Local Gas Research Articles

The SATIN project – I. Turbulent multiphase ISM in Milky Way simulations with SNe feedback from stellar clusters

ABSTRACT We introduce the star formation and supernova (SN) feedback model of the satin (Simulating AGNs Through ISM with Non-Equilibrium Effects) project to simulate the evolution of the star forming multiphase interstellar medium (ISM) of entire disc galaxies. This galaxy-wide implementation of a successful ISM feedback model tested in small box simulations naturally covers an order of magnitude in gas surface density, shear and radial motions. It is implemented in the adaptive mesh refinement code ramses at a peak resolution of 9 pc. New stars are represented by star cluster (sink) particles with individual SN delay times for massive stars. With SN feedback, cooling, and gravity, the galactic ISM develops a three-phase structure. The star formation rates naturally follow observed scaling relations for the local Milky Way gas surface density. SNe drive additional turbulence in the warm (300 < T < 104 K) gas and increase the kinetic energy of the cold gas, cooling out of the warm phase. The majority of the gas leaving the galactic ISM is warm and hot with mass loading factors of 3 ≤ η ≤ 10 up to h = 5 kpc away from the galaxy. While the hot gas is leaving the system, the warm and cold gas falls back onto the disc in a galactic fountain flow. The inclusion of other stellar feedback processes from massive stars seems to be needed to reduce the rate at which stars form at higher surface densities and to increase/decrease the amount of warm/cold gas.

REGIONAL AND LOCAL SYSTEMS OF METHANE GAS DISTRIBUTION IN THE COAL-BEARING MASSIFS OF THE DONETS BASIN

Determining the regional and local peculiarities of methane gas distribution in the coal-bearing massifs of the Donets basin will help solve several important problems at once: creating safe conditions for mining operations, using methane as an alternative fuel, and improving the environmental situation in technologically loaded regions. Local gas-saturated systems of coal-rock massifs combining individual coal seams and their host rocks are primarily the result of accumulation and minimal impact of the following geodynamic processes. Important characteristics of rocks and coal as natural gas reservoirs are porosity and gas permeability. Changes in the initial indicators of coal substance indicate a deep transformation that coal seams undergo under fluid dynamic impact, which is determined by regional and local changes in the coal-bearing massifs of the basin.
 Gas content and gas migration in different strata of coal-bearing massifs are related by age and quality characteristics. The qualitative characteristics of the gas mixture of coal deposits are constantly changing along the section and dip of the seam and are particularly distinct in tectonically disturbed areas of coal massifs. All components of the gas mixture of coal seams are controlled by a mosaic of physical parameters of its various parts, both in the undisturbed and in the mined massif. Structural, shielded deposits are often found in relatively undisturbed mine massifs and can be developed as a local gas field. Depending on the condition of the coal and gas reservoir, the gas component can vary widely. During active maximum gas recovery, a large amount of heavy and unsaturated hydrocarbons rise in the workings, which can provoke gas-dynamic phenomena.
 On the basis of isotopic and geochemical studies of gas mixtures of coal-rock massifs, the polygenetic composition of natural gas in coal-bearing strata of the Ukrainian coal basins is substantiated and proved.

Analysis of the local gas hold-up, under constant retrofitted power input in a multiphasic mycelial fermentation model

Multiphase fermentations are still poorly understood since much of the available information focused on global rather than local data and the most used parameter to control the dispersion of gas in the stirred tank is the agitation rate. However, the energy dissipated in the stirred tank is influenced by the properties of the broths, such as viscosity. Therefore, the objective of this work was to use a retrofitted power input strategy in order to maintain constant the total power input per unit volume (Pg/V), studying the local gas hold-up (φ) and interfacial area (a) values in three regions in a pilot-scale stirred tank at different values of Trichoderma harzianum mycelial biomass concentration, airflow rate and constant Pg/V. We found that the constant Pg/V regime was an effective strategy that allows to discern the effects of different parameters in the local values of gas hold-up and interfacial area. Under constant retrofitted total gassed power input, the biomass concentration showed no influence on the local values of interfacial area and gas hold-up. Depending on the position of the probe, φ and a varied up to 60.6% and 63.8%, respectively. The highest Pg/V and airflow rate conditions determined the highest values in φ and a, but not in the same proportion in the three zones tested.

