Gas Outflow Research Articles

Experimental Determination of the Flow Coefficient for a Constrictor Nozzle with a Critical Outflow of Gas

Reduction of energy expenditures required for various technological processes is a pressing issue in today’s economy. One of the ways to solve this issue in regard to liquefied natural gas (LNG) storage is the recovery of its vapours from LNG tanks using an ejector system. In that respect, studies on the outflow of the real gas through the nozzle, the main element of the ejector, and identifying differences from the ideal gas outflow, are of high relevance. Particularly, this concerns the determination of the discharge coefficient µ as the ratio of the actual flowrate to the ideal one, taking into account the energy losses at gas outflow through the nozzle. The discharge coefficient values determined to date for various nozzle geometries are, as a rule, evaluated empirically and contradictory in some cases. The authors suggest determining the discharge coefficient by means of an experiment. This paper includes µ values determined using this method for the critical outflow of air to atmosphere through constrictor nozzles with different outlet diameters (0.003 m; 0.004 m; 0.005 m) in the pressure range at the nozzle inlet of 0.5–0.9 MPa. The obtained results may be used for the design of an ejector system for the recovery of the boil-off gas from LNG tanks, as well as in other fields of industry, for the design of technical and experimental devices with nozzles for various applications.

Experimental study of thermal conditions of the formation of aerosol from graphite grade GВ-50/12 in the power plant of a T-64B tank

The results of an experimental investigation of the properties of GV-50/12 graphite and the measurement of the thermal parameters of the gas outflow in the power plant of the T-64B tank on the subject of the formation of an aerosol from expandable graphite are presented in the work. The method of improving the thermal smoke apparatus is disclosed, which consists in the injection of graphite powder into the bypass gas duct of the power setup of the T-64 tank, causing the release of an aerosol cloud from the power setup of the tank. The experimental study was divided into two parts: the study of the expanding coefficient of graphite GV-50/12; study of the temperature of the exhaust gases in the area of the gas duct outlet. The coefficient of an expansion of graphite was determined based on the results of the ratio of the bulk mass of graphite before heating and after heating at a constant measuring volume. Graphite mass was measured on an ADG200C analytical scales. The change in shape of graphite as a result of thermal shock was studied on an optical microscope with an image magnification of 140 times. According to the research results, it was found that the bulk density of GV-50/12 graphite decreases by 26 times as a result of thermal shock. It was determined that graphite particles acquire a three-dimensional structure. It is this structure that leads to a decrease in the bulk density of this substance. Therefore, in the case of using expanded graphite GV-50/12 as an aerosol substance, prolonged stability of the aerosol curtain is achieved due to low hydraulic coarseness. The study of the temperature of the exhaust gases in the area of the gas duct cover of the T-64B tank was carried out while the 5TDF engine was operating on the spot, while driving in 1st, 2nd, and 3rd gears. To measure the gas temperature, a K-type thermocouple was installed in the gas duct outlet, which has a temperature measurement range from 0 °C to + 800 °C. It was determined that in order to create an aerosol from graphite, it is necessary to increase the temperature of the gas in the outlet channel from 250-330 °С to 1000 °С. The increase in gas temperature can be achieved due to the combustion of fuel in the exhaust gases, given the presence of a sufficient concentration of oxygen. A sufficient concentration of oxygen in the exhaust gases is caused by the combustion of fuel in the engine with an excess of air by 1.8-2 times and by blowing the cylinders of the 5TDF engine with air.

