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At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Crystallographic texture formation in Fe-9wt%Si alloy during deformation and phase transition at high pressure

SUMMARY The seismic anisotropy of the Earth's solid inner core has been the topic of much research. It could be explained by the crystallographic preferred orientation (CPO) developing during convection. The likely phase is hexagonal close-packed iron (hcp), alloyed with nickel and some lighter elements. Here we use high energy synchrotron X-rays to study CPO in Fe-9wt%Si, uniaxially compressed in a diamond anvil cell in radial geometry. The experiments reveal that strong preferred orientation forms in the low-pressure body-centred cubic (bcc) phase that appears to be softer than pure iron. CPO is attributed to dominant {110}<111> slip. The onset of the bcc→hcp transition occurs at a pressure of ≈15 GPa, and the alloy remains in a two phase bcc + hcp state up to 40 GPa. The hcp phase forms first with a distinct {11$\bar{2}$0} maximum perpendicular to compression. Modelling shows that this is a transformation texture, which can be described by Burgers orientation relationship with variant selection. Experimental results suggest that bcc grains oriented with <100> parallel to compression transform into hcp first. The CPO of the hcp changes only slowly during further pressure and deviatoric stress increase at ambient temperature. After heating to 1600 K, a change in the hcp CPO is observed with alignment of (0001) planes perpendicular to compression that can be interpreted as dominant (0001)<11$\bar{2}$0> slip, combined with {10$\bar{1}$2}<$\bar{1}$011> mechanical twinning, which is similar to the deformation modes suggested previously for pure hcp iron at inner core conditions.

Vasin, Roman N.↗
DOE OSTI2024

Effect of the Chemical States of Copper on Methanol Decomposition and Oxidation

Here, the decomposition and oxidation reactions of CH 3 OH over metallic Cu(100) and Cu 2 O-covered Cu(100) surfaces are studied using a combination of in-situ ambient-pressure X-ray photoelectron spectroscopy, Auger electron spectroscopy, and density functional theory calculations. We identify the sequential chemical transformation pathways from bond cleavage to the formation of intermediates and final products under operational conditions. Accumulative surface adsorption of CH 3 O species on metallic Cu(100) impedes the decomposition of CH 3 OH. Co-dosing on metallic Cu(100) with low pressures of 1·10 -4 Torr CH 3 OH + 1·10 -4 Torr O 2 results in partial oxidation of CH 3 OH, where the chemisorbed O ads reduces surface sites available for CH 3 O adsorption, decreasing the surface activity for CH 3 OH decomposition. In contrast, the Cu 2 O overlayer formed under the elevated pressures of 0.33 Torr CH 3 OH + 0.66 Torr O 2 promotes the total oxidation of CH 3 OH into the final products of CO 2 and H 2 O, arising from the active reaction 2 between lattice O within Cu 2 O and intermediates of CH 3 O, CH 2 O, HCOO, and CO. Despite the more favorable O-H bond scission, C-O bond scission also occurs to result in surface accumulation of CH x on metallic Cu(100), blocking active sites for decomposition reactions of CH 3 OH and CH 3 O. By comparison, the CH x species on the Cu 2 O-covered Cu(100) undergo oxidation into CO 2 and H 2 O with lattice O in the Cu 2 O overlayer, thereby freeing active sites for the total oxidation of CH 3 OH. These results highlight the distinct roles of metallic Cu and Cu 2 O in the pathways of CH 3 OH decomposition and oxidation reactions, offering practical insights for the design of Cu-based catalysts with tailored reactivity and selectivity.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Re-establishment of Sandia National Labs super-critical carbon dioxide testing autoclave capability for exposure of metal alloys and polymers (Level 4 Milestone Report)

