Discrete element model and structure of logistics bulk material transshipment transmission system

Abstract

According to the discrete element model and structure of the logistics bulk material transshipment transmission system, a discrete element method is introduced to research the movement process of the particle flow in the material belt type conveyor transshipment system, and visualization of the material transshipment process is achieved. Three working parameters of flow, granularity and belt speed are changed, and the influence of the three parameters on the flowing stability and abrasion condition of materials in the transfer system is judged through contrastive analysis. Transfer systems of the stepped striker plate and the arc-shaped striker plate are simulated respectively, when the arc-shaped plate is selected, material flow centering performance is good, a conveying belt is not prone to deviation, flowing stability is high, and the probability of material spilling and material leakage is low. The chute structure is optimized, the geometric dimensions of all the sections of the chute are determined, the values of the inclination angle and the arc radius of the chute inlet of the structural form are finally obtained according to the minimum abrasion loss, a set of transfer system reliable in work and efficient in transportation is designed, and the problems of material blockage and leakage, serious impact abrasion, large vibration noise, much raised dust and the like are solved.

Description

Technical Field

[0001] The present application relates to a model and structure of a logistics bulk material transfer system, in particular to a discrete element model and structure of a logistics bulk material transfer and transportation system, and belongs to the technical field of logistics material transportation model structures. Background Art

[0002] Logistics conveyor transfer systems are widely used in various bulk material conveying systems in industries such as coal, electricity, metallurgy, chemical industry, medicine, food, and ports. As one of the key conveying devices, belt conveyors need to control and connect the conveying direction of materials in multiple places. Therefore, the quality of its transfer system directly affects the working performance of the belt conveyor. A belt conveyor, also known as a belt machine, can achieve long-distance, large-capacity, automated, and high-speed transportation of objects or powdery and granular materials. It can not only complete the conveying within workshops and enterprises, but even gradually develop into the material handling between enterprises and between cities, becoming an indispensable part of the mechanization and automation of the material conveying system. Belt conveyors have the advantages of low power consumption, simple structure, convenient maintenance, low cost, strong versatility, etc., and operate smoothly and reliably, with flexible conveying lines, and can complete horizontal or inclined conveying operations. Therefore, it can bring good working and economic benefits to production practice. Currently, higher requirements are also put forward for the conveying system. The transfer system is an important part of the belt conveyor and also needs to continuously improve and perfect itself to overcome the faults that are prone to occur during actual use in order to play a greater role in industrial transportation.

[0003] To meet production operations, it is necessary to arrange multiple conveying operation lines at different heights or angles through a combination of multiple conveyors, and corresponding transfer devices are often designed at the transfer points to control the trajectory of material movement. The relative positions of the upper-level conveyor belt and the lower-level conveyor belt are in a relationship of spatial intersection or parallelism. During the process of material transfer and falling, its potential energy, speed, and direction are constantly changing, and the movement trajectory of the material, the impact force of the material on the conveying cover or chute, and the position where the material falls on the lower-level conveyor belt also change accordingly. In the past, qualitative analysis of the above changes was carried out manually or using empirical formulas, which was neither accurate nor time-consuming.

[0004] In recent years, the transportation conditions of large flow rate, high belt speed, and long distance have become the development direction of conveyors. The transfer system thus also faces great challenges. The transfer systems designed based on experience in the past can no longer meet the normal working needs. In order to ensure the smooth progress of the material transfer process, it is particularly important to reasonably design a reliable and efficient transfer system at each transfer point. Analyzing the flow behavior and wear problems during the material transfer process is the focus of current belt conveyor system research.

[0005] The problems that need to be solved by the existing bulk material transfer system model and structure and the key technical difficulties of this application include:

[0006] (1) When bulk materials are transferred, there are many unstable factors, such as the material throwing trajectory problem. Due to the influence of many properties such as particle material, particle shape, particle size, viscosity, conveying flow rate, etc., the interaction between particles and between particles and the external environment is very complex, making the movement of particles difficult to determine. The existing technology cannot well constrain the movement trajectory of the material transfer process, affecting the stability of material flow, and it is easy to cause material spillage and blockage. At the same time, the energy of particles with a certain initial velocity is constantly changing under the action of gravity, collision, friction, impact, inertia, etc., and may be a large mutation, which poses a challenge to the bearing capacity of the conveying equipment. These problems make the transfer part the weakest link in the belt conveyor system. The existing technology mostly relies on the experience accumulated in engineering practice to design the transfer system. Problems such as blockage and leakage, severe impact wear, high vibration and noise, and high dust have not been properly solved, resulting in a short equipment life, frequent maintenance, and environmental pollution, which restricts the improvement of production efficiency and economic benefits and brings troubles to the development of industrial and mining enterprises. The existing technology lacks a complete and systematic design method from theory to experiment to solve the problems currently suffered by the belt conveyor transfer system.

[0007] (2) The chute is crucial to the life of the receiving conveyor and is the key part and weak link of the transfer system. However, when used in occasions with relatively large conveying volumes, the chute is prone to failure, which is a difficult problem that needs to be solved urgently in bulk material transportation equipment. Unreasonable chute design leads to material blockage, easy generation of more dust, serious chute wear, wear of the receiving belt, deviation, and serious damage to the support and mixing. The above problems are first of all the unreasonable shape of the chute, which leads to greater resistance when the material slides in the chute, thus generating greater friction. Secondly, when the material falls on the conveyor belt, the angle between its speed and the running direction of the conveyor belt is too large, and it directly collides with the conveyor belt, thus generating a greater impact force. Finally, the material falling speed along the running direction of the conveyor belt is greatly different from the belt speed. Whether the falling speed is greater than or less than the belt speed, a relative movement will be generated due to friction, which will aggravate the wear of the belt surface. The difficulty of chute design lies in reducing the transfer drop of the chute. The chute line should be arranged short and with fewer bends; removable lining plates should be added to the bottom and sides of the chute to increase its wear resistance. Use a reasonable chute shape to avoid material blockage. Minimize the angle between the material speed at the impact point and the chute surface; minimize the inclination angle at the end of the chute while ensuring smooth material flow, and make the material speed at the outlet close to the belt speed; keep the material speed stable when sliding in the chute without sudden changes.

[0008] (3) The design and operation of the transfer system face the following problems: targeted non-standard design for different conveyor belt layouts, characteristics of different materials, conveying flow rates, conveyor powers and other working parameters; controlling the diversion and collection processes of materials. When unloading materials, it is necessary to ensure that the materials do not directly impact the next conveyor belt vertically after leaving the upper conveyor belt, but must slide along the chute into the conveyor belt after a certain turn; ensuring smooth flow of materials during the transfer process without blockage or spillage; since the velocity direction of the materials deflects, part of the kinetic energy is lost, and the gravitational potential energy of the materials caused by the transfer height difference continuously increases. This energy change will impact and wear the transfer system, seriously affecting the equipment life and also causing problems such as machine vibration and noise; it is also necessary to consider the formation of induced wind in the system and suppress dust generation. The design concept of the prior art severely impacts the baffle, chute, and buffer air-lock, reducing the equipment life. At the same time, it results in poor sealing effect of the material guide trough system at the material dropping point and serious powder leakage; the impact between scattered materials and the impact between materials and the plate chute cause material leakage and serious dust emission, forming a harsh working condition at the transfer point. Uneven material receiving on the conveyor belt at the material dropping point causes belt deviation, resulting in belt wear and tear. The dust removal equipment has frequent failures and high operation and maintenance costs. Frequent gantry flushing wastes water resources. When conveying materials with high water content, the chute of the prior art design is severely blocked, greatly restricting the conveying efficiency of the system. The transfer system has serious problems such as leakage, deviation, dust emission, and blockage in engineering practice.

[0009] (4) The relative positions of the upper and lower conveyor belts of the transfer device are in a spatially staggered or parallel relationship. During the falling process of material transfer, its potential energy, velocity, and direction are constantly changing, and the movement trajectory of the material, the impact force of the material on the conveying cover or chute, and the position where the material falls on the lower conveyor belt also change accordingly. The prior art uses manual or empirical formula for qualitative analysis of the above changes, which is neither accurate nor time-consuming. It can no longer adapt to the current transportation conditions of large flow rate, high belt speed, and long distance. The transfer system also faces great challenges. The transfer system designed according to experience can no longer meet the normal working needs. To ensure the smooth progress of the material transfer process, it is urgent to analyze the flow behavior and wear problems during the material transfer process and reasonably design a reliable and efficient transfer system at each transfer point. Summary of the Invention

[0010] This application uses the discrete element method to study the movement process of particle flow in the material belt conveyor transfer system, and realizes the visualization of the material transfer process. By changing the three working parameters of flow rate, particle size and belt speed, the speed distribution and impact force of material transfer under different levels of each parameter are simulated, and the influence of the three parameters on the stability of material flow and wear in the transfer system is judged by comparative analysis. The transfer systems of the stepped baffle plate and the arc baffle plate are simulated respectively. When the arc plate is selected, the material flow is better in neutrality, it is not easy to make the conveyor belt deviate, the flow stability is strong, and the probability of spilling and leaking is low. Optimize the chute structure. First, analyze that the combination of arc segment and straight segment has better force and can reduce the spatial size of the chute. Then further determine the geometric dimensions of each section of the chute, obtain the material flow rate through discrete element simulation experiments, substitute it into the formula to calculate the wear of the chute and conveyor belt, and finally obtain the value of the inlet inclination angle and arc radius of the chute of this structure according to the minimum wear, which also conforms to the simulation results of energy loss. A set of reliable and efficient transfer systems has been rationally designed at each transfer point to ensure the smooth progress of the material transfer process and solve problems such as blockage and leakage, severe impact and wear, loud vibration and noise, and excessive dust.

