Local Gas Research Articles

Contributing to a Greener New York: Analysis of Methane Emissions in New York State

New York state is reducing its carbon footprint through the Community Leadership and Climate Protection Act. One important target is methane, a potent greenhouse gas that contributes 35% of the state’s CO2-equivalent emissions.1 Here we present the results of mobile observations conducted to better identify and quantify emissions of methane in central New York. We discovered a modest source of methane following numerous visits to a mining operation. During repeated visits the facility produced two distinct plumes with ethane and methane ratios of 0.010 and 0.007, which differ from local natural gas infrastructure. Using a Gaussian plume approach, we estimate the emission flux to be 70−100 kg/h. Additional observations are required to better refine our estimate.

Atomic oxygen abundance toward Sagittarius B2

A substantial fraction of oxygen in diffuse clouds is unaccounted for by observations and is postulated to be in an unknown refractory form, referred to as unidentified depleted oxygen (UDO), which, depending on the local gas density, may contribute up to 50% of the total oxygen content. Previous Infrared Space Observatory (ISO) observations suggest that a significant fraction of oxygen in even denser, translucent clouds may be in atomic form. We have analyzed velocity-resolved archival SOFIA observations of the 63 μm fine-structure [O I] transition toward the high-mass star-forming region Sgr B2(M) in the Central Molecular Zone. The foreground spiral-arm clouds as well as the extended Sgr B2 envelope between the Sun and the background dust continuum source produce multiple [O I] absorption components, spectrally separated in velocity space. The gas-phase atomic oxygen column density in foreground clouds toward Sgr B2 is well correlated with the total hydrogen column density, with an average atomic oxygen abundance of (2.51 ± 0.69) × 10−4 with respect to hydrogen nuclei. This value is in good agreement with the earlier ISO measurements on the same line of sight, and is about 35% lower than the total interstellar medium oxygen abundance in the low-density warm gas, as measured in the UV. We find no evidence that a significant fraction of the oxygen on the line of sight toward Sagittarius B2 is in the form of UDO.

Geodynamic factors of multilayer hydrocarbon fields stratification: formation of horizontal fracture zones and vertical spatio-temporal permeability within local structures

This article is devoted to the generalization of the conceptions of local oil and gas bearing platform structures development, tectonophysical, geodynamic and hydrodynamic studies, which complement and introduce new ideas into the mechanism for creating capacitive parameters of traps, as well as the processes of their filling with hydrocarbons and stratification of deposits, which are inextricably linked with it. Keywords: abnormally high formation pressures; fracturing; multilayer fields; fluid migration.

A numerical study on knock combustion suppression using targeted fuel injection in an SI engine

A novel concept to suppress knock combustion using the targeted fuel injection in a spark-ignition (SI) engine is proposed, which utilizes a customized injector to inject a small portion of the total fuel toward the end-gas region in the late compression stroke so that charge cooling effect by fuel vaporization is imposed on the local mixtures. CFD studies were carried out to evaluate the effects of various targeted fuel injection strategies on the processes of charge cooling, air-fuel mixing and combustion in a 1.2-L gasoline SI engine with a high compression ratio. A knock prediction model adopting a level set G-equation model coupled with a transported Livengood-Wu integral correlation was applied to predict the knock event by capturing the occurrence of end-gas auto-ignition. It was found that the local gas temperatures in the sprayed region decreased and knock combustion tendency was suppressed indeed, and the degree of the reduction in local gas temperature and knock tendency was affected by the selected targeted injection strategy. However, the results also indicated that excessive fuels injected could result in worsen air-fuel mixing that led to incomplete combustion. Hence, the injection strategy needs to be optimized by balancing the knock tendency and combustion efficiency. The study further shown that the spark timing could be advanced by 3.3° crank angle in a particular injection strategy case by comparing with the non-targeted-injection case, which demonstrated the effectiveness of the proposed concept.

