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Aspiration coefficient (A) as a function of flange angle () with length d = 4R by dimensionless updraft velocity, v =-0.01 (a), v =-0.02 (b), v =-0.05 (c), v =-0.1 (d), v =-0.2 (e), v =-0.5 (f).
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A cone hood is an efficient device for capturing dust releases generated by a variety of process equipment. For stationary airflow conditions, a circular cone hood with a round flange is the most efficient design. The goal of this paper is to determine the effect that inflow velocity, suction velocity and terminal settling velocity of dust particle...
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... Vortex zone outlines, velocity fields and current lines were traced using the discrete vortex method (DVM) or, more precisely, the vortex ring method (axisymmetric formulation). A detailed treatment of the computational algorithm involving this method was given in [44,45] where vortex zones (VZ) occurring at the inlet of a circular flanged hood were considered in an A discrete mathematical model is plotted in Fig. 2 As a result, LDC values (ζ) were determined using a previously described technique [51] for the RSM EWT combination at every refinement stage. Additionally, the mean dimensionless distance y+ characterizing grid resolution over the boundary layer [50] was determined (Fig. 3 b). ...
Local exhaust ventilation systems are the most effective – yet power-consuming – method of capturing contaminants. Shaping of the ventilation ductwork elements is an approach that is actively pursued now as a means of reducing energy losses. Past research concerned with determining vortex zone outlines at inlet of circular exhaust hoods and shaping the hood along these outlines has shown shaping to be highly efficient as a means of reducing pressure losses at the inlet of the exhaust hood. The goal of this study is to determine the vortex zone outline in a setting where a flanged hood is placed over an impermeable plane, and to determine the distance at which shaping will retain its effectiveness. Using the discrete vortices method, we examined variations in characteristic vortex zones of exhaust hoods with tilt angles α = 0°, 30°, 60°, 90° and lengths of 0.5, 1.5, 2.5, 5.0 times gauge (gauge defined as the air duct radius). We determined distances away from the plane at which the vortex zone dimensions cease to show any difference from the case of an exhaust hood in unlimited space. It follows from natural experiment performed by us that pressure losses at the inlet of a shaped exhaust hood remain the same when the hood is set at a distance up to one gauge away from the plane. The discovered vortex zone outlines can be used for shaping a circular exhaust hoods above an impermeable plane. This will reduce its local resistance factor, eliminate vortex zones.
... В ходе расчетов решали внутреннюю газодинамическую задачу движения газодисперсного потока в полости пылеулавливающего аппарата. Воздействие частиц пыли на воздушный поток не учитывали, так же как и в работах [12][13][14]. ...
A rotary dust collector has been developed that works on the principle of a centrifugal separator. A feature of its design is the presence of a bypass recirculation channel of cleaned air with a flow regulator, two outlet pipes with flow uncoilers in the form of spiral channels. The calculation of the motion of dust particles with a density of 3000 kg/m ³ and a diameter of 1 to 100 microns has been performed. Research has been carried out to improve the efficiency of the apparatus using a central compositional plan and to establish rational design and operating parameters of the mixer for recirculating and purified air.
... Формирование веерной струи снижает скорость взаимодействия с загруженным материалом, а следовательно, и пылеобразование при загрузке материала. На основании уравнений динамики воздушных потоков построены траектории пылевых частиц [5][6][7][8] при загрузке бункера с формированием веерной струи, характеризующие ее сепарационные особенности (рис. 3). ...
On the basis of the obtained analytical dependencies, the expediency of fan loading of bunkers with powdery bulk material has been proved. The design of an annular charging device, which reduces dust formation, using the Coanda effect is proposed. The rational design and technological parameters of the developed device are numerically and experimentally determined.
... The use of a system of aspiration and ventilation devices is a traditional approach to improve air quality [1,3,6,7]. Such systems include fans, air inlet and outlet devices, ventilation grilles, air heaters, air curtains, air ducts, various aspiration units, including dust collectors, cyclone dust collectors, ejector or jet venturi scrubber, etc. [8,9]. The characteristics of the components of such an aspiration and ventilation system, their spatial location and operating modes can significantly affect the air dynamics and the concentration of aerosols in different parts of the workshop, respectively [6,7,10]. ...
Our numerical models are aimed at solving the problems of industrial safety, labor protection and improving the efficiency of the ventilation and aspiration system at the design stage of an industrial facility. We are developing an approach for modeling the dynamics of air and pollutants based on Lagrangian smoothed particles, which allows solving the following three problems in a cross-cutting way. First, it is the construction of air velocity fields using the SPH method for the equations of gas dynamics. The second is the setting of boundary conditions on solid surfaces of complex geometry using a system of fixed smoothed particles. Finally, modeling the pollutants propagation is convenient on the basis of particles ensembles with appropriate characteristics both in the limit of a fine fraction or gaseous component and large dust grains whose velocity differs significantly from the air velocity. This end-to-end method is effective for parallelization on GPUs.
