Gas Core Research Articles

An idealized model for collapse of a molecular core within a filament

ABSTRACT We present an analytic treatment of the self-similar collapse of a uniform density ellipsoid to linear order in the deviations from sphericity. First we obtain a self-consistent closed-form solution for the evolution of an isolated ellipsoid and then impose the effects of an external forcing. This model describes the evolution under gravity of a pre-stellar core of molecular gas embedded in a much larger and lower-density filament. We compare with numerical solutions for the collapse without the limitation of small deviations. These show how the external perturbing force producing the initial deviation from sphericity is eventually surpassed by the anisotropic forces generated by the collapsing ellipsoid itself. This model should be useful in interpreting the way in which environment shapes the evolution of pre-stellar cores.

External Validity of Two Scores for Predicting the Risk of Chemotherapy Toxicity Among Older Patients With Solid Tumors: Results From the ELCAPA Prospective Cohort.

Severe chemotherapy-related toxicities are frequent among older patients. The Chemotherapy Risk Assessment Scale for High-Age Patients (CRASH) and the Cancer and Aging Research Group Study (CARG) score were both developed to predict these events. The objective of this study was to evaluate the scores' predictive performance in a prospective cohort, which included patients aged 70 years and older referred for a geriatric assessment prior to chemotherapy for a solid tumor. The main endpoints were grades 3/4/5 toxicities for the CARG score and grades 4/5 hematologic toxicities and grades 3/4/5 non-hematologic toxicities for the CRASH score. A total of 248 patients were included, of which 150 (61%) and 126 (51%) experienced at least one severe adverse event as defined respectively in CARG and CRASH studies. The incidence of adverse events was not significantly greater in the intermediate and high-risk CARG groups than in the low-risk group (odds ratio (OR) [95% CI] = 0.3 [0.1-1.4] (P = .1) and 0.4 [0.1-1.7], respectively). The area under curve (AUC) was 0.55. Similarly, the incidence of severe toxicities was no greater in the intermediate-low, intermediate-high, and high-risk CRASH groups than in the low-risk CRASH group (OR [95%CI] = 1 [0.3-3.6], 1 [0.3-3.4], and 1.5 [0.3-8.1], respectively). The AUC was 0.52. The type of cancer, performance status, comorbidities, body mass index, and MAX2 index were independently associated with grades 3/4/5 toxicities. In an external cohort of older patients referred for a pretherapeutic GA, the CARG and CRASH scores were poor predictors of the risk of chemotherapy severe toxicities.

3D radiative transfer modelling and virial analysis of starless cores in the B10 region of the Taurus molecular cloud

ABSTRACT Low-mass stars like our Sun begin their evolution within cold (10 K) and dense (∼105 cm−3) cores of gas and dust. The physical structure of starless cores is best probed by thermal emission of dust grains. We present a high-resolution dust continuum study of the starless cores in the B10 region of the Taurus Molecular Cloud. New observations at 1.2 and 2.0 mm (12 and 18 arcsec resolution) with the NIKA2 instrument on the IRAM 30m have probed the inner regions of 14 low-mass starless cores. We perform sophisticated 3D radiative transfer modelling for each of these cores through the radiative transfer framework pandora, which utilizes RADMC-3D. Model best-fits constrain each cores’ central density, density slope, aspect ratio, opacity, and interstellar radiation field strength. These ‘typical’ cores in B10 span central densities from 5 × 104 to 1 × 106 cm−3, with a mean value of 2.6 × 105 cm−3. We find the dust opacity laws assumed in the 3D modelling, as well as the estimates from Herschel, have dust emissivity indices, β’s, on the lower end of the distribution constrained directly from the NIKA2 maps, which averages to β = 2.01 ± 0.48. From our 3D density structures and archival NH3 data, we perform a self-consistent virial analysis to assess each core’s stability. Ignoring magnetic field contributions, we find nine out of the 14 cores (64 per cent) are either in virial equilibrium or are bound by gravity and external pressure. To push the bounded cores back to equilibrium, an effective magnetic field difference of only ∼15 $\mu$G is needed.

