Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “BURNING PROCESS”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,207 records · Page 67
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Study of aluminum particle combustion in solid propellant plumes using digital in-line holography and imaging pyrometry

The combustion of molten metals is an important area of study with applications ranging from solid aluminized rocket propellants to fireworks displays. Our work uses digital in-line holography (DIH) to experimentally quantify the three-dimensional position, size, and velocity of aluminum particles during combustion of ammonium perchlorate (AP) based solid-rocket propellants. Additionally, spatially resolved particle temperatures are simultaneously measured using two-color imaging pyrometry. To allow for fast characterization of the properties of tens of thousands of particles, automated data processing routines are proposed. In using these methods, statistics from aluminum particles with diameters ranging from 15 to 900 µm are collected at an ambient pressure of 83 kPa. In the first set of DIH experiments, increasing initial propellant temperature is shown to enhance the agglomeration of nascent aluminum at the burning surface, resulting in ejection of large molten aluminum particles into the exhaust plume. The resulting particle number and volume distributions are quantified. In the second set of simultaneous DIH and pyrometry experiments, particle size and velocity relationships as well as temperature statistics are explored. The average measured temperatures are found to be 2640 ± 282 K, which compares well with previous estimates of the range of particle and gas-phase temperatures. The novel methods proposed here represent new capabilities for simultaneous quantification of the joint size, velocity, and temperature statistics during the combustion of molten metal particles. The proposed techniques are expected to be useful for detailed performance assessment of metalized solid-rocket propellants.

36 MATERIALS SCIENCE↗
DOE OSTI2023

When less is more: How increasing the complexity of machine learning strategies for geothermal energy assessments may not lead toward better estimates

Previous moderate- and high-temperature geothermal resource assessments of the western United States utilized data-driven methods and expert decisions to estimate resource favorability. Although expert decisions can add confidence to the modeling process by ensuring reasonable models are employed, expert decisions also introduce human and, thereby, model bias. This bias can present a source of error that reduces the predictive performance of the models and confidence in the resulting resource estimates. Our study aims to develop robust data-driven methods with the goals of reducing bias and improving predictive ability. We present and compare nine favorability maps for geothermal resources in the western United States using data from the U.S. Geological Survey's 2008 geothermal resource assessment. Two favorability maps are created using the expert decision-dependent methods from the 2008 assessment (i.e., weight-of-evidence and logistic regression). With the same data, we then create six different favorability maps using logistic regression (without underlying expert decisions), XGBoost, and support-vector machines paired with two training strategies. The training strategies are customized to address the inherent challenges of applying machine learning to the geothermal training data, which have no negative examples and severe class imbalance. We also create another favorability map using an artificial neural network. We demonstrate that modern machine learning approaches can improve upon systems built with expert decisions. We also find that XGBoost, a non-linear algorithm, produces greater agreement with the 2008 results than linear logistic regression without expert decisions, because the expert decisions in the 2008 assessment rendered the otherwise linear approaches non-linear despite the fact that the 2008 assessment used only linear methods. The F1 scores for all approaches appear low (F1 score < 0.10), do not improve with increasing model complexity, and, therefore, indicate the fundamental limitations of the input features (i.e., training data). Until improved feature data are incorporated into the assessment process, simple non-linear algorithms (e.g., XGBoost) perform equally well or better than more complex methods (e.g., artificial neural networks) and remain easier to interpret.