Timing control of impulse self balancing latch opening of expansion wave gun

Aiming at the problem of accurate latch opening control of expansion wave gun automatic gun, the mathematical model of accurate latch opening time is established, the travel curve of projectile and expansion wave, the velocity curve of projectile and expansion wave are studied, and the occurrence time of expansion wave and the time close to projectile are simulated and analyzed; The time-space evolution relationship between expansion wave velocity and local sound velocity, projectile velocity and gas velocity is simulated; The average pressure time curve and chamber resultant force curve of the two launch modes are compared and analyzed. After the projectile moves for 2.7ms, the chamber pressure and chamber resultant force of expansion wave launch are significantly reduced; The dynamic model of inertial latch opening is established; The changes of projectile initial velocity and recoil force under different latch opening times are studied. The test shows that the recoil force and recoil distance are greatly reduced when the projectile initial velocity decreases very weakly, which shows that the simulation calculation of latch opening time is accurate.

A novel ironmaking decarbonisation technology — co-injection of hydrogen and biochar (CoHB): A CFD study of combustion in the raceway under simulated blast furnace conditions

In this paper, a novel ironmaking decarbonisation technology — co-injection of hydrogen and biochar (CoHB) in blast furnaces (BFs) is proposed for a feasible and sustainable carbon-neutral ironmaking. As the first study, to understand the fundamentals of internal combustion behaviour in the raceway related to CoHB, a three-dimensional (3D) computational fluid dynamics (CFD) model is developed to describe the multiphase reacting flow under simulated BF conditions. Particularly, the present model features a new treatment of volatile matter (VM) and an improved sub-model for hydrogen combustion. The model is successfully validated by the measurements of biochar injection and co-injection of hydrogen and coal, respectively. The typical in-furnace phenomena as well as the interaction between the hydrogen and biochar are analysed comprehensively. The results indicate that the proper injection of hydrogen through the annulus of the fuel lance is beneficial as the high local gas temperatures (1500 K to 1800 K) from the hydrogen combustion provide a biochar burnout enhancement of 6% during the biochar devolatilisation process. However, char reactions are hindered due to the oxygen competition with hydrogen combustion, resulting in a slightly reduced final biochar burnout. This study provides a quantitative insight into the combustion details related to this novel technology and serves as a reference to strive towards the net-carbon ironmaking initiative.

Numerical investigation of water and heat recovery from flue gas by using nanoporous ceramic membrane tubes

Direct emission of high humidity flue gas results in great wastage of water and thermal energy. Ceramic membrane technology has been widely regarded as a potential technology for water and heat recovery from flue gas. This study presents numerical investigations of water and heat recovery processes from flue gas by using nanoporous ceramic membrane tubes (CMTs). A comprehensive mathematical model is developed based on the Kelvin equation, and the Hagen–Poiseuille equation is applied to calculate the bilateral pressure difference needed for continuous recovery operation. Decreasing the pore size of the separation layer of the ceramic membrane improves the capillary condensation flux but also drastically increases the required bilateral pressure difference. CMT with a pore size of 20 nm is appreciated for the studied conditions. The performances of the CMTs located in the last rows along the flow direction are limited by local low gas temperature and humidity. Twelve rows of tubes are suggested to be arranged along the gas flow direction for ceramic membrane devices with pore sizes of 20 nm and higher. A low transverse spacing obviously improves the overall water and heat recovery efficiency of the device, decreases the performance of each tube, and enhances the gas flow resistance. A transverse spacing ratio of less than 1.4 is suitable for the studied conditions. A combined arrangement by substituting the tubes located in the last rows with those of smaller pore size is a better method than using uniform tubes. The device with combined 20 and 10 nm CMTs is suggested for the studied conditions.

Influence of internal components on the hydrodynamic properties of the scrubbing-cooling chamber

The bubble-breaking plate is a crucial internal component in the scrubbing-cooling chamber. The study of hydrodynamics under its influence is the basis for designing and scaling up industrial installations. Experimental measurements of characteristic bubble parameters and liquid phase structure parameters at local locations were carried out using a conductivity probe and a pitot tube, respectively, to investigate the effects of five types of bubble-breaking plate installation on the hydrodynamic properties of the annular gap bubble bed. The experimental results show that the staggered placement of two plates is the most favorable for increasing the gas holdup, reducing the bubble size, increasing the gas–liquid interface area, improving the liquid velocity distribution and suppressing the turbulence fluctuations. In addition, a dimensionless mathematical model predicted the radial distribution of local gas holdup and axial time-averaged liquid velocity, and the expected results agreed with the experimental values.