The new Kr-86 excess ice core proxy for synoptic activity: West Antarctic storminess possibly linked to Intertropical Convergence Zone (ITCZ) movement through the last deglaciation

Abstract. Here we present a newly developed ice core gas-phase proxy that directly samples a component of the large-scale atmospheric circulation: synoptic-scale pressure variability. Surface pressure changes weakly disrupt gravitational isotopic settling in the firn layer, which is recorded in krypton-86 excess (86Krxs). The 86Krxs may therefore reflect the time-averaged synoptic pressure variability over several years (site “storminess”), but it likely cannot record individual synoptic events as ice core gas samples typically average over several years. We validate 86Krxs using late Holocene ice samples from 11 Antarctic ice cores and 1 Greenland ice core that collectively represent a wide range of surface pressure variability in the modern climate. We find a strong spatial correlation (r=-0.94, p<0.01) between site average 86Krxs and time-averaged synoptic variability from reanalysis data. The main uncertainties in the analysis are the corrections for gas loss and thermal fractionation and the relatively large scatter in the data. Limited scientific understanding of the firn physics and potential biases of 86Krxs require caution in interpreting this proxy at present. We show that Antarctic 86Krxs appears to be linked to the position of the Southern Hemisphere eddy-driven subpolar jet (SPJ), with a southern position enhancing pressure variability. We present a 86Krxs record covering the last 24 kyr from the West Antarctic Ice Sheet (WAIS) Divide ice core. Based on the empirical spatial correlation of synoptic activity and 86Krxs at various Antarctic sites, we interpret this record to show that West Antarctic synoptic activity is slightly below modern levels during the Last Glacial Maximum (LGM), increases during the Heinrich Stadial 1 and Younger Dryas North Atlantic cold periods, weakens abruptly at the Holocene onset, remains low during the early and mid-Holocene, and gradually increases to its modern value. The WAIS Divide 86Krxs record resembles records of monsoon intensity thought to reflect changes in the meridional position of the Intertropical Convergence Zone (ITCZ) on orbital and millennial timescales such that West Antarctic storminess is weaker when the ITCZ is displaced northward and stronger when it is displaced southward. We interpret variations in synoptic activity as reflecting movement of the South Pacific SPJ in parallel to the ITCZ migrations, which is the expected zonal mean response of the eddy-driven jet in models and proxy data. Past changes to Pacific climate and the El Niño–Southern Oscillation (ENSO) may amplify the signal of the SPJ migration. Our interpretation is broadly consistent with opal flux records from the Pacific Antarctic zone thought to reflect wind-driven upwelling. We emphasize that 86Krxs is a new proxy, and more work is called for to confirm, replicate, and better understand these results; until such time, our conclusions regarding past atmospheric dynamics remain speculative. Current scientific understanding of firn air transport and trapping is insufficient to explain all the observed variations in 86Krxs. A list of suggested future studies is provided.

Microbubbles preparation by partial vaporization of low boiling condensate for crude oil/water separation

The poor adhesion of oil droplets and bubbles in the flotation process leads to inefficient separation of oil and water. In this paper, condensate bubbles were prepared by partial vaporization of low boiling point condensate to increase the oil removal effect. The purpose of partial vaporization was achieved by bringing emulsified condensate droplets into the produced water at different temperatures. The structure of the bubble is composed of condensate film wrapped around the gas core of the vaporized portion. The contact angle between condensate bubble and oil surface is >150°, which show great similarity-intermiscibility. The average bubble size prepared at 303 K - 318 K is 20 - 100 μm. The stability of bubbles decreased with an increase in temperature, the half-decay time decreased from 340 s to 110 s, and the zeta potential decreased from −31 mV to −12 mV. However, the gas hold-up of the bubbles first increased and then decreased with the increase in temperature, while the highest gas holdup was 21 % at 313 K. The rise of the condensate/water ratio (Rcon-wat) did not increase the stability of the bubbles, but the gas holdup increase. The condensate bubble flotation experiment found that at the optimum temperature 313 K, the oil removal efficiency of 1.5 % Rcon-wat can reach 85 %. In contrast, the oil removal efficiency of the dissolved air flotation experiment is <75 %. Otherwise, with a smaller amount of flocculant (ferric chloride), the oil removal efficiency of condensate bubble flotation can reach >95 %.