15 GEOTHERMAL ENERGY↗
DOE OSTI2023

Heavy-element production in a compact object merger observed by JWST

The mergers of binary compact objects such as neutron stars and black holes are of central interest to several areas of astrophysics, including as the progenitors of gamma-ray bursts (GRBs), sources of high-frequency gravitational waves (GWs) and likely production sites for heavy-element nucleosynthesis by means of rapid neutron capture (the r -process). Here we present observations of the exceptionally bright GRB 230307A. We show that GRB 230307A belongs to the class of long-duration GRBs associated with compact object mergers and contains a kilonova similar to AT2017gfo, associated with the GW merger GW170817. We obtained James Webb Space Telescope (JWST) mid-infrared imaging and spectroscopy 29 and 61 days after the burst. The spectroscopy shows an emission line at 2.15 microns, which we interpret as tellurium (atomic mass A = 130) and a very red source, emitting most of its light in the mid-infrared owing to the production of lanthanides. These observations demonstrate that nucleosynthesis in GRBs can create r -process elements across a broad atomic mass range and play a central role in heavy-element nucleosynthesis across the Universe.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Nonlinear physics of shear Alfvén waves

Shear Alfvén waves (SAW) play fundamental roles in thermonuclear plasmas of fusion interest, since they are readily excited by energetic particles in the MeV range as well as by the thermal plasma components. Thus, understanding fluctuation induced transport in burning plasmas requires understanding nonlinear SAW physics. There exist two possible routes to nonlinear SAW physics: (i) wave-wave interactions and the resultant spectral energy transfer; (ii) nonlinear wave-particle interactions of SAW instabilities with energetic particles. Within the first route, it is advantageous to understand and describe nonlinear processes in term of proximity of the system to the Alfvénic state, where wave-wave interactions are minimized due to the cancellation of Reynolds and Maxwell stresses. Here, various wave-wave nonlinear dynamics are elucidated in terms of how they break the Alfvénic state. In particular, we discuss the qualitative and quantitative modification of the SAW parametric decay process due to finite ion compressibility and finite ion Larmor radius. We also show that toroidal geometry plays a crucial role in the nonlinear excitation of zonal structures by Alfvén eigenmodes. Within the second route, the coherent nonlinear dynamics of structures in the energetic particle phase space, by which secular resonant particle transport can occur on meso- and macro-scales, must be addressed and understood. These 'nonlinear equilibria' or 'phase-space zonal structures' dynamically evolve on characteristic (fluctuation induced) turbulent transport time scales, which are generally of the same order of the nonlinear time scale of the underlying fluctuations. In this work, we introduce the general structure of nonlinear Schrödinger equations with complex integro-differential nonlinear terms, which govern these physical processes. To elucidate all these aspects, theoretical analyses are presented together with numerical simulation results.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2026

Low-energy measurement of the 25 Mg ⁢(𝛼,𝑛)⁢ 28 Si reaction via neutron spectroscopy

During core helium and carbon burning in massive stars, neutrons are produced mainly by the 22 Ne⁢ (𝛼,𝑛) ⁢25 Mg reaction. Some of these released neutrons are captured by heavy seed nuclei from previous nucleosynthesis events, resulting in the slow production of many of the elements between masses 60 ≤ 𝐴 ≤ 90 via the weak 𝑠 process. Determining the overall neutron flux available in this environment is one of the main challenges in modeling its contributions to heavy element production. Not only must the reaction rate be well defined for the primary neutron source, but the rates of neutron poison and recycling reactions must also be well determined. One critical reaction in the simulation network is 25 Mg ⁢(𝛼,𝑛) ⁢ 28 Si. This reaction, together with 25 Mg ⁢(𝑛,𝛾)⁢ 26 Mg and 25 Mg⁢ (𝛼,𝛾) ⁢ 29 Si, determine how 25 Mg nuclei affect the available neutron flux. Past attempts to measure the 25 Mg ⁢(𝛼,𝑛)⁢ 28 Si cross section using neutron moderator counters have been greatly hindered by lower-𝑍 background reactions. Here, in the present work, neutron spectroscopy with deuterated liquid scintillator detectors has been used. The experimental spectra have been analyzed by applying spectrum unfolding techniques to achieve improved background discrimination for the 25 Mg⁢ (𝛼,𝑛)⁢ 28 Si reaction at low energies, down to 𝐸 𝛼 = 1.75 MeV. The separation of the different background contributions gives further insight into the results of previous moderator counter measurements and the measurements lead to a revised and more reliable determination of the reaction rate.

