Ejection of air by the stream of bulk materials in a vertical perforated channel

Were obtained and solved the hydrodynamic equations for estimating intercomponent communication in a vertical perforated chute when moving there gravitational flows of granular materials and ejected air. Identified parameters that provide the greatest decrease in volumes of ejection through recycling air. The research is being supported by the Council for Grants of the President of the Russian Federation (projects NSH-588.2012.8), RFBR (project number 12-08-97500-p_center_a), and Strategic Development Plan of BSTU named after. V. G. Shukhov

Peculiarities of air entrainment with a loose material flow at the variable aerodynamic resistance of falling particles

Gravity flows of loose-matter particles are accompanied with aerodynamic forces that produce ejection of air in the loading and unloading chutes. A flow of loose matter acts like a blower. Head created by this blower (which we choose to call ejection head) comprises a sum total of aerodynamic forces of falling particles divided by cross-sectional area of the flow [1]. Flows of loose material in loading and unloading chutes that arise during operation of high-performance bucket elevators feature elevated volumetric concentrations as high as β0.01y. Estimates of air ejection caused by such flows should be based upon instantaneous rather than averaged aerodynamic drag coefficient ψy. Within the range of significant volumetric concentrations, varying volumetric concentration of falling particles leads to fluctuations in instantaneous values of the coefficient ψ. These fluctuations cause the ejection head, even in the case of short chutes, to significantly diverge from the head determined using averaged coefficient ψy. In order to compute ejection heads inside loading and unloading chutes, it is necessary to introduce an adjustment coefficient K (K is the ratio of the true value of ejection head in an inclined chute to the mean value of this pressure ) the value of which will noticeably diverge from one at small initial velocities of particle flow. It is possible to view flows of particles in chutes at 0.1В(B is the ratio of the average coefficient of drag encountered by a falling particle to the drag coefficient of an individual particle in the self-similarity area) as blowers with a performance curve determined with formula 330113ekkQQpQKznSvSv(Q is the volumetric flow rate of air ejected through the loading chute of the elevator, z is a relative velocity of particles in a pipe, defined as the difference vu,v is the velocity of falling particles, u is the velocity of ejected air, ,nkvvis the fall velocity of particles at outlet of the chute, /nknvv, S is the cross-sectional area of the chute) in view of the resulting coefficient 0K(0K is the ratio K absent ejection airflow). 636 For a flow of wheat (3ed mm) within the ranges 0.5nand β0.001y, increasing drag coefficient along the fall height is only able to produce negligibly small changes in the intensity of ejection head. The adjustment coefficient may be dispensed with (01KK), and head value will then be determined using formula 333τψε1φφ23ymmkeyKnGvPSa (.mGis mass flow rate of the material, τa is the acceleration which, for chutes installed at an angle to horizontal surface,ε is the ratio of air density to particle density, φ is ejection coefficient)

Basic regularities of ejection air by flow of freely falling particles

Entrained air (ejection process) by flow of freely falling particles of the bulk material is considered by us from the position of the classical laws of dynamics of twocomponent streams "particulate matter - the air." The nature of this process is determined by the volumetric intercomponent interaction, detected as a result of excessive speed over the speed of the incident particles of ejected air. The research is being supported by the Council for Grants of the President of the Russian Federation (projects NSH-588.2012.8), RFBR (project number 12-08-97500-p_center_a), and Strategic Development Plan of BSTU named after. V. G. Shukhov

Aerodynamic properties of particles in the gravitational flow of a chuted bulk material

Chutes are a linking element of transportation lines used for transfers of reprocessed materials from one transporting group or equipment to another. The mode of the chuted material motion and the nature of the associated aerodynamic processes are determined by the aggregate physical and mechanical properties of the material being transferred and structural design of chutes. Structurally chutes are subdivided into prismatic, cylindrical and pyramid-shaped (bin) chutes by shape and into vertical, tip and kinked chutes by the bottom slope angle. The most common in practice are tip chutes of a prismatic or a pyramid shape. The purpose of this work was the study of particle movement of granular materials in the sloping chute. In the result of the research, we revealed the following

