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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 1,531 records · Page 85
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Extending the Operational Envelope of a Turbofan Engine Simulation into the Sub-Idle Region

In many non-linear gas turbine simulations, operation in the sub-idle region can lead to model instability. This paper lays out a method for extending the operational envelope of a map based gas turbine simulation to include the sub-idle region. This method develops a multi-simulation solution where the baseline component maps are extrapolated below the idle level and an alternate model is developed to serve as a safety net when the baseline model becomes unstable or unreliable. Sub-idle model development takes place in two distinct operational areas, windmilling/shutdown and purge/cranking/startup. These models are based on derived steady state operating points with transient values extrapolated between initial (known) and final (assumed) states. Model transitioning logic is developed to predict baseline model sub-idle instability, and transition smoothly and stably to the backup sub-idle model. Results from the simulation show a realistic approximation of sub-idle behavior as compared to generic sub-idle engine performance that allows the engine to operate continuously and stably from shutdown to full power.

gas path dynamics↗
NASA NTRS1974

Parametric study of STOL short-haul transport engine cycles and operational techniques to minimize community noise impact

The effect of aircraft operational techniques in the terminal area on community noise impact of future short haul aircraft was investigated. Aircraft equipped with mechanical flap (MF) and aircraft with externally blown flap (EBF) were used to study the noise impact at four U.S. airports. The four airports were: (1) Hanscom Field (Boston), (2) Washington National (D.C.), (3) Midway (Chicago) and (4) Orange County (California). With the exception of Washington National (D.C.), the study showed that a reduction of approximately 40 percent in the number of people highly annoyed can be obtained by using the recommended operational techniques. The evaluation procedures and methodology developed in the study represent an advance in acoustical state-of-the-art and provide an effective and useful tool for determining aircraft noise impact on the airport community.

Source record↗
NASA NTRS2008

6H-SiC Transistor Integrated Circuits Demonstrating Prolonged Operation at 500 C

The NASA Glenn Research Center is developing very high temperature semiconductor integrated circuits (ICs) for use in the hot sections of aircraft engines and for Venus exploration where ambient temperatures are well above the approximately 300 degrees Centigrade effective limit of silicon-on-insulator IC technology. In order for beneficial technology insertion to occur, such transistor ICs must be capable of prolonged operation in such harsh environments. This paper reports on the fabrication and long-term 500 degrees Centigrade operation of 6H-SiC integrated circuits based on epitaxial 6H-SiC junction field effect transistors (JFETs). Simple analog amplifier and digital logic gate ICs have now demonstrated thousands of hours of continuous 500 degrees Centigrade operation in oxidizing air atmosphere with minimal changes in relevant electrical parameters. Electrical characterization and modeling of transistors and circuits at temperatures from 24 degrees Centigrade to 500 degrees Centigrade is also described. Desired analog and digital IC functionality spanning this temperature range was demonstrated without changing the input signals or power supply voltages.

Neudeck, Philip G.↗
NASA NTRS2010

Contamination Impact of Station Brush Fire on Cleanroom Facilities

Brush and forest fires, both naturally occurring and anthropogenic in origin, in proximity to space flight hardware processing facilities raise concerns about the threat of contamination resulting from airborne particulate and molecular components of smoke. Perceptions of the severity of the threat are possibly heightened by the high sensitivity of the human sense of smell to some components present in the smoke of burning vegetation.On August 26th, 2009, a brushfire broke out north of Pasadena, California, two miles from the Jet Propulsion Laboratory. The Station Fire destroyed over 160,000 acres, coming within a few hundred yards of JPL. Smoke concentrations on Lab were very heavy over several days. All Lab operations were halted, and measures were taken to protect personnel, critical hardware, and facilities. Evaluation of real-time cleanroom monitoring data, visualinspection of facilities, filter systems, and analysis of surface cleanliness samples revealed facility environments andhardware were minimally effected.Outside air quality easily exceeded Class Ten Million. Prefilters captured most large ash and soot; multi-stage filtration greatly minimized the impact on the HEPA/ULPA filters. Air quality in HEPA filtered spacecraft assembly cleanrooms remained within Class 10,000 specification throughout. Surface cleanliness was inimally affected, as large particles were effectively removed from the airstream, and sub-micron particles have extremely long settling rates. Approximate particulate fallout within facilities was 0.00011% area coverage/day compared to 0.00038% area coverage/day during normal operations. Deposition of condensable airborne components, as measured in real time, peaked at approximately1.0 ng/cm2/day compared to 0.05 ng/cm2/day nominal.