Experimental investigation of the laminar burning velocity of iron-air flames in a tube burner

This paper presents the results of experimental measurements of the laminar burning velocity of iron-air-flames in a model tube burner. Carbonyl iron powder with an average Sauter diameter of about 13 µm was mixed with air at ambient temperature and pressure in an air knife seeder and fed to the tube burner. An iron-air-flame was stabilised without additional fuel, air preheating, increasing the amount of oxygen in the gas phase, or pilot flame. The diameter distribution of the used iron powder was determined under operating conditions. The conical flames were visualised with a camera at short exposure times. The images were used to extract the local angle of the flames. In addition, Particle Imaging Velocimetry was applied to determine the local gas phase and particle velocities at the burner outlet. The local velocity and the local flame angle were used to determine the laminar burning velocity of the iron-air flames. The results show that the laminar burning velocity is about 14 cm/s for the experimental conditions studied and no dependency of the global equivalence ratio or the mean inlet velocity on the laminar burning velocity were found for the investigated conditions. The results are in good agreement with literature data.

Risk informed floating storage and re-gasification unit (FSRU) location selection for local natural gas supply

In the present energy market due to high demand of liquefied natural gas (LNG) and the limited availability of land-based LNG import terminals, the use of offshore LNG terminals is destined to increase. Such terminals are referred to as LNG floating storage and re-gasification units (FSRUs). An FSRU terminal is a cost-effective and a time-efficient solution to quickly open up supply to onshore users with minimal environmental impact. This work focuses on the selection from a safety point of view of a possible location for an offshore or nearshore FSRU, given alternative candidate locations. For decision making, the maritime and process safety aspects of the LNG resupply operation have to be considered. This involves the approach of an LNG Carrier (LNGC) to resupply the FSRU. The whole resupply process is divided into three consecutive parts, beginning with the LNGC navigating in the inbound channel, going through its berthing operation, and ending with transfer of the LNG. The safety of the third part, the LNG transfer to the FSRU, could be evaluated by means of a quantitative risk assessment. For the maritime operations this was not possible and evaluation had to rely on expert elicitation. To create a comparison basis of navigating, turning and berthing hazards with the risks of the LNG transfer process, a novel safety utility value (SUV) was defined existing of five ranges. Hazard attributes of navigating and of turning and berthing of the maritime operations were identified/confirmed by simulator runs, their importance was ranked, as well as their safe operating ranges determined with the aid of queries to a large group of experts. Importance ranking was based on pairwise comparison judgment, responses aggregated by means of fuzzy number fits, processed in square matrices. Expert elicitation yielded safety attribute values (SAVs) for the five SUV ranges which were statistically treated. QRA provided potential loss of life (PLL) values, which also were converted into SUV ranges. Based on the importance ranking of the three parts and the SUVs, final results were obtained.

Breakthrough in drilling and completion equipment and key technologies for 8000m-class ultra-deep wells onshore China

With the exploration and development of a group of deep ultra-deep large oil and gas fields in Tarim basin and Sichuan Basin, deep oil and gas reservoirs will be the main productivity replacement area and the main exploration focus area. Drilling and completion still face severe challenges such as high temperature and high pressure, complex pressure systems, complex accidents and poor drillability. This paper describes the technology of domestic oil and gas fields with 8000m level drilling and completion. Considering the demand of exploration and development of local oil and gas fields while standardizing the international advanced level, the insufficiency of technology and equipment improvement demand of each block are discussed, and the research direction of technology and equipment is prospected.

Numerical investigation of the effect of slit-width on the combustion characteristics of a micro-combustor with a centrally slotted bluff body

The effect of slit-width on the combustion characteristics of a micro-combustor with a centrally slotted bluff body is numerically studied. The non-dimensional fractional slit-width (d) is varied in the range of 0.1–0.8. Simulations are performed for inlet velocities ranging from 6 m/s to 35 m/s. The effect of slit-width on the combustion efficiency is observed to be a function of the inlet velocity. At smaller inlet velocities, the combustion efficiency increases upon increasing the slit-width initially (d ≤ 0.4), decreases (d = 0.4 to 0.5) and monotonously increases from thereon. On the contrary, at higher values of inlet velocity, the combustion efficiency monotonously increases with the increasing slit-width. It is observed that the average exhaust gas temperature increases with the increasing slit-width, reaches a maximum at moderate slit-widths (d = 0.6 and 0.7) and then decreases. It is observed that the local exhaust gas temperature at moderate slit-widths for higher values of inlet velocities follows a bi-modal distribution. It is also observed that the operating range of the micro-combustor with moderate slit-width (d = 0.6 and 0.7) is limited by the phenomenon of longitudinal flame splitting.