[0011] In order to achieve the above technical effects, the technical solutions adopted in this application are as follows:

[0012] The discrete element model and structure of the bulk material transfer and transmission system of logistics are optimized, and the particle size, flow rate and belt speed model closely related to the operation of the transfer system are established. The reference value of the system parameters and the horizontal level index factors are set, and the influence of the change of each factor on the speed distribution of the transferred materials and the impact force on the system is investigated. The conclusion is:

[0013] Conclusion 1: The change of particle size causes the fluctuation of the average material speed. When the particle size exceeds 32mm, the material flow stability is poor, the trajectory is scattered, and it is easy to spill or leak. In addition, the 40mm particle has the greatest impact on the system, and the plate wall or belt is more likely to be penetrated by the particle. In the design, the corresponding lining structure should be set according to the maximum impact point position simulated by the discrete element method.

[0014] Conclusion 2: Under different unloading flow rates, the trend of the change of the average particle velocity is basically the same, which has little effect on the flow stability. However, with each increase of 100t / h in flow rate, the average velocity of the material at the outlet below the chute decreases by 0.1m / s. At the same time, the flow change has a more obvious effect on the maximum impact force of the system. The larger the flow rate, the greater the total impact force of the system. However, the increase in the thickness of the buffer layer leads to a smaller maximum impact force. When designing the transfer and transportation flow rate, it is best to use a large flow rate without exceeding the system load limit to improve transportation efficiency and reduce wear.

[0015] Conclusion 3: The speed of the receiving conveyor belt affects the impact and friction on the belt and the supports. The greater the speed of the receiving belt, the less material is carried per unit length, and the smaller the total impact force. However, when the belt speed reaches 2.5 m / s, the maximum impact force on the conveyor belt rises sharply, resulting in severe impact wear and friction wear at the receiving end. When designing the operating speed of the receiving conveyor belt, the belt speed should not be too high or too low. A reasonable balance point should be found to ensure the conveying efficiency while minimizing impact wear;

[0016] Based on the above conclusions, the transfer structure in the engineering example is optimized. Discrete element simulation models of the impact force are established for different-shaped baffle plates. Compared with the stepped plate, the arc plate causes less total impact force on the transfer system, improves the load-bearing limit of the transfer system, and has a better diversion and turning effect, resulting in less vibration and noise. Based on the analysis of particle kinematics, a theoretically more reasonable chute structure form, namely a chute composed of a circular arc section and a straight line section, is proposed to reduce the impact force of the material on the chute and the receiving belt, and reduce the space size of the chute. Then, the geometric dimensions of each section of the chute are further determined. The material flow velocity is obtained through the discrete element simulation model and substituted into the formula to calculate the wear amount of the chute and the conveyor belt. Finally, the inlet angle and the radius of the circular arc of the chute of this structure form are obtained according to the minimum wear amount.

[0017] Preferably, the motion modeling analysis of material discharging: First, the motion of the particles is modeled and analyzed. Ignoring the effects of air resistance and material viscosity, assuming the belt conveyor runs horizontally and the thickness of the belt is negligible, the particle m about to leave the belt is taken as the analysis object. With the center of the discharge end roller as the coordinate origin, the direction of the conveyor belt speed is taken as the x-axis, and the y-axis is vertically downward to establish a plane rectangular coordinate system. Assuming that the particle m starts to leave the belt at point A and the elastic force received is zero, and the particle makes a projectile motion, the following equations are obtained:

[0018]

[0019] Then:

[0020] The velocity of the particle m at point A is:

[0021] In the X direction: v x = v·cosα

[0022] In the Y direction: v y = v·sinα Equation 3

[0023] The corresponding displacement equations:

[0024] In the X direction: x = v x ·t = v·cosα·t Equation 4

[0025] In the Y direction: y = v v ·t + 0.5gt2 = v·sinα·t + 0.5gt 2 Equation 5

[0026] Substituting Equation 4 into Equation 5 gives the particle trajectory equation as follows:

[0027] y = xt sinα / (tcosα) + 0.5gt 2 = xtgα + 0.5gx 2 / (vcosα) 2 Equation 6

[0028] By calculating and analyzing the movement trajectory of the stacked material, the length and width of the material flow are obtained, and the dimensions of the baffle are designed. When the conveyor belt runs to the discharge end of the conveyor, the belt gradually transitions from a trough shape to a flat shape from the idler to the drum, and the cross-section of the material is approximately in the shape of a bow;

[0029] To calculate the overall movement trajectory of the material, the height of the material's center of gravity needs to be calculated first. Assuming the cross-sectional area of the material is A, when the conveying capacity is Q, the belt speed is v, and the material density is γ, based on the constant cross-sectional area of the material, we get:

[0030]

[0031] The geometric parameters of the cross-section of the material on the discharge end drum are obtained, where ρ is the dynamic angle of repose of the material, and the radius of curvature r of the cross-section 1 is:

[0032]

[0033] The height of the center of gravity of the cross-section is:

[0034]

[0035] The height of the top of the material is:

[0036] h = r 1 (1 - cosρ) Equation 10

[0037] So: h 0 = δ B + h C Equation 11

[0038] The velocity v of the center of gravity at the material separation point r The components in the x and y directions are respectively:

[0039] v rx = v r cosα Equation 12

[0040] v ry = v r sinα Equation 13

[0041] Without considering the influence of material viscosity, when the material is projected, the speeds of the topmost particles and the bottommost particles are different and are calculated separately. The speed of the material at the surface of the conveyor belt is:

[0042]

[0043] v r1x = v r1 cosα

[0044] v r1y = r 11 sinα Equation 14

[0045] The speed at the vertex of the material surface is:

[0046]

[0047] v r2x = v r2 cosα

[0048] v r2y = v r2 sinα Equation 15

[0049] The motion model of the bulk material discharging is obtained.

[0050] Preferably, the motion trajectory of the material center of gravity:

[0051] The position of the material center of gravity separation point is:

[0052] x c0 = R sinα

[0053] y c0 = -R cosα Equation 16

[0054] The corresponding trajectory equation is:

[0055] In the X direction: x c = x c0 + v rx t = R sinα + tv r cosα Equation 17

[0056] In the Y direction: y c = y c0 + v ry ·t + 0.5gt 2 = -R cosα + tv r sinα + 0.5gt 2 Equation 18

[0057] The motion trajectory of the material center of gravity is obtained.

[0058] Preferably, the movement trajectory of the material at the conveyor belt surface:

[0059] The radius of curvature of the material at the conveyor belt surface is:

[0060] R 1 = r + δ B Equation 19

[0061] The position of the departure point:

[0062] x 10 = R 1 sinα Equation 20

[0063] y 10 = -R 1 cosα Equation 21

[0064] The corresponding trajectory equation is:

[0065] In the X direction: x 1 = x 10 + v r1x t = R 1 sinα + tv r1 cosα Equation 22

[0066] In the Y direction: y 1 = y 10 + v r1y ·t + 0.5gt 2 = -R 1 cosα + tv r1 sinα + 0.5gt 2 Equation 23

[0067] The movement trajectory of the material at the conveyor belt surface is obtained.

[0068] Preferably, the movement trajectory of the material at the highest point:

[0069] The radius of curvature of the highest point on the material surface is:

[0070] R 2 = r + δ B + h Equation 24

[0071] The position of the departure point at the highest point is:

[0072] x 20 = R 2 sinα Equation 25

[0073] y 20 = -R 2 cosα Equation 26

[0074] The corresponding trajectory equation is:

[0075] In the X direction: x 2 = x 20 + v r2x t = R 2 sinα + tv r2 cosα Equation 27

[0076] In the Y direction: y 2 = y 20 + v r2y ·t + 0.5gt 2 = -R 2 cosα + tv r2 sinα + 0.5gt 2 Equation 28

[0077] When the transfer height is H, the length of the particle flow is:

[0078] x H = 2 H -x 1H = h sinα + t H (v r2 -v r1 )cosα Equation 29

[0079] The width of the particle flow is:

[0080] b = 2r 1 sinρ Equation 30

[0081] After calculating the angle α of the material separation point, calculate the discharge trajectory of the material flow according to the above equations, and determine the basic dimensions of the baffle accordingly. When the particle contacts the plate, under the condition that the angle between the direction of the velocity cut-in and the plate is less than 30°, the combined effect of the impact force and the frictional force on the plate is small. By calculating the discharge trajectory of the material, determine the point where the angle between the tangent line of the parabola and the vertical direction is less than 30° as the installation position of the baffle, and use an arc-shaped baffle that is easier to achieve contact with the material flow at a smaller angle as an optimization to replace the stepped baffle.

[0082] Preferably, the baffle structure analysis and construction: respectively obtain the total force, the maximum force, and the average force of the interaction between the material and the baffle, study whether the replacement of the stepped plate and the baffle has an impact on the magnitude of the impact force on the receiving area inside the transfer system, and also test the impact force on the chute and the receiving belt. The impact force curves on the chute and the receiving belt under the arc-shaped plate are mostly above the respective impact force curves when the stepped plate is installed;

[0083] Take the average value of each force within 3 to 6 s and calculate the force coefficient for comparison. The impact force and the impact coefficient of the arc-shaped baffle itself are significantly smaller than those of the stepped baffle;

[0084] By calculating the percentage change in the average impact force, the average force on the arc-shaped plate is reduced by more than half compared to the stepped plate. The performance of the arc-shaped plate structure is better than that of the stepped plate, but the arc-shaped plate does not improve the stress conditions of the chute and the conveyor belt, and the chute structure still needs to be optimized.

