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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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115 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

On the oceanic origin for the enhanced seasonal cycle of SST in the midlatitudes under global warming

Climate models project an enhancement in SST seasonal cycle over the midlatitude oceans under global warming. However, the maintaining mechanism for this enhancement is still under debate. This study investigates the SST seasonal cycle enhancement under quadrupling CO2 using a set of partially coupled experiments, in which the contribution from direct CO2 forcing (without the effect of wind changes) and wind effects can be isolated. Results indicate that both the direct CO2 and total wind effects contribute to the enhancement in the SST seasonal cycle, with the former (latter) effect being more important in the Northern Hemisphere (Southern Hemisphere). Further decomposition of the wind effect into the wind stress feedback and wind-evaporation-SST (WES) feedback through the change of wind speed reveals the importance of the wind stress-driven ocean response in the change of SST seasonal cycle, a result in contrast to a previous study that ascribed the midlatitude SST seasonal cycle change to the thermodynamic WES feedback. The direct CO2 effect regulates SST seasonal cycle mainly through the mediating effects of the ocean mixed layer depth (MLD): i) the CO2 induced warming leads to MLD shoaling, thus reducing its effective heat capacity; ii) the climatological MLD is greater in winter than summer, given the same amount of energy flux from the surface, SST warming in winter should be smaller. Notably, the surface wind seasonal cycle change due solely to the direct CO2 effect is found to bear a great resemblance to the full wind response, implicating that the direct CO2 effect is the root source for the enhancement of the midlatitude SST seasonal cycle. This is further supported by an ocean-alone experiment that replicates the SST seasonal cycle enhancement under a spatially and temporally homogeneous surface thermal forcing into the ocean.

Liu, Fukai↗
NASA NTRS1994

Fundamental phenomena on fuel decomposition and boundary layer combustion processes with applications to hybrid rocket motors

An experimental study on the fundamental processes involved in fuel decomposition and boundary layer combustion in hybrid rocket motors is being conducted at the High Pressure Combustion Laboratory of the Pennsylvania State University. This research should provide a useful engineering technology base in the development of hybrid rocket motors as well as a fundamental understanding of the complex processes involved in hybrid propulsion. A high pressure slab motor has been designed and manufactured for conducting experimental investigations. Oxidizer (LOX or GOX) supply and control systems have been designed and partly constructed for the head-end injection into the test chamber. Experiments using HTPB fuel, as well as fuels supplied by NASA designated industrial companies will be conducted. Design and construction of fuel casting molds and sample holders have been completed. The portion of these items for industrial company fuel casting will be sent to the McDonnell Douglas Aerospace Corporation in the near future. The study focuses on the following areas: observation of solid fuel burning processes with LOX or GOX, measurement and correlation of solid fuel regression rate with operating conditions, measurement of flame temperature and radical species concentrations, determination of the solid fuel subsurface temperature profile, and utilization of experimental data for validation of a companion theoretical study (Part 2) also being conducted at PSU.

Kuo, Kenneth K.↗
DOE OSTI2025

Energizing Robust Sulfur/Lithium Electrochemistry via Nanoscale-Asymmetric-Size Synergism

Sluggish redox kinetics and dendrite growth perplex the fulfillment of efficient electrochemistry in lithium–sulfur (Li–S) batteries. The complicated sulfur phase transformation and sulfur/lithium diversity kinetics necessitate an all-inclusive approach in catalyst design. Herein, a compatible mediator with nanoscale-asymmetric-size configuration by integrating Co single atoms and defective CoTe 2–x (Co SA -CoTe 2–x @NHCF) is elaborately developed for regulating sulfur/lithium electrochemistry synchronously. Substantial electrochemistry and theoretical analyses reveal that CoTe 2–x exhibits higher catalytic activity in long-chain polysulfide transformation and Li 2 S decomposition, while monodispersed Co sites are more effective in boosting sulfur reduction kinetics to regulate Li 2 S deposition. Such cascade catalysis endows Co SA -CoTe 2–x @NHCF with the all-around service of “trapping-conversion-recuperation” for sulfur species during the whole redox reaction. Furthermore, it is demonstrated by in situ transmission electron microscopy that initially formed electronic-conductive Co and ionic-conductive Li 2 Te provide sufficient lithiophilic sites to regulate homogeneous Li plating and stripping with markedly suppressed dendrite growth. Consequently, by coupling the Co SA -CoTe 2–x @NHCF interlayer and Li@Co SA -CoTe 2–x @NHCF anode, the constructed Li–S full batteries deliver superior cycling stability and rate performance, and the flexible pouch cell exhibits stable cycling performance at 0.3 C. In conclusion, the gained insights into the synergistic effect of asymmetric-size structures pave the way for the integrated catalyst design in advanced Li–S systems.

