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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 1,099 records · Page 61
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Explosion behavior investigation and safety assessment of large-format lithium-ion pouch cells

We report large-format lithium-ion (Li-ion) batteries with high energy density for electric vehicles are prone to thermal runaway (or even explosion) under abusive conditions. In this study, overcharge induced explosion behaviors of large-format Li-ion pouch cells with Li[Ni 0.8 Co 0.1 Mn 0.1 ]O 2 cathode at different current rates (C-rates) (0.5C, 1C, 2C) were investigated. The explosion characteristics of the cells were elucidated by discussing the evolution of the cell voltage, the surface temperature and the shock wave pressure. Generally, the whole overcharge process could be divided into four stages according to the evolution of several key parameters and the overcharge behaviors; the overcharge C-rate has a great influence on cells’ thermal behaviors. The experimental results showed that the thermal runaway process of Li-ion cells caused by overcharging consisted of two kinds of explosions, physical explosion and chemical explosion. The existence of observable negative pressure zone in the pressure curves indicated that the Li-ion cells are not a self-supplying oxygen system during the explosion. Further, the explosion dynamics parameters were matched. An explosion TNT-equivalent conversion strategy that depended on the pressure of the shock wave was utilized to evaluate the released energy and its hazards. In addition, with respect to the overcharge of Li-ion pouch cells, a safety assessment method and a safety management method were proposed based on the explosion behaviors. From the perspective of battery safety, this study is of great significance for the safety design of Li-ion cells and can provide guidance for engineers to optimize the safety function of battery packs.

25 ENERGY STORAGE↗
NASA NTRS1971

A note on the acceleration phase of high-energy particles in the solar flare on 7 July, 1966.

The acceleration phase of solar cosmic rays and relativistic electrons is studied on the basis of the observational data available on the optical, radio, X-ray, and particle events associated with the solar flare that occurred on July 7, 1966. The generating process of hydromagnetic shock waves which excited the type-II radio burst detected at a frequency below about 100 MHz is also discussed. The results of the study suggest that no secondary acceleration process after the explosive phase can contribute much to the generation of high energy particles. The ejection of solar cosmic rays and relativistic electrons seems to be related to the expansion of the magnetic bulge which can trap accelerated electrons from the triggering region of solar flares.

Sakurai, K.↗
DOE OSTI2015

Steam explosion of oil palm residues for the production of durable pellets

Here we investigated the effect of steam explosion pretreatment on the physical and mechanical properties of the pellets made from empty fruit bunch (EFB) and palm kernel shell (PKS) and we compared to that of softwood Douglas fir (DF). We found that the high heating value of the empty fruit bunch was increased by 21% after steam explosion pretreatment. The pellet density of EFB and Douglas fir pellets did not change while the pellet density of PKS increased from 1.13 to 1.21 g/cm 3 after steam explosion. That may be attributed to the rapid volatilization of high mass fraction extractives during high pressure steaming and lead to the shrinkage of micropores of the PKS fibers. The maximum brealdng strength of steam exploded EFB and PKS were increased by 63% and 45%, respectively. The required compaction energy for the steam exploded EFB pellet is 44.50 J/g while that of the untreated EFB pellet is 30.15 J/g. Similar to Douglas fir, the required extrusion energy for the steam exploded EFB pellet was about 6 times than that of the untreated EFB pellet. The increased extrusion energy is mainly contributed by the increase in mono-saccharides by auto-hydrolysis during steam explosion pretreatment.