[0085] Preferably, the motion modeling analysis of the material in the chute: First, assume that the material is located in the arc-shaped chute and the material flow is continuous. Then the flow rates of the material flow at the inlet and outlet of the chute are equal:

[0086] ρ 0 A 0 V 0 =ρ e A e V e Equation 31

[0087] Where: ρ 0 、ρ e are the bulk densities of the material at the inlet and outlet of the chute respectively, with the unit of t / m 3 ;

[0088] A 0 、A e are the cross-sectional areas of the material at the inlet and outlet of the chute respectively, with the unit of m 2 ;

[0089] V 0 、V e are the velocities of the material at the inlet and outlet of the chute respectively, with the unit of m / s;

[0090] When the material passes through the chute, the bulk density remains unchanged, that is, ρ 0 =ρ e , Equation 31 is simplified to:

[0091] A 0 V 0 =A e V e Equation 32

[0092] Make the velocity of the material at the outlet of the chute as close as possible to the velocity of the receiving conveyor belt, adopt the form of a gradually changing chute, and control the material flow velocity by changing the cross-sectional area of the material in the chute;

[0093] Establish a rectangular coordinate system, take a material particle m, then the particle is subjected to the gravity mg, the reaction support force N of the chute surface and the friction force f. Apply Newton's second law to the particle in the normal and tangential directions respectively to obtain:

[0094]

[0095] Where: a tis the normal acceleration of the particle, in m / s 2 ; a n is the tangential acceleration of the particle, in m / s 2 ;μ E is the equivalent friction factor between the material and the chute, and the combined results are:

[0096] mgcosθ-ma t –μ E ·(mg sinθ+ma n )=0 Formula 34

[0097] After simplification, it becomes:

[0098] a t +μ E a n +g(μ E sinθ-cosθ)=0 Formula 35

[0099] Let a t =S″, v = S′, we get:

[0100]

[0101] Then formula 35 can be further obtained:

[0102]

[0103] Where: R is the radius of curvature of the chute at the mass point, unit: m; S is the distance from the chute entrance to the mass point, unit: m;

[0104] The cross-section of the chute is rectangular, and the pressure of the material on the bottom plate of the chute is evenly distributed. On the two side plates, the pressure increases linearly from the material surface to the bottom of the chute. The equivalent friction coefficient μ is derived based on the pressure distribution. E The analytical expression of the total friction force per unit length along the length of the chute is:

[0105] F=μPB+μK V PH formula 38

[0106] Let F = μ E PB, substituting into equation 35, we obtain:

[0107]

[0108] Where: μ is the friction factor between the material and the bottom plate of the chute; P is the uniform pressure at the bottom of the chute, unit: Pa / m; H is the height of the material flow layer in the chute, unit: m; B is the cross-sectional width of the chute, unit: m; K V It is the ratio of the lateral pressure to the vertical pressure at the bottom of the chute, ranging from 0.4 to 0.6;

[0109] When the material properties and the chute material are both determined, μ is a definite value, and K V is known. Then, the equivalent friction coefficient is proportional to the ratio of the height of the material flow layer to the cross-sectional width of the chute. The larger this ratio is, the larger the equivalent friction coefficient is, the greater the frictional resistance to the material flow is, and the more difficult the flow is;

[0110] Based on the motion equation of the material, the flow velocity of the material in the chute is derived. For a straight chute with a rectangular cross-section, when R→∞ in Equation 38, then:

[0111] S″ = g(cosθ - μ E sinθ) Equation 40

[0112] The material moves with a uniform acceleration in the straight chute, and the acceleration is a constant. Then, the flow velocity of the material in the straight chute is:

[0113]

[0114] For a circular arc chute with a rectangular cross-section and a constant curvature, the approximate solution of Equation 37 is:

[0115]

[0116] In the formula:

[0117] For a circular arc where the initial velocity of the material is v 0 , and the direction makes an angle θ 0 with the vertical:

[0118]

[0119] When v = v 0 , θ 0 = 0:

[0120]

[0121] Then:

[0122]

[0123] The motion data of the material in the chute are obtained.

[0124] Preferably, calculate the wear of the chute and the belt:

[0125] The frictional wear of the chute occurs on the bottom plate and the side plates. Calculate the frictional wear on the bottom plate of the chute:

[0126]

[0127] Among them: Q m = 3600Aβvρ Equation 48

[0128]

[0129] Where: Q m is the material flow rate, unit: t / h; V s is the velocity of the material at the bottom plate of the chute, unit: m / s; V is the average flow velocity of the material, unit: m / s; is the sliding friction angle between the material and the chute plate; A is the cross-sectional area of the chute, unit: m 2 ; β is the filling coefficient of the chute cross-section; ρ is the bulk density of the material, unit: t / m 3 ; N WR is the dimensionless wear number;

[0130] The frictional wear between the material and the two side surfaces of the chute is much smaller than the wear with the bottom plate. The wear amount increases from zero on the material surface along the side plate to the maximum value at the bottom of the chute. The average wear amount it suffers is expressed by the following formula:

[0131]

[0132] The wear of the conveyor belt consists of frictional wear and impact wear, which is related to the velocity components of the material in the vertical direction and the conveyor belt running direction at the chute outlet. The wear amount calculation formula is as follows:

[0133]

[0134] Where: μ b is the friction coefficient between the material and the conveyor belt; v b is the conveyor belt speed, unit: m / s; v ey is the vertical component velocity of the material when it falls onto the receiving conveyor belt, unit: m / s; v ex is the horizontal component velocity of the material when it falls onto the receiving conveyor belt, unit: m / s.

[0135] Preferably, the inclination angle of the chute: The wear of the chute and the conveyor belt depends on the inclination angle and the radius of curvature of the chute. The velocity of the material when it enters the chute inlet is v 1 , and the velocity after impact and sliding down along the chute is v 2 :

[0136]

[0137] When , v 2 = 0. At this time, the material hangs on the chute surface and cannot flow smoothly. The value of the sliding friction angle is determined by the material properties and the smoothness of the chute surface. The minimum inclination angle of the chute that can satisfy the material flow is obtained as:

[0138]

[0139] α min = arctan μ E + 5° Equation 55

[0140] Adding 5° to Equation 55 takes into account the errors in the actual machining and installation of the chute to ensure reliable material flow. The inclination angle at the end of the chute is determined by the minimum inclination angle of the chute.

[0141] Preferably, the combination form of the chute: The combination of an arc section and a straight section is adopted. After giving the value of the inclination angle θ at the inlet of the chute, assuming that the height H of the chute and the distance x in the horizontal position are known values, the radius R of the arc section and the length S of the straight section of the chute are obtained by solving the following equations simultaneously:

[0142]

[0143] Determine the radius R of the arc section, the length S of the straight section of the chute and the combination form of the chute;

[0144] Analysis and construction of the chute structure: Import the chute structure of each scheme into the EDEM software for numerical simulation calculation. When the inclination angle at the inlet of the chute is 20° and the radius of the arc section is 1.4 m, according to the wear formula, the sum of the wear of the chute and the wear of the conveyor belt is the smallest. The energy loss of the material comes from the impact and frictional wear between the material and the chute and the belt;

[0145] The structure of the transfer chute should adopt the form of an arc section plus a straight section, and the inclination angle at the inlet of the chute should be selected as 20°, and the arc radius should be selected as 1.4 m. This can not only improve the wear conditions of the chute and the conveyor belt, but also reduce the space size of the transfer system.

[0146] Compared with the prior art, the innovation points and advantages of this application are:

[0147] (1) This application improves the bulk material conveying system. The discrete element method is used to study the movement process of particle flow in the transfer system of the belt conveyor for bulk materials. The discrete element software is used to simulate and model it, realizing the visualization of the material transfer process. By changing three operating parameters, namely flow rate, particle size, and belt speed, the velocity distribution and impact force of the material transfer under different levels of each parameter are simulated. Through comparative analysis, the effects of the three parameters on the stability of material flow and wear in the transfer system are judged, and the following conclusions are obtained: When the particle size exceeds 32 mm, the movement trajectory of the material begins to diverge, the velocity distribution fluctuates more intensively, the flow stability deteriorates, and the collisions between the particles and the wall become more frequent, and the maximum impact force also increases accordingly; The magnitude of the flow rate has little effect on the fluctuation of the particle velocity distribution, but the changes in both the flow rate and the speed of the receiving conveyor belt have a very obvious impact on the maximum impact force on the belt. When the flow rate increases by 100 t / h, it will cause the total impact force received by the system to increase by 6000 N, but the maximum impact force decreases by 5000 N accordingly; When the speed of the receiving belt is 2.5 m / s, although the total average impact force is small, the maximum impact force on the conveyor belt rises linearly to 16000 N, and when the belt speed exceeds 2.0 m / s, the change curve of the maximum impact force begins to level off. Based on the above conclusions, the operating parameters and structural forms of the transfer system are improved. While ensuring the stable flow of materials, reducing equipment wear has always been the transfer system.

[0148] (2) In order to select a reasonable baffle structure, the transfer systems of the stepped baffle and the arc baffle are respectively simulated with the discrete element software. Through force analysis, it is found that under the guiding action of the stepped plate, the impact forces on the chute and the receiving end belt are slightly smaller than those of the arc plate, but the force on the baffle itself is much larger than that of the arc plate. And when the arc plate is selected, the material flow has better centering, is not likely to cause the conveyor belt to deviate, has strong flow stability, and has a lower probability of material spillage and leakage. In order to optimize the chute structure, first, it is analyzed that the combination of the circular arc section and the straight line section has better force conditions and can reduce the space size of the chute. Then, the geometric dimensions of each section of the chute are further determined. The material flow velocity is obtained through discrete element simulation experiments and substituted into the formula to calculate the wear amounts of the chute and the conveyor belt. Finally, the values of the inlet angle and the circular arc radius of the chute in this structural form are obtained according to the minimum wear amount, which also conforms to the simulation results of energy loss. A set of reliable and efficient transfer system is reasonably designed at each transfer point, ensuring the smooth progress of the material transfer process and solving problems such as material blockage and leakage, serious impact wear, large vibration and noise, and more dust.