The sCO 2 system located in 916/160A, Sandia National Laboratories, CA, was constructed in 2014, for testing of materials in the presence of supercritical carbon dioxide (sCO 2 ) at high pressures (up to 3500 psi) and temperatures (up to 650°C). The basic design of the system consists of a thermally insulated IN625 autoclave, a high-pressure supercritical CO 2 compressor, autoclave heaters, temperature controllers, gas manifold, and temperature and pressure diagnostics. This system was modified in 2016 (sCO 2 compressor was removed) to enable corrosion studies with metal alloys in gaseous CO 2 at lower pressure (up to 300 psi) at 500°C. The capability was not used much afterwards until 2020, when preliminary tests using this capability (again without the supercritical CO 2 compressor) involved the exposure of fatigue and tensile specimens of HN 230 and 800H alloys to CO 2 gas for 168 hours in gaseous CO 2 . Using this capability, we finished experiments with low pressure (450 psi/ 3 MPa), high temperature (650°C) exposure of fatigue and tensile specimens of HN 230 and 800H alloys to CO 2 gas for 168 hours. The data from these experiments will be compared to that gathered from experiments performed in 2020 using the tube furnace and presented in a future report. It is to be noted that the tube furnace experiments ran 500-1500 hours, unlike the 168 hours of exposure in the recent experiment. This can help validate the use of the sCO 2 autoclave for both CO 2 and sCO 2 experiments.

36 MATERIALS SCIENCE↗
DOE OSTI2021

A tunable band gap of the layered semiconductor Zn 3 In 2 S 6 under pressure

The band gap is an important property of a semiconductor, and a candidate material with a highly tunable band gap under external tuning parameters will offer wider applications in optoelectronic devices and photocatalytic fields. Here, we show that the layered semiconductor Zn 3 In 2 S 6 possesses a band gap that is highly tunable with pressure. In situ optical absorption shows that the band gap unexpectedly widens with pressure up to ~13 GPa. Sudden gap narrowing then occurs above 14 GPa, which is followed by progressive gap decreases on further compression and the gap finally closes above 20 GPa. Our study, encompassing X-ray diffraction, Raman spectroscopy experiments and theoretical calculations revealed that the selective responses of the different bonds are responsible for the band gap increase in the low-pressure ranges. We show that the pressure-induced irreversible amorphization is responsible for the sudden gap narrowing whereas the semiconductor–metallic transition is related to the amorphous–amorphous transition at high-pressure due to a change in the local coordination number of Zn atoms. This work demonstrates the high tunability of the electronic and optical properties of layered ternary semiconductors under pressure, providing a potential way for wider applications of this class of materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Characterization of Performance Degradation Mechanisms in Low-Cost High Throughput DI-O3 Layer for Passivated Contact Silicon Solar Cells

Characterization and mitigating performance limiting defects in Silicon (Si) PV is one of key areas to be addressed to improve PV hardware costs and energy yield in order to lower the levelized cost of energy (LCOE) of installed PV cost to $0.02/kWh. As Si PV cells efficiencies have surpassed 22% and approaching 23%, the recombination at the metal contacts have become the focus point to be addressed. Passivated contact technologies—having a heterojunction with a band-gap larger than silicon between the metal and silicon—have emerged as a great potential for future highand ultrahigh-efficiency solar cells, as it concurrently reduces recombination and increases carrier selectivity, by incorporating thin films within the contact structure. Passivated contact Si solar cell technologies use a wide variety of tunnel layers—playing a crucial role to passivate metal contacts and tunnel charge carriers—including stoichiometric silicon oxide (SiO 2 ) grown by thermal oxidation and Low-Pressure Chemical Vapor Deposition (LPCVD) technique and silicon oxide (SiO x ) by hot nitric acid. However, thorough investigations on understanding the failure and performance degradation mechanisms associated with tunnel layers are still limited to date. Unlocking those degradation characteristics in crucial tunnel layers could improve the reliability and energy yield of passivated contact Si solar cells. Besides, the technique of growing aforementioned tunneling layers are low throughput, and requires high temperature processes and/or a vacuum environment. In this project, we investigated the performance degradation mechanisms of a low-cost high-throughput ozonated oxide (DI-O 3 ) tunnel layer for the passivated contact Si solar cells.