The fusion of deep learning and acoustic emission response methods for identifying solid particles in annular multiphase flows

Annular flows carrying sand are common flow patterns in high-production gas-bearing wells. The real-time monitoring of sand particle information in the annular flows of wellheads is critical for efficient commercial production. In this study, an experiment was designed to monitor sand production in annular multiphase flows, and methods were proposed to identify sand using empirical mode decomposition (EMD), the Hilbert–Huang transform (HHT), statistical analysis, and deep learning methods. Corresponding sand migration behaviours near pipe walls were observed by acoustic emission (AE); the behaviours included sand carried by the gas core (IMF1), forward liquid film (IMF2) and reverse liquid film (IMF3). Furthermore, relationships between the AE response and gas superficial velocity (14–18 m/s), liquid superficial velocity (0.00366–0.01351 m/s), and mean particle size (150–380 μm) were proposed, and the AE responses of different sand migration patterns were verified. Finally, CNN, LSTM, and CNN-LSTM deep learning models were constructed to identify particle sizes based on the optimized sand-carrying information. The accuracy of the CNN-LSTM model was 6.44% and 18.9% higher than that of the CNN model and the LSTM model, respectively, which significantly improved the accuracy of particle size identification in annular particle flows. Therefore, this research provides an efficient method for the intelligent identification of sand in multiphase annular flows.

Time evolution of ambient pressure sensitivity of microbubbles subharmonic response as a function of hydrostatic pressure and the filling gas

The ultrasound contrast microbubbles have shown a great ability to produce nonlinear oscillations in response to acoustic excitation which results in the generation of harmonics and subharmonics of the excitation. The subharmonic response of ½ order changes significantly with a change in hydrostatic pressure in the physiological range. This property is being investigated for subharmonic aided pressure estimation (SHAPE), a noninvasive alternative to current methods for vascular pressure measurement in critical organs. In this study, the ambient pressure sensitivity of the subharmonic response of microbubbles with different gas cores and shells was investigated over 25–700 kPa acoustic pressure and the hydrostatic pressure range of 0–25 kPa. The subharmonic showed different trends of increase and decrease with hydrostatic pressure. The sensitivity has shown gradual change over time which was observed to be related to the hydrostatic pressure magnitude and the gas core. These findings could help to calibrate the SHAPE.

Enhanced sonodynamic therapy by carbon dots-shelled microbubbles with focused ultrasound

Sonodynamic therapy involving the non-invasive and local generation of lethal reactive oxygen species (ROS) via ultrasound (US) with sonosensitizers has been proposed as an emerging tumor therapy strategy. However, such therapy is usually associated with inertial cavitation and unnecessary damage to healthy tissue because current sonosensitizers have insufficient sensitivity to US. Here, we report the use of a new proposed sonosensitizer, carbon dots (C-dots), to assemble microbubbles with a gas core (C-dots MBs). As the C-dots were directly integrated into the MB shell, they could effectively absorb the energy of inertial cavitation and transfer it to ROS. Our results revealed the appearance of 1O2, •OH, and H2O2 after US irradiation of C-dots MBs. In in vitro experiments, treatment with C-dots MBs plus US induced lipid peroxidation, elevation of intracellular ROS, and apoptosis in 32.5%, 45.3%, and 50.1% of cells respectively. In an animal solid tumor model, treatment with C-dots MBs plus US resulted in a 3-fold and 2.5-fold increase in the proportion of ROS-damaged cells and apoptotic cells, respectively, compared to C-dots MBs alone. These results will pave the way for the design of novel multifunctional sonosensitizers for SDT tumor therapy.