09 BIOMASS FUELS↗
DOE OSTI2017

Muon Creation in Supernova Matter Facilitates Neutrino-Driven Explosions

Muons can be created in nascent neutron stars (NSs) due to the high electron chemical potentials and the high temperatures. Because of their relatively lower abundance compared to electrons, their role has so far been ignored in numerical simulations of stellar core collapse and NS formation. However, the appearance of muons softens the NS equation of state, triggers faster NS contraction, and thus leads to higher luminosities and mean energies of the emitted neutrinos. This strengthens the postshock heating by neutrinos and can facilitate explosions by the neutrino-driven mechanism.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Influence of background sources and topographic resolution in the Weather Research and Forecasting Model on xenon plume characteristics at monitoring stations

For many atmospheric monitoring applications, networks of measurement sites—such as the radionuclide stations of the International Monitoring System—can be sparse. With measurement locations potentially hundreds to thousands of kilometers from a release it is important to quantify the effects of physical processes on transport and dispersion of plumes between source and measurement locations. This study addresses the effects of background sources and topography resolution near the release location of radionuclides. We use the Weather Research and Forecasting (WRF) model with inline chemistry to investigate (1) how an additional, time-varying source of 133 Xe, such as an operational medical isotope production facility, contributes to activity concentration measurements at monitoring sites, and (2) how complex topography influences on atmospheric conditions near emission sources impact plume concentrations at varying distances from the source. Two 133 Xe emission sources, including (1) a high flux rate of short duration representing an explosive event, and (2) a variable and continuous background source, are simulated. The continuous background source contributes significantly to total 133 Xe concentrations at several monitoring stations. Further, a WRF simulation at 9 km horizontal resolution is compared with a nested grid simulation, where the innermost domain has a resolution of 1 km. Increased topographic resolution leads to an improved representation of plume responses to local winds, with topographic influences greatest at locations closest to the sources. Differences between the two domain resolutions decrease at greater distances from the sources, as plumes have time to spread and mix and are influenced by synoptic scale circulation patterns that are represented similarly in both simulations.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Volcanic Radiative Forcing From 1979 to 2015

Using volcanic sulfur dioxide emissions in an aerosol-climate model, we derive a time series of global-mean volcanic effective radiative forcing (ERF) from 1979 to 2015. For 2005–2015, we calculate a global multiannual mean volcanic ERF of 0.08 W/m 2 relative to the volcanically quiescent 1999–2002 period, due to a high frequency of small-to-moderate-magnitude explosive eruptions after 2004. For eruptions of large magnitude such as 1991 Mt. Pinatubo, our model-simulated volcanic ERF, which accounts for rapid adjustments including aerosol perturbations of clouds, is less negative than that reported in the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5) that only accounted for stratospheric temperature adjustments. We find that, when rapid adjustments are considered, the relation between volcanic forcing and volcanic stratospheric optical depth (SAOD) is 13–21% weaker than reported in IPCC AR5 for large-magnitude eruptions. Further, our analysis of the recurrence frequency of eruptions reveals that sulfur-rich small-to-moderate-magnitude eruptions with column heights =10 km occur frequently, with periods of volcanic quiescence being statistically rare. Small-to-moderate-magnitude eruptions should therefore be included in climate model simulations, given the >50% chance of one or two eruptions to occur in any given year. Not all of these eruptions affect the stratospheric aerosol budget, but those that do increase the nonvolcanic background SAOD by ~0.004 on average, contributing ~50% to the total SAOD in the absence of large-magnitude eruptions. This equates to a volcanic ERF of about 0.10 W/m 2 , which is about two thirds of the ERF from ozone changes induced by ozone-depleting substances.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Radio Frequency Characteristics of Volcanic Lightning and Vent Discharges

In this study, we analyze the pulse width and spectral content of vent discharges and volcanic lightning flashes. We made measurements of electrical activity with a broadband very high frequency antenna (20–80 MHz) during an explosive eruption of Sakurajima volcano on November 8, 2019. The individual impulses that comprise vent discharges and volcanic lightning were analyzed to determine the fundamental width of the impulses and the rate of fall-off of their energy spectral density. The results show that vent discharges are more similar to volcanic lightning than they are different. Here, the mean pulse width for both vent discharges and volcanic lightning was 50 ns. Both types of electrical activity had similar spectral content; the average slope of the amplitude spectra was –3.4 for both. Further, examination of the pulse width and spectral slope distributions showed that while the distributions of volcanic lightning and vent discharges are statistically distinct from each other, the distribution of vent discharges is a subset of the distribution of volcanic lightning.