A NOVEL HYBRID METHOD TO DESIGN HORIZONTAL GAS-LIQUID SEPARATORS

Separators are a vital part of almost every oil and gas production facility. Because of their importance, optimal separator design is critical. Semi-empirical design method is a conventional and more primitive way of determining the optimal dimensions for separators. However, because of the simplifying assumptions used to derive semi-empirical correlations, this method can only be used to obtain a rough estimate for separator dimensions. In this study, a novel hybrid method to design multiphase separators is presented using experimentation, dimensional analysis, and CFD simulation. This method contains performing experiments on a pilot two-phase separation unit; CFD simulating of the laboratory-scale separator and validating the simulation using the experimental data; determining a range for the slenderness ratio of practical surface separators using dimensional analysis; CFD simulating the separators with slenderness ratios within the specified range using the procedure, and determining the optimum slenderness ratio. The pilot two-phase separation unit consists of a laboratory-scale horizontal two-phase separator, pumps, compressors and a static mixer to create a two-phase flow, and a liquid filter to extract liquid droplets from the separator gas outflow. The diameter of the trapped liquid droplets and their weight are, then, determined by imaging and weighing processes. The CFD model is validated with the experimental data (with less than 8% relative error). Using these steps, the dimensions of a surface separator for one of the production wells located in phase 9 of South Pars gas field are determined. One of the most important achievements of this research is to provide the necessary basis for the optimal design of surface separators.

Kinematics, Structure, and Mass Outflow Rates of Extreme Starburst Galactic Outflows

We present results on the properties of extreme gas outflows in massive (M * ∼ 1011 M ⊙), compact, starburst (star formation rate, SFR∼ 200 M ⊙ yr−1) galaxies at z = 0.4–0.7 with very high star formation surface densities (ΣSFR ∼ 2000 M ⊙ yr−1 kpc−2). Using optical Keck/HIRES spectroscopy of 14 HizEA starburst galaxies, we identify outflows with maximum velocities of 820–2860 km s−1. High-resolution spectroscopy allows us to measure precise column densities and covering fractions as a function of outflow velocity and characterize the kinematics and structure of the cool gas outflow phase (T ∼ 104 K). We find substantial variation in the absorption profiles, which likely reflects the complex morphology of inhomogeneously distributed, clumpy gas and the intricacy of the turbulent mixing layers between the cold and hot outflow phases. There is not a straightforward correlation between the bursts in the galaxies’ star formation histories and their wind absorption line profiles, as might naively be expected for starburst-driven winds. The lack of strong Mg ii absorption at the systemic velocity is likely an orientation effect, where the observations are down the axis of a blowout. We infer high mass outflow rates of ∼50–2200 M ⊙ yr−1, assuming a fiducial outflow size of 5 kpc, and mass loading factors of η ∼ 5 for most of the sample. While these values have high uncertainties, they suggest that starburst galaxies are capable of ejecting very large amounts of cool gas that will substantially impact their future evolution.

Об эффективности легкосбрасываемых конструкций, расположенных в покрытии

The dynamics of the development of an internal explosion is studied considering the action of blast relief panels. The time spent on the exit of the blast relief panel from the opening, as well as the effect of gravity, are considered. The processes are investigated from the moment the blast relief panel leaves the opening and until it is fully opened. A model is formed considering the initial speed of the blast relief panel at the exit from the opening. The model is limited to considering the pressures, at which it is assumed that the degree of expansion of gases during combustion is unchanged, and to determine the rate of gas outflow, the Bernoulli equation for an incompressible liquid is applicable. Dimensionless complexes and parameters characterizing the process under study are established. As a final result, the dependence of the maximum pressure during the opening-up of the opening (the first peak) from the dimensionless complex based on the initial data is proposed. Among them are the characteristics of the blast relief panel, the combustion rate, the geometric shape, and dimensions of the opening. It is concluded that the maximum possible pressure at the first peak does not directly depend on the area of the opening. The rate of pressure relief at the moment of opening-up of the opening is determined by the area of the side space calculated as the product of the perimeter of the opening to the amount of displacement of the blast relief panel. A method is proposed for reducing pressure at the first peak by increasing the number of openings while maintaining the total area for pressure relief, which depends on the bearing capacity of panels. The results obtained allow to establish under what conditions the pressure at the first peak exceeds the pressure at the second one. Thanks to this, it is possible to adjust the explosion resistance of an object by changing the design of a blast relief panel, or by strengthening the load-bearing elements.