Depositional-diagenetic process and their implications for pore development of Wufeng-Longmaxi shales in the Jiangdong block, Fuling shale gas field, SW China

Depositional environment and diagenesis are important factors affecting pore characteristics, whereas how differential depositional and diagenetic processes affect pore development and preservation in shale remains controversial. In this study, based on geochemical analysis, low-temperature gas (including N2 and CO2) physisorption, core observation, thin section and field emission-scanning electron microscopy, the influences of various paleoenvironmental conditions and diagenetic pathways on pore development of the Wufeng and Longmaxi Formations are investigated. The results indicate that paleoenvironmental conditions determine primary mineral composition and content of organic matter, resulting in the various shale lithofacies. Subsequently, minerals in different shale lithofacies experienced various diagenetic events and evolution pathways, finally affecting pore generation and evaluation. Three system tracts, including transgressive systems tract (TST), early highstand systems tract (EHST) and late highstand systems tract (LHST) are identified in the Wufeng and Longmaxi Formations. Siliceous shale, mainly deposited in the TST, contains large amounts of biogenic authigenic quartz and abundant organic matter. Authigenic quartz aggregates effectively inhibit compaction and protect abundant pores. The contents of extrabasinal components increase during the EHST, while biogenic quartz and organic matter decrease to mainly develop mixed shale. Insufficient microcrystalline authentic quartz and high content of clay minerals lead to higher degree of compaction in mixed shale than siliceous shale, resulting in fewer residual pores. In contrast, clay minerals in clay-rich shale, deposited in the LHST, undergo strong compaction and illitization of smectite during diagenesis, resulting in strong deformation and loss of primary pores. As a result, higher amount of OM pores is generated and preserved in the organic-rich siliceous shales from the bottom of Wufeng and Longmaxi Formation, and gradually decreases in the mixed shale, while clay-rich shale in the upper section of the Longmaxi has the lowest amount of pore volume.

Core-Shell Particles: From Fabrication Methods to Diverse Manipulation Techniques.

Core-shell particles are micro- or nanoparticles with solid, liquid, or gas cores encapsulated by protective solid shells. The unique composition of core and shell materials imparts smart properties on the particles. Core-shell particles are gaining increasing attention as tuneable and versatile carriers for pharmaceutical and biomedical applications including targeted drug delivery, controlled drug release, and biosensing. This review provides an overview of fabrication methods for core-shell particles followed by a brief discussion of their application and a detailed analysis of their manipulation including assembly, sorting, and triggered release. We compile current methodologies employed for manipulation of core-shell particles and demonstrate how existing methods of assembly and sorting micro/nanospheres can be adopted or modified for core-shell particles. Various triggered release approaches for diagnostics and drug delivery are also discussed in detail.

Microbubble Delivery Platform for Ultrasound-Mediated Therapy in Brain Cancers.

The blood-brain barrier (BBB) is one of the most selective endothelial barriers that protect the brain and maintains homeostasis in neural microenvironments. This barrier restricts the passage of molecules into the brain, except for gaseous or extremely small hydrophobic molecules. Thus, the BBB hinders the delivery of drugs with large molecular weights for the treatment of brain cancers. Various methods have been used to deliver drugs to the brain by circumventing the BBB; however, they have limitations such as drug diversity and low delivery efficiency. To overcome this challenge, microbubbles (MBs)-based drug delivery systems have garnered a lot of interest in recent years. MBs are widely used as contrast agents and are recently being researched as a vehicle for delivering drugs, proteins, and gene complexes. The MBs are 1-10 μm in size and consist of a gas core and an organic shell, which cause physical changes, such as bubble expansion, contraction, vibration, and collapse, in response to ultrasound. The physical changes in the MBs and the resulting energy lead to biological changes in the BBB and cause the drug to penetrate it, thus enhancing the therapeutic effect. Particularly, this review describes a state-of-the-art strategy for fabricating MB-based delivery platforms and their use with ultrasound in brain cancer therapy.

