austenite stacking fault energies, decreased martensite start temperatures, and modified phase transformation windows. Mechanical properties of MMLS are comparable to 3rd generation AHSS, attributable to the unique, multiphase microstructures, and the array of strengthening mechanisms that can be accessed. Despite this, challenges and unknowns remain with respect to their industrial implementation, and new processing routes may need to be developed. Here, this review aims to highlight the composition effects, processing methods, microstructural evolution, deformation behavior, and application properties geared toward manufacturing and performance, altogether assessing the potential of MMLS for transportation applications.

36 MATERIALS SCIENCE↗
DOE OSTI2018

An Innovative Software Tool Suite for Power Plant Model Validation and Parameter Calibration using PMU Measurements

Maintaining good quality of power plant stability models is of critical importance to ensure the secure and economic operation and planning of today’s power grid with its increasing stochastic and dynamic behavior. According to North American Electric Reliability (NERC) standards, all generators in North America with capacities larger than 10 MVA are required to validate their models every five years. Validation is quite costly and can significantly affect the revenue of generator owners, because the traditional staged testing requires generators to be taken offline. Over the past few years, validating and calibrating parameters using online measurements including phasor measurement units (PMUs) and digital fault recorders (DFRs) has been proven to be a cost-effective approach. In this paper, an innovative open-source tool suite is presented for validating power plant models using PPMV tool, identifying bad parameters with trajectory sensitivity analysis, and finally calibrating parameters using an ensemble Kalman filter (EnKF) based algorithm. The architectural design and the detailed procedures to run the tool suite are presented, with results of test on a realistic hydro power plant using PMU measurements for 12 different events. The calibrated parameters of machine, exciter, governor and PSS models demonstrate much better performance than the original models for all the events and show the robustness of the proposed calibration algorithm.

Li, Yuanyuan↗
DOE OSTI2022

High Throughput Computational Framework of Materials Properties for Extreme Environments

This project aims to establish a framework capable of efficiently predicting the properties of structural materials for service in harsh environments over a wide range of temperatures and over long periods of time. The approach is to develop and integrate high throughput first-principles calculations in combination with machine learning (ML) methods, perform high throughput CALPHAD (calculations of phase diagrams) modeling, and carry out finite element method (FEM) simulations. Relevant to high temperature service in fossil power system, nickel-based superalloys such as Inconel 740 and Haynes 282 as well as the associated (Ni-Cr-Co)-Al-C-Fe-Mn-Mo-Nb-Si-Ti system, were investigated. The present framework was built on the concept of phase-based property data, in which properties of individual phases are modeled as a function of internal and external independent variables. This project established an open-source infrastructure with the following capabilities: (1) High throughput implementation of first-principles calculations at finite temperatures and variable compositions using both accurate phonon calculations and the efficient Debye model for thermodynamic properties, elastic constants, diffusion coefficients, vacancy formation, stacking and twin faults, and dislocation mobility; i.e., using the developed code DFTTK; (2) Machine learning capabilities to predict the above properties so that the number of first-principles calculations can be significantly reduced; e.g., using the developed code SIPFENN; (3) High throughput CALPHAD modeling of the above properties as a function of temperature and composition using our unique capability based on ESPEI and PyCalphad; (4) New capabilities to predict the stress-strain behavior of individual phases; and (5) New models for tensile strength prediction in common FEM software with the crystal plasticity finite element simulations (CPFEM).

, Ni-based superalloys↗
NASA NTRS1993

Development of a methodology for assessing the safety of embedded software systems

A Dynamic Flowgraph Methodology (DFM) based on an integrated approach to modeling and analyzing the behavior of software-driven embedded systems for assessing and verifying reliability and safety is discussed. DFM is based on an extension of the Logic Flowgraph Methodology to incorporate state transition models. System models which express the logic of the system in terms of causal relationships between physical variables and temporal characteristics of software modules are analyzed to determine how a certain state can be reached. This is done by developing timed fault trees which take the form of logical combinations of static trees relating the system parameters at different point in time. The resulting information concerning the hardware and software states can be used to eliminate unsafe execution paths and identify testing criteria for safety critical software functions.