A Study of Trace Atmospheric Gases at the Water–Atmosphere Interface Using Remote and Local IR Laser Gas Analysis: A Review

A Study of Trace Atmospheric Gases at the Water–Atmosphere Interface Using Remote and Local IR Laser Gas Analysis: A Review

Influence of oxygen content in the shielding gas chamber on mechanical properties and macroscopic structure of Ti-6Al-4V during wire arc additive manufacturing

Wire arc additive manufacturing (WAAM) of titanium parts shows promising potential for aerospace application due to its high deposition rates allowing a fast and economical production of large components. The cost savings are high, especially for expensive alloys like Ti-6Al-4V. However, due to high oxygen affinity of Ti-6Al-4V at elevated temperatures an excellent shielding gas coverage seems necessary to prevent embrittlement of the material during the welding process. Regarding the future development of local shielding gas coverage set-ups for gas metal arc welding (GMAW) based WAAM, this study investigates the influence of the oxygen content in the shielding gas chamber on mechanical properties of Ti-6Al-4V during the welding process. Samples are welded at different oxygen contents in the shielding gas chamber and stress-relief heat treated afterwards. Inert gas milling and hot gas extraction are used to determine the material oxygen content at different deposition heights. Metallographic methods are used to show macroscopic grain structure, evaluate possible α-case thickness and its dissolution by the subsequent layer. Hardness testing is used to investigate possible material inhomogeneities in the deposit and tensile properties of the material welded at different chamber oxygen contents are displayed. It is concluded, that even at high chamber oxygen levels of 6000 ppm the welding process is stable, the forming α-case at top of the layer dissolves in the melt pool of the subsequent layer and that the aerospace requirements on tensile properties can be reached.

Co-firing characteristics and fuel-N transformation of ammonia/pulverized coal binary fuel

As a feasible way to decarbonize coal combustion under the background of carbon neutrality in recent years, ammonia co-firing with pulverized coal is receiving considerable critical attention from the academic and industrial communities. This paper investigates the effects of coal type, NH3 injection mode, temperature, excess air ratio (α) and NH3 co-firing ratio (ENH3) on combustion characteristics and fuel-N transformation of ammonia/pulverized coal in a 6 kW drop tube furnace. Emission of O2, CO2, CO, NO, NO2 and NH3 at the furnace exit was monitored online. The unburned carbon (UBC) content and elementary composition in fly ash were also tested. Results show that NOx generation behaviors of premixed and staged modes are significantly different. Typically, NOx emission peaks at ENH3 = 20 % under high temperature and staged mode. As for NH3/coal cases at 1000 °C, NOx level is even lower than pure coal combustion, but NH3 residue is higher. The water gas shift reaction (WGSR) under fuel-rich condition generates more CO, and the conversion ratio from fuel-N to NOx decreases when α diminishes. Ammonia co-firing can achieve lower CO emission with anthracitic coal from Gongyi (GY-coal) while lower NOx emission with bituminous coal from Inner Mongolia (IM-coal). Ammonia co-firing can considerably improve the transformation from fuel-N to N2. From the perspective of emission control and decarbonization, ENH3 = 40 % is an optimal ammonia co-firing ratio which not only can reduce half of CO2 but also brings the conversion ratio from fuel-N to NOx and residual NH3 to the minimum level. The micromorphology of ash samples is greatly affected by coal/ammonia co-firing. In premixed mode, the surface of ash sample is porous and adhered to each other; while in staged mode, obvious fractures and cuts exist between the ash particles due to the sharp decrease of local gas temperature.

Effect of N2 and CO2 bubbles on gas volume fraction and flow pattern in a quasi-2D bubble column by shadow imaging

This study reports the effect of N2 and CO2 bubbles on dilute to dense gas-liquid two-phase bubbly flow. A shadowgraph imaging technique captured bubble images at a high spatiotemporal resolution. The recordings of bubble images allow us to compute gas fraction distribution. It requires challenging segmentation and gas-liquid interface detection approaches in image processing. Hence a novel gas contour characterization technique has been introduced in this study that analyses light intensity per pixel for quantifying the effect of local gas volume fraction. The dominant gas structure and repetitive gas pattern have also been determined here using Fourier transform-based power spectral density and 2D cross-correlation functions, respectively. Gas-liquid flow regimes of dissolved CO2 bubbles are found quite different than that of N2 bubbles. The plausible reasons are that gas fraction distribution at the sparger region may inhibit bubble coalescence and the positive surface charge of CO2 bubbles acts as a barrier to the interface deformation.