58 GEOSCIENCES↗
DOE OSTI2021

Dynamics of filaments during the edge-localized mode crash on NSTX

Edge localized modes (ELMs) are routinely observed in H-mode plasma regimes of the National Spherical Torus Experiment (NSTX). Due to the explosive nature of the instability, only diagnostics with high temporal and spatial resolution could provide a detailed insight into the dynamics associated with the ELMs. Gas-puff imaging at NSTX provides 2D measurements of the magnetic field aligned fluctuations (e.g., ELM filaments) in the scrape-off layer and at the plasma edge with 2.5 μs temporal and 10 mm optical resolution. A novel analysis technique was developed to estimate the frame-by-frame velocities and the spatial parameters of the dominant structures associated with the ELMs. The analysis was applied to single ELM events to characterize the ELM crash dynamics and then extended to a database of 159 ELM events. Statistical analysis was performed in order to find the characterizing dynamics of the ELM crash. The results show that on average, an ELM crash consists of a filament with a circular cross section, which is propelled outward with a characterizing peak radial velocity of ~3.3 km/s. The radial velocity was found to be linearly dependent on the distance of the filament from the separatrix, which has never been seen before. The ELM filament is characterized by propagation in the ion-diamagnetic direction poloidally with a peak velocity of 11.4 km/s. The ELM crash lasts for approximately 100 μs until the radial propulsion settles back to the pre-ELM level. Furthermore, the experimental findings were compared with analytical theory. Two possible mechanisms were identified for explaining the observations: the curvature interchange model and the current–filament interaction model.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

Big Data Analytics for Demand Response: Clustering Over Space and Time

The pervasive deployment of advanced sensing infrastructure in Cyber-Physical systems, such as the Smart Grid, has resulted in an unprecedented data explosion. Such data exhibit both large volumes and high velocity characteristics, two of the three pillars of Big Data, and have a time-series notion as datasets in this context typically consist of successive measurements made over a time interval. Time-series data can be valuable for data mining and analytics tasks such as identifying the “right” customers among a diverse population, to target for Demand Response programs. However, time series are challenging to mine due to their high dimensionality. In this paper, we motivate this problem using a real application from the smart grid domain. We explore novel representations of time-series data for BigData analytics, and propose a clustering technique for determining natural segmentation of customers and identification of temporal consumption patterns. Our method is generizable to large-scale, real-world scenarios, without making any assumptions about the data. We evaluate our technique using real datasets from smart meters, totaling ~ 18,200,000 data points, and show the efficacy of our technique in efficiency detecting the number of optimal number of clusters.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2014

Pulsed electron beam generation with fast repetitive double pulse system

Longer duration high voltage pulse (∼ 100 kV, 260 ns) is generated and reported using helical pulse forming line in compact geometry. The transmission line characteristics of the helical pulse forming line are also used to develop fast repetition double pulse system with very short inter pulse interval. It overcomes the limitations caused due to circuit parameters, power supplies and load characteristics for fast repetitive high voltage pulse generation. The high voltage double pulse of 100 kV, 100 ns with an inter pulse repetition interval of 30 ns is applied across the vacuum field emission diode for pulsed electron beam generation. The electron beam is generated from cathode material by application of negative high voltage (> 100 kV) across the diode by explosive electron emission process. The vacuum field emission diode is made of 40 mm diameter graphite cathode and SS mesh anode. The anode cathode gap was 6 mm and the drift tube diameter was 10 cm. The initial experimental results of pulsed electron beam generation with fast repetitive double pulse system are reported and discussed. (author)

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Dynamics of filaments during the edge-localized mode crash on NSTX

