Theoretical and Experimental Studies of Uneven Dust Suction from a Multi-Cyclone Settling Tank in a Two-Stage Air Filter

In this paper, the uneven air stream distribution problem of individual cyclones is studied in the multi-cyclones of intake air filters in special vehicles’ engines. This problem increases in multi-cyclones, in which several dozen cyclones have a common dust trap from which the collected dust is continuously removed by ejection suction. The aim of this study is the recognition of the theoretical and experimental possibility of reducing the streams’ unevenness, which should result in an efficiency increase in multi-cyclone separation. The methods that led to obtaining a relative stream uniformity from the suction of individual cyclones was analyzed. The method for creating equal pressure drops between the suction streams in the channels was used to achieve this goal. For this purpose, the internal structure of the multi-cyclone settler was changed. The multi-cyclone settling tank space was divided by vertical partitions into independent segments. The settling tank segment was then divided with horizontal shelves into suction channels of different heights, which were assigned a specific number of individual cyclones. The suction channels’ height was theoretically selected in terms of the equal resistance to air stream flow through the channels. For this purpose, the multi-cyclone dust settler segment model was developed. The theoretically determined suction channel’s height was verified by performing experimental flow tests in four (A, B, C, D) dust settler variants. Suction streams of satisfactory uniformity from the cyclones of the variant D settling tank were obtained at a level of 5%. In the next stage, experimental tests of the segment cyclones were carried out with dust before and after the division into suction channels of variant D for the settling tank. A significant increase was achieved from 93.73% to 96.08% in the cyclones’ separation efficiency, which were located as far away from the suction stub as possible and led to a reduction in the non-uniformity of cyclone efficiency in the segment. It follows that the multi-cyclone dust settling segment’s internal structure change gave the expected results.

Non-Keplerian spirals, a gas-pressure dust trap, and an eccentric gas cavity in the circumbinary disc around HD 142527

ABSTRACT We present ALMA observations of the 12CO, 13CO, C18O J = 2-1 transitions and the 1.3 mm continuum emission for the circumbinary disc around HD 142527, at an angular resolution of ≈ 0${_{.}^{\prime\prime}}$3. We observe multiple spiral structures in intensity, velocity, and velocity dispersion for the 12CO and 13CO gas tracers. A newly detected 12CO spiral originates from the dust horseshoe, and is rotating at super-Keplerian velocity or vertically ascending, whilst the interspiral gas is rotating at sub-Keplerian velocities. This new spiral possibly connects to a previously identified spiral, thus spanning >360°. A spatial offset of 30 au is observed between the 12CO and 13CO spirals, to which we hypothesize that the gas layers are propagating at different speeds (surfing) due to a non-zero vertical temperature gradient. Leveraging the varying optical depths between the CO isotopologues, we reconstruct temperature and column density maps of the outer disc. Gas surface density peaks at r ≈ 180 au, coincident with the peak of continuum emission. Here, the dust grains have a Stokes number of ≈ 1, confirming radial and azimuthal trapping in the horseshoe. We measure a cavity radius at half-maximum surface density of ≈ 100 au, and a cavity eccentricity between 0.3 and 0.45.

Dust traps and the formation of cavities in transition discs: a millimetre to sub-millimetre comparison survey

ABSTRACT The origin of the inner dust cavities observed in transition discs remains unknown. The segregation of dust and size of the cavity is expected to vary depending on which clearing mechanism dominates grain evolution. We present the results from the Discs Down Under program, an 8.8-mm continuum Australia Telescope Compact Array (ATCA) survey targeting 15 transition discs with large (≳20 au) cavities and compare the resulting dust emission to Atacama Large millimetre/sub-millimetre Array (ALMA) observations. Our ATCA observations resolve the inner cavity for 8 of the 14 detected discs. We fit the visibilities and reconstruct 1D radial brightness models for 10 sources with a S/N > 5σ. We find that, for sources with a resolved cavity in both wavebands, the 8.8 mm and sub-mm brightness distributions peak at the same radius from the star. We suggest that a similar cavity size for 8.8 mm and sub-mm dust grains is due to a dust trap induced by the presence of a companion.