airborne particulate contamination↗
NASA NTRS1999

Physiologic and thermal responses of male and female patients with multiple sclerosis to head and neck cooling

Personal cooling systems are used to alleviate symptoms of multiple sclerosis and to prevent increased core temperature during daily activities. The objective of this study was to determine the thermal and physiologic responses of patients with multiple sclerosis to short-term maximal head and neck cooling. A Life Support Systems, Inc. Mark VII portable cooling system and a liquid cooling helmet were used to cool the head and neck regions of 24 female and 26 male patients with multiple sclerosis in this study. The subjects, seated in an upright position at normal room temperature (approximately 22 degrees C), were cooled for 30 min by the liquid cooling garment, which was operated at its maximum cooling capacity. Oral, right, and left ear temperatures and cooling system parameters were logged manually every 5 min. Forearm, calf, chest, and rectal temperatures, heart rate, and respiration rate were recorded continuously on a U.F.I., Inc. Biolog ambulatory monitor. This protocol was performed during the winter and summer to investigate the seasonal differences in the way patients with multiple sclerosis respond to head and neck cooling. No significant differences were found between the male and female subject group's mean rectal or oral temperature responses during any phase of the experiment. The mean oral temperature decreased significantly (P < 0.05) for both groups approximately 0.3 degrees C after 30 min of cooling and continued to decrease further (approximately 0.1-0.2 degrees C) for a period of approximately 15 min after removal of the cooling helmet. The mean rectal temperatures decreased significantly (P < 0.05) in both male and female subjects in the winter studies (approximately 0.2-0.3 degrees C) and for the male subjects during the summer test (approximately 0.2 degrees C). However, the rectal temperature of the female subjects did not change significantly during any phase of the summer test. These data indicate that head and neck cooling may, in general, be used to reduce the oral and body temperatures of both male and female patients with multiple sclerosis by the approximate amount needed for symptomatic relief as shown by other researchers. However, thermal response of patients with multiple sclerosis may be affected by gender and seasonal factors, which should be considered in the use of liquid cooling therapy.

NASA Discipline Environmental Health↗
NASA NTRS2015

The Importance of the Cathode Plume and Its Interactions with the Ion Beam in Numerical Simulations of Hall Thrusters

Hall2De is a first-principles, 2-D axisymmetric code that solves the equations of motion for ions, electrons, and neutrals on a magnetic-field-aligned grid. The computational domain downstream of the acceleration channel exit plane is large enough to include self-consistently the cathode boundary. In this paper, we present results from numerical simulations of the H6 laboratory thruster with an internally mounted cathode, with the aim of highlighting the importance of properly accounting for the interactions between the ion beam and cathode plume. The anomalous transport of electrons across magnetic field lines in Hall2De is modelled using an anomalous collision frequency, νanom, yielding νanom approximately equal to omega ce (i.e., the electron cyclotron frequency) in the plume. We first show that restricting the anomalous collision frequency to only regions where the current density of ions is large does not alter the plasma discharge in the Hall thruster as long as the interaction between the ion beam and the cathode plume is captured properly in the computational domain. This implies that the boundary conditions must be placed sufficiently far as to not interfere with the electron transport in this region. These simulation results suggest that electron transport across magnetic field lines occurs largely inside the beam and may be driven by the interactions between beam ions and electrons. A second finding that puts in relevance the importance of including the cathode plume in numerical simulations is on the significance of accounting for the ion acoustic turbulence (IAT), now known to occur in the vicinity of the cathode exit. We have included in the Hall2De simulations a model of the IAT-driven anomalous collision frequency based on Sagdeev's model for saturation of the ion-acoustic instability. This implementation has allowed us to achieve excellent agreement with experimental measurements in the near plume obtained during the operation of the H6 thruster at nominal conditions (300V, 20A) and chamber background pressure of approximately 1.5 x 10(exp -5) Torr. In addition, the numerical results obtained with the latter approach exhibit less sensitivity to background pressure than previous attempts at explaining the features of the plasma properties in the near plume.

