Rectangular Hopper Research Articles

Numerical study of granular discharge flows through centred and off-centred rectangular hoppers using discrete element simulations

Gravity-driven particle flow through outlets with inclined angles and outlets with off-centred positions is investigated numerically by discrete element simulations. The measured particle discharge rates are well fitted by Beverloo's law, demonstrating a fairly linear relationship with orifice size to a power 3/2. The impacts of the hopper angle and the eccentric position of the outlet on the particle velocity and orifice volume fraction distribution are systematically investigated. The particle velocity and volume fraction distributions for different hopper angles are found to exhibit self-similar features that are well described by a mixed parabolic and power law with fractional exponents. The coefficients involved in determining the particle velocity and volume fraction distribution have clear physical significance. In the case of hopper angles in the range of 55°- 90°, the values of these determining coefficients are quite similar at each angle, leading to identical discharge rates of particles. The predicted mass flow rate derived from the velocity and volume fraction curves is found to be in satisfactory agreement with that obtained in the experimental works of Mendez et al. (2021) and Darias et al. (2020). Regarding the hopper with an eccentrical outlet, an asymmetry behavior appears. Moreover, the outlet directly at a wall generates a significantly higher flow rate than other locations. In the end, an extension of the self-similarity laws is proposed to allow the prediction of granular discharge for the rectangular hopper, from the centred to the border outlet case.

Вплив забрудненості порошку на поріг протікання металокерамічних композитів, що отримуються на основі полідисперсних порошкових сумішей

A theoretical method of finding by simulation computer modeling the percolation limit of composites of powder origin, which are obtained on the basis of polydisperse powder mixtures of the conductive and insulating phase, is proposed. At the same time, the degradation of the conductivity of conductor particles skeleton due to oxidation or other contamination of the surface of the particles is taken into account. To study the flow threshold of materials obtained on the basis of polydisperse powder mixtures, the use of regular packings of particles, which are considered in the classic problems of perco¬lation theory, for example, square or hexagonal packing, is not acceptable even in the first approximation. Because in such packages all particles are the same, or the ratio of particle sizes is fixed. At the same time, as is known from the practice of obtaining metal-ceramic composites, the size distribution of conductor and insulator particles is one of the determining factors. Therefore, a generator of random filling of a polydisperse mixture of round particles into a rectangular hopper was developed using the Fortran programing language. The influence of the particle size ratio of the conductive and insulating phases and the relative contamination of the conductor particles on the percolation limit in the composite was studied. It is shown that in the case when the size of the conductor particles decreases in relation to the size of the insulator particles, the value of the percolation limit decreases, that is, conductivity can be achieved even with asmall content of the conductive phase. In this way, the conductivity of the metal-ceramic composite can be controlled without changing the concentration of the conductive phase, but only by varying the size of the metal and ceramic particles. But as the simulation results showed, this method of controlling the conductivity is very sensitive to the oxidation of the metal powder. Even a relative oxidation of the powder surface of 0,1 doubles the concentration of the metal phase required for percolation. Keywords:bidisperse packaging, percolation limit, ballistic filling, metal-ceramic composites, oxidized metal powders.

Investigation of the Main Stages in Modeling Spherical Particles of Inhomogeneous Materials

This scientific study deals with the main issues related to the process of filling inhomogeneous materials into a rectangular hopper. The article develops an algorithm for filling particles of structurally inhomogeneous materials. A micrograph of the structure of samples of inhomogeneous materials is presented. It was found that the structure of samples of heterogeneous materials consists of three layers: external, internal and impurities of various grinding aggregates. Based on microstructural analysis, the presence of particles of various shapes and sizes was justified. On the basis of which the main initial conditions for filling the package with spherical particles were described. The basic physical and mechanical properties of structurally inhomogeneous materials were studied using the obtained results. We also constructed an approximate dependence of porosity on the particle diameter of inhomogeneous materials.

Automatically Controlled Dust Generation System Using Arduino.