Measuring the atomic composition of planetary building blocks

Context. Volatile molecules are critical to terrestrial planetary habitability, yet they are difficult to observe directly where planets form at the midplanes of protoplanetary disks. It is unclear whether the inner ∼1 AU of disks are volatile-poor or if this region is resupplied with ice-rich dust from colder disk regions. Dust traps at radial pressure maxima bounding disk gaps can cut off the inner disk from these types of volatile reservoirs. However, the trap retention efficiency and atomic composition of trapped dust have not been measured. Aims. We present a new technique to measure the absolute atomic abundances in the gas accreting onto T Tauri stars and infer the bulk atomic composition and distribution of midplane solids that have been retained in the disk around the young star TW Hya. Methods. We identify near-infrared atomic line emission from gas-phase material inside the dust sublimation rim of TW Hya. Gaussian decomposition of the strongest H Paschen lines isolates the inner disk hydrogen emission. We measure several key elemental abundances, relative to hydrogen, using a chemical photoionization model and infer dust retention in the disk. With a 1D transport model, we determine approximate radial locations and retention efficiencies of dust traps for different elements. Results. Volatile and refractory elements are depleted from TW Hya’s hot gas by factors of ∼102 and up to 105, respectively. The abundances of the trapped solids are consistent with a combination of primitive Solar System bodies. Dust traps beyond the CO and N2 snowline cumulatively sequester 96% of the total dust flux, while the trap at 2 AU, near the H2O snowline, retains 3%. The high depletions of Si, Mg, and Ca are explained by a third trap at 0.3 AU with >95% dust retention. Conclusion. TW Hya sports a significant volatile reservoir rich in C- and N-ices in its outer submillimeter ring structure. However, unless the inner disk was enhanced in C by earlier radial transport, typical C destruction mechanisms and the lack of a C resupply should leave the terrestrial planet-forming region of TW Hya “dry” and carbon-poor. Any planets that form within the silicate dust trap at 0.3 AU could resemble Earth in terms of the degree of their volatile depletion.

Holocene dust dynamics: Introduction to the special issue

This article is a brief introduction to the Special Issue on Holocene Dust Dynamics, which brings together recent research on a key aspect of the Earth’s changing climate through its effects on radiative balance, cloud cover and biogeochemical cycles. The aim of the Special Issue is to contribute to a better understanding of the role of dust aerosols by analysing the evolution and climatic impact of atmospheric dust over long and short timescales within the Holocene. Here, we introduce the rationale behind the Special Issue and the eight research papers, which include long-term records of dust deposition from different types of natural archive (e.g. peatlands, ice, loess and lake sediments) as well as present-day multi-annual dust trap records and process studies from various climatic regimes that have global implications.

Efficient dust ring formation in misaligned circumbinary discs

ABSTRACT Binary systems exert a gravitational torque on misaligned discs orbiting them, causing differential precession which may produce disc warping and tearing. While this is well understood for gas-only discs, misaligned cirumbinary discs of gas and dust have not been thoroughly investigated. We perform SPH simulations of misaligned gas and dust discs around binaries to investigate the different evolution of these two components. We choose two different disc aspect ratios: A thin case for which the gas disc always breaks, and a thick one where a smooth warp develops throughout the disc. For each case, we run simulations of five different dust species with different degrees of coupling with the gas component, varying in Stokes number from 0.002 (strongly coupled dust) to 1000 (effectively decoupled dust). We report two new phenomena: First, large dust grains in thick discs pile up at the warp location, forming narrow dust rings, due to a difference in precession between the gas and dust components. These pile ups do not form at gas pressure maxima, and hence are different from conventional dust traps. This effect is most evident for St ∼ 10–100. Secondly, thin discs tear and break only in the gas, while dust particles with St ≥ 10 form a dense dust trap due to the steep pressure gradient caused by the break in the gas. We find that dust with St ≤ 0.02 closely follow the gas particles, for both thin and thick discs, with radial drift becoming noticeable only for the largest grains in this range.

Пылевая плазма в сильно неоднородном магнитном поле

The paper presents for the first time studies of dusty plasmas formed in a glow discharge in a region of a strongly inhomogeneous magnetic field. The inhomogeneity of the magnetic field is estimated as 0.2 T/cm. A steady dust trap has been detected. The geometric characteristics of the plasma-dust structure were determined; the angular velocity of rotation was measured in several sections perpendicular to the axis of the discharge tube. The mechanism of rotation of the plasma-dust structure is proposed, quantitative estimates are made that confirm the experimental data.

Self-induced dust traps around snow lines in protoplanetary discs

ABSTRACT Dust particles need to grow efficiently from micrometre sizes to thousands of kilometres to form planets. With the growth of millimetre to metre sizes being hindered by a number of barriers, the recent discovery that dust evolution is able to create ‘self-induced’ dust traps shows promises. The condensation and sublimation of volatile species at certain locations, called snow lines, are also thought to be important parts of planet formation scenarios. Given that dust sticking properties change across a snow line, this raises the question: how do snow lines affect the self-induced dust trap formation mechanism? The question is particularly relevant with the multiple observations of the carbon monoxide (CO) snow line in protoplanetary discs, since its effect on dust growth and dynamics is yet to be understood. In this paper, we present the effects of snow lines in general on the formation of self-induced dust traps in a parameter study, and then focus on the CO snow line. We find that for a range of parameters, a dust trap forms at the snow line where the dust accumulates and slowly grows, as found for the water snow line in a previous work. We also find that, depending on the grains’ sticking properties on either side of the CO snow line, it could be either a starting or braking point for dust growth and drift. This could provide clues to understand the link between dust distributions and snow lines in protoplanetary disc observations.