Understanding the Chemical Evolution of Blue Edge-on Low Surface Brightness Galaxies

We present a sample of 330 blue edge-on low surface brightness galaxies (ELSBGs). To understand the chemical evolution of ELSBGs, we derived the gas-phase abundance and the [α/Fe] ratio. Compared with star-forming galaxies, ELSBGs show a flatter trend in the mass–metallicity (M *–Z) relation, which suggests that the oxygen abundance enhancement is inefficient. We focused on 77 ELSBGs with H i data and found that the closed-box model cannot explain their gas fraction and metallicity relation, which implies that infall and/or outflow is needed. We derived the [α/Fe] ratio of normal ELSBG (<109.5 M ⊙) and massive ELSBG (> = 109.5 M ⊙) using single stellar population grids from the MILES stellar library. The mean [α/Fe] ratios are 0.18 and 0.4 for normal ELSBG and massive ELSBG, respectively. We suggest that the long timescales of star formation and/or metal-rich gas outflow events caused by SNe Ia winds are likely to be responsible for the α-enhancement of massive ELSBGs.

A study of the fixed choke and constant outflow method for riser gas handling

Riser gas events appear during offshore drilling operations when there is a presence of gas in a marine riser above the subsea BOP, which has been recognized as a hazardous situation. The selection of pressure control methods during such events significantly impacts the safety and efficiency of riser gas handling (RGH). This paper performed a numerical simulation study on the fixed choke and constant outflow method as one of the most discussed and positively perceived pressure control methods for RGH currently in the industry. The processes of RGH with the proposed fixed choke and constant outflow method were simulated with a comprehensive riser gas influx simulator. The multiphase flow dynamics in a riser were simulated by a drift-flux model with the inclusion of various sub-models and coupled with a multiphase choke flow model. Measurement data (including distributed fiber optic sensing data) from a set of full-scale experiments conducted at the Petroleum Engineering Research, Training, & Testing (PERTT) Laboratory at Louisiana State University (LSU) was used for the calibration and validation of the developed simulator. The performance of the proposed method is evaluated based on the maximum gas and liquid outflow rates and the peak choke upstream pressure during RGH. A series of sensitivity analyses and a contingency case study was conducted to evaluate the applicability and the extendibility of the fixed choke and constant outflow method. The proposed pressure control method shows great potential in enhancing the safety of RGH for a wide range of riser lengths and gas influx sizes with the available managed pressure drilling (MPD) and riser gas handling equipment. The sensitivity analyses revealed that the selection of the initial circulation rates and choke positions has a significant impact on the safety and time efficiency of the RGH operations and should be carefully determined based on the influx and riser system status. This study deepens the understanding of gas influx movement and pressure behaviors in a marine riser during riser gas events. The numerical simulations in this study help to improve the design of riser gas handling strategies.

A new apparatus for investigating gas transport property in geomaterials with ultralow permeability

The gas flow in geological materials with ultra-low permeability can vary dramatically, i. e., from almost no measurable quantity of gas before breakthrough to a massive gas flux at breakthrough. It is a great challenge to realize the whole process measurement of gas transport in saturated geomaterials with ultra-low permeability. In this work, a newly designed temperature-controlled triaxial apparatus was developed. In which, a water-to-gas-exchanger was designed for precise injection of gas at a constant pressure or constant injection rate, due to that water is less compressible and much more difficult to leak through the seal of a regulator. Meanwhile, eddy current sensors and displacement transducer with high resolutions were utilized to accurately measure the specimen deformation at different locations in a non-contact way to explore the mechanism of gas entry and breakthrough. In addition, a gas flow detection device that contains four gas flowmeters with different measurement ranges and can automatically switch between these flowmeters was developed to monitor the gas outflow of the whole process. To validate the performance of the developed apparatus, systematic gas injection tests on Gaomiaozi (GMZ) bentonite were conducted, during which the helium gas was injected in a constant rate. Real-time data on inlet gas pressure, gas outflow rate, stress state (both isotropic and axial stresses) and volume deformation (both axially and radially) were monitored. Results show that the developed apparatus could successfully capture the gas entry and the subsequent breakthrough points of the compacted bentonite with ultralow permeability. For compacted bentonite with high saturation, capillary flow, dilatant flow and interfacial leakage could co-exist during the gas transport process and the dominated mechanism was closely related to the gas injection pressure.