hydrostatic stellar nucleosynthesis↗
DOE OSTI2015

Environmental Restoration Operations: Consolidated Quarterly Report (Oct. - Dec 2014)

This Sandia National Laboratories, New Mexico Environmental Restoration Operations (ER) Consolidated Quarterly Report (ER Quarterly Report) fulfills all quarterly reporting requirements set forth in the Hazardous and Solid Waste Amendments (HSWA) Module of the Resource Conservation and Recovery Act Permit, and the Compliance Order on Consent. The 33 sites in the Corrective Action regulatory process are listed in Table I-1. The 33 sites consist of 25 Solid Waste Management Units and 8 Areas of Concern (AOCs). A summary of post-closure care activities performed in accordance with the Chemical Waste Landfill Post-Closure Care Permit is also included in this document. The Burn Site Groundwater and Technical Area V Groundwater AOCs are not included on the current HSWA Permit, but have been added as AOCs to the revised Hazardous Waste Facility Permit, which is pending approval by the New Mexico Environment Department at this time, and are included within this Consolidated Quarterly Report for completeness. Suspect waste includes radionuclides, metals, organic compounds, and explosives.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Landsat near-infrared (NIR) band and ELM-FATES sensitivity to forest disturbances and regrowth in the Central Amazon

Forest disturbance and regrowth are key processes in forest dynamics, but detailed information on these processes is difficult to obtain in remote forests such as the Amazon. We used chronosequences of Landsat satellite imagery (Landsat 5 Thematic Mapper and Landsat 7 Enhanced Thematic Mapper Plus) to determine the sensitivity of surface reflectance from all spectral bands to windthrow, clear-cut, and clear-cut and burned (cut + burn) and their successional pathways of forest regrowth in the Central Amazon. We also assessed whether the forest demography model Functionally Assembled Terrestrial Ecosystem Simulator (FATES) implemented in the Energy Exascale Earth System Model (E3SM) Land Model (ELM), ELM-FATES, accurately represents the changes for windthrow and clear-cut. The results show that all spectral bands from the Landsat satellites were sensitive to the disturbances but after 3 to 6 years only the near-infrared (NIR) band had significant changes associated with the successional pathways of forest regrowth for all the disturbances considered. In general, the NIR values decreased immediately after disturbance, increased to maximum values with the establishment of pioneers and early successional tree species, and then decreased slowly and almost linearly to pre-disturbance conditions with the dynamics of forest succession. Statistical methods predict that NIR values will return to pre-disturbance values in about 39, 36, and 56 years for windthrow, clear-cut, and cut + burn disturbances, respectively. The NIR band captured the observed, and different, successional pathways of forest regrowth after windthrow, clear-cut, and cut + burn. Consistent with inferences from the NIR observations, ELM-FATES predicted higher peaks of biomass and stem density after clear-cuts than after windthrows. ELM-FATES also predicted recovery of forest structure and canopy coverage back to pre-disturbance conditions in 38 years after windthrows and 41 years after clear-cut. The similarity of ELM-FATES predictions of regrowth patterns after windthrow and clear-cut to those of the NIR results suggests the NIR band can be used to benchmark forest regrowth in ecosystem models. Our results show the potential of Landsat imagery data for mapping forest regrowth from different types of disturbances, benchmarking, and the improvement of forest regrowth models.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1981

Combustion experiments in space

Pivotal areas for needed combustion observations (available through space shuttle experimentation) include: (1) single- and two-phase premixed flame propagation and extinction limits; (2) noncoherent flame propagation and extinction; (3) autoignition of premixed single-phase and two-phase combustible reactants; (4) upper pressure limit combustion phenomena and ignition, propagation, and extinction processes in the neighborhood of such limits; (5) oscillatory combustion associated with the hydrocarbon-oxygen and with the carbon monoxide-oxygen systems; (6) two-phase flame spread and extinction involving lage liquid-gas or solid-gas interfaces; (7) radiative ignition of solids and liquids; (8) pool burning; (9) smoldering of solid combustibles and the associated transition to flaming or extinction; (10) laminar gas jet combustion; and (11) transient responses of combustible systems to time variation in gravitational field strengths. A number of these may be impacted by undesirably high g-jitter effects.