[0149] (3) The discrete element method of this application provides a numerical simulation means for solving and analyzing the motion laws between discontinuous media. Through the particle velocity and mechanical simulation based on the discrete element method, the flow state of materials in the transfer system and the impact force on equipment are simulated and analyzed. By establishing the geometric model and simulation model of the transfer system, it is concluded from the analysis of the particle velocity distribution and the magnitude of the impact force that for the flow stability of materials and the impact wear on equipment under different particle sizes, flow rates and belt speeds, it helps to provide a reference basis for the design of belt conveyors. While improving the conveying efficiency, it can maintain stable material dropping, reduce impact and extend the service life of conveying equipment. It also realizes the visualization of the material movement trajectory, avoids the randomness of the turning design, and can find the point with the maximum impact force on the system equipment, so as to configure necessary lining plates or buffer plates for the transfer system. Through the simulation of different forms of baffle plates and chutes by discrete element software, a reasonable baffle plate shape and the optimal chute structure form are obtained, and the transfer operation of materials is better completed, minimizing the impact damage suffered by the transfer system. It provides an experimental basis for solving problems such as equipment wear, vibration noise, material spilling and blockage that often occur when belt conveyors transfer materials, reduces the maintenance cost of belt conveyors, improves the production environment of industrial and mining enterprises, and promotes the improvement of economic benefits. Description of the Drawings

[0150] Figure 1 It is a three-dimensional model diagram of the logistics bulk material transfer and transmission system.

[0151] Figure 2 It is a schematic diagram of each factor and its level of the discrete element model simulation.

[0152] Figure 3 It is a force analysis diagram of the moving modeling mass point of material discharging.

[0153] Figure 4 It is a schematic diagram of the cross-sectional geometric parameters of the material on the discharging end roller.

[0154] Figure 5 It is a schematic diagram of the structural models of two baffle plates in the experiment.

[0155] Figure 6 It is a schematic diagram of the percentage change in the average impact force constructed by the baffle plate structure analysis.

[0156] Figure 7 It is a schematic diagram of the comparison value of the impact force constructed by the baffle plate structure analysis.

[0157] Figure 8 It is a schematic diagram of the contact model between the material and the baffle plate.

[0158] Figure 9 It is a schematic diagram of the material velocity at the chute outlet.

[0159] Figure 10 It is a schematic diagram of the size comparison between a curved chute and a straight chute at the same inclination angle. Specific implementation manners

[0160] The following further describes the technical solutions of the discrete element model and structure of the logistics bulk material transfer and transportation system provided in this application in conjunction with the accompanying drawings, so that those skilled in the art can better understand this application and be able to implement it.

[0161] Optimize the design parameters, establish particle size, flow rate, and belt speed models that are closely related to the operation of the transfer system, set reference values of system parameters and horizontal level index factors, and respectively investigate the influence of changes in each factor on the velocity distribution of the transferred material and the impact force received by the system, and draw the following conclusions:

[0162] Conclusion 1: The change in particle size causes fluctuations in the average velocity of the material. When the particle size exceeds 32 mm, the flow stability of the material is poor, the trajectories are dispersed, and there are prone to phenomena of material spilling and leakage. Moreover, for particles with a size of 40 mm, the impact force on the system is the largest, and the plate wall or belt is more likely to be penetrated by the particles. During design, the corresponding lining structure should be set according to the position of the maximum impact point simulated by the discrete element method.

[0163] Conclusion 2: Under different discharging flow rates, the change trend of the average velocity of the particles is basically the same, and it has little influence on the flow stability. However, as the flow rate increases by 100 t / h each time, the average velocity of the material at the outlet under the chute decreases by 0.1 m / s. At the same time, the influence of the flow rate change on the maximum impact force of the system is more obvious. The greater the flow rate, the greater the total impact force of the system. However, the increase in the thickness of the buffer layer results in a smaller maximum impact force. When designing the transfer and transportation flow rate, without exceeding the load-bearing limit of the system, a large flow rate should be adopted as much as possible to improve the transportation efficiency and reduce wear.

[0164] Conclusion 3: The speed of the receiving conveyor belt affects the impact and friction conditions of the belt and the idlers. The greater the speed of the receiving belt, the less material carried per unit length, and the smaller the total impact force. However, when the belt speed reaches 2.5 m / s, the maximum impact force on the conveyor belt rises sharply, resulting in serious impact wear and friction wear at the receiving end. When designing the operating speed of the receiving conveyor belt, the belt speed should not be too large or too small, and a reasonable balance point should be found to ensure the transportation efficiency and at the same time have less impact wear.

[0165] Based on the above conclusions, the transfer structure in the engineering example is optimized, and the discrete element simulation models of the impact force of different-shaped baffle plates are established. Compared with the stepped plate, the arc plate causes less total impact force on the transfer system, improves the bearing limit of the transfer system, and has a better diversion and steering effect, resulting in less vibration and noise. Based on the analysis of particle kinematics, a theoretically more reasonable chute structure form, namely a chute composed of a circular arc section and a straight line section, is proposed to reduce the impact force of the material on the chute and the receiving belt, and reduce the space size of the chute. Then, the geometric dimensions of each section of the chute are further determined. The material flow velocity is obtained through the discrete element simulation model and substituted into the formula to calculate the wear amount of the chute and the conveyor belt. Finally, the values of the inlet inclination angle and the circular arc radius of the chute with this structure form are obtained according to the minimum wear amount.

[0166] I. Discrete Element Model of Bulk Material Transfer System

[0167] Through the velocity distribution diagram and impact force curve obtained by analyzing the discrete element model, analyze the influence of material particle size, discharge flow rate, and conveyor belt speed on material flow and the wear of the baffle plate, chute, and conveyor belt, so as to provide a reasonable reference for selecting the working parameters of material transfer and transportation.

[0168] The belt conveyor consists of two end drums and a closed conveyor belt tightly sleeved on them. The driving drum is at the discharge end of the transfer system to increase the friction force. The material is fed from the feeding end and falls on the rotating conveyor belt, and is transported to the discharge end by the friction of the conveyor belt and unloaded. The redirecting drum is installed at the receiving end of the transfer system, only to change the movement direction of the conveyor belt. After the material is unloaded from the discharge end, it is guided by the baffle plate and chute and transferred to the bottom receiving conveyor belt.

[0169] The selection of the belt conveyor determines the parameters according to the requirements of the material handling system, various conditions at the material loading and unloading locations, relevant production processes, and the characteristics of the material, including:

[0170] 1) Conveying capacity: The amount of material conveyed per unit time, calculated by the mass or volume of the material conveyed per hour;

[0171] 2) Conveying speed: Increasing the conveyor belt speed can improve the transportation capacity, but high-speed operation will cause vibration, noise, and starting and braking problems, especially bringing greater impact force and wear to the transfer equipment during the transfer process;

[0172] 3) Material properties: including: loose density, particle size of the material, humidity of the material, angle of repose, abrasiveness, adhesiveness, and friction coefficient of the material;

[0173] 4) Conveying length and inclination: It directly affects the total resistance and required power of the conveyor;

[0174] The conveying length and inclination angle are for the layout of the conveying line and have little to do with the working process of the transfer system. Therefore, 1), 2), and 3) are the factors affecting the operation of the transfer system. Among them, the particle size of the material has a great influence on the wear of the receiving-end conveyor belt, and the relative sliding situation generated during material dropping is closely related to the particle size of the material.

[0175] The control factors of the model should be set to three indicators: the particle size of the material, the discharge flow rate, and the conveyor belt speed. The problems of blockage, wear, vibration, and noise in the transfer system are evaluated through the velocity distribution of particles and the impact forces on the chute and belt. A discrete element model is used for simulation, and the simulation results are collected and recorded.

[0176] (I) Discrete element model simulation

[0177] Use SolidWorks drawing software to establish a simplified three-dimensional model, as Figure 1 shown. Take the diameter of the material particles, the discharge flow rate, and the speed of the receiving conveyor belt as variable factors, and select appropriate values according to the working ranges of the parameters of the above model system. The arrangement of each factor and its level is as Figure 2 shown. Adopt the method of single-factor rotation, and only change one working parameter in each simulation.

[0178] 1. Establish a boundary model

[0179] a. Import the geometry of the transfer system: The geometry of the transfer system has been created in SolidWorks and is directly imported into EDEM. The transfer system is displayed as consisting of 4 parts in the model display, namely discharging_belt, baffle_plate, chute, and receiving_belt;

[0180] b. Set the movingplane parameters: Add discharging_belt and receiving_belt as MovingPlane and set their linear velocities;

[0181] 2. Define material parameters

[0182] a. Set the gravity and define the material;

[0183] b. Define the interactions between materials, including the interactions between materials, between materials and the conveyor belt, and between materials and the transfer structure.

[0184] 3. Create a particle factory

[0185] a. Uniformly set the particle shape to spherical to shorten the simulation time;

[0186] b. The particle factory is a 600×600 rectangular plane at a height of 450 mm directly above the unloading conveyor belt. Select factorytype as Dynamics, select the number of generated particles as unlimited total, set the particle generation rate to 5500 particles / s; set the initial parameters of the particle factory: size as fixed, Position as random, Velocity as fixed, set the Z-direction component of velocity to -2 m / s, and the other directions default to 0.

[0187] 4. Run the simulation

[0188] a. Set the time options, confirm that collision calculation is required, set the time step to 2.3% (4.33e-05 s), set totaltime to 6 s, and the data write-out frequency writeoutevery to 0.01 s;

[0189] b. Set the grid options: set gridsize to 2Rmin, ensure that the number of gridcells is less than 1.8×10°.