Hydrodynamic evolution of Sgr A East: the imprint of a supernova remnant in the Galactic Centre

ABSTRACT We perform three-dimensional numerical simulations to study the hydrodynamic evolution of Sgr A East, the only known supernova remnant (SNR) in the centre of our Galaxy, to infer its debated progenitor supernova (SN) type and its potential impact on the Galactic Centre environment. Three sets of simulations are performed, each of which represents a certain type of SN explosion (SN Iax, SN Ia, or core-collapse SN) expanding against a nuclear outflow of hot gas driven by massive stars, whose thermodynamical properties have been well established by previous work and fixed in the simulations. All three simulations can simultaneously roughly reproduce the extent of Sgr A East and the position and morphology of an arc-shaped thermal X-ray feature, known as the ‘ridge’. Confirming previous work, our simulations show that the ridge is the manifestation of a strong collision between the expanding SN ejecta and the nuclear outflow. The simulation of the core-collapse SN, with an assumed explosion energy of 5 × 1050 erg and an ejecta mass of 10 M⊙, can well match the X-ray flux of the ridge, whereas the simulations of the SN Iax and SN Ia explosions underpredict its X-ray emission, due to a smaller ejecta mass. All three simulations constrain the age of Sgr A East to be ≲1500 yr and predict that the ridge should fade out over the next few hundred years. We address the implications of these results for our understanding of the Galactic Centre environment.

Cold molecular gas outflow encasing the ionized one in the Seyfert galaxy NGC 3281

ABSTRACT We present ALMA CO (2-1) observations of the Seyfert 2 galaxy NGC 3281 at ∼100 pc spatial resolution. This galaxy was previously known to present a bi-conical ionized gas outflow extending to 2 kpc from the nucleus. The analysis of the CO moment and channel maps, as well as kinematic modelling, reveals two main components in the molecular gas: one rotating in the galaxy plane and another outflowing and extending up to ∼1.8–2.6 kpc from the nucleus, partially encasing the ionized component. The mass of the outflowing molecular gas component is Mmol, out = (2.5 ± 1.6) × 106 $\rm {{\rm M}_{\odot }}$ , representing ∼1.7–2 per cent of the total molecular gas seen in emission within the inner 2.3 kpc. The corresponding mass outflow rate and power are $\dot{M}_{\mathrm{out},\mathrm{mol}}$ = 0.12–0.72 $\rm {{\rm M}_{\odot }\, yr^{-1}}$ and $\dot{E}_{\mathrm{out},\mathrm{mol}}$ = (0.045–1.6) ${\times }\, 10^{40}$ $\rm {erg\, s^{-1}}$ , which translates to a kinetic coupling efficiency with the AGN power of only 10−4–0.02 per cent. This value reaches up to 0.1 per cent when including both the feedback in the ionized and molecular gas, as well as considering that only part of the energy couples kinetically with the gas. Some of the non-rotating CO emission can also be attributed to inflow in the galaxy plane towards the nucleus. The similarity of the CO outflow – encasing the ionized gas one and the X-ray emission – to those seen in other sources, suggests that this may be a common property of galactic outflows.