14 SOLAR ENERGY↗
DOE OSTI2025

Implications of high-pressure oxygen hydrates on radiolytic oxygen in Jovian icy moons

Various icy moons, such as Europa and Ganymede, have thin oxygen atmospheres and exhibit spectral features attributed to oxygen held in their surface ices. The oxygen forms from the radiolysis of water. The interiors of these bodies are subject to high pressures and it is not known how deep into icy moons oxygen-bearing ices can penetrate, or the structures formed by the oxygen–water system at high pressure. Here, we show that oxygen hydrates are stable to 2.6 GPa, allowing them to penetrate deep into icy moons, both above and below proposed sub-surface liquid-water oceans. Similarities between oxygen and hydrogen hydrates indicate potentially enhanced recombination rates, transforming them back into water and offering a resolution to the discrepancy between predicted and measured radiolysis rates. In addition to the low-pressure CS-II clathrate, our results find three high-pressure phases in the oxygen–water system: an ST clathrate, a C 0 hydrate, and a filled ice isomorphous with methane hydrate III. This shows a vast storage potential for molecular oxygen in icy moons and indicates that Europa could still be absorbing oxygen into its crustal ice.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Crystal structure, compressibility, and thermal expansion of uranium mononitride

The behavior of the uranium mononitride (UN) crystal structure at nonambient conditions is disputed, with studies proposing various mutually exclusive distortions and transformations of the conventional face-centered-cubic structure at extreme temperatures and pressures. Here, in this study, we investigated the UN lattice with diamond anvil cell x-ray diffraction experiments at pressures up to 92 GPa and with density functional theory calculations at temperatures up to 1000 K and pressures up to 90 GPa. We determined that while the UN structure is nearly cubic at ambient conditions, its lattice angle (𝛼) varies as a function of pressure and temperature, meaning its structure can be more precisely described as face-centered-rhombohedral with 𝛼 ≈ 90∘. Over the range of conditions we investigated, UN exhibits a single, isostructural phase transition at ≈ 35 GPa, where 𝛼 collapses to ≈ 86°. Measurements and calculations agree that the compressibility of UN increases significantly beyond this transition, with the bulk modulus falling from ≈ 200 GPa in the low-pressure phase to 121 ± 3 GPa (according to calculations) or 58 ± 4 GPa (according to measurements) in the high-pressure phase. Our measurements also allowed us to constrain the bulk modulus of 𝛼−U 2 ⁢N 3 to 240 ± 10 GPa.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Magnetic probe diagnostics of nonlinear standing waves and bulk ohmic electron power absorption in capacitive discharges

It is recognized that standing wave effects appearing in large-area, very-high-frequency capacitively coupled plasma (CCP) reactors cause center-high plasma non-uniformity. Using a high-frequency magnetic probe, we present a direct experimental diagnostic of the nonlinear standing waves and bulk ohmic electron power absorption dynamics in low pressure CCP discharges for different driving frequencies of 13.56, 30, and 60 MHz. The design, principle, calibration, and validation of the probe are described in detail. Spatial structures of the harmonics of the magnetic field, determined by the magnetic probe, were used to calculate the distributions of the harmonic current and the corresponding ohmic electron power deposition, providing insights into the behavior of nonlinear harmonics. At a low driving frequency, i.e. 13.56 MHz, no remarkable nonlinear standing waves were identified and the bulk ohmic electron power absorption was observed to be negligible. Here, the harmonic magnetic field/current was found to increase dramatically with the driving frequency, due to decreased sheath reactance and more remarkable nonlinear standing waves at a higher driving frequency, leading to the enhancements of the ohmic heating and the plasma density in the bulk, specifically at the electrode center. At a high driving frequency, i.e. 60 MHz, the high-order harmonic current density and the corresponding ohmic electron power absorption exhibited a similar node structure, with the main peak on axis, and one or more minor peaks between the electrode center and the edge, contributing to the center-high profile of the plasma density.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Particle Separator for Improved Flameless Pressurized Oxy-Combustion