[0190] c. Run the simulation settings: set geometrydisplaymode to mesh and view the progress of the simulation;

[0191] d. Element coloring: Color the particles through the Coloring tab;

[0192] e. Export the data.

[0193] (2) Conclusions of the bulk material transfer system

[0194] By simulating the particle flow and force conditions in the transfer system and comparing the average particle velocity distribution and interaction forces inside the transfer system under different particle sizes, unloading flow rates, and receiving belt speeds, the following conclusions are obtained:

[0195] 1) When the particle size of the bulk material exceeds 32 mm, the average particle velocity distribution fluctuates greatly, and the flow stability is worse;

[0196] 2) When the particle size varies between 16 mm and 24 mm, the maximum impact force increases relatively fast. When the particle size is 32 mm, the impact points begin to become scattered, and the system wall is more likely to be penetrated by larger-sized particles;

[0197] 3) The change in flow rate has little effect on the flow stability of the material, but when the flow rate increases by 100 t / h each time, the average velocity at the chute outlet of the material decreases to 0.1 m / s;

[0198] 4) The greater the flow rate, the greater the total impact force, which subjects the entire system to more impact wear. However, when the flow rate increases by 100 t / h, the maximum impact force decreases by 5000 N, avoiding erosion at local impact points.

[0199] 5) When the receiving belt speed is 2.5 m / s, the maximum impact force is 16000 N. The thickness of the particle layer decreases, causing the maximum impact force on the wall to increase sharply, resulting in severe local wear, while the total impact force decreases. And when the belt speed exceeds 2.0 m / s, the changing trend of the impact force is no longer obvious.

[0200] Based on the above conclusions, information is provided for the design and setting of working parameters of the conveyor transfer system, including adding lining plates in the impact point area when the particle size of the conveyed material exceeds 16 mm; trying to make the particle size of the material less than 32 mm to improve flow stability; selecting a reasonable receiving belt speed of 1.6 m / s to form a buffer layer of a certain thickness under the condition of ensuring no material blockage, so that the conveyor belt is subject to less impact wear; setting the flow rate less than 300 t / h to make the horizontal speed of the material close to the belt speed when it falls on the receiving machine belt.

[0201] II. Structural Design of the Transfer and Transmission System

[0202] There are two most critical structures in the transfer system, namely the baffle plate and the chute. During the process of the material being transferred from the discharge end to the bottom receiving end, the magnitude and direction of the impact force when the particles contact the baffle plate, chute, and conveyor belt are important indicators to measure the performance of the transfer system. If the design is not good, it will not only exacerbate the wear of the equipment but also easily generate vibration and noise. Therefore, the rationality of the structures of the baffle plate and the chute is particularly important.

[0203] (I) Structural Design of the Baffle Plate

[0204] The baffle plate restricts the movement trajectory of the material after it is thrown out from the discharge end, completing the turning of the material flow velocity from horizontal to vertical. The baffle plate mostly exists in the form of a buffer box. After the material falls on the buffer box, it does not directly impact the surface of the buffer box but collides with the material piled up on the buffer box, and then falls onto the next-level buffer box, collides with the surface of the piled-up material again, and then rolls onto the receiving conveyor belt to achieve the transfer of the material. However, the buffer box also has deficiencies, including the uncontrollability of the velocity direction after the collision of the material, which is prone to material spillage. Therefore, the buffer box is designed to be relatively large in size, occupying a large space and being prone to blockage, making it inconvenient for cleaning and maintenance. So the buffer box is gradually replaced by the structural combination of a vertical stepped plate and a chute.

[0205] 1. Kinematic Modeling Analysis of Material Discharge

[0206] When the vertical stepped baffle completes the baffle operation, the velocity of the material in the horizontal direction drops to 0, and the kinetic energy lost is all loaded on the baffle in the form of impact collision. Therefore, the baffle is severely damaged. To obtain a baffle with a more reasonable structure, first, the motion of the particles is modeled and analyzed. Ignoring the effects of air resistance and material viscosity, assuming the belt conveyor runs horizontally and the thickness of the belt is negligible, the particle m about to leave the belt is taken as the analysis object. Taking the center of the discharge end roller as the coordinate origin, the velocity direction of the conveyor belt as the x-axis, and the y-axis vertically downward, a plane rectangular coordinate system is established. Figure 3 The force condition of the particle m is shown as follows.

[0207] Assume that the particle m starts to leave the belt at point A, the elastic force it receives is zero, and the particle makes a projectile motion. The following equations can be obtained:

[0208]

[0209] Then:

[0210] The velocity of the particle m at point A is:

[0211] In the X direction: v x = v·cosα

[0212] In the Y direction: v y = v·sinα Equation 3

[0213] The corresponding displacement equations:

[0214] In the X direction: x = v x ·t = v·cosα·t Equation 4

[0215] In the Y direction: y = v y ·t + 0.5gt 2 = v·sinα·t + 0.5gt 2 Equation 5

[0216] Substituting Equation 4 into Equation 5, the trajectory equation of the particle is obtained as follows:

[0217] y = xt sinα / (t cosα) + 0.5gt 2 = xtgα + 0.5gx 2 / (vcosα) 2 Equation 6

[0218] By calculating and analyzing the motion trajectory of the accumulated material, the length and width of the material flow are obtained, and the size of the baffle is designed. When the conveyor belt runs to the discharge end of the conveyor, the belt gradually transitions from a trough shape to a flat shape from the idler to the roller, and the cross-section of the material is approximately in the shape of a bow. As Figure 4 .

[0219] To calculate the overall movement trajectory of the material, it is necessary to first calculate the height of the material's center of gravity. Let the cross-sectional area of the material be A. When the conveying volume is Q, the belt speed is v, and the material density is γ, according to the constant cross-sectional area of the material, we get:

[0220]

[0221] The cross-sectional geometric parameters of the material on the discharge end roller are as Figure 4 , where ρ is the dynamic angle of repose of the material, then the radius of curvature r of the cross-section 1 is:

[0222]

[0223] The height of the cross-sectional center of gravity is:

[0224]

[0225] The height of the top of the material is:

[0226] h = r 1 (1 - cosρ) Equation 10

[0227] So: h 0 = δ B + h C Equation 11

[0228] The velocity v of the center of gravity at the material separation point r The components in the x and y directions are respectively:

[0229] v rX = v r cosα Equation 12

[0230] v ry = v r sinα Equation 13

[0231] Without considering the influence of material viscosity, when the material is projected, the velocities of the top and bottom particles are different and are calculated separately; the velocity of the material at the conveyor belt surface is:

[0232]

[0233] v r1x = v r1 cosα

[0234] v r1y = v r1 sinα Equation 14

[0235] The velocity at the vertex of the material surface is:

[0236]

[0237] v r2x = v r2 cosα

[0238] v r2y = v r2 sinα Equation 15

[0239] (1) Trajectory of the center of gravity of the material

[0240] The position of the point where the center of gravity of the material breaks away is:

[0241] x c0 = R sinα

[0242] y c0 = -R cos α Equation 16

[0243] The corresponding trajectory equation is:

[0244] In the X direction: x c = x c0 + v rx t = R sinα + tv r cosα Equation 17

[0245] In the Y direction: y c = y c0 + v ry ·t + 0.5gt 2 = -Rcosα + tv r sinα + 0.5gt 2 Equation 18

[0246] (2) Trajectory of the material at the surface of the conveyor belt

[0247] The radius of curvature of the material at the surface of the conveyor belt is:

[0248] R 1 = r + δ B Equation 19

[0249] Position of the breakaway point:

[0250] x 10 = R 1 sinα Equation 20

[0251] y 10 = -R 1 cosα Equation 21

[0252] The corresponding trajectory equation is:

[0253] In the X direction: x 1 = x 10 + v r1x t = R1 sinα + tv r1 cosα Equation 22

[0254] In the Y direction: y 1 = y 10 + v r1y ·t + 0.5gt 2 = -R 1 cosα + tv r1 sinα + 0.5gt 2 Equation 23

[0255] (3) The movement trajectory of the material at the highest point

[0256] The radius of curvature of the highest point on the material surface is:

[0257] R 2 = r + δ B + h Equation 24

[0258] The position of the separation point at the highest point is:

[0259] x 20 = R 2 sinα Equation 25

[0260] y 20 = -R 2 cosα Equation 26

[0261] The corresponding trajectory equation is:

[0262] In the X direction: x 2 = x 20 + v r2x t = R 2 sinα + tv r2 cosα Equation 27

[0263] In the Y direction: y 2 = y 20 + v r2y ·t + 0.5gt 2 = -R 2 cosα + tv r2 sinα + 0.5gt 2 Equation 28

[0264] When the transfer height is H, the length of the particle flow is:

[0265] x H = x 2H - x 1H = h sinα + t H (v r2 - v r1 )cosα Equation 29

[0266] The width of the particle flow is:

[0267] b = 2r 1 sinρ Equation 30

[0268] After calculating the angle α of the material separation point, calculate the discharge trajectory of the material flow according to the above formulas, and determine the basic dimensions of the baffle accordingly. When the particle contacts the plate, under the condition that the angle between the direction of the velocity cut-in and the plate is less than 30°, the combined effect of the impact force and the frictional force on the plate is relatively small. By calculating the discharge trajectory of the material, determine the point on the parabola where the tangent line makes an angle less than 30° with the vertical direction as the installation position of the baffle. Use an arc-shaped baffle that is easier to achieve contact with the material flow at a smaller angle as an optimization to replace the stepped baffle.