A dust generator was developed to disperse and maintain a desired concentration of airborne dust in a controlled environment chamber to study poultry physiological response to sustained elevated levels of particulate matter. The goal was to maintain an indicated PM10 concentration of 50 µg/m3 of airborne dust in a 3.7 m × 4.3 m × 2.4 m (12 ft × 14 ft × 8 ft) controlled environment chamber. The chamber had a 1.5 m3/s (3200 cfm) filtered recirculation air handling system that regulated indoor temperature levels and a 0.06 m3/s (130 cfm) exhaust fan that exchanged indoor air for fresh outdoor air. Dry powdered red oak wood dust that passed through an 80-mesh screen cloth was used for the experiment. The dust generator metered dust from a rectangular feed hopper with a flat bottom belt to a 0.02 m3/s (46 cfm) centrifugal blower. A vibratory motor attached to the hopper ran only when the belt was operated to prevent bridging of powdered materials and to provide an even material feed rate. A laser particle counter was used to measure the concentration of airborne dust and provided feedback to an Arduino-based control system that operated the dust generator. The dust generator was operated using a duty cycle of one second on for every five seconds off to allow time for dispersed dust to mix with chamber air and reach the laser particle counter. The control system maintained an airborne PM10 dust concentration of 54.92 ± 6.42 µg/m3 in the controlled environment chamber during six weeks of continuous operation using red oak wood dust. An advantage of the automatically controlled dust generator was that it continued to operate to reach the setpoint concentration in response to changes in material flow due to humidity, partial blockages, and non-uniform composition of the material being dispersed. Challenges included dust being trapped by the recirculation filter and the exhaust fan removing airborne dust from the environmental chamber.

Discharge Characteristics of Different Shaped Particles from an Inclined Bottom Rectangular Hopper

In order to further explore the discharge characteristics of different shaped particles from the inclined bottom hopper, the discharge of four shaped particles from an inclined bottom rectangular hopper was studied based on the discrete element method (DEM). Non-spherical particles were established based on the multi-spheres method. The effects of geometric parameters, particle properties, and interaction parameters on discharge were investigated. Some interesting results have been found that regular spherical particles are more easily discharged from the hopper, and the time required to empty the hopper is the shortest. The influence of particle shape on discharge takes precedence over that of solid fraction. Both the critical angle (55°) and the correlation between the 2/3 power of the mass discharge rate and the orifice width are independent of the particle shape. Blockage occurs as the angle and/or the ratio of particle size to orifice width increases. The dihedral angle is the key factor affecting the blockage. Compared with spherical particles, non-spherical particles are more prone to blockage and have stronger blockage strength.

Rancang bangun dan uji performansi mesin pencampur beberuk, makanan khas Lombok

During this time the process of making beberuk was still done traditionally using a mortar as a mixer, so that production is very limited, while the market demand is quite high. To increase productivity, it is necessary to design a machine that can increase the production capacity of the beberuk. The research method begins with the mixing machine design process, then continues with the assembly process and engine performance test. The design of the mixing machine is done with two approaches namely functional approach and structural approach. Test engine performance on 3 power variations namely 144, 168, and 192 watts and 3-time variations namely 30, 45, and 60 seconds. The results showed that the cylindrical mixing chamber has a diameter of 20 cm and a height of 50 cm. The mixing tube has a rectangular hopper with dimensions of 37 cm long and 9 cm wide. Engine performance test results showed the best results on 168 watts of power treatment and 30 seconds with the results of mixing not bubbly and still looks tomato chunks and is not too smooth according to the standard beberuk food.

Local Percolation of a Binary Particle Mixture in a Rectangular Hopper with Inclined Bottom during Discharging.

To reveal the local percolation characteristics of a binary particle mixture in a rectangular hopper with inclined bottom, the discrete element method (DEM) is used to simulate the discharging process. A local percolation evaluation method is proposed, and the percolation strength grid maps are drawn. The effects of geometric parameters, particle properties, and interaction parameters on percolation are investigated. Apart from the free surface, percolation is mainly concentrated near the wall and at the bottom. With the increase in the orifice width, the average local percolation strength index (ALPSI) of the near-wall region increases and that of the bottom region decreases. The effect of the angle on percolation in the near-wall region can be ignored. The effect of friction on local percolation is significant. Increasing the fine particle mass fraction and reducing the difference in particle size can effectively avoid percolation.