36 MATERIALS SCIENCE↗
NASA NTRS1995

Fuel decomposition and boundary-layer combustion processes of hybrid rocket motors

Using a high-pressure, two-dimensional hybrid motor, an experimental investigation was conducted on fundamental processes involved in hybrid rocket combustion. HTPB (Hydroxyl-terminated Polybutadiene) fuel cross-linked with diisocyanate was burned with GOX under various operating conditions. Large-amplitude pressure oscillations were encountered in earlier test runs. After identifying the source of instability and decoupling the GOX feed-line system and combustion chamber, the pressure oscillations were drastically reduced from +/-20% of the localized mean pressure to an acceptable range of +/-1.5% Embedded fine-wire thermocouples indicated that the surface temperature of the burning fuel was around 1000 K depending upon axial locations and operating conditions. Also, except near the leading-edge region, the subsurface thermal wave profiles in the upstream locations are thicker than those in the downstream locations since the solid-fuel regression rate, in general, increases with distance along the fuel slab. The recovered solid fuel slabs in the laminar portion of the boundary layer exhibited smooth surfaces, indicating the existence of a liquid melt layer on the burning fuel surface in the upstream region. After the transition section, which displayed distinct transverse striations, the surface roughness pattern became quite random and very pronounced in the downstream turbulent boundary-layer region. Both real-time X-ray radiography and ultrasonic pulse-echo techniques were used to determine the instantaneous web thickness burned and instantaneous solid-fuel regression rates over certain portions of the fuel slabs. Globally averaged and axially dependent but time-averaged regression rates were also obtained and presented.

Chiaverini, Martin J.↗
DOE OSTI2026

pyRMG: A framework for high-throughput, large-cell DFT calculations on supercomputers

Exascale computing delivers the raw power to simulate ever larger and more chemically realistic systems, but realizing this potential requires codes that can efficiently use thousands of processors. Our real-space multigrid (RMG) density functional theory (DFT) code’s grid-decomposition approach scales nearly linearly with the number of graphics processing units (GPUs), even for simulations exceeding thousands of atoms. This scalability makes RMG a compelling tool for high-throughput DFT studies of materials that would otherwise be bottlenecked in other codes (for example, by global fast Fourier transforms in plane-wave DFT). However, the limited workflow infrastructure for RMG has thus far constrained its adoption to a small user community. In this work, we present pyRMG, a Python package designed to streamline the setup and execution of RMG DFT calculations. Built on the pymatgen and ASE (Atomic Simulation Environment) computational materials science Python packages, pyRMG automates input generation and convergence checking, and it integrates with modern job schedulers (e.g., Flux) on leadership-class platforms such as Frontier and Perlmutter. Here, we demonstrate pyRMG for a high-throughput study of strain effects in 2D 2L-Bi 2 Se 3 /2L-NbSe 2 heterostructures, which offers chemical insights into this system and shows that RMG-based workflows can converge with limited user intervention.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Scalable electrified cementitious materials production and recycling

The production of Portland cement, the industry-standard cement, contributes ~8% of global CO 2 emissions through fossil-fuel heating and decomposition of limestone (the primary cement raw material). Decarbonization, e.g., via direct electrification, of this 200-year-old liming routine is extremely challenging at the industry scale. We propose a scalable electrochemical decarbonization approach to circumvent the limestone use by switching to carbon-free calcium silicates from abundant minerals and recycled concrete. Water electrolysis produces protons and hydroxides to drive a pH gradient that accelerates Ca 2+ ion leaching from calcium silicates and captures atmospheric CO 2 to form carbon-negative CaCO 3 , which serves as the feedstock for cement manufacturing or as the carbon-mineralized product for cement substitution with permanent carbon storage. Value-added co-products amorphous silica and green H 2 further enhance cement performance and supplant fossil fuels for net-zero transition, respectively. The products readily meet present-day regulatory standards and demands, and the approach readily synergizes with business-as-usual cement manufacturing and concrete construction, which are important for upscaling and structural safety, promising ready reception by the public and industries. Blended Portland cement produced through our approach with carbon-negative CaCO 3 and silica demonstrates enhanced resilience and achieves carbon neutrality or negativity when incorporating storage or circulation of CO 2 from cement plant flue gas, respectively. This low-cost, electrochemical cement production approach using abundant ubiquitous raw materials enables electrification, transition to clean fuel, and decarbonization at a gigaton scale.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Hydrogen generation via ammonia decomposition on highly efficient and stable Ru-free catalysts: approaching complete conversion at 450 °C

We report Hydrogen (H 2 ) is a prospective zero-carbon and high-energy-density fuel alternative to fossil fuels for generating power and clean energy. Ammonia (NH 3 ) is a promising H 2 (17.7%) carrier, which can easily overcome the challenges associated with H 2 storage and transportation. Thermocatalytic ammonia decomposition reaction (ADR) is an effective way to produce clean H 2 but it relies on the use of expensive and rare ruthenium (Ru)-based catalysts at elevated temperatures (>500 °C), hence is not sustainable and economically feasible. Herein, we report a synergistic strategy to design a heterostructured Ru-free catalyst, consisting of CoNi alloy nanoparticles well-dispersed on a MgO–CeO 2 –SrO mixed oxide support with potassium promotion. The resulting K–CoNi alloy –MgO–CeO 2 –SrO catalyst presents 97.7% and 87.5% NH 3 conversion efficiency at 450 °C at gas hourly space velocities (GHSVs) of 6000- and 12 000-mL h -1 g cat -1 , respectively. At 500 °C, the H 2 production rate (57.75 mmol g cat -1 min -1 ) becomes comparable to that of most of the reported Ru-based catalysts. The catalyst stability has been successfully demonstrated in both a fixed-bed reactor under high pressure (120 h at 5.0 bar) and a membrane reactor prototype (600 h at 1.5 bar) at 500 °C. High-temperature in situ XPS analysis, temperature-programmed desorption/reduction, and density functional theory calculations have been carried out to elucidate the possible active sites and performance enhancement mechanisms. This work highlights the importance of constructing optimal interfaces between active metal nanoparticles and oxide support for boosting the NH 3 to H 2 conversion efficiency and long-term stability.

25 ENERGY STORAGE↗