Garrett, C. J.↗
NASA NTRS1988

Friction of ice

Frictional sliding experiments were performed on saw-cut samples of laboratory-made polycrystalline water ice, prepared in the same way as the material used by Kirby et al. (1987) in ice deformation experiments. The data show that the maximum frictional stress is a function of the normal stress but is not measurably dependent on temperature or sliding rate over the ranges covered in these experiments (77-115 K and 0.0003-0.03 mm/s, respectively). The sliding behavior was invariably stick slip, with the sliding surfaces exhibiting only minor gouge development. In samples with anomalously low strength, a curious arrangement of densely packed short vertical fractures was observed. The results of these experiments were applied to a model of near-surface tectonic activity on Ganymede, one of Jupiter's icy moons. The results indicate that a global expansion on Ganymede of 3 linear percent will cause extensional movement on preexisting faults at depths to 7 + or - 3 km.

Beeman, M.↗
NASA NTRS1993

Geologic controls on the West Antarctic Ice Sheet

The stability of the West Antarctic Ice Sheet is intertwined with its geologic history. The sub-ice geology and the possibility of active rifting and associated elevated heat-flux and volcanism might be determining factors in ice-sheet behavior. Seismic monitoring of natural events at the base of Ice Stream C reveals the presence of a young sedimentary basin beneath the ice stream. The sediments are presumed to be of glacio-marine origin, similar to those beneath Ice Stream B and in the Ross Sea. The young sediments are approximately 1/2 km thick at UpC camp, but thin abruptly southward to 100 m or less. We hypothesize the presence of a fault with a throw of 400 m to account for this (though we have not directly detected the fault), rather than invoking unrealistic basement dips. To extend these studies to critical inland regions, we suggest an expanded explosive-source seismic survey of the Byrd Subglacial Basin to determine the extent and character of the hypothesized rift basin. High-resolution seismic monitoring will detect layering in the sedimentary column, as well as possibly imaging faults directly.

Anandakrishnan, Sridhar↗
DOE OSTI2018

Integrating diagnostics and model-based optimization

Energy Management and Information Systems are a family of analytics technologies that include energy information systems, fault detection and diagnostics (FDD), and automated system optimization tools. Such systems have the potential to enable buildings to meet energy management goals of reducing total energy consumption and cost. Most current market offerings use data-driven and rule-based analytics. However, the use of physics-based models in the analytics offers potential improvements by providing an accurate estimation of outputs based on representation of the physical principles governing the building system behaviors. This also permits the use of design stage models to inform commissioning and operation. This paper describes the development and testing of a hybrid data-driven and physics model-based operational tool for energy efficiency in central cooling plants. The tool offers FDD functionality, setpoint optimization, and visualization of key performance parameters. It was demonstrated at a university campus in the mixed-humid ASHRAE Climate Zone 4A. Key performance metrics that were analyzed include plant electricity use reduction, plant model calibration, and system economics. Annual simulations indicate the tool can provide electricity savings of greater than 10% for approximately six months of the year, mainly during the winter season when wet bulb temperatures are low, though only 1.38% savings for the entire year. Additionally, over a 4-day period in April, recommended optimal setpoints were implemented, resulting in 17% savings versus metered baseline consumption. With respect to model calibration, the difference between model-predicted and measured parameters was less than 10% for 90% of data points acquired for three of six chillers, and for each ten cooling towers. Finally, the tool users reported that satisfaction with the capabilities was equal to or better than that with the preexisting BAS system.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2017

Influence of annealing parameters on phase evolution and recrystallization kinetics of a Mn-Al-Si alloyed duplex steel