[0269] Model the vertical stepped baffle and the arc-shaped baffle to obtain the advantages and disadvantages of the performance of the two baffles in the transfer system;

[0270] During the transfer process, there are three places where the material collides, namely: the area on the baffle where the material hits at a certain speed, the area where the material freely falls into the chute after being guided by the baffle, and the area where the material falls onto the receiving conveyor belt after sliding out of the chute; the speed of the material changes the most in these three areas, which is likely to cause damage to the transfer system. Take the force conditions in these three areas as evaluation indicators for comparative analysis. Use the impact coefficient as the evaluation indicator for the force condition of the plate parts during the transportation of bulk materials. There are 2 impact coefficients. One is the total force impact coefficient, which represents the ratio of the total force received by the transfer system in the test area to the total gravity of the material particles in this area; the other is the maximum force impact coefficient, which represents the ratio of the maximum force received by the transfer system in the test area to the gravity of a single material particle.

[0271] 2. Baffle simulation experiment

[0272] The structural models of the two baffles in this experiment are as Figure 5 shown. Select an arc-shaped plate with an appropriate curvature according to the parabola equation of a single particle, replace the parts into the three-dimensional model of the transfer system drawn previously, and then import it into the discrete element simulation software, that is, dp = 24mm, Vdis = 1.6m / s, vrec = 1.6m / s, Qp = 400t / h. After the simulation is completed, record the video and make a dynamic comparison with the particle flow condition of the stepped plate transfer system.

[0273] 3. Baffle structure analysis and construction

[0274] Obtain the total force, maximum force, and average force of the interaction between the material and the baffle respectively. After being guided by the baffle, the material falls onto the chute and conveyor belt, causing a certain degree of impact. The magnitude of the impact force is one of the issues concerned during the material receiving process. To study whether the replacement of the stepped plate and the baffle affects the magnitude of the impact force on the material receiving area inside the transfer system, the impact forces on the chute and the conveyor belt are also tested. The impact force curves on the chute and the conveyor belt under the arc plate are mostly above the respective impact force curves when the stepped plate is installed.

[0275] To intuitively obtain the force performance of the two types of baffles, the average value of each force within the time range of 3 to 6 s is taken, and the force coefficient is calculated for comparison. The results are as Figure 7 shown. The impact force and impact coefficient received by the arc-shaped baffle itself are significantly smaller than those of the stepped baffle, which is attributed to the smaller tangential force on the arc plate. However, in the test area of the chute and the conveyor belt, the force condition and impact coefficient of using the stepped plate are slightly smaller than those of the arc plate. A reasonable explanation is that due to the existence of steps on the stepped plate, a small part of the material will accumulate. Therefore, when the particles impact the baffle, there is a greater chance of first contacting the accumulated material, resulting in the phenomenon of material hitting material, which plays a buffering role and will lose a part of the kinetic energy. So when it falls onto the chute and the conveyor belt, the speed becomes smaller, and the impact force on them also decreases accordingly.

[0276] By calculating the percentage change in the average impact force, quantitatively compare and analyze the force effects of the two types of baffles, as Figure 6 shown. The average force received by the arc plate is reduced by more than half compared to the stepped plate, while the forces received by the chute and the conveyor belt increase by 11% and 5% respectively. Therefore, although using the arc plate can significantly improve the force condition of the baffle structure, the chute and the receiving belt bear more loads. As can be seen from Figure 8 , the guiding effect of the arc plate on the material flow is significantly better than that of the stepped plate, and its flow stability is better. Overall, the performance of the arc plate structure is slightly better than that of the stepped plate. However, using the arc plate does not improve the force condition of the chute and the conveyor belt, so the chute structure still needs to be optimized.

[0277] (2) Chute Structure Design

[0278] 1. Kinematic Modeling Analysis of Materials in the Chute

[0279] First, assume that the material is located in the arc-shaped chute and the material flow is continuous. Then the flow rates of the material flow at the inlet and outlet of the chute are equal:

[0280] ρ 0 A 0 V 0 =ρ e A eV e Formula 31

[0281] Where: 0 , e They are the bulk density of the material at the inlet and outlet of the chute, in t / m 3 ;

[0282] A 0 , A e They are the cross-sectional areas of the material at the inlet and outlet of the chute, in m 2 ;

[0283] V 0 、V e They are the speed of the material at the inlet and outlet of the chute, in m / s;

[0284] When the material passes through the chute, the bulk density remains unchanged, that is, ρ 0 =ρ e , Equation 31 is simplified to:

[0285] A 0 V 0 =A e V e Formula 32

[0286] Make the material speed at the chute outlet as close as possible to the speed of the receiving conveyor belt, adopt a gradual chute, and control the material flow speed by changing the cross-sectional area of ​​the material in the chute;

[0287] Establish a rectangular coordinate system, take a material point m, and the point is subject to gravity mg, the chute surface counter-support force N and friction f. Apply Newton's second law to the point in the normal and tangential directions to obtain:

[0288]

[0289] Where: a t is the normal acceleration of the particle, in m / s 2 ; a n is the tangential acceleration of the particle, in m / s 2 ;μ E is the equivalent friction factor between the material and the chute, and the combined results are:

[0290] mg cosθ-ma t -μ E ·(mg sinθ+ma n )=0 Formula 34

[0291] After simplification, it becomes:

[0292] α t +μ E an +g(μ E sinθ - cosθ) = 0 Equation 35

[0293] Let a t = S″, v = S′, we get:

[0294]

[0295] Then Equation 35 can be further obtained as:

[0296]

[0297] Where: R is the radius of curvature of the chute at the particle, in m; S is the distance from the chute inlet to the particle, in m;

[0298] The cross - section shape of the chute is rectangular, the pressure distribution of the material on the bottom plate of the chute is uniform, while on the two side plates, the pressure increases linearly from the material surface to the bottom of the chute. According to the pressure distribution, the analytical expression of the equivalent friction coefficient μ E is derived, and the total frictional force per unit length along the length direction of the chute is:

[0299] F = μPB + μK V PH Equation 38

[0300] Let F = μ E PB, substituting into Equation 35, we get:

[0301]

[0302] Where: μ is the friction factor between the material and the bottom plate of the chute; P is the uniform pressure at the bottom of the chute, in Pa / m; H is the height of the material flow layer in the chute, in m; B is the width of the chute cross - section, in m; K V is the ratio of the lateral pressure to the vertical pressure at the bottom of the chute, taking values from 0.4 to 0.6;

[0303] When the material properties and the chute material are both determined, μ is a determined value, K V is known, then the equivalent friction coefficient is proportional to the ratio of the material flow layer height to the chute cross - section width. The larger the ratio, the larger the equivalent friction coefficient, the greater the frictional resistance to material flow, and the more difficult the flow;

[0304] According to the motion equation of the material, the flow velocity of the material in the chute is derived. For a straight - section chute with a rectangular cross - section, when R → ∞ in Equation 38, then:

[0305] S″ = g(cosθ - μ E sinθ) Equation 40

[0306] The material moves with a uniform acceleration in the straight chute. If the acceleration is a constant, the flow velocity of the material in the straight chute is:

[0307]

[0308] For the arc chute with a rectangular cross-section and a constant curvature, the approximate solution of Equation 37 is:

[0309]

[0310] In the formula:

[0311] For a section of arc where the initial velocity of the material is v 0 , and the angle between the direction and the vertical is θ 0 :

[0312]

[0313] When v = v 0 , θ 0 = 0:

[0314]

[0315] Then:

[0316]

[0317] The motion data of the material in the chute are obtained.

[0318] 2. Calculate the wear of the chute and the belt

[0319] The wear of the chute includes two parts: impact wear and friction wear. The impact wear of the chute occurs at the landing point where the material enters the chute or at the point where the flow direction of the material suddenly changes. According to the solution of the motion equation of the material in the chute, the curvature radius and inclination angle of the chute are reasonably designed to reduce the impact wear.

[0320] The friction wear of the chute occurs on the bottom plate and the two side plates. Calculate the friction wear on the bottom plate of the chute:

[0321]

[0322] Among them: Q m = 3600Aβvρ Equation 48

[0323]

[0324]

[0325] In the formula: Q m is the material flow rate, in t / h; V sis the velocity of the material at the chute bottom plate, with the unit of m / s; V is the average flow velocity of the material, with the unit of m / s; is the sliding friction angle between the material and the chute plate surface; A is the cross-sectional area of the chute, with the unit of m 2 ; β is the filling coefficient of the chute cross-section; ρ is the bulk density, with the unit of t / m 3 ; N WR is the dimensionless wear number;

[0326] The friction and wear between the material and the two side surfaces of the chute are much smaller than the wear with the bottom plate. The wear amount increases from zero on the material surface along the side plate to the maximum value at the bottom of the chute. The average wear amount it suffers is expressed by the following formula:

[0327]

[0328] The wear of the conveyor belt consists of friction wear and impact wear, which is related to the velocity components of the material in the vertical direction and the conveyor belt running direction at the chute outlet. The wear amount calculation formula is as follows:

[0329]

[0330] In the formula: μb is the friction coefficient between the material and the conveyor belt; v b is the conveyor belt velocity, with the unit of m / s; vey is the component velocity of the material in the vertical direction when it falls onto the receiving conveyor belt, with the unit of m / s; v ex is the horizontal component velocity of the material when it falls onto the receiving conveyor belt, with the unit of m / s.

[0331] 3. Inclination angle of the chute

[0332] The wear of the chute and the conveyor belt depends on the inclination angle and the radius of curvature of the chute, Figure 9 is the schematic diagram of the velocity change before and after the collision when the material enters the chute. The velocity of the material when it enters the chute inlet is v 1 , and the velocity after the impact and sliding down along the chute is v 2 :

[0333]

[0334] When , v 2 = 0. At this time, the material hangs on the chute surface and cannot flow smoothly. The value of the sliding friction angle is determined by the material characteristics and the smoothness of the chute surface. The minimum inclination angle of the chute that can satisfy the material flow is obtained as:

[0335]

[0336] α min = arctanμ E + 5° Formula 55

[0337] Adding 5° to Equation 55 takes into account the errors in the actual machining and installation of the chute to ensure reliable material flow. The inclination angle at the end of the chute is determined by the minimum inclination angle of the chute.