Berlad, A. L.↗
NASA NTRS2018

Low Temperature Hybrid Mars Ascent Vehicle Concept Development and Planning at MSFC

Return of samples from Mars has been a goal of NASA's for decades. The current Mars Sample Return mission concepts have a multiple launch rocket from the earth, where one mission delivers a caching rover to collect and package the Martian soil samples. Another rocket sends the Mars Ascent Vehicle that takes those samples to orbit. Another rocket sends an orbiter, that also meets up with the samples in orbit, and brings them back to earth. Our tasks have been focused on the Mars Ascent Vehicle. To leave the Martian surface, it requires a two burn trajectory, one to get off the planet and another to circularize the orbit. Recent studies have led to the investigation of a hybrid rocket solution. That technology has been under development for several years. This paper will discuss some of the work going on at MSFC to understand how to process the fuel, some test firings done to characterize some design features and some planning done to scope out what it would take to qualify a hybrid rocket motor for this application.

Story, George↗
NASA NTRS2003

Trace Gas Measurements in Nascent, Aged and Cloud-processed Smoke from Africa Savanna Fires by Airborne Fourier Transform Infrared Spectroscopy (AFTIR)

We measured stable and reactive trace gases with an airborne Fourier transform infrared spectrometer (AFTIR) on the University of Washington Convair-580 research aircraft in August/September 2000 during the SAFARI 2000 dry season campaign in Southern Africa. The measurements included vertical profiles of C02, CO, H20, and CH4 up to 5.5 km on six occasions above instrumented ground sites and below the TERRA satellite and ER-2 high-flying research aircraft. We also measured the trace gas emissions from 10 African savanna fires. Five of these fires featured extensive ground-based fuel characterization, and two were in the humid savanna ecosystem that accounts for most African biomass burning. The major constituents we detected in nascent CH3OOH, HCHO, CH30H, HCN, NH3, HCOOH, and C2H2. These are the first quantitative measurements of the initial emissions of oxygenated volatile organic compounds (OVOC), NH3, and HCN from African savanna fires. On average, we measured 5.3 g/kg of OVOC and 3.6 g/kg of hydrocarbons (including CH4) in the initial emissions from the fires. Thus, the OVOC will have profound, largely unexplored effects on tropical tropospheric chemistry. The HCN emission factor was only weakly dependent on fire type; the average value (0.53 g/kg) is about 20 times that of a previous recommendation. HCN may be useful as a tracer for savanna fires. Delta O3/Delta CO and Delta CH3COO/Delta CO increased to as much as 9% in <1 h of photochemical processing downwind of fires. Direct measurements showed that cloud processing of smoke greatly reduced CH30H, NH3, CH3COOH, SO2, and NO2 levels, but significantly increased HCHO and NO.

Yokelson, Robert J.↗
NASA NTRS1996

Application of Two-Phase CFD to the Design and Analysis of a Subscale Motor Experiment to Evaluate Propellant Slag Production