DEM study on the effects of pellet characteristics on particle flow in rectangular hopper

In this work, a non-cohesive and multi-element particle model of discrete element method (DEM) was constructed, which was used in combination with experiments to investigate the particle flow characteristics in retangular hopper equipped with the screw discharging machine. On this basis, different diameter pellets (dp = 20 mm, 25.02 mm) with various sphericities (φ = 0.868, 0.985, 1) and particle size distribution (a = 0:1, 0.1:0.9, 0.15:0.85, 0.2:0.8) were selected to examine the effects of sphericity and particle size distribution on the distribution of particle average velocity, motion distance and voidage. Our results showed that as the a increased, the particle average vertical velocity was first decreased and then increased. The motion distance of particles at 1/2 bed height was relatively stable. Furthermore, the average voidage of cylindrical particles was the largest and that of ellipsoidal particles was the smallest. Finally, the specific position of the lag of particle motion is revealed.

Discharge characteristics of binary particles in a rectangular hopper with inclined bottom

The stable discharge of particles through the hopper plays a key role in many industrial applications. In order to investigate the discharge characteristics of binary particles in a rectangular hopper with an inclined bottom, the discrete element method (DEM) was used to simulate the discharge process. The accuracy of DEM was validated by comparing calculated and experimental values. The influences of geometric parameters (hopper width, orifice width, and hopper angle) and particle parameters (friction coefficient between particles, friction coefficient between particles and wall, fine particle mass fraction, and particle size ratio) on the discharge were studied. Some interesting results have been found that the effect of hopper width on discharge is minimal. The mass discharge rate is linearly related to the 3/2 power of orifice width, and it can be predicted by the modified Beverloo correlation which developed for a rectangular hopper with flat bottom. The mass discharge rate increases exponentially with the decrease in hopper angle, which is different from that of monosized particles. The mass discharge rate is more sensitive to low friction coefficient, and the friction coefficient between particles plays a leading role. Fine particles can promote the discharge process, and this effect is enhanced as particle size ratio increases.

Hopper discharge of elongated particles of varying aspect ratio: Experiments and DEM simulations

Steady flow of particulate or granular materials and bulk solids through a hopper plays a critical role in many industrial and process engineering applications. The present work investigates hopper discharge of non-spherical particles, specifically cylindrical particles, from a rectangular hopper. The behavior of steel cylindrical particles with varying aspect ratio (both varying diameter with constant length and varying length with constant diameter) was explored experimentally and via DEM simulations. In addition, the effects of fill height, particle friction, hopper orifice width and hopper cone angle on hopper discharge rate of non-spherical particles were studied via DEM simulations and compared with previously published experimental correlations, experimental results of spherical particles. The results indicate that DEM simulations are fully capable of reproducing trends that are established experimentally. The results with particles of high aspect ratio indicate a different trend than that previously observed with rounded particles. As the fill height increases, the mass discharge rate increases and then asymptotes; further increases in fill height cause a decrease in the mass discharge rate. Further, the effect of particle friction showed a significant influence on the hopper discharge behavior. In addition, a decrease in the hopper angle from 90 degree to critical angle 55 degree decreases the mass discharge rate flow and further decrease in hopper angle increases the discharge rate rapidly.

Dependence of wall stress ratio on wall friction coefficient during the discharging of a 3D rectangular hopper

Discharging of a 3D rectangular hopper is simulated by Discrete Element Method (DEM) to understand the influence of wall friction on wall stress ratio. The role of the side and face walls in supporting the particle load by friction is interpreted by force network analysis. With the increase of wall friction coefficient, the relative density of the force chains attaching the walls increases, which enhances the contribution of the walls to supporting the particle load. The enhanced supporting of one wall due to wall friction will weaken the supporting of its neighboring wall. However, the formed force chains attaching one wall will exert normal stress on its neighboring wall. When the wall friction coefficient is large enough, the strength of the relative strong force chains attaching the walls eventually relies on the internal friction coefficient and the length of the hopper along the normal direction of the walls, making the wall stress ratio less sensitive to wall friction coefficient. The wall stress ratio is predicted with Walker's model, in which the effective internal friction angle is replaced by a modified effective internal friction angle to relate to the wall and internal friction coefficients. The prediction is more accurate than with the assumption of critical equilibrium state.