The team of Southwest Research Institute® (SwRI®), ITEA, Electric Power Research Institute, Inc. (EPRI), and General Electric Global Research (GE) is advancing Flameless Pressurized Oxy-combustion (FPO), a novel coal technology. This effort seeks to develop a particle separator for the hot-gas stream leaving the FPO loop. In order to maximize the energy extracted from the cycle, the hot gas is put through a turbo-expander before flue-gas treatment. The particle separator designed under this project sought to operate at high temperature and with low-pressure drop, protecting the turbo-expander from erosion damage. The team engaged potential vendors for the test, developed plans for the pilot test loop modification, and refined requirements for the commercial turbo-expander.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2021

Numerical investigation of a fueled pre-chamber spark-ignition natural gas engine

Pre-chamber spark-ignition (PCSI) is a leading advanced ignition concept for internal combustion engines with the potential to enable diesel-like efficiency in medium-duty/heavy-duty (MD/HD) natural gas (NG) engines. By leveraging distributed ignition sources from multiple turbulent jets, the PCSI technology can deliver extremely short combustion duration in ultra-lean mixtures and significantly improve the engine thermal efficiency. However, in the automotive industry there is a lack of adequate science base and predictive simulation tools required for commercial development of PCSI engines. Here, in this study, Reynolds-Average Navier-Stokes simulations are carried out to describe the combustion process in lean-burn NG engines, focusing on the combustion modeling approach. Two combustion models, multi-zone well-stirred reactor (MZ-WSR) and G-equation, are used to simulate the combustion process in an MD NG engine equipped with a fueled-PCSI system for four operating conditions close to the lean operating limit. A skeletal chemical mechanism and a laminar flame speed tabulation are used to compute the combustion accurately. Simulation results are compared with experimental data regarding measured cylinder pressure, heat release rate, and combustion duration. By dividing the PCSI combustion process into four distinct phases, the difference between the two models’ results for each phase is analyzed in detail. The MZ-WSR model overestimates the combustion duration for early flame kernel growth in the pre-chamber due to the lack of a specific formulation to take turbulence-chemistry interaction into account. Despite the prolonged combustion duration and low pressure built-up inside the pre-chamber, the model matches the combustion rate in the main-chamber. In contrast, the G-equation model delivers good agreements for the pre-chamber combustion and turbulent jet-driven combustion processes. However, the model starts to underestimate the combustion rate in the main-chamber, especially under ultra-lean mixture conditions. Finally, improvements are needed for both models to simulate the later combustion stage that occurred in the near-wall regions.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2026

Characterization of Precipitation-Induced Radon Progeny Deposition Events Using a City-Scale Sensor Network

Networks of radiation detectors provide a platform for real-time radioactive source detection and identification in urban environments. Detection algorithms in these systems must adapt to naturally-occurring changes in background, which requires well-characterized relationships between precipitation events and their corresponding radiological signature. Here, we present a quantitative and qualitative description of rain-induced radon progeny deposition events occurring in Chicago from September 2023 to February 2024. We measure ambient gamma radiation levels, precipitation rate, temperature, pressure, and relative humidity in a network of sensor nodes. For each identified precipitation period, we decompose spectra into static- and radon-associated components as defined by a non-negative matrix factorization (NMF) algorithm. We find a consistent power-law relationship between a precipitation-dependent peak of the radon progeny proxy (RPP) and the peak strength of the radon-associated NMF component for most precipitation events. We conduct a case study of a rainfall period with abnormally high levels of implied radon progeny concentration and describe its temporal and spatial evolution. We hypothesize that this phenomenon is due to the air mass path that intersects a uranium-rich region of Wyoming. Finally, we cluster precipitation events into three distinct categories. One category roughly corresponds to events with deep low-pressure systems and high relative radon concentration, while another is characteristic of light stratiform rain with slightly higher temperatures and intermediate relative radon concentration. The third category appears to contain weak-gradient or lake breeze convection showers with intermittent precipitation and low relative radon concentration. These findings suggest that radiological anomaly detection could be improved by training unique background models corresponding to each category of meteorological event.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Rational Design of Superconducting Metal Hydrides via Chemical Pressure Tuning**