Correction of JET bolometric maximum likelihood tomography for local gas puffing

Tomography is applied daily to bolometric data in magnetically controlled nuclear fusion devices to infer important quantities of the studied plasmas, such as the emissivity profiles or the radiated power in different locations of the main chamber. Tomographic reconstructions are also crucial for power balance analysis and to estimate heat fluxes for turbulence studies. One of the issues, associated with any tomographic technique, resides in the ill-posed nature of the mathematical problem, meaning that more than one possible emissivity profile is compatible with the measurements within the estimated uncertainties. Therefore, a careful evaluation of the quality of the obtained reconstructions is an important step of the analysis. On Joint European Torus (JET), since the two cameras are located in different toroidal locations, axial symmetry of the plasma radiation must be assumed to perform traditional tomographic reconstructions. Such a specific hypothesis, however, cannot be guaranteed in the case of symmetry-breaking mechanisms, such as strong local gas puffing for fuelling. The present contribution addresses this problem of local plasma fuelling, focusing on the observed significant mismatch between measured and back-calculated projections in specific pulses, including the last JET DT campaign (DTE2) carried out in 2021. The analysis indicates that the observed discrepancy, due to the gas injected primarily from valves located in the same octant where one of the bolometer arrays is located, can be rectified acceptably well by a physically-based correction. The sensible improvements in the bolometric maximum likelihood tomography’s outputs are also documented, and the possible physical explanation for such a phenomenon is discussed. The study performed in this article is expected to have a significant impact on the analysis of JET data and on the physical interpretation of the results obtained during the recent DTE2 experiments, for which a proper evaluation of the radiated power estimates is of non-negligible relevance.

Risk assessment of ionizing radiation and radiological thresholds to compound an environmental baseline for the unconventional gas industry.

The exploration of unconventional hydrocarbons may be very effective in promoting economic development and confronting energy crisis around the world. However, the environmental risks associated with this practice might be an impediment if not adequately dimensioned. In this context, naturally occurring radioactive materials and ionizing radiation are sensitive aspects in the unconventional gas industry that may compromise the environmental sustainability of gas production and they should be properly monitored. This paper provides a radioecological assessment of the São Francisco Basin (Brazil) as part of an environmental baseline evaluation regarding the Brazilian potential for exploring its unconventional gas reserves. Eleven and thirteen samples of surface waters and groundwater were analyzed for gross alpha and beta using a gas flow proportional counter. A radiological background range was proposed using the ± 2 Median Absolute Deviation method. Using geoprocessing tools, the annual equivalent doses and lifetime cancer risk indexes were spatialized. Gross alpha and beta background thresholds in surface water ranged from 0.04-0.40Bq L-1 to 0.17-0.46Bq L-, respectively. Groundwater radiological background varies from 0.006-0.81Bq L-1 to 0.06-0.72Bq L-1 for gross alpha and beta, respectively. All environmental indexes are relatively higher in the south of the basin, probably a direct response to the local volcanic formations. Traçadal fault and local gas seepages might also influence the gross alpha and beta distribution. All samples have radiological indexes below the environmental thresholds, and should remain at acceptable levels with the development of the unconventional gas industry in Brazil.

Characterization of local parameters of inclined upward air–water bubbly two-phase flows in a round pipe

The present work seeks to develop a detailed experimental database and characterize the local effects of inclination on horizontal and upward bubbly air–water two-phase flows. Experimental conditions are selected to investigate bubbly flows at a variety of orientations while reducing the influence of flow regime transition. Detailed time-averaged data is collected using state-of-the-art four-sensor conductivity probes for measurements across the flow area for five flow conditions at five inclination orientations in a 25.4 mm inner diameter pipe. Using the newly established database, effects of inclination on bubbly flows are analyzed, as are changes in liquid and gas flow rate at different orientations. The observations include (1) bubble migration and agglomeration at the top pipe wall as orientation changes from vertical to horizontal; (2) reducing the angle from vertical reduces the local gas velocity, and correspondingly reduces the global slip from greater than unity at 90° to less than unity for 60° and lower; (3) changes in the bubble size distribution are primarily at the interface between the bubble cluster and the liquid region of the pipe, not coalescence within the bubble cluster. Physical mechanisms for these observations are proposed, and the present trends at different orientations support previous experiments in horizontal two-phase flows.