A study on the influence of particle shape on the mechanical interactions of granular media in a hopper using the Discrete Element Method

In this study experimental and numerical investigations with the Discrete Element Method (DEM) on the mechanical interactions of particles with varying sphericity and aspect ratio in a rectangular hopper are conducted. In the DEM the test particles are approximated by four commonly used approximation schemes.A decrease of particle sphericity or an increase of the aspect ratio results in an more uneven, intermittend particle flow and overall lower discharge rate. It was deducted from the measurement results that changing these geometric particle properties elevates the shear strength of the particle bed and, hence, has a significant influence on the discharge properties of a hopper.Simulation results are in good general agreement with the experiments and thus demonstrate the adequacy of the DEM to predict the mechanical interactions in granular media consisting of non-spherical particles. The results presented in this study show only a minor influence of the method used to approximate particle shape within the DEM. Obviously the discharge characteristics are much stronger related to macroscopic geometric parameters than the fine scale resolution of particle geometry.

Experimental Study of Wet Cohesive Particles Discharging from a Rectangular Hopper

The present work investigates discharge phenomenon for wet cohesive particles from a rectangular hopper. Three specific characteristic of the hopper flow are investigated: discharge rate, angle of repose of the material, and size of clumps formed during the discharge. These characteristics are compared to predictions from previously published Discrete Element Method (DEM) simulations. The primary objective of this work is simulation validation. The current experimental results agree well with previous simulation results. Generally, as cohesion increases, the discharge rate decreases, the angle of repose increases, and the size of the clumps increases.

Polyhedral Particles Hopper Flowrate Predictions using Discrete Element Method

Discrete, or Distinct, element modelling, DEM, is used to investigate the effect of particle shape on hopper flowrate. Firstly, simulation results using a model based on spherical particles are validated against solid discharge rates predicted by the modified Beverloo equation. The validated model is then used to investigate the shape effects on discharge rate from a flat bottomed rectangular hopper. Two regular rounded polyhedral particles are studied. The discharge rate varies significantly with particle shape. A reduction on flowrate of up to 49% and 41% is observed for tetrahedral and octahedral particles, respectively. The effects of friction, cohesion, and damping on flowrate are also investigated with DEM.

Flow Behaviors of Non-spherical Granules in Rectangular Hopper

Flow behaviors of four kinds of granular particles ( i. e. sphere, ellipsoid, hexahedron and binary mixture of sphere and hexahedron) in rectangular hoppers were experimentally studied. The effects of granular shape and hopper structure on flow pattern, discharge fraction, mean particle residence time and tracer concentration distribution were tested based on the visual observation and particle tracer technique. The results show that particle shape affects significantly the flow pattern. The flow patterns of sphere, ellipsoid and binary mixture are all parabolic shape, and the flow pattern shows no significant difference with the change of wedge angle. The flowing zone becomes more sharp-angled with the increasing outlet size. The flow pattern of hexahedron is featured with straight lines. The discharge rates are in increasing order from hexahedron, sphere, binary mixture to ellipsoid. The discharge rate also increases with the wedge angle and outlet size. The mean particle residence time becomes shorter when the outlet size increases. The difference of mean particle residence time between the maximum and minimum values decreases as the wedge angle increases. The residence time of hexahedron is the shortest. The tracer concentration distribution of hexahedron at any height is more uniform than that of binary mixture. The tracer concentration of sphere in the middle is lower than that near the wall, and the contrary tendency is found for ellipsoid particles.