... In this case, the values of the local drag coefficients (LDC) ζ and the outlines of vortex zones (VZ) were determined ( fig. 2). The method for determining the LDC on the results of the numerical solution is described in detail in [24][25][26]. From the distribution of the stream function at the inlet and outlet boundaries, the values of the stream function corresponding to the free streamline are found, and so on, the outlines of the vortex zones. ...
Ventilation systems are characterized by a large waste of energy due to air movement through the channels duct fitting. There is an effective way to reduce such losses – shaping along the outlines of vortex zones. For this, it is first necessary to determine such outlines and their dependence on the design and operating parameters. For the duct fittings in the form of symmetrical junction tees, there is a design option with a baffle vane, which has a reduced resistance along one of the side branches. The article presents the results of computer simulation of the flow in such a tee. The most optimal dimensions of the partition, leading to the least resistance, have been determined. It is shown that a decrease in resistance along a branch with a lower flow rate occurs due to the ejection effect and an increase in resistance along the other branch – with a higher flow rate. The outlines of vortex zones have been determined, the size of which does not depend on the baffle size, that is, it is possible to use them for shaping both for tees with and without baffles.
... A combination of boundary integral equation (BIE) method and discrete vortex method (DVM) [11][12][13][14] was used for airflow simulation. With the BIE method, dummy sources (sinks) of intensity unknown beforehand were planned along the flow area boundary. ...
An intense dust emissions occur when bulk materials are unloaded by wagons into receiving cones of coarse crushing bodies (CCB). The most reliable, but energy-intensive way to localize dust emissions is the use of local exhaust ventilation systems. For the correct calculation of the performance of the exhaust ventilation system, it is necessary to determine the flow rate of air entrained in bulk material (flow rate of ejected air), which is the main source of dust emission distribution. The volume of air carried away by bulk material is determined based on the use of the classical theory of mechanics of two -component flows. Using the methods of boundary integral equations, a mathematical motion of the air flow in the cavity of the receiving cone of the CCB has been developed. A laboratory model of the CCB receiving cone was created, where the air flow carried away by the bulk material was modelled using a smoky jet flowing out of the supply nozzle. Based on the conducted computational and field experiments, the location of the local ventilation suction and mechanical screens are selected to increase the efficiency of local exhaust ventilation and reduce the energy consumption of the aspiration system.
... Note that these were plotted using findings from a numerical simulation carried out in a manner similar to the method described in [30]. Thus, for a straight pipe without a shaped hood, even though the vortex zone itself ended (section I, 0.73 < x/D < 0, the precise section boundaries determined by the method are described in detail in [32]), deformations still occur at a considerable distance (section II, 6.47 < x/D < 0.73). This is followed by a section (III, 12.28 < x/D < 6.47) of linear pressure drop caused exclusively by frictional forces. ...
... Further, even though the length of section II, where the inlet flow deformation is significant, is reduced considerably in the case of a shaped hood, it still exists. The lengths of these sections were determined by analyzing the change in the total pressure drop along the duct to determine the LDC values, as described in [32]. As determined by the numerical calculations, the LDC for a straight pipe was ζ = 0.961, which is only 4% from the known value for a freely positioned sink [6]. ...
... The exhaust devices discussed to date are of round and slotted [15,42] shapes and must be supplemented with square and rectangular [43] exhaust hoods, of which the vortex zone outlines are not yet determined based on the hood length and tilt angle. It is also necessary to determine the extent to which dust particle capture behavior around the exhaust hood [32,[44][45][46] is affected by shaping. The first attempt to determine the effects of shaping on the range of dust particle capture was made in a previous study of ours [47]. ...
In this study, we experimentally determined the local drag coefficient (LDC) of a round exhaust hood that was improved with different shaped inlet sections along the boundaries of the vortex zones occurring in the flow at the inlet of an exhaust hood. The LDC measurements were performed using two methods. The first method used a micromanometer and pneumometric tube to determine the LDC with and without considering frictional losses. Meanwhile, the second method determined the LDCs using the pressure and velocity distributions in the boundary layer with specially designed pressure miniprobes. The experimental and numerical results show that it is possible to achieve a drag reduction of more than 90% by shaping the inlet edges of the exhaust hood. This increases the range of contaminant capture, reduces noise, and prevents contaminants from escaping from the exhaust hood by eliminating the vortex zones and reducing the fan power.
... The characteristic parameter was LDC, and the mesh refinement control parameter was chosen to be either Ystar (y*) for SWF or Yplus (y+) for EWT [48]. LDCs for the flow bypassing the midpoint lateral orifice ζ P and the flow entering the orifice into the duct ζ O were determined following the method from [49], using the formulas: ...