Experiment and Modeling of Interfacial Area Concentration of Liquid Film in Upward Annular Two-Phase Flow

To accurately quantify the interfacial transfer terms in the two-fluid model, the reliable prediction of the interfacial area concentration (IAC) is crucial. The IAC in annular flow, especially the interface between the liquid film and gas core, is particularly important due to its relevance to critical heat flux and reactor operation safety. However, very few experimental and analytical studies have been performed that focus on the IAC of the liquid film in annular flow. In this work, the IAC of the liquid film is measured using a parallel-wire conductance probe for upward annular flow in a 25.4-mm one-dimensional pipe. A total of 25 flow conditions are measured with the range of superficial liquid velocity from 0.15 to 2.00 m/s and the range of superficial gas velocity from 10.0 to 29.6 m/s. The IAC radial profile is obtained from the liquid film time trace measured by the conductance probe, and the accuracy of this method is verified by flow visualization. The effects of the inlet gas and liquid flow rates on the characteristics of the IAC radial distribution as well as area-averaged IACs are analyzed. A new model is developed to predict the IAC radial distribution of the liquid film. The IAC profiles predicted by the model agree very well with the measured IAC profiles for typical annular flow conditions and have a reasonable agreement for the wispy annular flow conditions.

Generation of condensate bubble aphrons (CBA) by partially vaporized condensate to enhance oil removal from produced water

This paper demonstrates flotation separation for dispersed oil droplets and dissolved organics by preparing condensate bubble aphrons (CBA) by partially vaporizing condensate. The results show that the new CBA consists of a condensate membrane and a gas core, with a three-phase contact angle above 140° from the oil surface due to excellent wettability. At different temperatures and condensate compositions, bubbles are about 25–100 µm in size. The half-life time (140–230 s) of CBA and gas hold-up (10–25%) is much higher than nitrogen bubbles. It shows that the CBA has good stability and dispersibility. The flotation experiment of CBA found that the condensate group distribution ratio was optimally adapted to the temperature, and the optimum oil removal efficiency of up to 87% was obtained when the operating temperature was higher than the bubble point of 25–35 °C. The experimental experiment shown the recommended initial oil concentration (400 mg/L) and the mixing ratio of condensate and water (1.0%). Otherwise, CBA flotation efficiency was 10% higher than dissolved gas flotation. With the addition of flocculant, the CBA flotation efficiency can reach 97% of oil droplets and can achieve 50% removal of Acetic acid (HAc).

Flow and heat transfer model for turbulent-laminar/turbulent gas-liquid annular flows

• Physical process of heat transfer for annular flow was mathematically formulated. • Effect of flow orientations and parameters on heat transfer process was analyzed. • Heat transfer was significantly enhanced by gas in flow regime of annular flow. • Dependence of heat transfer multiplier on void fraction and pressure drop multiplier was identified. • A heat transfer correlation was developed based on Chilton & Colburn analogy. Two-phase gas-liquid annular flows are characterized by the liquid flowing in the annular-shaped channels as liquid film and gas flowing in the center as gas core. Adequate understanding of the flow and heat transfer mechanism is important. This paper aims at developing a model for flow and heat transfer in two-phase annular flows. First, the physical process of flow and heat transfer for two-phase annular flow is mathematically formulated and a new heat transfer model is developed based on two-fluid concept. Then, the new model is well validated using the experimental void fraction, liquid film thickness, and heat transfer coefficient collected from various sources. Third, the effect of the orientations and flow parameters on the heat transfer of two-phase annular flows are comprehensively investigated. Finally, the dependence of the two-phase heat transfer multipliers on the void fractions and pressure multipliers is identified quantitatively and a simple heat transfer correlation is developed based on Chilton & Colburn analogy.