The redesigned solid rocket motor (RSRM) Pressure Perturbation Investigation Team concluded that the cause of recent pressure spikes during both static and flight motor burns was the expulsion of molten aluminum oxide slag from a pool which collects in the aft end of the motor around the submerged nozzle nose during the last half of motor operation. It is suspected that some motors produce more slag than others due to differences in aluminum oxide agglomerate particle sizes which may relate to subtle differences in propellant ingredient characteristics such as particle size distribution, contaminants, or processing variations. In order to determine the effect of suspect propellant ingredient characteristics on the propensity for slag production in a real motor environment, a subscale motor experiment was designed. An existing 5 inch ballistic test motor was selected as the basic test vehicle due to low cost and quick turn around times. The standard converging/diverging nozzle was replaced with a submerged nozzle nose design to provide a positive trap for the slag which would increase both the quantity and repeatability of measured slag weights. Computational fluid dynamics (CFD) was used to assess a variety of submerged nose configurations to identify the design which possessed the best capability to reliably collect slag. CFD also was used to assure that the final selected nozzle design would result in flow field characteristics such as dividing streamline location, nose attach point, and separated flow structure which would have similtude with the RSRM submerged nozzle nose flow field. It also was decided to spin the 5 inch motor about its longitudinal axis to further enhance slag collection quantities. Again, CFD was used to select an appropriate spin rate along with other considerations, including the avoidance of burn rate enhancement from radial acceleration effects.

Whitesides, R. Harold↗
NASA NTRS1998

Making Intercontinental Burning Influences Quantitative: Lessons on Transport and Geochemistry From the 3-D Simulation of CO in PEM-T A and TRACE-A

We report on two aspects of the simulation of global transport of plumes originating from subtropical biomass fires. We use of meteorological assimilation (MM5) at 2-degree resolution with a Grail cloud parameterization and a Blackadar-based planetary boundary layer parameterization. Ames's GRACES model provides emissions, transport, and an appropriate level of simulated chemical transformation. We have worked with passive-tracer CO or linear chemistry. This is appropriate since we find major work to be done in evaluating CO source strengths and transport mechanisms before chemical integrations could be meaningful. First, we present mechanisms by which CO and other pollutants are introduced into the free troposphere, and are then transported with hate dilution from approx. 0 to approx. 180 degrees longitude. One principal conduit for these plumes is the vernal subtropical jet; however the plumes appear at various altitudes and latitudes as they influenced by frontal motions and (most likely) radiative processes. A common, repeated pattern of transport has pollutant plumes arriving in the distant Pacific Ocean from Africa and South America at 25 degrees south and 14 km altitude. Following this, there is then a general appearance of pollution at extending down to 5 kin at more equatorial (10 S) and polar latitudes (to 45 S). Second, we evaluate the quantitative success of our simulation. (Such success requires efforts considerably beyond trajectory analyses, and is necessary for our community to claim an understanding of the effects of biomass burning on global atmospheric chemistry and the planet's trend in oxidizing capacity.) We find that we simulate most pollution episodes sampled by Glenn Sachse's CO instrument and the Blake hydrocarbon analyses during PENT A. We will present our current ideas on why our general levels appear satisfactory when the observations are within 20 ppb of background levels, but substantially miss the variability associated with the most intense biomass burning plumes. As time allows, we will speculate on the origins of a class of plumes that appear in the mid-troposphere, but are missing from our simulations.

Chatfield, Robert↗
NASA NTRS1997

Vertical Transport Processes for Inert and Scavenged Species: TRACE-A Measurements