Lopez Ortega, Alejandro↗
DOE OSTI2022

CFD-trained ANN Model for Approximating Near-occupant Condition in Real-time Simulations

The main drawback of Computational Fluid Dynamics (CFD) simulations has been the time and resource consuming nature which is not suitable for real-time applications. In this work, we first generated numerous CFD models of a given indoor space to obtain airspeed, temperature, and mean radiant temperature near an occupant as training data. Several artificial neural networks (ANN) models were trained using this CFD simulated data to approximate near real-time environmental conditions for a given occupant. This trained ANN model approach is a part of a real-time simulation of building operations using a combination of software and real hardware (HVAC equipment) approaches. The preliminary results suggest that the CFD- generated training data and the trained ANN model can accurately approximate such conditions in a real-time application, a method that has great potential in building simulation and building digital twin areas of research.

Zhang, Yun↗
DOE OSTI2020

Spatial Atomic Layer Deposition of Aluminum Oxide as a Passivating Hole Contact for Silicon Solar Cells

In this work, tunneling aluminum oxide (Al 2 O 3 ) passivation layers are demonstrated to be a candidate for hole collecting, passivating contacts when coupled with a boron-doped surface. Here, these very thin Al 2 O 3 films (1.5-3 nm) are deposited using spatial atomic layer deposition (ALD) on boron diffused (110-115 Ω –1 ) hydrophilic surfaces operating as metal-insulator-semiconductor (MIS) contacts. Emitter saturation current density values of approximately ≈57 fA cm 2 are achieved for Al 2 O 3 film thicknesses of 2 nm before metallization. At this same thickness, contact resistivity values of 33 mΩ cm 2 are obtained after metallization. Most importantly, the boron diffusion, wet chemical surface preparation, and spatial ALD of Al 2 O 3 used to create these MIS structures were all performed with industrially relevant equipment on Cz wafers.

14 SOLAR ENERGY↗
DOE OSTI2023

Uncertainty quantification in scientific machine learning: Methods, metrics, and comparisons

Neural networks (NNs) are currently changing the computational paradigm on how to combine data with mathematical laws in physics and engineering in a profound way, tackling challenging inverse and ill-posed problems not solvable with traditional methods. However, quantifying errors and uncertainties in NN-based inference is more complicated than in traditional methods. This is because in addition to aleatoric uncertainty associated with noisy data, there is also uncertainty due to limited data, but also due to NN hyperparameters, overparametrization, optimization and sampling errors as well as model misspecification. Although there are some recent works on uncertainty quantification (UQ) in NNs, there is no systematic investigation of suitable methods towards quantifying the total uncertainty effectively and efficiently even for function approximation, and there is even less work on solving partial differential equations and learning operator mappings between infinite-dimensional function spaces using NNs. In this work, we present a comprehensive framework that includes uncertainty modeling, new and existing solution methods, as well as evaluation metrics and post-hoc improvement approaches. Further, to demonstrate the applicability and reliability of our framework, we present an extensive comparative study in which various methods are tested on prototype problems, including problems with mixed input-output data, and stochastic problems in high dimensions. In the Appendix, we include a comprehensive description of all the UQ methods employed. Further, to help facilitate the deployment of UQ in Scientific Machine Learning research and practice, we present and develop in [1] an open-source Python library (github.com/Crunch-UQ4MI/neuraluq), termed NeuralUQ, that is accompanied by an educational tutorial and additional computational experiments.

11 physics-informed neural networks↗
DOE OSTI2023

High-power helicon system commissioning and conditioning progress on DIII-D

The high-power helicon, aka fast wave in the lower hybrid range of frequencies (LHRF), program has completed initial experiments at DIII-D. A 30-element comb-line traveling wave antenna successfully coupled over 0.3 MW of rf power at 476 MHz into both L-mode and ELMing H-mode plasmas for approximately 0.2 s. Here, we describe the helicon systems that enabled high-power operations, and the progress of conditioning in June 2021. Upgraded vacuum feedthroughs are described.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Impact of mechanical tolerances on partial turn skipping in helical flux compression generator

Maintaining tight mechanical tolerances of the components used in helical flux compression generators is crucial for optimizing device performance. Moving beyond current literature, which provides various approximations for acceptable tolerances, a 3D simulation of the armature stator interaction during generator operation was developed, revealing that existing equations frequently misestimate the tolerance limits. Without restricting the generality of the presented approach, the focus was primarily on the armature’s concentricity and roundness, comparing the acceptable tolerance limits between generators of different sizes. An analytical approach for select geometries was developed, confirming the 3D results. Quantitative results reveal that a steeper Gurney angle and increased winding pitch allow for less restrictive tolerances for eccentricity and ellipticity. Even small deviations from the ideal armature positioning and shape will result in fluctuations of the output current time-derivative, observed experimentally and in simulation. Larger deviations then cause partial turn skipping, associated with loss of magnetic flux. The simulation elucidates the impact of tolerance deviations on generator performance by offering precise tolerance ranges for various generator sizes, thereby facilitating informed design decisions.