Climate agenda of the leading US oil companies

The authors investigate characteristics of the fourth energy transition from fossil fuel to renewables that is currently underway on the global scale and its impact on the oil and gas sector. They study evolution of the climate agenda of oil companies and its main drivers. The article explores specifics of the American model of oil majors’ decarbonization and analyzes key differences between the American and European models. The authors assess the main reasons for the high climate responsibility of the European oil companies. They study the key drivers of climate policy of the US majors, e.g. greening of financial institutions and investors, consumers’ preferences, etc. A special focus is made on the evolution of the US government climate strategy. Recently, the US majors have been demonstrating greater climate awareness and began to announce their net zero commitments. The authors study specific decarbonization measures taken by the main US oil companies (ExxonMobil, Chevron, ConocoPhillips, and Occidental Petroleum), such as R&amp;D in the sphere of biofuels, carbon capture, utilization and storage, control of methane leakages, production of hydrogen, etc. The article emphasizes that the US oil companies, in contrast to their European counterparts, are reluctant to diversify their asset portfolio by expanding the share of renewables. Their reluctance might stem from the fact that oil companies that possess considerable proved reserves of hydrocarbons and that made significant investments in upstream are not eager to focus on renewables. Currently, the American majors continue to bet on the long-term future of oil and gas, remain loyal to their core oil and gas business and pursue climate agenda mainly by enhancing their energy efficiency through the use of their competitive advantages, primarily technological supremacy. The authors believe that under Joe Biden’s administration the climate agenda of the leading US oil companies will be strengthened further.

CFD Study on the Influence of Liquid Viscosity on the Swirling Gas-Liquid Flow

Swirling two-phase flow is important in industrial mixing and separation systems. In this work, the effect of liquid viscosity was investigated numerically using the Euler-Euler Computational Fluid Dynamics (CFD) model where the liquid and the gas acted as the continuous and dispersed phases, respectively. CFD simulations were performed to model the gas-liquid flow inside a horizontal pipe equipped with a static mixer element with liquid viscosities of 1, 5, 10, and 50 cP. The gas volume fraction contours in the central axial plane show that the evolution of gas distribution is strongly influenced by the liquid viscosity, especially in the region downstream of the element. The calculated results show that the higher the viscosity, the shorter the gas core downstream of the element. Gas separation after the element occurs over a shorter distance with higher liquid viscosity. A possible explanation is that the swirling flow decays faster at higher liquid viscosities, and the buoyancy force dominates over the centrifugal force.

Structural Optimization of a Circular Symmetric Threaded Connection System Based on the Effect of the Upper Stabbing Flank Corner Radius

In order to boost shale gas drilling efficiency, oil and gas exploration and drilling distances have risen along with the number of horizontal definitions and directions. As a result, the joints of oil wells and core gas pipes are under continual stress and compression, internal and external pressures, and extreme bending stresses. This will negatively impact the drilling system’s sustainability and the performance requirements are therefore reinforced. Good thread design is crucial because premium threaded connections are typically employed in joints, and the construction of reliable premium connections to external limitations is closely related to the choice of pertinent parameters as optimal values. In this article, new premium connection systems will be created and constructed that can show good vibration and durability under such stressful conditions. The amount of von Mises stress that is received from the threaded connection depends on how each parameter is changed. In particular, the values of the “upper stabbing flank corner radius” were used to examine the von Mises stress variations in the entire structure. An optimized design for the premium connection system is proposed with the best value of upper stabbing flank corner radius according to minimized stress on the teeth of the premium connection against compressive forces. The study’s findings suggest that it is feasible to create a premium connection that can lower stress following the genuine demand of the industry.

Is the mm/submm dust polarization a robust tracer of the magnetic field topology in protostellar envelopes? A model exploration