The TRACE-A mission of the NASA DC-8 aircraft made a large-scale survey of the tropical and subtropical atmosphere in September and October of 1992. Both In-situ measurements of CO (G. Sachsen NASA Langley) and aerosol size (J. Browell group, NASA Langley) provide excellent data sets with which to constrain vertical transport by planetary boundary layer mixing and deep-cloud cumulus convection. Lidar profiles of aerosol-induced scattering and ozone (also by Bremen) are somewhat require more subtle interpretation as tracers, but the vertical information on layering largely compensates for these complexities. The reason this DC-8 dataset is so useful is that very large areas of biomass burning over Africa and South America provide surface sources of appropriate sizes with which to characterize vertical and horizontal motions; the major limitation of our source description is that biomass burning patterns move considerably every few days, and daily burning inventories are a matter of concurrent, intensive research. We use the Penn State / NCAR MM5 model in an assimilation mode on the synoptic and intercontinental scale, and assess the success it shows in vertical transport descriptions. We find that the general level of emissions suggested by the climatological approach (Will. Has, U. of Montana) appears to be approximately correct, possibly a bit low, for this October, 1992, time period. Vertical transport in planetary boundary layer mixing to 5.5 kin was observed and reproduced in our simulations. Furthermore we find evidence that Blackader "transilient" or matrix-transport scheme is needed, but may require some adaptation in our tracer model: CO seems to exhibit very high values at the top of the planetary boundary layer, a process that stretches the eddy-diffusion parameterization. We will report on progress in improving the deep convective transport of carbon monoxide: the Grail scheme as we used it at 100 kin resolution did not transport enough material to the upper troposphere. We expect to be able to attribute this to either parameterization reasons (inadequacy of this parameterization at the large 100km scale) or other reasons. Nevertheless, the qualitative nature of deep transport by clouds shows up well in the simulations. As for scavengable species, the simulations predict tens of micrograms per standard cubic meter of smoke aerosol in the boundary layer. In a straightforward illustration of our simple bulk-mass scavenging parameterization, to one or two micrograms per standard cubic meter of smoke aerosol in the free troposphere just above the source regions: very high concentrations for the free troposphere. We expect to report on comparisons of these predictions to a variety of observations.

Chatfield, Robert B.↗
DOE OSTI2019

Mechanical, Fire Retardant, Water Absorption and Soil Biodegradation Properties of Poly(3-hydroxy-butyrate-co-3-valerate) Nanofilms

Biopolymers provide potential substitution to synthetic polymers derived from scarce petroleum materials which are not environmental friendly and biodegradable. However, there exists challenging or unanswered questions for biopolymers to be used in biomedical, film packaging, automobile, construction and commercial industries such as their mechanical performance, thermal and fire retardancy, and durability when exposed to water. In this study, we investigated one such potential biopolymer, poly(3-hydroxy-butyrate-co-3-valerate) (PHBV) for the aforementioned properties. At first, 0–15 wt% halloysite nanotubes (HNTs) was dispersed in PHBV polymer using ultrasonication process in presence of chloroform solvent. The solvent was then evaporated and PHBV/HNTs films were prepared by solution casting method. PHBV films without HNTs (neat) were also prepared for baseline comparison. Thermogravimetric analysis (TGA) and tensile tests were then performed to study the thermal and mechanical properties of these films. The horizontal burning test (HBT) was also carried out to investigate the fire retardancy behavior. Finally, the water absorption and soil biodegradability behavior of these composites were investigated by submerging the films in water and Alabama soil conditions. PHBV films with 3 wt% loading showed optimum enhancement in thermal stability and tensile properties. In contrast, films with 10–15 wt% HNTs loading showed superior fire-retardancy, better water resistance and faster soil degradation over neat counterpart.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Economic and operational investigation of CO 2 sequestration through enhanced oil recovery in unconventional reservoirs in Colorado, USA