Opportunities for CO2 utilisation in the Northern Territory

The Northern Territory (NT) aims to grow the gross state product to $40 billion by 2030 and reach net zero emissions by 2050. Alongside other carbon abatement approaches, CO2 utilisation technologies have the potential to enable the development of a low-emission manufacturing industry that can support the NT’s decarbonisation and economic growth targets. CO2 utilisation is the process of using CO2, captured from industrial emissions or directly from the atmosphere, to produce valuable products. The Northern Territory is relatively well positioned to deploy CO2 utilisation technologies due to the local established natural gas industry, export links with the Asia-Pacific region and high renewable electricity potential. This report explores the potential to deploy five CO2 utilisation opportunities in the NT: methanol, jet fuel, urea, methane, and mineral carbonates. Techno-economic analysis of the levelised cost of production for each of these products found that they are not cost competitive with conventional products. However, cost reductions are expected as the relevant technologies mature. The full report discusses potential scale-up pathways for each application. Commercial-scale CO2 utilisation will require orders of magnitude increases in the scale of CO2 sources, renewable hydrogen, and renewable electricity. CSIRO is collaborating with industry and government partners to develop a business case for a Northern Territory Low Emissions Hub with a particular focus on carbon capture, utilisation, and storage. This abstract provides the high-level finding from the full public report, which is one input into the development of this business case.

A Multicriteria Evaluation and Cascaded Optimization Framework for Integrated Energy System of Steel Industry

Integrated Energy System (IES) involving coal, by-product gas, power, etc., plays a pivotal role in steel industry, which greatly requires reasonable utilization scheme for avoiding extensive energy consumption and intensive environment pollution. While due to the complex coupling relationship among the multiple energy and the contradiction existed between the optimization of global IES and local sub-system, an effective solution for this important practical problem is still highly required in real-world application. As such, a multi-criteria evaluation and cascaded optimization framework is proposed in this study. In order to make a comprehensive evaluation, criteria including global energy consumption and local gas emission are respectively evaluated from the perspective of both the entire IES and the by-product gas subsystem. Then, a cascaded optimization model is accordingly established, where a Reinforcement Learning based cascaded algorithm is also designed for efficiently and effectively acquiring an optimal trade-off as the final solution. The following experiments carried out on practical industrial data clearly demonstrated that the proposed framework gives scientifically reasonable as well as practically available energy utilization scheme, which is beneficial for energy-saving and emission reduction in practical application.

Simultaneous application of soot and temperature measurements in a pressurized turbulent flame by laser-induced incandescence and coherent anti-Stokes Raman scattering for particle sizing

Simultaneous application of multi-channel laser-induced incandescence (LII) and shifted vibrational coherent anti-Stokes Raman scattering (SV-CARS) to study sooting flames is demonstrated for the first time. The potential of this diagnostics combination is evaluated on the basis of characterization of soot particles and correlation of soot presence with temperature. For that purpose, a sooting swirl flame operated at three bars has been employed with ethylene as fuel. The novel combination of CARS and time-resolved LII (TiRe LII) enables the estimation of particle size and correlation of this quantity with local gas temperature; simultaneously acquired 2D LII images provide information on the soot distribution in the ambience of the measurement volume which is used by CARS and TiRe LII. Even if the used LII model is approximative in some respect, the detected LII decay times indicate very small particle size throughout the flame relative to an atmospheric laminar diffusion flame which was used for comparison. In most instances, soot presence relates to local gas temperatures in a range between 1600 and 2400 K. Rare soot events at cooler temperatures occur near the nozzle exit and are attributed to transported soot. Comparison of the peak soot temperatures during the LII process shows a significant decrease in the turbulent pressurized flame relative to the laminar atmospheric reference flame. This is attributed to a less-efficient LII heat-up process at turbulent pressurized conditions due to beam steering. The background blackbody temperature, which can be derived by evaluating the signal captured in the different color channels of the LII system towards the end of the LII process, has been identified to be mostly controlled by hotter soot filaments between the laser plane and the detector. Thus, the LII signal tail is not a good measure of the local gas temperature in the measurement volume for this type of configuration.