Context. High-resolution millimeter and submillimeter (mm and submm) polarization observations have opened a new era in the understanding of how magnetic fields are organized in star forming regions, unveiling an intricate interplay between the magnetic fields and the gas in protostellar cores. However, to assess the role of the magnetic field in the process of solar-type star formation, it is important to understand to what extent the polarized dust emission is a good tracer of the magnetic field in the youngest protostellar objects. Aims. In this paper, we present a thorough investigation of the fidelity and limitations of using dust polarized emission to map the magnetic field topologies in low-mass protostars. Methods. To assess the importance of these effects, we performed an analysis of magnetic field properties in 27 realizations of magnetohydrodynamics (MHD) models following the evolution of physical properties in star-forming cores. Assuming a uniform population of dust grains the sizes of which follow the standard MRN size distribution, we analyzed the synthetic polarized dust emission maps produced when these grains align with the local B-field because of radiative torques (B-RATs). Results. We find that mm and submm polarized dust emission is a robust tracer of the magnetic field topologies in inner protostellar envelopes and is successful at capturing the details of the magnetic field spatial distribution down to radii ~100 au. Measurements of the line-of-sight-averaged magnetic field line orientation using the polarized dust emission are precise to &lt;15° (typical of the error on polarization angles obtained with observations from large mm polarimetric facilities such as ALMA) in about 75%–95% of the independent lines of sight that pass through protostellar envelopes. Large discrepancies between the integrated B-field mean orientation and the orientation reconstructed from the polarized dust emission are mostly observed in (i) lines of sight where the magnetic field is highly disorganized and (ii) those that probe large column densities. Our analysis shows that the high opacity of the thermal dust emission and low polarization fractions could be used to avoid using the small fraction of measurements affected by large errors.

Experimental study of the spray characteristics of twin-fluid atomization: Focusing on the annular flow regime

The characteristics of twin-fluid atomization operating in the annular flow regime were studied experimentally under various gas-to-liquid ratios (GLRs) and injection pressures. The macroscopic morphology of the spray was obtained by shadowgraph, while the droplet size and velocity were measured using a phase-Doppler particle analyzer technique. It was found that the spray cone angle increases almost linearly with the GLR, and the axial distance required for droplet coalescence to outweigh the breakup decreases with increasing GLR. The Sauter mean diameter (SMD) first decreases and then increases along the axial direction due to the competition between turbulent breakup and droplet coalescence. The droplet size follows a lognormal distribution; the droplet velocity distribution is closer to a lognormal distribution under large GLRs, while it follows normal distribution with GLR = 3%. Regarding the radial distribution, low GLRs (3% and 5%) lead to a bimodal spatial velocity distribution, while for large GLRs, the droplet velocity decreases monotonically toward the far field. The spray tends to become more stable with increasing GLR and injection pressure Pinj, whereas the SMD increases with increasing Pinj. The underlying atomization mechanism in a twin-fluid injector in the annular flow state can be regarded as the disintegration of the initial liquid sheet by longitudinal Kelvin–Helmholtz instability followed by transverse Rayleigh–Taylor instability, which yields a direct proportionality of the droplet size to the initial liquid sheet thickness ΔL. Subsequently, for high Pinj, the gas core shrinks and ΔL increases, which results in an increased SMD but enhanced atomization efficiency ΔL/SMD.

Research on Factors and Influencing Correlation of Coal Core Temperature during Coring.

The core-tube method is a common method to measure the coal seam gas content (CSGC). However, cutting heat and friction heat will be generated in the core-tube coring process, which will increase the coal core temperature and the coal core gas loss, thus resulting in a large error in the determination of the gas content. The accuracy of the gas content determination is closely related to the temperature variation of coal core during core-taking. Based on this, the team developed the "thermal effect simulation device of coal core in the core-taking process" and carried out the temperature change test experiment of the coal core in the core-taking process under different conditions. The results show that the temperature variation of the coal core during the core-taking process shows four stages: constant temperature, rapid temperature rise, slow temperature rise, and temperature drop. The temperature rise rate, temperature rise duration, and temperature rise peak of the coal core increase with the increase in rotate speed, coal strength, friction area, and frictional load. In the axial direction, the closer to the upper end of the core pipe, the higher the core temperature. In the radial direction, the closer the core is to the wall of the core pipe, the higher the core temperature is. Under the influence of cutting heat and friction heat in the process of core-taking, the maximum heating rate of the core-taking tube wall within 8 min is 20 °C/min, the peak temperature is 158.4 °C, the average temperature of the wall is above 100 °C, and the average temperature rise of the coal core reaches 55.7 °C. Within 60 min, the average temperature of the coal core remained above 50 °C. The order of influence of coal core temperature from large to small is as follows: rotate speed, frictional load, friction area, and coal strength. It can provide a reference for accurately determining CSGC using the core-tube method or designing a coring device to eliminate or reduce the thermal effect during coring.