[0338] 4. Combined form of the chute

[0339] For a given transfer height and inclination angle at the end of the chute, as Figure 10 shown, the structural dimensions of the curved chute are smaller than those of the straight chute, and the occupied space is also smaller. However, the velocity direction of the material flowing in the curved chute is constantly changing, and the pressure between the material and the bottom plate of the chute is greater than that of the straight chute, and the friction force is also greater. In the straight chute, the material moves in a uniform acceleration motion and the flow is relatively stable. The two forms of chutes are combined together.

[0340] Adopting the combined form of the chute with an arc section and a straight section, after giving the value of the inclination angle θ at the entrance of the chute, assuming that the height H of the chute and the distance x in the horizontal position are known values, the radius R of the arc section and the length S of the straight section of the chute are obtained by solving the following equations simultaneously:

[0341]

[0342] Determine the radius R of the arc section and the length S of the straight section of the chute and the combined form of the chute.

[0343] 5. Chute simulation experiment

[0344] To finally determine the specific parameters of the chute structure in the research example of this application, select appropriate parameter values that determine the chute structure shape for discrete element simulation experiments to obtain the flow velocity V of the material s and V e , and the evaluation indicators are W c , W csw and W α . The minimum value of the end inclination angle α has been calculated to be 27°. By analysis, the entrance inclination angle θ is selected in the range of 0 to 53°, the chute height is 2.2 m, and 5 levels are selected for each factor.

[0345] Next, draw the corresponding three-dimensional chute structure diagram according to the experimental parameters. To reduce the simulation time, only the wear of the chute and the belt needs to be studied. Therefore, the chutes of the five experimental schemes are summarized in one simulation model. Then draw a plane at the entrance of each chute as a particle factory, with a particle generation speed of 5500 per second, and the particle shape is spherical, and its parameter settings are the same as those in the previous simulation.

[0346] 6. Chute structure analysis and construction

[0347] The chute structures of each solution are imported into the EDEM software for numerical simulation calculations. When the chute inlet inclination angle is 20° and the radius of the arc section is 1.4 m, the sum of the wear of the chute and the wear of the conveyor belt is calculated to be the smallest according to the wear formula. Ignoring the influence of air resistance, the energy loss of the material comes from the impact and frictional wear between the chute and the belt. Since the height difference between the position of the particle factory set in the 5 models and the conveyor belt is the same and the work done by gravity is the same, the energy loss of the material during the falling process is measured by the energy value of the material falling on the conveyor belt, that is, the wear conditions of the chute and the belt.

[0348] Therefore, the structure of the transfer chute should adopt the form of an arc section plus a straight section. The chute inlet inclination angle should be selected as 20°, and the arc radius should be selected as 1.4 m. This can not only improve the wear conditions of the chute and the conveyor belt but also reduce the space size of the transfer system.

[0349] This application first conducts a motion analysis of the material to examine the interaction forces between the material and the internal structure of the transfer system, and then obtains a theoretically more preferable structural form with better force conditions. Then, the discrete element software is used to simulate and compare the two solutions before and after the improvement. Finally, based on the principle of the smallest wear of the transfer system, a better structural design solution for the baffle and the chute is selected.

[0350] The use of an arc-shaped baffle plate causes less total impact force on the entire transfer system than a vertical stepped baffle plate. The movement trajectory of material transfer is simulated using a discrete element model. For different material trajectories, the shape of the arc-shaped baffle plate that best fits them is customized to enable the baffle plate to better play the role of blocking and redirecting the material.

[0351] The chute structure is optimized to obtain the chute structure form with the best comprehensive performance based on the force conditions and space size, that is, the combination of an arc section and a straight section. The velocity of the material is simulated using the discrete element software and substituted into the wear amount calculation formula to obtain the geometric parameters of the chute with the smallest total wear amount.

Claims

1. Discrete element model and structure of bulk material transfer and transmission system, characterized by: Optimize the design parameters, establish the particle size, flow rate and belt speed model closely related to the operation of the transfer system, set the system parameter reference value and horizontal level index factor, and examine the impact of each factor change on the speed distribution of the transferred material and the impact force on the system. The conclusion is: Conclusion 1: The change of particle size causes the fluctuation of the average material speed. When the particle size exceeds 32mm, the material flow stability is poor, the trajectory is scattered, and it is easy to spill or leak. In addition, the 40mm particle has the greatest impact on the system, and the plate wall or belt is more likely to be penetrated by the particle. In the design, the corresponding lining structure should be set according to the maximum impact point position simulated by the discrete element method. Conclusion 2: Under different unloading flow rates, the trend of the change of the average particle velocity is basically the same, which has little effect on the flow stability. However, with each increase of 100t / h in flow rate, the average velocity of the material at the outlet below the chute decreases by 0.1m / s. At the same time, the flow change has a more obvious effect on the maximum impact force of the system. The larger the flow rate, the greater the total impact force of the system. However, the increase in the thickness of the buffer layer leads to a smaller maximum impact force. When designing the transfer and transportation flow rate, it is best to use a large flow rate without exceeding the system load limit to improve transportation efficiency and reduce wear. Conclusion 3: The speed of the receiving conveyor belt affects the impact and friction of the belt and the support. The greater the receiving belt speed, the less material is carried per unit length and the smaller the total impact force. However, when the belt speed reaches 2.5m / s, the maximum impact force on the conveyor belt rises sharply, causing serious impact wear and friction wear at the receiving end. When designing the running speed of the receiving conveyor belt, the belt speed should not be too large or too small. A reasonable balance point should be found to ensure the conveying efficiency and at the same time reduce the impact wear. Based on the above conclusions, the transfer structure in the engineering example is optimized, and the discrete element simulation modeling of the impact force of the baffle plates of different shapes is carried out. Compared with the step plate, the total impact force caused by the material on the transfer system is smaller in the curved plate, which improves the bearing limit of the transfer system. The curved plate has a better diversion and steering effect, and the vibration and noise caused are also smaller. Based on the particle kinematic analysis, a more theoretically reasonable chute structure is proposed, that is, a chute composed of arc segments and straight segments, which reduces the impact force of the material on the chute and the receiving belt, reduces the spatial size of the chute, and then further determines the geometric dimensions of each section of the chute. The material flow rate is obtained through the discrete element simulation model, and the wear of the chute and the conveyor belt is calculated by substituting it into the formula. According to the minimum wear, the inlet inclination angle and arc radius of the chute of this structure are finally obtained.

2. According to claim 1, the discrete element model and structure of the bulk material transfer and transmission system is characterized in that: Motion modeling and analysis of material unloading: First, model and analyze the movement of particles, ignoring the influence of air resistance and material viscosity, assuming that the belt conveyor runs horizontally, the thickness of the belt is negligible, and the particle m that is about to leave the belt is taken as the analysis body. The center of the unloading end roller is taken as the coordinate origin, the speed direction of the conveyor belt is taken as the x-axis, and the y-axis is vertically downward. A plane rectangular coordinate system is established. It is assumed that the particle m begins to leave the belt at point A, and the elastic force is zero. The particle performs oblique projection motion, and the equation is as follows: but: The velocity of particle m at point A is: X direction: v x =v·cosα Y direction: v y =v·sinα Formula 3 The corresponding displacement equation is: X direction: x = v x ·t=v·cosα·t Formula 4 Y direction: y = v v t+0.5gt 2 =v·sinα·t+0.5gt 2 Formula 5 Substituting equation 4 into equation 5, we get the particle trajectory equation as follows: y = xt sinα / (t cosα) + 0.5gt 2 = xtgα + 0.5gx 2 / (vcosα) 2 Equation 6 The motion trajectory of the accumulated materials is calculated and analyzed to obtain the length and width of the material flow and design the size of the baffle. When the conveyor belt runs to the unloading end of the conveyor, the belt gradually changes from a groove type to a flat type from the supporting wheel to the roller, and the cross section of the material is approximately arched. To calculate the overall motion trajectory of the material, the height of the center of gravity of the material must be calculated first. Assuming the cross-sectional area of ​​the material is A, when the conveying volume is Q, the belt speed is v, and the material density is γ, the cross-sectional area of ​​the material remains unchanged and the following is obtained: The cross-sectional geometric parameters of the material on the drum at the discharge end are obtained, where ρ is the dynamic accumulation angle of the material, and the curvature radius r1 of the cross section is: The height of the centroid of the cross section is: The height of the top of the material is: h=r1(1-cosρ) Formula 10 So: h0=δ B +h C Formula 11 Velocity v of the center of gravity at the material detachment point r The components in the x and y directions are: v rx = v r cos α Equation 12 v ry = v r sinα Equation 13 Without considering the influence of material viscosity, when the material is ejected, the speed of the topmost particle is different from that of the bottommost particle, and they are calculated separately; the speed of the material on the conveyor belt surface is: v r|x =v r |cosα v r|y = v r1 sin α Equation 14 The velocity at the vertex of the material surface is: v r2x =v r2 cosα v r2y = v r2 sin α Equation 15 The motion model of bulk material unloading is obtained.

3. According to claim 2, the discrete element model and structure of the bulk material transfer and transmission system is characterized in that: Movement trajectory of the material's center of gravity: The location of the material's center of gravity separation point is: x c0 =R sinα y c0 = -R cosα Equation 16 The corresponding trajectory equation is: X direction: x c =x c0 +v rx t=R sinα+tv r cosα Equation 17 Y direction: y c = y c0 + v ry ·t + 0.5gt 2 = -R cosα + tv r sinα + 0.5gt 2 Equation 18 Get the motion trajectory of the center of gravity of the material.