Abstract The high critical superconducting temperatures ( T c s) of metal hydride phases with clathrate‐like hydrogen networks have generated great interest. Herein, we employ the Density Functional Theory‐Chemical Pressure (DFT‐CP) method to explain why certain electropositive elements adopt these structure types, whereas others distort the hydrogenic lattice, thereby decreasing the T c . The progressive opening of the H 24 polyhedra in MH 6 phases is shown to arise from internal pressures exerted by large metal atoms, some of which may favor an even higher hydrogen content that loosens the metal atom coordination environments. The stability of the LaH 10 and LaBH 8 phases is tied to stuffing of their shared hydrogen network with either additional hydrogen or boron atoms. The predictive capabilities of DFT‐CP are finally applied to the Y−X−H system to identify possible ternary additions yielding a superconducting phase stable to low pressures.

Hilleke, Katerina P.↗
DOE OSTI2022

Nonequilibrium plasma in water vapor

A kinetic model of a non-equilibrium water vapor plasma created by a nanosecond pulsed discharge at elevated temperatures and at low pressure is presented. The model includes equations for electron, vibrational and gas temperatures combined with equations for neutral, charged, electronically and vibrationally excited species. Simulation results are compared with the available experimental data and show good agreement in dynamics of the plasma decay and electron drift velocities. It is shown that the plasma decay in pure water vapor is controlled by the dissociative recombination. Under the conditions simulated, the concentration of electronically excited species is low, but we observe a formation of vibrationally excited species. Finally, a significant decrease in the electrical conductivity of water plasma with time, which depends on the level of initial ionization, is shown.

42 ENGINEERING↗
DOE OSTI2020

Tritium Pressure Enhancement on the TPBAR Cladding by Physical Processes at the Getter

Tritium for the U.S. nuclear weapon stockpile is produced in tritium producing burnable absorber rods (TPBARs) inserted into Tennessee Valley Authoritys (TVA) light-water nuclear reactors. The rods are stainless steel tubes with a permeation barrier coating and internal components that generate and contain the tritium. The TPBAR incorporates a Ni-plated Zircoloy getter tube to capture tritium and prevent it from reaching the rod cladding and permeating into the environment. Under the conventional view of getter behavior, the tritium pressure outside the getter tube is expected to be limited to the equilibrium vapor pressure of Zr hydride at the temperature of the rod as long as the total hydrogen concentration remains below the capacity of the hydride. Since the tritium pressure is higher within the rod core, this behavior relies on the thin getters ability to hold off a differential tritium pressure. The effective tritium pressure on the cladding can also be enhanced by isotope exchange. Hydrogen ingress through the cladding from the reactor coolant creates a hydrogen pressure on the outer surface of the getter that can exchange with tritium, allowing the tritium partial pressure to increase toward this hydrogen gettering pressure. The goal of this work was to use laboratory-scale experiments to examine these mechanisms and create a model of getter behavior that describes tritium transport within the TPBAR. A third mechanism wherein the concentration at the outer surface of the getter is increased by the temperature gradient within the getter tube wall (the Soret effect) is not experimentally tested but is captured in the model. While not conclusively demonstrated by the experiments due to low pressure, high temperature, and small gap volume conditions, the model shows that when combined, the three mechanisms can explain both the magnitude and time dependence of the tritium release observed for reactor fuel assemblies with TPBARs. The model also shows how various modifications of the TPBAR design can reduce this tritium release into the environment.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2020