Wave structure of the gas flow in a truncated nozzle with a long bell-shaped tip

In recent years, more and more attention has been paid to nozzles with an unconventional profile, which differs from that of the classical streamline-profiled Laval nozzle. In such nozzles, the flow fields typically include interacting supersonic and subsonic flows, often with recirculation regions and a complex wave structure of the flow. This work is concerned with a numerical study of the wave structure of the gas flow in a truncated supersonic nozzle with an elliptical bell-shaped tip whose length is long in comparison with the conical section upstream of the tip. The gas flow inside the nozzle and in the surrounding space was simulated using the ANSYS software package. The calculations were carried out in a non-stationary axisymmetric formulation based on the Reynolds-averaged Navier–Stokes equations closed with the use of the SST turbulence model with near-wall functions and a compressibility correction. In the calculations, the nozzle inlet pressure and the ambient pressure were varied. The correctness of the methodological approaches to the solution of the problem was confirmed in the authors’ previous works. The study showed the following. At low values of the nozzle inlet pressure (P0 &lt; 50 bar) and an ambient pressure of 1 bar, the tip wall exhibits a developed separation zone with a large-scale vortex and a small-scale one (near the tip exit). The first "barrel" of the outflowing gas shows a "saddle" low-intensity compression wave structure. In the case of a separated flow, the tip wall pressure in the separation zone is about 15% less than the ambient pressure. At P0 &gt; 100 bar, the tip wall pressure is nearly proportional to the nozzle inlet pressure. In the upper atmosphere, when going in a radial direction from the nozzle axis at the tip exit cross-section, the static pressure monotonically decreases, reaches a minimum, and then increases linearly to the its maximum value on the tip wall. In the case of a separated flow in the tip at a sea-level ambient pressure, the static pressure at the tip exit cross-section behaves in the same manner for inlet pressures P0 &gt; 50 bar. At P0 = 50 bar, there exist two extrema: the pressure first deceases to its minimum value, then increases to its maximum value, and then decreases slightly to its value on the tip wall.

Influences of pore fluid on gas production from hydrate-bearing reservoir by depressurization

In addition to the temperature and pressure conditions, the pore fluid composition and migration behavior are also crucial to control hydrate decomposition in the exploitation process. In this work, to investigate the effects of these factors, a series of depressurization experiments were carried out in a visible one-dimensional reactor, using hydrate reservoir samples with water saturations ranging from 20% to 65%. The results showed a linear relationship between gas production rates and gas saturations of the reservoir, suggesting that a larger gas-phase space was conducive to hydrate decomposition and gas outflow. Therefore, the rapid water production in the early stage of hydrate exploitation could release more gas-phase space in the water-rich reservoir, which in turn improved the gas production efficiency. Meanwhile, the spatiotemporal evolution of pore fluids could lead to partial accelerated decomposition or secondary formation of hydrates. In the unsealed reservoir, the peripheral water infiltration kept reservoir at a high water saturation, which hindered the overall production process and caused higher water production. Importantly, depressurization assisted with the N2 sweep could displace the pore water rapidly. According to the results, it is recommended that using the short-term N2 sweep as an auxiliary means in the early stage of depressurization to expand the gas-phase space in order to achieve the highest production efficiency.

GTC/CanariCam Mid-infrared Polarimetry of Magnetic Fields in Star-forming Region W51 IRS2

We present 0.″4 resolution imaging polarimetry at 8.7, 10.3, and 12.5 μm, obtained with CanariCam at the Gran Telescopio Canarias, of the central 0.11 pc × 0.28 pc (4.″2 × 10.″8) region of W51 IRS2. The polarization, as high as ∼14%, arises from silicate particles aligned by the interstellar magnetic field (B-field). We separate, or unfold, the polarization of each sightline into emission and absorption components, from which we infer the morphologies of the corresponding projected B-fields that thread the emitting- and foreground-absorbing regions. We conclude that the projected B-field in the foreground material is part of the larger-scale ambient field. The morphology of the projected B-field in the mid-infrared (mid-IR) emitting region spanning the cometary H ii region W51 IRS2W is similar to that in the absorbing region. Elsewhere, the two B-fields differ significantly with no clear relationship between them. The B-field across the W51 IRS2W cometary core appears to be an integral part of a champagne outflow of gas originating in the core and dominating the energetics there. The bipolar outflow, W51north jet, that appears to originate at or near SMA1/N1 coincides almost exactly with a clearly demarcated north–south swath of lower polarization. While speculative, comparison of mid-IR and submillimeter polarimetry on two different scales may support a picture in which SMA1/N1 plays a major role in the B-field structure across W51 IRS2.