Simulation Study on the Corrugated Plate Gas-Liquid Separator with the Assistance of the Drainage Hook.

Corrugated plate separators are widely used in the field of gas-liquid separation because of their excellent separation performance. The separation effect is very sensitive to the internal auxiliary structure of drainage hooks, so it is extremely important to study the action principle of drainage hooks to optimize the performance of corrugated plate separators. In this paper, Fluent is used as the solver and the realizable k-ε model is used to compare the separation performance of unhooked, single-hooked, and double-hooked corrugated plates. The results show that the separation efficiency of wave plates with hooks can reach 100%, the separation efficiency of wave plates without hooks is about 90%, and the superiority of the separation efficiency of single-hook and double-hook wave plates is related to the droplet partition diameter, which is positively correlated with Re. The pressure drop and separation efficiency increase with the increase of plate hook spacing, and the pressure drop and separation efficiency of single-hook and double-hook corrugated plates have different performance advantage zones influenced by Re and K a. When the Re is 9.64 × 103 and K a is 0.294, the separation effect of corrugated plates with the single hook and double hook is the same. Through the analysis of the gas-phase flow field and droplet motion trajectory, it is found that the drainage hook enhances the separation effect of the corrugated plate separator by increasing the local gas velocity and forming a vortex inside the drainage hook.

Kinematics of the Local Group gas and galaxies in the hestia simulations

ABSTRACT We investigate the kinematic properties of gas and galaxies in the Local Group (LG) using high-resolution simulations performed by the hestia (High-resolution Environmental Simulations of The Immediate Area) collaboration. Our simulations include the correct cosmography surrounding LG-like regions consisting of two main spiral galaxies of ∼1012 M⊙, their satellites and minor isolated galaxies, all sharing the same large-scale motion within a volume of a few Mpc. We characterize the gas and galaxy kinematics within the simulated LGs, from the perspective of the Sun, to compare with observed trends from recent HST/COS absorption-line observations and LG galaxy data. To analyse the velocity pattern of LG gas and galaxies seen in the observational data, we build sky maps from the local standard of rest, and the Galactic and LG barycentre frames. Our findings show that the establishment of a radial velocity dipole at low/high latitudes, near the preferred barycentre direction, is a natural outcome of simulation kinematics for material outside the Milky Way virial radius after removing Galaxy rotation when the two main LG galaxies are approaching. Our results favour a scenario where gas and galaxies stream towards the LG barycentre producing a velocity dipole resembling observations. While our study shows in a qualitative way the global matter kinematics in the LG as part of its ongoing assembly, quantitative estimates of gas-flow rates and physical conditions of the LG gas have to await a more detailed modelling of the ionization conditions, which will be presented in a follow-up paper.

On the illusion of auxotrophy: met15Δ yeast cells can grow on inorganic sulfur, thanks to the previously uncharacterized homocysteine synthase Yll058w

Organisms must either synthesize or assimilate essential organic compounds to survive. The homocysteine synthase Met15 has been considered essential for inorganic sulfur assimilation in yeast since its discovery in the 1970s. As a result, MET15 has served as a genetic marker for hundreds of experiments that play a foundational role in eukaryote genetics and systems biology. Nevertheless, we demonstrate here through structural and evolutionary modeling, invitro kinetic assays, and genetic complementation, that an alternative homocysteine synthase encoded by the previously uncharacterized gene YLL058W enables cells lacking Met15 to assimilate enough inorganic sulfur for survival and proliferation. These cells however fail to grow in patches or liquid cultures unless provided with exogenous methionine or other organosulfurs. We show that this growth failure, which has historically justified the status of MET15 as a classic auxotrophic marker, is largely explained by toxic accumulation of the gas hydrogen sulfide because of a metabolic bottleneck. When patched or cultured with a hydrogen sulfide chelator, and when propagated as colony grids, cells without Met15 assimilate inorganic sulfur and grow, and cells with Met15 achieve even higher yields. Thus, Met15 is not essential for inorganic sulfur assimilation in yeast. Instead, MET15 is the first example of a yeast gene whose loss conditionally prevents growth in a manner that depends on local gas exchange. Our results have broad implications for investigations of sulfur metabolism, including studies of stress response, methionine restriction, and aging. More generally, our findings illustrate how unappreciated experimental variables can obfuscate biological discovery.