Edge localized modes (ELMs) are routinely observed in H-mode plasma regimes of the National Spherical Torus Experiment (NSTX). Due to the explosive nature of the instability, only diagnostics with high temporal and spatial resolution could provide a detailed insight into the dynamics associated with the ELMs. Gas-puff imaging (GPI) at NSTX provides 2D measurements of the magnetic field aligned fluctuations (e.g. ELM filaments) in the scrape-off layer and the at the plasma edge with 2.5 us temporal and 10 mm optical resolution.A novel analysis technique was developed to estimate the frame-by-frame velocities and the spatial parameters of the dominant structures associated with the ELMs. The analysis was applied to single ELM events to characterize the ELM crash dynamics, and then extended to a database of 169 ELM events.Statistical analysis was performed in order to find the characterizing dynamics of the ELM crash. The results show that on average an ELM crash consists of a filament with a circular cross-section which is propelled outwards with a characterizing peak radial velocity of ~3.3 km/s. The radial velocity was found to be linearly dependent on the distance of the filament from the separatrix, which has never been seen before. The ELM filament is characterized by propagation in the ion-diamagnetic direction poloidally with a peak velocity of 11.4 km/s. The ELM crash lasts for approximately 100us until the radial propulsion settles back to the pre-ELM level. The experimental findings were compared with analytical theory. Two possible mechanisms were identified for explaining the observations: the curvature interchange model and the current-filament interaction model.

correlation↗
NASA NTRS1967

Generation of radio sources.

Radio source model applied to small sources of high surface brightness occurring at great distances from explosion centers

Burbidge, G.↗
NASA NTRS1977

An emerging flux model for the solar flare phenomenon

An outline is presented of the physical processes involved in the emerging flux model, which appears to explain naturally many solar flare observations. The separate physical phases of the basic model include a preflare heating phase as the new flux emerges, an impulsive phase as high-energy particles are accelerated, a flash (or explosive) phase when the H-alpha intensity increases, and a main phase while it decreases. The extent and morphology of the main phase emission depend on the structure of the magnetic field region in which the new flux finds itself imbedded. It is suggested that a (small) simple loop flare occurs if the new flux appears in a region where no great amount of magnetic energy in excess of potential is stored. A two-ribbon flare occurs if the flux emerges near the polarity inversion line of an active region that has begun to develop filaments.

Heyvaerts, J.↗
NASA NTRS1988

The Sudbury Structure (Ontario, Canada) and Vredefort Structure (South Africa): A comparison

Both the Sudbury Structure (SS) and the Witwatersrand Basin surrounding the Vredefort Structure (VS) host some of the most important base and precious metal deposits on earth. In both structures Precambrian igneous, sedimentary and volcanic rocks were affected by the structure forming process, either meteorite impact or endogenic explosion, or as some VS workers propose, by high strain tectonics. Besides these general features there are some geological and geophysical characteristics that are strikingly similar in both structures. There are, however, some obvious differences. Directly related to the structure forming processes are breccias in the footwall rocks of both structures. Pseudotachylite breccias occurring in both structures display great similarities. Chemical and physical characteristics of the pseudotachylites are similar in both structures. Both structures are characterized by overturned collar rocks, not evident everywhere around the SS. The VS is rimmed by an up or overturned collar of sediments and volcanics of the Witwatersrand, Ventersdorp and Transvaal Supergroups. Drilling information proved that the strata of the Witwatersrand Supergroup in the south of the VS are lying horizontally. Shockmetamorphic features such as planar microdeformations in rock forming minerals and shatter cones are present in both structures in the footwall rocks and in the SS also in the breccias of the OF. Both structures have large geophysical anomalies associated with them. In both structures the anomalies were interpreted as being caused by mafic-ultramafic complexes underlying the structures.