Coma composition of comet 67P/Churyumov-Gerasimenko from radio-wave spectroscopy

We present the results of a molecular survey of comet 67P/Churyumov-Gerasimenko undertaken with the Institut de RadioAstronomie Millimétrique (IRAM) 30-m radio telescope in November–December 2021, when it had its most favourable apparition in decades. Observations at IRAM 30-m during the 12–16 November period covered 8 GHz bandwidth at 3 mm, 16 GHz at 2 mm, and 60 GHz in the 1 mm window domain. These were completed by snapshots at 1 mm on 12–13 December and a short observation of the H2O line at 557 GHz with the Odin sub-millimetre observatory on 17.0 November 2021, and with 18-cm observations of OH with the Nançay radio telescope. Less sensitive observations obtained at a previous perihelion passage on 18–22 September 2015 with IRAM and 9–12 November 2015 with Odin are also presented. The gas outflow velocity, outgassing pattern, and temperature have been accurately constrained by the observations. They are perfectly consistent with those measured in situ with the Rosetta/MIRO sub-millimetre instrument in 2015. In particular, the asymmetry of the line is well represented by a jet concentrating three-quarters of the outgassing in about π steradians. We derived abundances relative to water for seven molecules and significant upper limits for approximately five others. The retrieved abundances were compared to those measured in situ at the previous perihelion with Rosetta. While those of HCN, CH3OH, and HNCO are comparable, 67P is found to be depleted in H2S and relatively normal in CS (H2S/CS ≈ 3) in strong contradiction with the Rosetta/ROSINA mass spectrometer measurement of the H2S/CS2 (≈100) abundance ratio. While the formaldehyde total abundance found with IRAM 30-m when assuming it to be mostly produced by a distributed source (Haser parent scale length ≈8000 km) is similar to the one derived by Rosetta/ROSINA, we find that the formaldehyde coming from the nucleus is one order of magnitude less abundant than measured in situ by Rosetta/ROSINA.

Disk Wind Feedback from High-mass Protostars. II. The Evolutionary Sequence

Star formation is ubiquitously associated with the ejection of accretion-powered outflows that carve bipolar cavities through the infalling envelope. This feedback is expected to be important for regulating the efficiency of star formation from a natal prestellar core. These low-extinction outflow cavities greatly affect the appearance of a protostar by allowing the escape of shorter-wavelength photons. Doppler-shifted CO line emission from outflows is also often the most prominent manifestation of deeply embedded early-stage star formation. Here, we present 3D magnetohydrodynamic simulations of a disk wind outflow from a protostar forming from an initially 60 M ⊙ core embedded in a high-pressure environment typical of massive star-forming regions. We simulate the growth of the protostar from m * = 1 M ⊙ to 26 M ⊙ over a period of ∼100,000 yr. The outflow quickly excavates a cavity with a half opening angle of ∼10° through the core. This angle remains relatively constant until the star reaches 4 M ⊙. It then grows steadily in time, reaching a value of ∼50° by the end of the simulation. We estimate a lower limit to the star formation efficiency (SFE) of 0.43. However, accounting for continued accretion from a massive disk and residual infall envelope, we estimate that the final SFE may be as high as ∼0.7. We examine observable properties of the outflow, especially the evolution of the cavity's opening angle, total mass, and momentum flux, and the velocity distributions of the outflowing gas, and compare with the massive protostars G35.20-0.74N and G339.88-1.26 observed by the Atacama Large Millimeter/submillimeter Array (ALMA), yielding constraints on their intrinsic properties.

Nuclear high-ionisation outflow in the Compton-thick AGN NGC 6552 as seen by the JWST mid-infrared instrument