Evaluation of Steam Cycle Upgrades to Improve the Competitiveness of U.S. Coal Power Plants (Final Scientific / Technical Report)

Increasing the competitiveness of the existing pulverized-coal utility fleet in the United States may be achieved by decreasing heat rate, via increases in steam cycle efficiency through upgraded steam temperatures and use of latest technology available in steam turbine and blading design. The average net plant efficiency of the US coal-fired fleet is approximately 33% (HHV). Plant efficiency increases to approximately 41.4% (HHV) at 1,350°F (732°C) steam temperature. However, achieving these Advanced Ultra-Super Critical (AUSC) steam conditions requires the use of advanced high-temperature materials. While there has been a significant amount of DOE-funded materials R&D, most of the related design work has focused on new (greenfield) units, rather than on opportunities to retrofit this advanced technology to the existing utility fleet. If technology, based upon the advanced materials required for AUSC steam conditions, may be applied to the existing fleet, using an economically viable retrofit, a higher capacity factor can be expected as a result of the increased plant competitiveness. The Electric Power Research Institute (EPRI) was awarded a project by the US Department of Energy to examine the technical and economic feasibility of a series of steam cycle upgrades to the two most prevalent types of U.S. coal power plants: 2,400 psig (16.6 MPa) subcritical and 3,500 psig (24.1 MPa) supercritical pulverized coal units. The nine upgrade options that were originally being considered included increasing the main and reheat steam temperatures from 1,000°F (538°C) to 1,100°, 1,200°, and 1,350°F (593°C, 649°C, and 732°C) while holding the steam pressures constant at their original design values, and cases where just the main steam or reheat steam temperatures were increased. The objective was to minimize the modifications required to the existing power plant while still providing a significant improvement in heat rate. The upgrade options assumed that the boiler enclosure envelope remained unchanged from each base case, and that all applicable OEM design guidelines for normal commercial units were imposed. For the highest temperature supercritical case, an option of using a low-pressure molten salt loop to transfer heat from the furnace to the steam was examined. The first major task of the work scope was designed to examine the technical feasibility of various upgrade options, while the subsequent work determined economic viability of the technically feasible upgrade options. Prior to evaluating the effect of these increased temperatures, a “base case” model of a subcritical and supercritical PC boiler was created, which was used for comparative purposes. Upgrade options were evaluated at full-load, part-load and dynamic transient conditions. Once the technical feasibility of each upgrade option was evaluated, the economic value of the heat rate improvement of each feasible option was determined by detailed modeling of unit dispatch in several regional power markets. The dispatch model was used to estimate the amount of revenue from power sales the upgraded unit would receive in comparison to a non-upgraded version of the same power plant. As a parallel task to the dispatch analysis, the capital cost of implementing the upgrades was estimated. The capital cost estimates were then compared to the increased revenue estimated by the dispatch modeling to determine the economic attractiveness of each upgrade option. Several upgrade options were determined to be technically feasible. The net present value (NPV) of the costs for steam cycle upgrades considered in this study ranged from approximately $\$$111 to $\$$130 million. The economic modeling results show that the unit dispatch changes resulting from steam cycle upgrades are relatively small, due largely to heat rate (and operating cost) changes being relatively small. Additionally, the cost of each upgrade exceeds the net revenue increases associated with the upgrade case. Note that the breakeven values are higher for subcritical retrofits, but the capital costs for the subcritical upgrades are also slightly higher. In typical new pulverized coal plants, fuel accounts for approximately 25% of the cost of electricity (COE), while capital costs represent around 50% of the COE. Therefore, in order to improve the heat rate by 4% one can only afford to increase the capital cost by 2%, at the same cost of electricity. The conclusion of this study is that without a cost for emitting CO 2 , it will be difficult to pay for significant efficiency improvements on plants firing low cost coals.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2022