Discrete element method modeling of corn-shaped particle flow in rectangular hopper

Discrete element method (DEM) was developed to simulate the corn-shaped particles flow in the hopper. The corn-shaped particle was described by four overlapping spheres. Contact force and gravity force were considered when establishing the model. In addition, flowing characteristic of particles in the hopper was studied. The effect of friction coefficient on the wall pressure, voidage and velocity distribution was analyzed. The results show that the discharge rate decreases with the friction coefficient increasing; and the “over-pressure” phenomenon occurs in the discharging process for two different friction coefficients. The voidage also increases as the friction coefficient increasing. And the velocity distribution is more uniformity and is closer to the mass flow with the friction coefficient deceasing.

Segregation of cohesive granular materials during discharge from a rectangular hopper

Granular materials may readily segregate due to differences in particle properties such as size, shape, and density. Segregation is common in industrial processes involving granular materials and can occur even after a material has been uniformly blended. The specific objective of this work is to investigate via simulation the effect of particle cohesion due to liquid bridging on particle segregation. Specifically, a bi-disperse granular material flowing from a 3-D hopper is simulated using the discrete element method (DEM) for cohesive particles and the extent of discharge segregation is characterized over time. The cohesion between the particles is described by a pendular liquid bridge force model and the strength of the cohesive bond is characterized by the Bond number determined with respect to the smaller particle species. As the Bond number of the system increases, the extent of discharge segregation in the system decreases. A critical value of Bo = 1 is identified as the condition where the primary mechanism of segregation in the cohesionless hopper system, i.e. gravity-induced percolation, is essentially eliminated due to the liquid bridges between particles.

Discrete element method modeling of non-spherical granular flow in rectangular hopper

Discrete element method (DEM) was developed to simulate the corn-shaped particles flow in the hopper. The corn-shaped particle was described by four overlapping spheres. Contact force and gravity force were considered when establishing the model. In addition, the velocity distribution and voidage variance of corn-shaped and spherical particles were investigated. The results show that the vertical velocity difference between centre and side wall and the horizontal velocity of corn-shaped particles are relatively larger than that of spherical particles. The mean voidage for corn-shaped particles is smaller than for spherical particles in any hopper. And the mean voidage values decrease with the increase of the ratio of width and length ( D/ L) and the ratio of height and width ( H/ D) for both corn-shaped and spherical particles. The local voidage profiles in hoppers with different D/ L were also studied. It demonstrates that the wall effect on the voidage of spherical particles is more remarkable than that of the corn-shaped particles. The voidage fluctuations of corn-shaped and spherical particles decrease obviously with increasing D/ L when the particles are far away from the wall. And when the particles are discharging, the wall effect on the spherical particles is more remarkable than the condition of packing naturally.

A study on adjusted contact force laws for accelerated large scale discrete element simulations

The aim of this work is to systematically investigate the effect of the normal force law and the applied stiffness on the behavior of single particles and particle systems. A detailed review of the literature regarding altered stiffnesses and their use in force laws is provided. The effect on macroscopic simulation properties such as contact numbers, velocity profiles, discharge rates and quality of dispersion for different fractions of maximum overlap is studied in the case of a stirrer vessel and a rectangular hopper. In order to provide further acceleration beyond the limits imposed by classical force models, a number of alternative force laws are developed which have a more favorable ratio between contact time and maximal overlap. Their employment in large scale simulations is investigated in light of their applicability. Some of the suggested force law modifications reveal artificial characteristics requiring further alteration.

Predicting discharge dynamics of wet cohesive particles from a rectangular hopper using the discrete element method (DEM)

Accurate prediction of the discharge rate from hoppers is important in many industrial processes involving the handling of granular materials. The present work investigates the parameters affecting the discharge rate of a wet cohesive system from a quasi-3-D, rectangular hopper using the discrete element method (DEM). The cohesion between the particles is described by a pendular liquid bridge force model and the strength of the cohesive bond is characterized by a Bond number. The Beverloo correlation is applied to cohesive systems by modifying the Beverloo constant as a function of Bond number. The predictions obtained from this modified correlation fit the simulation data reasonably well. In addition, the effect of hopper angle in cohesive systems is shown to follow a trend similar to cohesionless systems, where the discharge rate is insensitive to changes in hopper angle except below a critical angle (with respect to the vertical) where the discharge rate increases rapidly. This critical angle of flow decreases with increasing cohesion.