Context. During the commissioning of the James Webb Space Telescope (JWST), the mid-infrared instrument (MIRI) observed NGC 6552 with the MIRI Imager and the Medium-Resolution Spectrograph (MRS). NGC 6552 is an active galactic nucleus (AGN) at a redshift of 0.0266 (DL = 120 Mpc) classified as a Seyfert 2 nucleus in the optical and Compton-thick AGN in the X-ray. Aims. This work exemplifies and demonstrates the MRS capabilities to study the mid-infrared (mid-IR) spectra and characterise the physical conditions and kinematics of the ionised and molecular gas in the nuclear regions of nearby galaxies. Methods. MIRI Imager observations covers the full NGC 6552 galaxy at 5.6 μm. MRS observations covers its nuclear region (3.6×4.3 kpc at 17.7–27.9 μm) in a wavelength range between 4.9 and 27.9 μm. These observations were obtained with the aim to investigate the persistence of the MIRI detectors (residual signal left from previous bright source observations). However, NGC 6552 observations demonstrate the performance and power of the MIRI instrument even with a non-optimal observational strategy. Results. We obtained the nuclear, circumnuclear, and central mid-IR spectra of NGC 6552. They provide the first clear observational evidence for a nuclear outflow in NGC 6552. The outflow contributes to 67±7% of the total line flux independent of the ionisation potential (27–187 eV) and critical densities (104–4×106 cm−3), showing an average blue-shifted peak velocity of −127±45 km s−1 and an outflow maximal velocity of 698±80 km s−1. Since the mid-IR photons penetrate dusty regions as efficiently as X-ray keV photons, we interpret these results as the evidence for a highly ionised, non-stratified, AGN-powered, and fast outflowing gas in a low density environment (few 103 cm−3) located very close (&lt; 0.2 kpc) to the Compton-thick AGN. Nine pure rotational molecular Hydrogen lines are detected and spectrally resolved, and exhibit symmetric Gaussian profiles, consistent with the galactic rotation, and with no evidence of outflowing H2 material. We detect a warm H2 mass of 1.9 ± 1.1 × 107 M⊙ in the central region (1.8 kpc in diameter) of the galaxy, with almost 30% of that mass in the circumnuclear region. Line ratios confirm that NGC 6552 has a Seyfert nucleus with a black hole mass estimated in the range of 0.6–6 million solar masses. Conclusions. This work demonstrates the power of the newly commissioned MIRI Medium Resolution Spectrograph to reveal new insights in the kinematics and ionisation state of the interstellar medium around the dusty nuclear regions of nearby active galaxies.

Recommendation Machine for Gas Outflow in LPG Cylinder

Abstract: Liquefied petroleum gas (LPG) is commonly used in hotels and homes for all cooking purposes. Furthermore, despite the fact that many explosions have occurred as a result of LPG outflow, it is very user friendly to all users. We have implemented a module in our system to address these societal issues. In this system that includes a gas sensor to detect gas outflow. If the sensor detects the level of gas outflow and compares it to the threshold value previously set in the software. If it exceeds the fixed threshold value, the buzzer activates and the relay connected to the circuit turns on. The entire power supply will then be turned off. People nowadays are unaware of their daily gas usage, which causes a delay in refilling the LPG cylinder. To overcome such difficulties, our system has one more module. The load sensor is used to continuously monitor the gas level. The load cell's output is connected to the microcontroller. The microcontroller manipulates the data so that the weight of the gas cylinder, the level of gas leakage, and the amount of gas used per day are displayed on the LCD. If the gas cylinder's level falls dangerously low, a new cylinder is automatically booked and the status is transmitted to the user via the Wi-Fi module

Outflows driven by direct and reprocessed radiation pressure in massive star clusters

ABSTRACT We use 3D radiation hydrodynamic (RHD) simulations to study the formation of massive star clusters under the combined effects of direct ultraviolet (UV) and dust-reprocessed infrared (IR) radiation pressure. We explore a broad range of mass surface density Σ ∼ 102–$10^5 \, \mathrm{M}_{\odot } \, \mathrm{pc}^{-2}$, spanning values typical of weakly star-forming galaxies to extreme systems such as clouds forming super-star clusters, where radiation pressure is expected to be the dominant feedback mechanism. We find that star formation can only be regulated by radiation pressure for $\Sigma \lesssim 10^3 \, \mathrm{M}_{\odot } \, \mathrm{pc}^{-2}$, but that clouds with $\Sigma \lesssim 10^5 \, \mathrm{M}_{\odot } \, \mathrm{pc}^{-2}$ become super-Eddington once high star formation efficiencies (${\sim}80~{{\ \rm per\ cent}}$) are reached, and therefore launch the remaining gas in a steady outflow. These outflows achieve mass-weighted radial velocities of ∼15–$30\, \mathrm{km} \, \mathrm{s}^{-1}$, which is ∼0.5–2.0 times the cloud escape speed. This suggests that radiation pressure is a strong candidate to explain recently observed molecular outflows found in young super-star clusters in nearby starburst galaxies. We quantify the relative importance of UV and IR radiation pressure in different regimes, and deduce that both are equally important for $\Sigma \sim 10^3 \, \mathrm{M}_{\odot } \, \mathrm{pc}^{-2}$, whereas clouds with higher (lower) density are increasingly dominated by the IR (UV) component. Comparison with control runs without either the UV or IR bands suggests that the outflows are primarily driven by the impulse provided by the UV component, while IR radiation has the effect of rendering a larger fraction of gas super-Eddington, and thereby increasing the outflow mass flux by a factor of ∼2.

