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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 739 records · Page 41
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Approaches to Cycle Analysis and Performance Metrics

The following notes were prepared as part of an American Institute of Aeronautics and Astronautics (AIAA) sponsored short course entitled Air Breathing Pulse Detonation Engine (PDE) Technology. The course was presented in January of 2003, and again in July of 2004 at two different AIAA meetings. It was taught by seven instructors, each of whom provided information on particular areas of PDE research. These notes cover two areas. The first is titled Approaches to Cycle Analysis and Performance Metrics. Here, the various methods of cycle analysis are introduced. These range from algebraic, thermodynamic equations, to single and multi-dimensional Computational Fluid Dynamic (CFD) solutions. Also discussed are the various means by which performance is measured, and how these are applied in a device which is fundamentally unsteady. The second topic covered is titled PDE Hybrid Applications. Here the concept of coupling a PDE to a conventional turbomachinery based engine is explored. Motivation for such a configuration is provided in the form of potential thermodynamic benefits. This is accompanied by a discussion of challenges to the technology.

Parson, Daniel E.↗
DOE OSTI2018

Reductions in tree performance during hotter droughts are mitigated by shifts in nitrogen cycling

Climate warming should result in hotter droughts of unprecedented severity in this century. Such droughts have been linked with massive tree mortality, and data suggest that warming interacts with drought to aggravate plant performance. Yet how forests will respond to hotter droughts remains unclear, as does the suite of mechanisms trees use to deal with hot droughts. We used an ecosystem-scale manipulation of precipitation and temperature on piñon pine (Pinus edulis) and juniper (Juniperus monosperma) trees to investigate nitrogen (N) cycling-induced mitigation processes related to hotter droughts. We found that while negative impacts on plant carbon and water balance are manifest after prolonged drought, performance reductions were not amplified by warmer temperatures. Rather, increased temperatures for 5 years stimulated soil N cycling under piñon trees and modified tree N allocation for both species, resulting in mitigation of hotter drought impacts on tree water and carbon functions. These findings suggest that adjustments in N cycling are likely after multi-year warming conditions and that such changes may buffer reductions in tree performance during hotter droughts. The results highlight our incomplete understanding of trees' ability to acclimate to climate change, raising fundamental questions about the resistance potential of forests to long-term, compound climatic stresses.

Grossiord, Charlotte↗
DOE OSTI2015

Improve First-Cycle Efficiency and Rate Performance of Layered-Layered Li 1.2 Mn 0.6 Ni 0.2 O 2 Using Oxygen Stabilizing Dopant

The poor first-cycle Coulombic efficiency and rate performance of the Li-rich layered-layered oxides are associated with oxygen gas generation in the first activation charging and sluggish charge transportation along the layers. In this work, we report that barium doping improves the first-cycle efficiency of Li-rich layered-layered Li1.2Mn0.6Ni0.2O2 via suppression of the oxidation of O2– ions in the first charging. This effect can be attributed to the stabilizing effect of the barium cations on the oxygen radical intermediates generated during the oxidation of O2–. Meanwhile, because the stabilized oxygen radicals likely facilitate the charge transportation in the layered-layered structure, the barium-doped Li1.2Mn0.6Ni0.2O2 exhibits significant improvement in rate performance. Stabilizing the oxygen radicals could be a promising strategy to improve the electrochemical performance of Li-rich layered-layered oxides.

36 MATERIALS SCIENCE↗
DOE OSTI2024

The importance of cycle-by-cycle data in performing rapid battery technology development and validation