42 ENGINEERING↗
DOE OSTI2026

Large-scale real-time signal processing in physics experiments: the ALICE TPC FPGA pipeline

For LHC Run 3, the ALICE Time Projection Chamber was upgraded to operate in continuous readout mode. Interaction rates of up to 50 kHz in Pb-Pb collisions require real-time processing of more than 3 TB s -1 of raw detector data. This requirement is met by a custom FPGA-based processing pipeline that performs the complete front-end data treatment fully in-stream, including common-mode correction, pedestal subtraction, ion-tail filtering, zero suppression, and dense data packing. A central element of the design is a highly parallel common-mode correction algorithm operating directly on the streaming data. It robustly identifies signal-free readout channels on a time-bin basis and applies pad-dependent scaling to compensate for local variations in capacitive coupling in the GEM readout. In combination with pedestal subtraction and ion-tail filtering, this enables accurate baseline restoration under extreme high-occupancy conditions, preventing signal loss while efficiently suppressing noise prior to zero suppression. The pipeline operates continuously at the full detector bandwidth and reduces the raw input rate of approximately 3 TB s -1 to about 900 GBps for Pb-Pb collisions at the target interaction rate. Overall, it represents a large-scale FPGA-based real-time signal-processing implementation for high-energy physics detector readout.

Digital signal processing (DSP)↗
DOE OSTI2025

𝜂 and 𝜂′ meson production in 𝐽/𝜓 radiative decays from lattice QCD

We report on the computation of amplitudes describing the radiative decay processes 𝐽/𝜓 →𝛾⁢𝜂 and 𝐽/𝜓 →𝛾⁢𝜂′ from first principles via lattice quantum chromodynamics (QCD). Using lattices with two heavier than physical degenerate flavors of light quark where 𝑚 𝜋 ∼391 MeV, and a strange quark tuned to approximately the physical value, we compute three-point correlation functions using optimized meson operators with a range of momenta. The use of optimized operators allows access to the 𝜂′, even though it appears as an excited state, lying above the ground-state 𝜂 in the isoscalar pseudoscalar channel. Statistically precise signals are obtained in this disconnected process by averaging over large numbers of kinematically equivalent correlators. We determine transition form factors as a function of photon virtuality across the timelike region, which describe also the Dalitz processes 𝐽/𝜓 →𝑒 + ⁢𝑒 − ⁢𝜂 (′) . Significantly lower magnitudes of transition form factor for both the 𝜂 and 𝜂′ are found than those extracted from experimental data, and possible explanations for this observation are presented.

form factors↗
DOE OSTI2022

Perturbation theory under the truncated Wigner approximation: How system-environment entanglement formation drives quantum decoherence

In discrete quantum systems, quantum decoherence is the disappearance of simple phase relations as a result of interactions with an environment. For many applications, the question is not necessarily how to avoid (inevitable) system-environment interactions, but rather how to design environments that optimally preserve a system's phase relations in spite of such interactions. The formation of system-environment entanglement is a major driving mechanism for decoherence, and a detailed understanding of this process could inform strategies for conserving coherence optimally. This requires scalable, flexible, and systematically improvable quantum dynamical methods that retain detailed information about the entanglement properties of the environment, yet very few current methods offer this combination of features. Here, in this work, we address this need by introducing a theoretical framework wherein we combine the truncated Wigner approximation with standard time-dependent perturbation theory, allowing for computing expectation values of operators in the combined system-environment Hilbert space. We demonstrate the utility of this framework by applying it to the spin-boson model, representative of qubits and simple donor-acceptor systems. For this model, our framework provides an analytical description of perturbative contributions to expectation values. We monitor how quantum decoherence at zero temperature is accompanied by entanglement formation with individual environmental degrees of freedom. Based on this entanglement behavior, we find that the selective suppression of low-frequency environmental modes is particularly effective for mitigating quantum decoherence.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2021