The many reasons that the rotation curves of low-mass galaxies can fail as tracers of their matter distributions

ABSTRACT It is routinely assumed that galaxy rotation curves are equal to their circular velocity curves (modulo some corrections) such that they are good dynamical mass tracers. We take a visualization-driven approach to exploring the limits of the validity of this assumption for a sample of 33 low-mass galaxies ($60\lt v_\mathrm{max}/\mathrm{km}\, \mathrm{s}^{-1}\lt 120$ ) from the APOSTLE suite of cosmological hydrodynamical simulations. Only three of these have rotation curves nearly equal to their circular velocity curves at z = 0, the rest are undergoing a wide variety of dynamical perturbations. We use our visualizations to guide an assessment of how many galaxies are likely to be strongly perturbed by processes in several categories: mergers/interactions (affecting 6/33 galaxies), bulk radial gas inflows (19/33), vertical gas outflows (15/33), distortions driven by a non-spherical DM halo (17/33), warps (8/33), and winds due to motion through the intergalactic medium (5/33). Most galaxies fall into more than one of these categories; only 5/33 are not in any of them. The sum of these effects leads to an underestimation of the low-velocity slope of the baryonic Tully–Fisher relation (α ∼ 3.1 instead of α ∼ 3.9, where Mbar ∝ vα) that is difficult to avoid, and could plausibly be the source of a significant portion of the observed diversity in low-mass galaxy rotation curve shapes.

EXPERIMENTAL RESEARCH OF MIXING NATURAL GAS IMPINGING JETS AND AIR DURING COMBUSTION AT A VERTICAL REFRACTORY SURFACE

In the work determined the conditions for the start of chemical reactions of natural gas and air mixture at combustion on a refractory surface, when a single submerged turbulent impinging jet is fed from a natural gas collector at the angle α to the vertical refractory surface, at the relative distance L/d0 along the geometric axis of the jet. It is determined that combustion starts under the condition when the excess air coefficient in the mixture reaches about λ = 0.93, at which the laminar flame propagation velocity S°L, m/s, for a premixed mixture of methane and air is maximum. The dependence of the height of the flame Lf, m, on the relative dimensionless step of the location of the nozzles s/d0 in the row was obtained during studying the groups of gas nozzles with the supply of natural gas for combustion through them range diameters 1–3.5 mm (which are used at precent time in the construction of slot bottom burners). It was determined that the flame height of slot bottom burner during its operation on natural gas (tested for the pressure of natural gas in the collector from 2 kPa to 18 kPa, respectively, natural gas outflow velocity, WNG from about 60 m/s to 185 m/s) depends slightly on gas pressure, the relative distance L/d0 that the aerated jet of natural gas travels to the refractory surface in the range of 15 ≤ L/d0 ≤ 30 and the Reynolds number, and strongly depends from on the dimensionless step of the nozzles in the row — s/d0. It has been experimentally proven that by adjusting the dimensionless step of the nozzles (holes) s/d0 in the row of the slot bottom burner, it is possible to adjust the height of the flame and thus obtain the flame of the appropriate height for different heights of fireboxes and boilers powers. Bibl. 29, Fig. 3, Tab. 3.