The aerodynamics of a jet of particles in a channel

The main cause for dust discharge is ejection, i.e. formation of directional air flows in a stream of a bulk material due to the dynamic interaction of bombarding particles with air. Discovery of induced air flow occurrence regularities enables both forecasting the level of air pollutions with aerosol emission and choosing the optimum engineering solutions of air containment and dedusting. So far we have studied solid particles flowing in a chute and a jet of loose matter. Both situations represent extreme cases of the more general problem of material flowing through a duct with different distances between flow boundaries and duct walls. Without detriment to generality of the problem we shall consider a flat flow limited by vertical walls

Ejecting properties of a bucket elevator

Air inside the enclosure of a belt elevator may be brought into motion both by moving bucket belt and by spillage flows during loading and unloading of buckets. Initial findings from studies performed to evaluate air motion in ducts with mobile partitions have been published in our earlier monographs [1-3]. Here we’ll consider the process of air ejection in bucket elevators from the standpoint of classical laws of change in air mass and momentum. Direction of airflow inside enclosures of the carrying and return runs of a bucket elevator is determined by the drag of buckets and moving conveyor belt as well as ejection head created by a stream of spilled particles when buckets are unloaded. As a result of these forces acting together inside an enclosure, differential pressure arises. This differential pressure is equal to the sum total of ejection heads created by conveyor belt with buckets k E and flow rate of spilled material p E minus aerodynamic drag of enclosure walls. The ejection head k E created by a bucket-carrying conveyor belt is determined by aerodynamic coefficient ek с (proportional to the number of buckets, their head resistances and squared mid-sectional dimensions) together with an absolute value and the direction of bucket velocity relative to the velocity of airflow inside the enclosure. Ejection head of spilled particles p E depends on the drag coefficient of particles, their size and flow rate, as well as the enclosure length, enclosure cross-section and relative flow velocity of particles. When both the carrying and return runs of the conveyor belt are located in a common enclosure, the velocity of forward airflow varies over its length as a result of cross-flows of air through gaps between the conveyor runs and enclosure walls. Cross-flows are caused by a differential pressure between the carrying and return run enclosures and is dependent on the drag of the gap. Cross-flow direction depends on the ratio between v p and u p . Given identical size of elevator enclosures, change in absolute values of longitudinal velocities is identical and depends on absolute values of cross-flow velocities and geometrical dimensions of the gap, as well as enclosure cross-section. The momentum of longitudinal airflow in this case is determined by variable magnitudes of aerodynamic forces of buckets due to changes in their relative motion velocities. The flow rate of air in enclosures may be determined by numerically integrating three dimensionless combined differential equations

Cross-flow of air through sealed elevator enclosures

Both the direction and the flow rate of ejected air in bucket elevator [1,2] enclosures that feature a separate arrangement of carrying and idle conveyor runs would depend on the ratio between ejection heads and the difference between static pressures inside the enclosures of elevator head and elevator boot. A forward motion of air (along the bucket travel direction) arises inside the enclosure of the carrying run when ejection forces prevail and inside the return run enclosure at any ejection forces differential pressures. A counterflow of air is only possible in a single enclosure. Relative velocities and flow rates of air inside the elevator enclosures depend on two parameters, t and g, representing the ratio of differential pressures and resistances of enclosures to ejection forces. When pressures inside the upper and lower elevator enclosures are equal. With ejection forces large enough air velocities become equal to the velocity of traveling elevator buckets. Absolute velocities of airflows inside enclosures are dependent not only on the velocity of moving buckets but also on the differential pressure, head resistance of elevator buckets and aerodynamic drag of enclosures, as well as spillage of particles. In the case of a forward flow pattern, air flow rate inside the return run enclosure is greater than the one inside the carrying run enclosure of the elevator conveyor. The explanation is that ejection forces arise in an opposite direction to forces caused by differential pressure inside the carrying run enclosure (both forces act in the same direction inside the return run, thus intensifying the air ejection process and boosting additional ejection forces which occur when buckets are unloaded, producing streams of spilled particles), as well as different values of the drag coefficient for empty and laden buckets. When air moves in a counterflow pattern, ejection forces of buckets create additional drag and therefore the absolute flow rate of ascending air inside the return run enclosure, as well as descending air inside the carrying run enclosure, increase less markedly than in the forward flow case

Variations of cosmic rays according to the data of interplanetary probes Zond-3 and Venus-2

Cosmic ray intensity variation measured by Zond 3 and Venus 2 interplanetary probe

Radial diffusion of electrons with energy greater than 100 keV in the outer radiation belt

Electron diffusion and intensity variations in outer radiation bel