Rational Design of Superconducting Metal Hydrides via Chemical Pressure Tuning

The high critical superconducting temperatures (T c s) of metal hydride phases with clathrate-like hydrogen networks have generated great interest. Herein, we employ the Density Functional Theory-Chemical Pressure (DFT-CP) method to explain why certain electropositive elements adopt these structure types, whereas others distort the hydrogenic lattice, thereby decreasing the T c . The progressive opening of the H 24 polyhedra in MH 6 phases is shown to arise from internal pressures exerted by large metal atoms, some of which may favor an even higher hydrogen content that loosens the metal atom coordination environments. The stability of the LaH 10 and LaBH 8 phases is tied to stuffing of their shared hydrogen network with either additional hydrogen or boron atoms. Furthermore, the predictive capabilities of DFT-CP are finally applied to the Y-X-H system to identify possible ternary additions yielding a superconducting phase stable to low pressures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Joint Focal Mechanism Inversion Using Downhole and Surface Monitoring at the Decatur, Illinois, CO2 Injection Site

ABSTRACT The three-year CO2 injection period at the Illinois Basin - Decatur Project site (Decatur, Illinois, United States) produced a number of microseismic events distributed in very distinct spatiotemporal clusters with different orientations. Further characterization of the microseismicity encompasses the determination of the event source mechanisms. Initially, the microseismic monitoring network consisted solely of borehole sensors, but has been extended with surface sensors, thereby significantly improving the data coverage over the focal sphere. This article focuses on 23 events from the northernmost microseismic cluster (about 2 km from the injection point) and takes advantage of both, surface and downhole, recordings. The resulting strike-slip east–west-oriented focal planes are all consistent with the east–west orientation of the cluster in map view. The injection-related increase of pore pressure is far below the formation fracture pressure; however, small stress-field changes associated with the pore-pressure increase may reach as far as to the investigated cluster location. Monte Carlo modeling of the slip reactivation potential within this cluster showed that the observed maximum stress-field orientation of N068° is the optimum orientation for fault reactivation of the east–west-oriented cluster. Our results suggest that the east–west orientation of the investigated cluster is the main reason for its activation, even though the cluster is about 2 km away from the low-pressure injection point.

Geochemistry & Geophysics↗
DOE OSTI2024

Breakup dynamics in a pressure-swirl injector for urea-water solution applications: A computational study

The co-optimization of in-cylinder combustion and after-treatment technology has become a major aspect in engine design and development, with the goal of meeting the increasingly restrictive emission regulations in the transportation industry. Selective Catalytic Reduction is a robust technology to control the emission of NO x , and the injection of urea in water solution is the exhaust tailpipe is a key aspect of its operation. The proposed work uses high-fidelity Computational Fluid Dynamics to characterize the atomization dynamics of the liquid jet in relevant cross-flow conditions. The study focuses on a commercial low-pressure (9 bar) pressure-swirl injector which is characterized in its internal geometry through high-resolution X-ray micro-computational tomography. The internal two-phase flow has been modeled according to the volume-of-fluid approach in a large eddy simulation framework and validated against near-nozzle X-ray radiography measurement. Moreover, characterizing the breakup dynamics for the swirling hollow cone formation, and assessing the influence of the cross-flow in the breakup dynamics was completed. The results have been reported proposing Re-Oh maps and probability density functions of the spray kinematics. Higher cross-flow momentum generates an increase in the jet intact length and a reduction of the liquid droplet diameters. The axial momentum of the jet is affected by the cross-flow already in the near-nozzle region, determining a relevant deviation of the spray velocities. In conclusion, this work aims to inform the initialization of Eulerian-Lagrangian spray models through the assignment of droplet kinematics and static one-way coupling between volume-of-fluid results and Lagrangian spray parcels, to be used for system-size domain simulations.

33 ADVANCED PROPULSION SYSTEMS↗