Dressler, B. O.↗
NASA NTRS1988

Catastrophic volcanism as a cause of shocked features found at the K/T boundary and in cryptoexplosion structures

The presence of quartz grains containing shock lamellae at the Cretaceous/Tertiary (K/T) boundary is viewed by many as the single most compelling evidence of meteoritic or cometary impact because there is no known endogenous mechanism for producing these features. Similarly the presence of shocked quartz, shatter cones, coesite and stishovite at cryptoexplosion structures is comonly taken as conclusive evidence of impact. However, several recent studies have cast doubt on this interpretation. It is argued that basaltic volcanism, although not normally explosive, can under exceptional circumstances produce overpressures sufficiently high to produce shock features. The exceptional circumstances include a high content of volatiles, usually CO2, and no preestablished pathway to the surface. Rapid cooling of the saturated basaltic magma can occur if it underlies a cooler more evolved magma in a chamber. Initial slow cooling and partial exsolution of the volatiles will cause the density of the basaltic magma to become less than that of the overlying magma, leading to overturning and mixing. Gas will escape the magma chamber along planar cracks once the pressure becomes sufficiently high. In the vicinity of the crack tip there is a smallscale deviatoric stress pattern which is thought to be sufficiently high to produce transient cracks along secondary axes in the quartz crystals, causing the planar features. The CO2-rich fluid inclusions which have been found along planar elements of quartz in basement rocks of the Vredefort Dome were likely to have been emplaced by such a process. If the mechanism described is capable of producing shocked features as above, it would require a reassessment of the origin of many cryptoexplosion structures as well as seriously weakening the case for an impact origin of the K/T event.

Loper, D. E.↗
NASA NTRS1989

Spray automated balancing of rotors - How process parameters influence performance

This paper addresses the application of spray-automated balancing of rotors, and the influence that various operating parameters will have on balancing performance. Spray-automated balancing uses the fuel-air repetitive explosion process to imbed short, discrete bursts of high velocity, high temperature powder into a rotating part at an angle selected to reduce unbalance of the part. The shortness of the burst, the delay in firing of the gun, the speed of the disk and the variability in speed all influence the accuracy and effectiveness of the automated balancing process. The paper evaluates this influence by developing an analytical framework and supplementing the analysis with empirical data obtained while firing the gun at a rotating disk. Encouraging results are obtained, and it is shown that the process should perform satisfactorily over a wide range of operating parameters. Further experimental results demonstrate the ability of the method to reduce vibration levels induced by mass unbalance in a rotating disk.

Smalley, A. J.↗
NASA NTRS1991

Permanent wire splicing by an explosive joining process

The invention is an apparatus and method for wire splicing using an explosive joining process. The apparatus consists of a prebent, U-shaped strap of metal that slides over prepositioned wires. A standoff means separates the wires from the strap before joining. An adhesive means holds two ribbon explosives in position centered over the U-shaped strap. A detonating means connects to the ribbon explosives. The process involves spreading strands of each wire to be joined into a flat plane. The process then requires alternating each strand in alignment to form a mesh-like arrangement with an overlapped area. The strap slides over the strands of the wires, and the standoff means is positioned between the two surfaces. The detonating means then initiates the ribbon explosives that drive the strap to accomplish a high velocity, angular collision between the mating surfaces. This collision creates surface melts and collision bonding results in electron sharing linkups.

Bement, Laurence J.↗
NASA NTRS1993

Automata network models of galaxy evolution

Two ideas appear frequently in theories of star formation and galaxy evolution: (1) star formation is nonlocally excitatory, stimulating star formation in neighboring regions by propagation of a dense fragmenting shell or the compression of preexisting clouds; and (2) star formation is nonlocally inhibitory, making H2 regions and explosions which can create low-density and/or high temperature regions and increase the macroscopic velocity dispersion of the cloudy gas. Since it is not possible, given the present state of hydrodynamic modeling, to estimate whether one of these effects greatly dominates the other, it is of interest to investigate the predicted spatial pattern of star formation and its temporal behavior in simple models which incorporate both effects in a controlled manner. The present work presents preliminary results of such a study which is based on lattice galaxy models with various types of nonlocal inhibitory and excitatory couplings of the local SFR to the gas density, temperature, and velocity field meant to model a number of theoretical suggestions.

Chappell, David↗