Energetic Neutral Atom (ENA) Imaging Simulation of the Distant Planetary Magnetosphere and ENA Emission Discussion of the Solar Wind

We doubt whether the “Energetic Neutral Atom (ENA) ribbon” signals, especially the peak ones, scanned remotely by IBEX-Hi at the lunar resonance orbit, are really from the heliopause, which involves assessing the scale of solar wind particle energy loss throughout the solar system. The ENA imaging simulation results at the Earth’s orbit show that the scale of the planetary magnetosphere with a telemetry distance of AU magnitude is too small to contribute to the IBEX-Hi ribbon. However, the simulated effective ENA differential fluxes provide a reference for the physical scale evaluation of the huge magnetic structure in the heliopause. The ENA differential flux of the “ENA emission cone” generated by the charge exchange between the solar wind ion flow and local neutral gas near the Earth’s orbit is also comparable to the measured peak of the IBEX-Hi ribbon, which may be the main ENA emission source of the ribbon’s measured peak. The 2D ENA imaging measurements at the Lagrange points proposed here can be used to investigate the ENA ribbon origination by using the energy spectral lag vs the disparity of the ENA images.

An equilibrium model of NOx emission in gas turbine combustors

In this study, an equilibrium model for NOx emission in gas turbine combustors was developed. The model is based on the governing thermodynamic, materials, and energy balance equations. Results obtained from the model simulation were compared with operational data from a local gas turbine power plant. There was about a 3 to 6 percent deviation for the periods considered. Consequently, the model is reliable in the design of new combustors and in assessing the pollutant emission during operations. It was established that factors that affect NOx formation include flame temperature and quantity of excess air used. Furthermore, the results revealed that the most important parameter that governs the formation of NOx is flame temperature, as the formation of NOx rises exponentially with an increase in the combustor flame temperature.

Effect of resistance internal on hydrodynamic behaviours and bubble characteristics in a laboratory‐scale bubble column

AbstractA novel resistance internal is proposed to optimize the flow field and improve the gas–liquid contact in a co‐hydrogenation reactor of coal and vacuum residuum. Local gas holdup, local liquid velocity, and characteristics of the bubble were investigated in a scaled‐down laboratory model. The quantitative results showed that the resistance internals could reduce the thickness of the liquid reflux layer by a percentage up to 32% and reduce the difference in the local gas holdup at cross‐sections of up to 44%. The Sauter mean diameter of the bubble decreased from 20.30 to 16.00 mm, which aroused the increase in bubble surface area by a percentage of up to 71.9%. The resistance internal promoted the breakup of the bubble with multiple mechanisms and provided diversion to fluid. In this work, improvement at multiple scales was realized, and the technical support for industrial application was provided.

Chemical evolution in ices on drifting, planet-forming pebbles

Context. Planets and their atmospheres are built from gas and solid material in protoplanetary disks. Recent results suggest that solid material such as pebbles may contribute significantly to building up planetary atmospheres. In order to link observed exoplanet atmospheres and their compositions to their formation histories, it is important to understand how icy pebbles may change their composition when they drift radially inwards in disks. Aims. Our goal is to model the compositional evolution of ices on pebbles as they drift in disks, and track how their chemical evolution en route changes the ice composition relative to the ice composition of the pebbles in the region where they grew from micron-sized grains. Methods. A state-of-the-art chemical kinetics code was utilised for modelling chemical evolution. This code accounts for the time-evolving sizes of the solids that drift. Chemical evolution was modelled locally for 0.1 Myr at two starting radii, with the micron-sized solids growing into pebbles simultaneously. The pebbles and local gas, isolated as a parcel, were then exposed to changing physical conditions, which was intended to mimic the pebbles drifting inwards in the disk midplane, moving to 1 AU on three different timescales. A modelling simplification was that the pebbles are not moved through, or exposed to new gas, but they stayed in the same chemical gas surroundings in all models. Results. For ice species with initial abundances relative to hydrogen of >10-5, such as H2O, CO2, CH3OH, and NH3, the abundances change by less than 20% for both radii of origin, and for the two smaller drift timescales (10kyr and 100 kyr). For less abundant ice species, and the longest drift timescale (1 Myr), the changes are larger. Pebble drift chemistry generally increases the ice abundances of CO2, HCN, and SO, at the expense of decreasing the abundances of other volatile molecules.

Tarkib’s Contemporary Arts Festival in Baghdad

Tarkib’s Contemporary Arts Festival in Baghdad