Design and Investigation of a Novel Local Shielding Gas Concept for Laser Metal Deposition with Coaxial Wire Feeding

Laser metal deposition with coaxial wire feeding is a directed energy deposition process in which a metal wire is fed to a laser-induced melt pool. Oxidation occurring during the process is a major challenge as it significantly influences the mechanical properties of the produced part. Therefore, an inert gas atmosphere is required in the high temperature process zone, whereby local shielding offers significant cost advantages over an inert gas chamber. In this work, a novel local shielding gas nozzle was developed based on basic methods of fluid mechanics. A gas flow-optimized prototype incorporating internal cooling channels was additively manufactured by laser-powder bed fusion and tested for its effectiveness via deposition experiments. Using the developed local shielding gas concept, an unwanted mixing with the atmosphere due to turbulence was avoided and an oxide-free deposition was achieved when processing a stainless steel ER316LSi wire. Furthermore, the effects of the shielding gas flow rate were investigated, where a negative correlation with the melt pool temperature as well as the weld bead width was demonstrated. Finally, a solid cuboid was successfully built up without oxide inclusions. Overheating of the nozzle due to reflected laser radiation could be avoided by the internal cooling system. The concept, which can be applied to most commercially available coaxial wire deposition heads, represents an important step for the economical application of laser metal deposition.

Discovering Reactant Supply Pathways at Electrode/PEM Reaction Interfaces Via a Tailored Interface-Visible Characterization Cell.

In situ and micro-scale visualization of electrochemical reactions and multiphase transports on the interface of porous transport electrode (PTE) materials and solid polymer electrolyte (SPE) has been one of the greatest challenges for electrochemical energy conversion devices, such as proton exchange membrane electrolyzer cells (PEMECs), CO2 reduction electrolyzers, PEM fuel cells, etc. Here, an interface-visible characterization cell (IV-CC) is developed to in situ visualize micro-scaled and rapid electrochemical reactions and transports in PTE/SPE interfaces. Taking the PEMEC of a green hydrogen generator as a study case, the unanticipated local gas blockage, micro water droplets, and their evolution processes are successfully visualized on PTE/PEM interfaces in a practical PEMEC device, indicating the existence of unconventional reactant supply pathways in PEMs. Further comprehensive results reveal that PEM water supplies to reaction interfaces are significantly impacted with current densities. These results provide critical insights about the reaction interface optimization and mass transport enhancement in various electrochemical energy conversion devices.

CFD simulation and experimental validation of multiphase flow in industrial cyclone preheaters

A hybrid multiphase model (Dense Discrete Phase Model, DDPM) coupled with a k-ω sst turbulence model, which includes gas–solid heat exchange was developed for the simulation of industrial-scale cyclone preheaters operating under high solid loadings. The model results are validated by experimental measurements from an industrial cyclone preheater with a diameter of 1.6 m, with respect to the pressure drop, gas and particle exit temperature, local gas velocity profiles, measured using the LDA, and gas temperature profiles, measured using thermocouple and FTIR. Reasonable agreement between the data from experiments and simulations was obtained. In addition, the major trends, such as changes in the pressure drop, overall heat transfer rate, and flow pattern, caused by the changes in the operating parameters can be captured accurately by the model.

Standardization of Power-from-Shore Grid Connections for Offshore Oil & Gas Production

Offshore oil and gas (O&G) production is typically powered by local diesel engines or gas turbines. Power-from-shore (PFS) is an alternative that takes advantage of onshore renewable production and reduces greenhouse emissions but is limited to bespoke projects that are tailored to the characteristics of each site. This lack of repetition leads to an increase in the construction risk, delivery time, and lifecycle costs, therefore limiting their large-scale deployment. Furthermore, the absence of standardized designs is also notorious in mature applications such as offshore wind farms (OWF) despite their long-standing track record, with the negative consequences extensively covered in the literature. This research paper addresses offshore transmission standardization in two parts. First, by providing the scientific community with a review of the existing offshore O&G production and substations and secondly, by outlining a lean optioneering algorithm for the cost-optimized and technically feasible selection of the key design criteria. The exercise is centred on the main limiting component of the transmission systems—the cables. As such, it addresses their operational range and the cost to calculate the most effective configuration in terms of voltage and rated power. The end goal, based on the spread of connection proposals, is to cluster the candidates to a limited set of grid connection options, the achievement of which the model has been shown to be adequate.