Lithium-ion battery (LiB) technology is playing a crucial role in transforming the predominantly fossil fuel-based transportation and stationary storage sectors to achieve a low-carbon economy. Rapid innovation in the LiB materials to electrode to cell design is happening to satisfy the performance, life, and safety metrics required by those myriads of applications. Lately, advanced analytics, such as machine-learning or artificial intelligence (ML/AI) techniques, are being used more frequently to aid in expedited LiB technology development, performance validation, and life prediction. The success of these techniques often relies on a large volume of well-defined and high-quality battery test data. On the other hand, most battery developers and research and development (R&D) communities are still following a classical approach to develop batteries, which is running calendar- and/or cycle-aging tests, performing reference performance tests (RPTs), and conducting post-mortem analyses periodically without paying attention to the wealth of data often not collected during the calendar or cycle life aging tests. This sparse data collection approach is time- and resource-intensive, requiring data capture and evaluation of months to years of RPT data to diagnose accurate battery state of performance, health, and safety. Even so, the underlying aging modes and mechanisms can be missed. If collected properly, battery test data during cycling or calendaring can be efficiently combined with ML/AI techniques to create powerful tools in the rapid diagnosis of battery state of performance, health, and safety along with insights into underlying aging modes and mechanisms. In this report, we discuss the importance of effective cycle-by-cycle (CBC) data collection with example case studies. Within a reasonable timeframe, RPT data are often inadequate in capturing many of the crucial battery aging dynamics, which often predominantly show up in CBC test data. Finally, we also show examples of ML/AI techniques that use CBC data in rapid diagnosis and projection of LiB state of health (SOH) to motivate the scientific community in collecting and using CBC data to facilitate expeditious technology development and validation.

25 ENERGY STORAGE↗
NASA NTRS1980

Design, performance and life cycle cost relationships for a 500kW space solar array

The effects on life cycle costs of a number of technology areas are examined for a LEO, 500kW space solar array. A baseline system conceptual design is developed and the life cycle costs estimated in detail. The baseline system requirements and design technologies are then varied and their relationships to life cycle costs quantified. For example, the thermal characteristics of the baseline design are determined by the array materials and masses. The thermal characteristics in turn determine configuration, performance and hence life cycle cost.

Richardson, P. W.↗
NASA NTRS1952

Loiter performance of turbojet-powered aircraft performance determined by off-design cycle analysis

Loitering performance of airplanes equipped with various turbojet engines was analytically investigated. The engines used in this analysis were selected to show the effects of various engine design variables. Engine performance was determined by means of an off-design cycle analysismaking use of experimentally determined component characteristics. The method of off-design cycle analysis is presented herein and is verified by a check with experimental data.

Koutz, Stanley L↗
NASA NTRS1976

Future higher performance O2/H2 engine combustion cycle alternatives

The status of current and projected advanced O2/H2 rocket engine configurations for high-efficiency engine designs is examined. Particular attention is given to engine cycle configurations, operating pressures, and performance characteristics which can be foreseen for the engine configurations past the 1980 era for single-stage-to-orbit boosters and advanced space engines. The discussion covers potential O2/H2 performance gains achievable, engine cycle improvements, and projected O2/H2 engine component efficiency, weight, and other improvements foreseen through future development.

Wagner, W. R.↗
NASA NTRS1991

Advances In Li-TiS2 Cell Techno1ogy

JPL is involved in a NASA sponsored program to develop ambient temperature secondary Lithium - Titanium Disulfide Cells for future space missions. After several years of research on various lithium systems, the Li-TiS2 system was selected for development in view of its practically realizable high specific energy. In the last two years, the efforts were focused on improving the cycle life of the system and optimizing the cell design. A number of approaches, such as the use of mixed solvent electrolytes, the use of alternate anode materials, the operation of cells at low temperature, and the cycling of cells under optimized voltage limits, are examined to improve cycle life performance of this system. Cycling studies in small 150 mAh cell have identified 1.5 M LiAsF6/2-MeTHF, 1.5 M LiAsF6/EC+2-eTHF, and 1.5 M LiAsF6/THF+2-MeTHF+2-MeF as promising electrolytes for Li-TiS2 cells. Li-Al and Li-C were selected for further assessment as candidate anode materials after a detailed theoretical and experimental evaluation. Cycling of the cells at low temperature did not result in improving the cycle life of the cells. Charge and discharge voltage limits were found to have significant influence on the cycle life of the cells activated with 1.5 M LiAsF6/THF+2-MeTHF+2-MeF electrolyte. The influence of design variables, such as ratio of electrode capacity, quantity of electrolyte, pack tightness, cell configuration, etc., on the cycle life performance are being examined as a part of the design optimization study. Spiral-wound 1 Ah cells fabricated for the design studies have completed more than 500 cycles at 50% DOD. This paper summarizes the advances made in the Li-TiS2 technology at JPL since 1989.