This study is concerned with the development of an energy-efficient design of a duct fitting comprising a midpoint lateral exhaust orifice. This is an element often encountered in the practice of exhaust ventilation system design and engineering. A numerical study was performed to identify relationships between the drag of such an orifice and its dimensions and the ratio of the airflow entering the orifice and passing through the duct at the confluence, GO/GC. Findings are well supported by other authors’ data and by our own experimental study. For the first time, the outlines of a vortex zone occurring at the inlet of the flow have been identified and supported by experimental visualization. A relationship behind orifice dimensions and the flow rate of passing airflow has been determined. A geometric approximation has also been identified for the vortex zone, enabling outlines of any vortex zones to be traced out within the studied range of dimensions and GO/GC flow ratios. The discovered outlines have been used for an energy-efficient exhaust orifice design featuring reduced drag both for the airflow entering through and bypassing the orifice. A “one-type-fits-all” shape has been identified that minimizes drag over the entire variation range of the GO/GC ratio. Approximate formulas for all identified relationships have been derived and programmed into an online calculator to facilitate their use in the design of energy-efficient ventilation systems. By making the duct fitting energy-efficient, drag can be reduced by 20–400% compared to a standard design. Reduced pressure losses enable reduction both of power consumption and size/rating of ventilation units used in the system.
... Currently, people commonly use fume-cupboard dust exhaust hood (Candra, Pulung, and Sadashiv 2014;Cascetta and Rosano 2001;Chen 2018;Logachev, Ziganshin, and Averkova 2018;Zaripov, Gilfanov, and Maklakov 2010), semi-closed dust exhaust hood with blocking curtain (Betta et al. 2004;Deming 2015;Logachev, Ziganshin, and Averkova 2020) or spraying de-dusting (Zhou et al. 2019) to collect dust from open sources. Recently, Xiao et al. developed a dust-collecting device with square rotational air curtain and achieved a high dust-collecting efficiency of 92.6% (Xiao et al. 2020(Xiao et al. , 2019. ...
High-efficiency dust collection for open dust source has always been an important and difficult issue for air quality control at the workplace. This study performed simulations and experiments on three kinds of dust exhaust hoods, namely, updraft, side-draft and air-curtain exhaust hoods. Results show these three kinds of exhaust hoods varied significantly in dust-capturing efficiency. The dust-capturing efficiency of the updraft exhaust hood was the lowest (56.8%) while the air-curtain exhaust hood performed best in dust collection, with a dust-capturing efficiency of 93.8%. For a rectangular air-curtain exhaust hood with a size of 900 mm x 1200 mm, the dust-capturing efficiency first increased and gradually tended to stabilize with increasing air-curtain velocity and suction airflow rate. According to the present research results, the reasonable long-side air-curtain velocity and suction airflow rate were in the range 4 ~ 6.27 m/s and 5.4 ~ 9 m³/min, respectively. Under these conditions, dust-capturing efficiency can be as high as 79.6–86.5%.
Implications: This study performed simulations and experiments on three kinds of dust exhaust hoods: updraft, side-draft and air-curtain. Simulation results show the dust-capturing efficiency of the air-curtain exhaust hood is best of 93.8%. Experimental results show under reasonable conditions, the dust-capturing efficiency of a rectangular air-curtain exhaust hood is 79.6–86.5%. This research is very meaningful, which not only has important innovation in the study of micro mechanism of dust collectors but provides powerful theoretical and experimental support for technological innovation.
... There is a discussion of the effect the length and the flange tilt angle on the aspiration efficiency factor. Another paper [35] provides graphical plots showing the effect of dust particle terminal velocity, inflow velocity, suction velocity and hood tilt angle on the aspiration coefficient. The hood was placed horizontally i.e. with its symmetry axis parallel to the gravitational force vector. ...
... The reliability of the computational algorithm developed by us for plotting extreme trajectories of dust particles was demonstrated in the paper [35] concerned with the problem of determining the coefficient of aspiration for a circular exhaust inlet approached by incident airflow. ...
... Shaping this flange and the inlet opening of the hood will reduce noise and improve contaminant removal efficiency [36,37]. Our observations of dust particle behavior reported in this study differ considerably from past studies [3], [29][30][31][32] , [33][34][35] where the exhaust duct was set up vertically. ...
As a prerequisite for our goal of studying the entrainment of dust particles released by nail filing in nail salons we have identified their physical and mechanical properties that were previously unknown: density, particle-size distribution, dynamic shape coefficient and dust concentration in the manicurist's working zone. It was proven using a computational experiment a lateral exhaust would capture dust particles effectively. Using the discrete vortex method and numerical integration of the dust particle motion equation, a mathematical simulation was developed for the flow of dust-laden air around a flanged lateral hood. Relationships behind the dust particle capture range for an exhaust hood mounted on a horizontal table were identified in connection to the terminal velocity of dust particles, quantity and inclination angle of the initial escape velocity vector, velocity inside the duct, flange length, and duct inlet edge shaping along the identified vortex zone boundaries. Dust released by nail treatment can be trapped effectively with a tabletop-mounted lateral exhaust duct with a semicircular flange having a length of 2–4 times gauge (pipe radius). As a means of reducing drag, it is proposed to shape duct inlet edges along the identified boundaries of vortex zones occurring at duct inlet. For a local exhaust hood, such shaping will render the added benefit of reducing noise generated in vortex zones along with preventing contaminant release from these zones. Patterns in dust particle capture range identified by us can be used to determine the required performance of local exhaust ventilation.