Efficient direct numerical simulation of gas absorption in falling films using a combined high-throughput/high-performance approach

Direct Numerical Simulation (DNS) of liquid–gas mass transfer processes in falling film can model the transfer effect enhancement accurately, but requires huge computational effort. To improve the computational efficiency, we propose a hybrid parallel strategy combining high-throughput computing on the top level and high-performance unit simulations with different interface capture strategies on the bottom level. We investigate the CO2 absorption in methanol with different concentrations of Al2O3 nanoparticles using the proposed computation strategy to demonstrate its performance and assess the intensification mass transfer effect. Moreover, the Structural Similarity Index Measure (SSIM) is utilized in the case of oxygen absorption in water film to compare local gas concentration profiles obtained by the proposed approach, those obtained by the reduced modeling approach and the experimental data generated by a planar laser induced luminescence method under similar conditions. The results show that DNS model matches better the experimental data with high computational accuracy and efficiency.

Investigation of gas transport resistance in fuel cell catalyst layers via hydrogen limiting current measurements of CO-covered catalyst surfaces

The efficiency of fuel cell operation at high power strongly affects the total cost of ownership of fuel cell vehicles. Gas transport resistance at the cathode strongly suppresses efficiency during high-power operation. The resistance comprises Knudsen diffusion resistance in pores formed among the primary carbon aggregates and local gas transport resistance. The former is independent of the electrochemically active Pt surface area per geometrical electrode area (roughness factor: RF). The latter is proportional to the inverse of RF. Separate identification of these resistances in actual catalyst layers remains challenging because of experimental limitations. Herein, we propose a method that can identify the RF-dependent and RF-independent resistances separately using a single sample. RF can be controlled by partially covering the Pt surface by CO. The gas transport resistance can be ascertained from the hydrogen limiting current. Measuring the hydrogen limiting current at controlled CO coverages allows separate identification of the resistances. The RF-dependent resistance is separable further into ionomer/Pt interfacial resistance and permeation resistance through the ionomer thin film by combining the obtained ionomer-to-carbon weight ratio dependence of each resistance component with structural and electrochemical analyses. The separate resistances show the ionomer/Pt interfacial resistance to be dominant in the catalyst layer.

Star Formation Laws and Efficiencies across 80 Nearby Galaxies

We measure empirical relationships between the local star formation rate (SFR) and properties of the star-forming molecular gas on 1.5 kpc scales across 80 nearby galaxies. These relationships, commonly referred to as “star formation laws,” aim at predicting the local SFR surface density from various combinations of molecular gas surface density, galactic orbital time, molecular cloud free fall time, and the interstellar medium dynamical equilibrium pressure. Leveraging a multiwavelength database built for the Physics at High Angular Resolution in Nearby Galaxies (PHANGS) survey, we measure these quantities consistently across all galaxies and quantify systematic uncertainties stemming from choices of SFR calibrations and the CO-to-H2 conversion factors. The star formation laws we examine show 0.3–0.4 dex of intrinsic scatter, among which the molecular Kennicutt–Schmidt relation shows a ∼10% larger scatter than the other three. The slope of this relation ranges β ≈ 0.9–1.2, implying that the molecular gas depletion time remains roughly constant across the environments probed in our sample. The other relations have shallower slopes (β ≈ 0.6–1.0), suggesting that the star formation efficiency per orbital time, the star formation efficiency per free fall time, and the pressure-to-SFR surface density ratio (i.e., the feedback yield) vary systematically with local molecular gas and SFR surface densities. Last but not least, the shapes of the star formation laws depend sensitively on methodological choices. Different choices of SFR calibrations can introduce systematic uncertainties of at least 10%–15% in the star formation law slopes and 0.15–0.25 dex in their normalization, while the CO-to-H2 conversion factors can additionally produce uncertainties of 20%–25% for the slope and 0.10–0.20 dex for the normalization.