Numerical Evidence for Many-Body Localization in Two and Three Dimensions

Disorder and interactions can lead to the breakdown of statistical mechanics in certain quantum systems, a phenomenon known as many-body localization (MBL). Much of the phenomenology of MBL emerges from the existence of localized-bits, or l-bits, a set of conserved quantities that are spatially localized and binary (i.e., possess only ±1 eigenvalues). While MBL and l-bits are known to exist in one-dimensional systems, their existence in dimensions greater than one is a key open question. To tackle this question, we develop an algorithm that can find approximate binary l-bits in arbitrary dimensions by adaptively generating a basis of operators in which to represent the l-bit. We use the algorithm to study four models: the one-, two-, and three-dimensional disordered Heisenberg models and the two-dimensional disordered hard-core Bose-Hubbard model. For all four of the models studied, our algorithm finds high-quality l-bits at large disorder strength and rapid qualitative changes in the distributions of l-bits in particular ranges of disorder strengths, suggesting the existence of MBL transitions. Furthermore, these transitions in the one-dimensional Heisenberg model and two-dimensional Bose-Hubbard model coincide well with past estimates of the critical disorder strengths in these models which further validates the evidence of MBL-like behavior in the other two and three-dimensional models we examine. In addition to finding MBL-like behavior in higher dimensions, our algorithm can be used to probe MBL in various geometries and dimensionality.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Simulating large one-dimensional neutral-atom quantum systems

While abstract models of quantum computation assume a closed system of two-level states, practical quantum devices inevitably couple to the environment in some way, creating sources of noise. Understanding the tolerance to noise of specific quantum algorithms run on specific devices is important for determining the feasibility of quantum computing in the current noisy intermediate-scale quantum era. Of particular interest is understanding the noise sensitivity of these devices as more qubits are added to the system. Classical simulations are a useful tool to understand the effects of this noise, but direct classical simulations of open quantum systems are burdened by an exponentially growing cost in the number of qubits and a large local Hilbert space dimension. For onedimensional, shallow circuits, using tensor networks can replace this exponential cost with a linear one and simulate far wider systems than what would normally be available. In this paper, we describe a tensor network simulation of a neutral atom quantum system under the presence of noise, while introducing a purity-preserving truncation technique that compromises between the simplicity of the matrix product state and the positivity of the matrix product density operator. We apply this simulation to a near-optimized iteration of the quantum approximate optimization algorithm on a transverse field Ising model in order to investigate the influence of large system sizes on the performance of the algorithm. We find that while circuits with a large number of qubits fail more often under noise that depletes the qubit population, their outputs on a successful measurement are just as robust under Rydberg atom dissipation or qubit dephasing as smaller systems. However, such circuits might not perform as well under coherent multiqubit errors such as Rydberg atom crosstalk. We also find that the optimized parameters are especially robust to noise, suggesting that a noisier quantum system can be used to find the optimal parameters before switching to a cleaner system for measurements of observables.

Allen, James↗
DOE OSTI2020

A Numerical Study on the Impact of Cathode Catalyst Layer Loading on the Open Circuit Voltage

The open-circuit voltage (OCV) is the measured potential when no current is drawn from a cell. Additionally, theoretically this potential is given by the equilibrium potential, which is determined from thermodynamics based on the operating conditions. In practice, the actual potential at zero current is measured to be approximately 300 mV lower than the theoretical value.

42 ENGINEERING↗
DOE OSTI2025

Final Report for FE0032098: Improving the cost-effectiveness of algal CO2 utilization by synergistic integration with power plant and wastewater treatment operations

The overall goal of this project was to demonstrate an engineering-scale open raceway pond algae cultivation system (approximately 180 m²), including the integration of technologies that utilized carbon dioxide (CO₂) from a coal-fired power plant and wastewater-derived nutrient inputs for cost-effective and environmentally friendly biomass production. The key advantages associated with the innovative algae cultivation system and its integration with wastewater treatment functions, as described herein, had been demonstrated in previous bench- and pilot-scale work by the project team partners. This project combined those approaches to maximize practical benefits and available synergies, resulting in a significant reduction in the net cost of producing algal biomass products. The primary target algal species for the project was Spirulina, which served as a high-protein content ingredient for food and animal feed. Spirulina was selected because it had already been approved by the FDA, was in use as a food ingredient, and commanded prices of up to $30/kg. It had a typical protein content of 50–75%, comparable to other high-protein concentrates, featured high digestibility without requiring pretreatment, and offered a high conversion ratio in animal feed applications. In addition, Spirulina had a relatively high content of the blue pigment phycocyanin, which could be extracted as a high-value co-product prior to using the remaining biomass for nutritional purposes.

Schideman, Lance [University of Illinois]↗