The ongoing CCUS commercial projects are highly relied on the support of government incentives due to massive capital investment. Here, this study analyzes the economics of carbon capture utilization and sequestration (CCUS) projects, shows a state-wide CCUS deployment exercise, followed by simulation results of enhanced oil recovery (EOR) based CO 2 storage in unconventional reservoirs. The comprehensive economic analysis of capture, transportation, sequestration costs, enhanced 45Q tax credits, and EOR revenue implies the practicality of CO 2 -EOR to offset the high CCUS costs. With the economics understanding, we study the top CO 2 sources, existing CO 2 pipelines, and sequestration sinks in the state of Colorado, USA. This paper next presents results from EOR simulation in one section of the unconventional Denver-Julesburg (DJ) Basin Niobrara and Codell reservoirs. The simulation model is based on a geological static model, incorporated with hydraulic fracture stimulation, history matched to production, and calibrated to the microseismic and time-lapse surface seismic data. The CO 2 -EOR simulation results show that oil production can be increased and more CO 2 stored with: a longer primary production period; the presence of a shut-in period; higher injection rates; and multi-well injectors. The modeling results show that about 7–10 Mscf of CO 2 will be stored when recovering 1 stb of EOR oil. By adding the enhanced oil revenue and the carbon credits together, it is estimated that the most economic case can generate $\$13$ MM when oil price is assumed to be $\$80$/stb, and the EOR oil revenue is 3.4 times greater than that generated from 45Q incentives. It corresponds to the scenario that a five-year primary production is followed by CO 2 injection into four wells with the sequence of injection (4 MMscf/day for 6 months), shut-in (6 months) and production (12 months). The best practices in this study will provide valuable insights for similar CCUS projects in other unconventional fields. Furthermore, this study defines a term named “Carbon Neutrality Index (CNI)” by comparing the amount of CO 2 stored with that burned by EOR oil. The CNI value of 0 indicates the enhanced oil is carbon neutral; a negative CNI value implies there is a net reduction in carbon emission. The 4-year huff-n-puff (HnP) simulation leads to a positive CNI value, indicating that the EOR oil generated in this process is not carbon neutral yet.

03 NATURAL GAS↗
DOE OSTI2013

Synthesis, crystal structure and properties of a novel tetra-nuclear Cu complex of ANPyO

A transition metal Cu complex with 2,6-diamino-3,5-dinitropyridine-N-oxide (ANPyO) ligand has been synthesized and its crystal structure has been analyzed by X-ray diffraction methods. The crystal belongs to Triclinic system with space group P-1. The cell parameters are a=8.6710(17) nm, b=11.226(2) nm, c=18.741(4) nm, {alpha}=98.26(3), {beta}=102.60(3), {gamma}=109.17(3), V=1635.1(6) nm{sup 3}, D{sub c}=1.957 g/cm{sup 3}, {mu}=2.663 mm{sup -1}, F(000)=968, Z=2, R{sub 1}=0.0764, WR{sub 2}=0.1608. The thermal decomposition process of the title complex was studied by means of the TG-DTG and DSC at a heating rate of 20 K/min. It consists of two slow endothermic peaks and one violent exothermic peak with 37.22% residues. The apparent activation energy and pre-exponential factor of the complex in thermal decomposition process were calculated by means of the Kissinger method and Ozawa-Doyle method. The thermal decomposition of AP was accelerated due to the catalyst of the complex, it suggests that the complex can provide theoretical support to further performance study as it is added to the propellant formulations to regulate the burning rate. - Graphical abstract: A novel tetra-nuclear Cu complex of ANPyO was synthesized and its molecular structure was measured. Highlights: Black-Right-Pointing-Pointer We have synthesized and characterized a new tetra-nuclear Cu complex. Black-Right-Pointing-Pointer We have measured its molecular structure and thermal decomposition. Black-Right-Pointing-Pointer A special coordination mode between ligand and central copper atoms has been obtained. Black-Right-Pointing-Pointer It provides theoretical support to further performance study as energetic catalyst.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Structure of conducting channel of lightning

The spatial distribution of the plasma density in a lightning channel is studied theoretically. It is shown that the electric-field double layer is formed at the channel boundary. In this case, the electron temperature changes abruptly and ions are accelerated by the electric field of the double layer. The ion momentum flux density is close to the surrounding gas pressure. Cleaning of the channel from heavy particles occurs in particle-exchange processes between the plasma channel and the surrounding air. Hydrogen ions are accumulated inside the expanding channel from the surrounding air, which is enriched by hydrogen-contained molecules. In this case, the plasma channel is unstable and splits to a chain of equidistant bunches of plasma. The hydrogen-enrich bunches burn diffusely after recombination exhibiting the bead lightning behavior.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