Highlights: • Stacking fault energy calculated for Fe-9.8Mn-7.5Al-1.22Si-0.2C steel is 48.4 mJ/m{sup 2} • Austenite stability decreases with increasing temperature due to higher free energy • Mn{sub 5}(Al,Si)C precipitates evolve with concurrent disappearance of austenite at 1273 K • Decrease in austenite fraction stimulates boundary migration for recrystallization • The maximum value of Avrami exponent ~ 1 implies sluggish recrystallization kinetics - Abstract: In this study, the phase transformation and recrystallization behavior of hot-forged Fe-Mn-Al-Si-C alloyed duplex steel has been investigated in wide ranges of annealing temperatures (973-1273 K) and durations (15–150 min). The recrystallization kinetics has been evaluated employing Johnson-Mehl-Avrami-Kolmogorov model. A limited extent of phase transformation (i.e. duplex to single phase) has been found to take place during annealing in the range of 973-1173 K. However, during annealing at 1273 K, not only the transformation from duplex to ferritic microstructure accelerates, but also recrystallization is initiated in these ferrite grains. The changes in the free energy of the austenite with the annealing temperature play a pivotal role in dictating the stabilization of the corresponding phase. Moreover, the disappearance of the austenitic phase at 1273 K owing to higher free energy is compensated by the formation of Mn-Al-Si rich carbide precipitates. The phase evolution triggered by annealing at 1273 K affects the recrystallization kinetics of each of the phase constituents. A sharp rise in the Avrami exponent (n) value is noticed following annealing at 1273 K, which clearly denotes that the disappearing austenite-ferrite interfaces facilitate the migration of the ferrite boundaries that stimulate recrystallization. In spite of the increasing values of n with the annealing temperature, its maximum value (at 1273 K) remains close to 1. This is a clear indication of the sluggish nature of the recrystallization process in the developed alloy.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Hierarchical nanotwins in single-crystal-like nickel with high strength and corrosion resistance produced via a hybrid technique

High-density growth nanotwins enable high-strength and good ductility in metallic materials. However, twinning propensity is greatly reduced in metals with high stacking fault energy. In this study, we adopted a hybrid technique coupled with template-directed heteroepitaxial growth method to fabricate single-crystal-like, nanotwinned (nt) Ni. The nt Ni primarily contains hierarchical twin structures that consist of coherent and incoherent twin boundary segments with few conventional grain boundaries. In situ compression studies show the nt Ni has a high flow strength of ~2 GPa and good deformability. Moreover, the nt Ni has superb corrosion behavior due to the unique twin structure in comparison to coarse grained and nanocrystalline counterparts. The hybrid technique opens the door for the fabrication of a wide variety of single-crystal-like nt metals with unique mechanical and chemical properties.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2017

Modeling and Simulating Multiple Failure Masking enabled by Local Recovery for Stencil-based Applications at Extreme Scales

By obtaining multi-process hard failure resilience at the application level is a key challenge that must be overcome before the promise of exascale can be fully realized. Some previous work has shown that online global recovery can dramatically reduce the overhead of failures when compared to the more traditional approach of terminating the job and restarting it from the last stored checkpoint. If online recovery is performed in a local manner further scalability is enabled, not only due to the intrinsic lower costs of recovering locally, but also due to derived effects when using some application types. In this paper we model one such effect, namely multiple failure masking, that manifests when running Stencil parallel computations on an environment when failures are recovered locally. First, the delay propagation shape of one or multiple failures recovered locally is modeled to enable several analyses of the probability of different levels of failure masking under certain Stencil application behaviors. These results indicate that failure masking is an extremely desirable effect at scale which manifestation is more evident and beneficial as the machine size or the failure rate increase.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2023

In-Situ Transmission Electron Microscopy Study of the Evolution of Extended Defects in Oxide Nuclear Fuels

In-situ transmission electron microscopy (TEM) with simulated extreme environments is an effective tool for understanding and tracking microstructural changes down to the atomic scale. The objective of this research is to study the effect of temperature on the evolution of extended defects in ThO2 and UO2. Here, we present in-situ TEM isochronal thermal annealing experiments using a micro-electro-mechanical-system (MEMS)-based heating holder. ThO2 and UO2 single crystal specimens were grown inside an inert silver ampoule using hydrothermal synthesis. Both samples were irradiated using 2 MeV protons at 600oC up to 0.1 dpa at Texas A&M University’s Accelerator Laboratory. Fig. 1a shows a weak-beam dark field TEM image of ThO2 after irradiation, indicating the presence of faulted 1/3 <111> type dislocation loops. This presentation will discuss the effect of annealing temperature (600oC, 800oC, 1000oC, 1100oC, etc.) on dislocation loop density, size and distribution, loop nature (interstitial/vacancies) and Burgers vector, as well as the formation of voids in both ThO2 and UO2. This work will also discuss the interaction between defects during annealing. The in-situ TEM annealing cycle is shown in Fig 1b. This research significantly improves the understanding of defect behavior in oxide nuclear fuels with temperature and will aid computational modeling efforts. This work was supported as part of the Center for Thermal Energy Transport under Irradiation (TETI) Energy Frontier Research Center, funded by the U.S. Department of Energy Office of Science.

36 MATERIALS SCIENCE↗