Surampudi, S.↗
DOE OSTI2012

Influence of HTR core inlet and outlet temperatures on hydrogen generation efficiency using the sulfur-iodine water-splitting cycle

The performance of hydrogen production via thermochemical cycles is typically evaluated using thermal efficiency. In this study, the sulfur-iodine cycle with heat supplied by a high-temperature reactor (HTR) is analyzed. Two cases are examined: one flow sheet designed by General Atomics in the United States, the other by Commissariat a l'energie atomique et aux energies alternatives in France. In each case, HTR helium inlet and outlet temperatures are specified. Differences in these temperature specifications lead to process variations between the limy sheets and in how the hydrogen processes interface with the nuclear heat source. Two principal conclusions result from the analysis. First, the thermal efficiency tends to plateau above a certain outlet helium temperature. This is a characteristic effect of the method of Ozturk et al. for sulfuric acid decomposition. Second, it is clear that it is impractical to discuss efficiencies for the hydrogen process that are independent of defined operating parameters of the HTR. (authors)

08 HYDROGEN↗
DOE OSTI2026

Enhanced electrochemical performance and extended cycling of resorcinol-formaldehyde derived N-doped carbon xerogel for alkali metal-ion (Li/Na/K) batteries

Resorcinol formaldehyde-derived carbon xerogel (RFC) is a versatile material with tuneable properties, synthesized through a simple sol-gel method. This study presents nitrogen-doped RF carbon xerogel (N-RFC) with 11.8 at% nitrogen doping, offering a microporous architecture ideal for alkali metal-ion (Li, Na, K) batteries. The porous N-doped framework enhances electrochemical performance by improving ion transport, increasing active storage sites, and significantly boosting metal-ion adsorption, particularly through pyrrolic nitrogen, as revealed by first-principles calculations supported by XPS analysis. N-RFC anodes showed excellent cycling stability, high-capacity retention, and fast charge/discharge capabilities, rendering them suitable for commercial applications. Notably, the N-RFC anode demonstrates high-rate long-term cycling stability, retaining its capacity of 83.5 % (188 mAh/g at 2 C-rate) and 50 % (133 mAh/g at 1250 mA/g) over 1000 cycles for Li and Na-ion batteries, respectively, favorable for commercial battery applications. Additionally, N-RFC demonstrates a reversible capacity of 120 mAh/g after 394 cycles with a retention of 82 % for K-ion batteries. The ability of the material to accommodate larger ions like Na + and K + further emphasizes its versatility and potential application in diverse alkali metal-ion battery systems.

25 ENERGY STORAGE↗
NASA NTRS1994

Advanced Low-Cost O2/H2 Engines for the SSTO Application

The recent NASA Access to Space study examined future Earth to orbit (ETO) transportation needs and fleets out to 2030. The baseline in the option 3 assessment was a single stage to orbit (SSTO) vehicle. A study was conducted to assess the use of new advanced low cost O2/H2 engines for this SSTO application. The study defined baseline configurations and ground rules and defined six engine cycles to explore engine performance. The cycles included an open cycle, and a series of closed cycles with varying abilities to extract energy from the propellants to power he turbomachinery. The cycles thus varied in the maximum chamber pressure they could reach and in their weights at any given chamber pressure. The weight of each cycle was calculated for two technology levels versus chamber pressure up to the power limit of the cycle. The performance in the SSTO mission was then modeled using the resulting engine weights and specific impulse performance using the Access to Space option 3 vehicle. The results showed that new O2/H2 engines are viable and competitive candidates for the SSTO application using chamber pressures of 4,000 psi.

Goracke, B. David↗
NASA NTRS1985

Life-cycle costs of high-performance cells

A life cycle cost analysis of high efficiency cells was presented. Although high efficiency cells produce more power, they also cost more to make and are more susceptible to array hot-spot heating. Three different computer analysis programs were used: SAMICS (solar array manufacturing industry costing standards), PVARRAY (an array failure mode/degradation simulator), and LCP (lifetime cost and performance). The high efficiency cell modules were found to be more economical in this study, but parallel redundancy is recommended.

Daniel, R.↗