4. According to claim 2, the discrete element model and structure of the bulk material transfer and transmission system is characterized in that: Movement trajectory of materials on the conveyor belt surface: The radius of curvature of the material on the conveyor belt surface is: R1 = r + δ B Equation 19 Location of the breakaway point: x 10 =R1sinα Formula 20 y 10 =-R1cosα Formula 21 The corresponding trajectory equation is: X direction: x1 = x 10 +v r|x t=R1sinα+tv r1 cosα Equation 22 Y direction: y1=y 10 +v r1y ·t+0.5gt 2 =-R1cosα+tv r1 sinα+0.5gt 2 formula 23 Get the movement trajectory of the material on the conveyor belt surface.

5. According to claim 2, the discrete element model and structure of the bulk material transfer and transmission system is characterized in that: The movement trajectory of the material at the highest point: The radius of curvature at the highest point of the material surface is: R2=r+δ B +h formula 24 The highest breakaway point is located at: x 20 =R2sinα Formula 25 y 20 =-R2cosα Formula 26 The corresponding trajectory equation is: X direction: x2=x 20 +v r2x t=R2sinα+tv r2 cosα Equation 27 Y direction: y2 = y 20 +v r2y t+0.5gt 2 =-R2cosα+tv r2 sinα+0.5gt 2 Formula 28 When the transfer height is H, the length of the particle flow is: x H = x 2H -x 1H = h sinα + t H (v r2 - v r1 )cosα Equation 29 The width of the particle stream is: b=2r1sinρ Formula 30 After calculating the angle α of the material separation point, the unloading trajectory of the material flow is calculated according to the above formulas, and the basic size of the baffle plate is determined accordingly. When the particles contact the plate, under the condition that the angle between the direction of speed cutting and the plate is less than 30°, the combined effect of the impact force and friction force on the plate is small. By calculating the unloading trajectory of the material, the point where the angle between the tangent on the parabola and the vertical direction is less than 30° is determined as the installation position of the baffle plate. An arc baffle that is easier to contact with the material flow at a smaller angle is used as an optimization to replace the step baffle plate.

6. According to claim 1, the discrete element model and structure of the bulk material transfer and transmission system is characterized in that: Analysis and construction of the baffle plate structure: The total force, maximum force and average force of the interaction between the material and the baffle plate are obtained respectively, and the impact force on the receiving area of ​​the transfer system is studied after the replacement of the step plate and the baffle plate. The impact force on the chute and the receiving belt is also tested. The impact force curves on the chute and the receiving belt under the curved plate are above the impact force curves when the step plate is installed most of the time. Take the average value of each force within 3 to 6 seconds, and calculate the force coefficient for comparison. The impact force and impact coefficient of the arc baffle plate itself are obviously much smaller than those of the step baffle plate. By calculating the percentage change of the average impact force, it is found that the average force on the curved plate is reduced by more than half compared with the step plate. The performance of the curved plate structure is better than that of the step plate. However, the curved plate does not improve the stress conditions of the chute and conveyor belt, and the chute structure needs to be optimized.

7. The discrete element model and structure of the bulk material transfer and transmission system according to claim 1 is characterized in that: Modeling and analysis of material movement in the chute: First, assume that the material is in an arc chute and that the material flow is continuous. The flow rate of the material at the inlet and outlet of the chute is equal: ρ0A0V0=ρ e A e V e formula 31 Where: ρ0, ρ c They are the bulk density of the material at the inlet and outlet of the chute, in t / m 3 ; A0, A e They are the cross-sectional areas of the material at the inlet and outlet of the chute, in m 2 ; V0, V e They are the speed of the material at the inlet and outlet of the chute, in m / s; When the material passes through the chute, the bulk density remains unchanged, that is, ρ0 = ρ e , Equation 31 is simplified to: A0V0=A e V e Formula 32 Make the material speed at the chute outlet as close as possible to the speed of the receiving conveyor belt, adopt a gradual chute, and control the material flow speed by changing the cross-sectional area of ​​the material in the chute; Establish a rectangular coordinate system, take a material point m, and the point is subject to gravity mg, the chute surface counter-support force N and friction f. Apply Newton's second law to the point in the normal and tangential directions to obtain: Where: a t is the normal acceleration of the particle, in m / s 2 ; a n is the tangential acceleration of the particle, in m / s 2 ; μ E is the equivalent friction factor between the material and the chute, and the combined results are: mg cosθ - ma t -μ E ·(mg sinθ + ma n ) = 0 Equation 34 After simplification, it becomes: a t +m E a n +g(μ E sinθ-cosθ)=0 Equation 35 Let a t =S′, v = S, we get: Then formula 35 can be further obtained: Where: R is the radius of curvature of the chute at the particle point, unit: m; S is the distance from the chute entrance to the mass point, in m; The cross-section of the chute is rectangular, and the pressure of the material on the bottom plate of the chute is evenly distributed. On the two side plates, the pressure increases linearly from the material surface to the bottom of the chute. The equivalent friction coefficient μ is derived based on the pressure distribution. E The analytical expression of the total friction force per unit length along the length of the chute is: F=μPB+μK V PH formula 38 Let F = μ E PB, substituting into equation 35, we obtain: Where: μ is the friction factor between the material and the bottom plate of the chute; P is the uniform pressure at the bottom of the chute, unit: Pa / m; H is the height of the material flow layer in the chute, unit: m; B is the cross-sectional width of the chute, unit: m; K V It is the ratio of the lateral pressure to the vertical pressure at the bottom of the chute, ranging from 0.4 to 0.6; When the material properties and chute material are determined, μ is the determined value, K V It is known that the equivalent friction coefficient is proportional to the ratio of the material flow layer height to the chute cross-sectional width. The larger the ratio, the larger the equivalent friction coefficient, the greater the friction resistance of material flow, and the more difficult the flow. The flow velocity of the material in the chute is derived based on the motion equation of the material. For a straight segment chute with a rectangular cross section, when R→∞ in equation 38, then: S″ = g(cosθ - μ E sinθ) Equation 40 The material moves with uniform acceleration in the straight segment chute, and the acceleration is a constant. Then the flow velocity of the material in the straight segment chute is: For a circular arc chute with a rectangular cross section and constant curvature, the approximate solution of equation 37 is: Where: For a circular arc with an initial material velocity of v0 and an angle of θ0 with the vertical direction: When v=v0,θ0=0: but: Get the movement data of materials in the chute.

8. The discrete element model and structure of the bulk material transfer and transmission system according to claim 1 is characterized in that: Calculation of chute and belt wear: The friction and wear of the chute occurs on the bottom plate and the two side plates. The friction and wear on the bottom plate of the chute is calculated as follows: Where: Q m =3600Aβvρ Formula 48 Where: Q m is the material flow rate, unit t / h; V s is the velocity of the material at the bottom of the chute, in m / s; V is the average flow velocity of the material, in m / s; is the sliding friction angle between the material and the chute plate surface; A is the cross-sectional area of ​​the chute, unit: m 2 ; β is the filling coefficient of the chute section; ρ is the bulk material density, unit t / m 3 ; N WR is the dimensionless wear number; The friction wear between the material and the two sides of the chute is much smaller than the wear with the bottom plate. The wear amount increases along the side plate from zero on the material surface to the maximum value at the bottom of the chute. The average wear amount is expressed by the following formula: The wear of the conveyor belt consists of friction wear and impact wear, which is related to the velocity component of the material in the vertical direction and the running direction of the conveyor belt at the chute outlet. The wear amount is calculated as follows: Where: μ b is the friction coefficient between the material and the conveyor belt; v b is the conveyor belt speed in m / s; v ey v is the vertical velocity of the material when it falls onto the receiving belt, in m / s; ex It is the horizontal velocity of the material when it falls onto the receiving belt, in m / s.

9. The discrete element model and structure of the bulk material transfer and transmission system according to claim 1 is characterized in that: Inclination of the chute: The wear of the chute and the conveyor belt depends on the inclination and curvature radius of the chute. The speed of the material entering the chute entrance is v1, and the speed of the material sliding down the chute after impact is v2: when When v2 = 0, the material hangs on the surface of the chute and cannot flow smoothly. The sliding friction angle The value of is determined by the material properties and the smoothness of the chute surface. The minimum inclination angle of the chute that can satisfy the material flow is: α min = arctan μ E + 5° Equation 55 Adding 5° to Formula 55 takes into account the error of the chute in actual processing and installation to ensure that the material can flow reliably. The inclination angle at the end of the chute is determined by the minimum inclination angle of the chute.

10. The discrete element model and structure of the bulk material transfer and transmission system according to claim 1 is characterized in that: Combination of chutes: The combination of arc segments and straight segments is adopted. After the value of the inlet inclination angle θ of the chute is given, assuming that the chute height H and the distance x of the horizontal position are known values, the arc segment radius R and the straight segment length S of the chute are obtained by the following formula: Determine the arc segment radius R and straight segment length S of the chute and the combination form of the chute; Chute structure analysis and construction: The chute structure of each scheme was imported into EDEM software for numerical simulation calculation. When the inlet inclination of the chute is 20° and the radius of the arc segment is 1.4m, the wear formula is used to calculate that the sum of the wear of the chute and the wear of the conveyor belt is the smallest. The energy loss of the material comes from the impact and friction wear between the chute and the belt. The structure of the transfer chute should be in the form of an arc segment plus a straight line segment, and the inlet inclination angle of the chute should be 20°, and the arc radius should be 1.4m. This will not only improve the wear of the chute and conveyor belt, but also reduce the spatial dimensions of the transfer system.

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