Columnar flexible cut tobacco drying simulation analysis method based on CFD-DEM numerical simulation

Abstract

The invention discloses a CFD-DEM numerical simulation-based simulation analysis method for cylindrical flexible tobacco shred drying, which comprises the following steps of: solving continuous phase physical parameters and discrete phase physical parameters of fluid by adopting CFD and DEM methods, and coupling the DEM method with the CFD method so as to describe temperature and moisture change rules of tobacco shreds in a roller tobacco shred dryer; and determining a change rule between the temperature and moisture of the tobacco shreds and an optimal process parameter and structure parameter combination which enables the moisture of the tobacco shreds at an outlet to reach a target value and keep stable. The cylindrical flexible particle structure is adopted to construct the tobacco shred model, the calculation speed is increased, the flow field flow characteristic parameters are directly coupled with the flexible tobacco shred particle model, and a flow-heat-solid three-field coupling system is constructed, so that the temperature and moisture change of tobacco shreds in the drum cut-tobacco dryer is accurately simulated, and the calculation accuracy is improved. Accurate control over the moisture of the outlet tobacco shreds is achieved, moisture volatility is reduced, the tobacco shred utilization rate is increased, and resource waste is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of tobacco processing, and more specifically, relates to a simulation analysis method for drying columnar flexible shredded tobacco based on CFD-DEM numerical simulation. Background Art

[0002] With the continuous development of the cigarette industry, people have higher and higher requirements for the intrinsic quality of cigarettes. There are more than 130 countries and regions in the world that grow tobacco, and the economic benefits brought by its industrial product cigarettes are huge; at present, most of the complete sets of cigarette equipment produced at home and abroad are designed with corresponding devices that can dry tobacco, but the control of the moisture target value of exported tobacco and the moisture stability of exported tobacco still cannot achieve the ideal effect, and the drying process needs to be further optimized. The drying of tobacco is a crucial step in tobacco processing, which directly affects the quality and processing efficiency of tobacco. However, the existing traditional drying technology has many challenges in practical application. Traditional drying equipment mainly relies on hot air convection heating. Although this method can meet the basic drying requirements, it is difficult to achieve accurate control of temperature and moisture. Due to the unevenness of hot air flow and temperature fluctuations during the drying process, the moisture content of tobacco is often difficult to stably control, which not only affects the quality of the final product, but also leads to waste of energy and resources. In addition, the traditional method is difficult to ensure the uniform drying of tobacco, and it is easy to cause local overheating or uneven drying, which in turn affects the overall consistency of tobacco. Although sensors are installed in the drying drum to monitor the temperature and moisture of the tobacco, this traditional sensor technology still faces problems such as high loss and insufficient data spatial resolution, making it difficult to fully capture the complex dynamic changes in the drying process.

[0003] On the other hand, actual tobacco shreds present complex shapes and curvatures during thermal processing, which poses great challenges for accurate geometric modeling and simulation. The complex and large number of tobacco shreds during the drying process make accurate modeling and simulation almost impossible, making it difficult for existing technologies to fully predict and optimize the drying process; these problems limit the in-depth understanding and optimization of the drying process. Summary of the invention

[0004] In order to solve the deficiencies in the prior art, the present invention proposes a simulation analysis method for columnar flexible tobacco drying based on CFD-DEM (computational fluid dynamics-discrete element method) numerical simulation. By directly coupling the flow characteristic parameters of the flow field with the flexible tobacco particle model, a fluid-heat-solid three-field coupling system is constructed to accurately simulate the temperature and moisture changes of tobacco in the drum drying machine, thereby achieving precise control of the moisture content of the exported tobacco, reducing moisture volatility, improving tobacco utilization, and reducing resource waste.

[0005] The present invention provides a simulation analysis method for drying columnar flexible tobacco shreds based on CFD-DEM numerical simulation, comprising the following steps:

[0006] Step (1) parameterizing the characteristics of the tobacco shreds according to the physical characteristics and geometric properties of the tobacco shreds during the drying process;

[0007] Step (2) constructing a digital model of the columnar flexible tobacco according to the physical properties and geometric attribute parameters obtained in step (1);

[0008] Step (3) according to the actual model of the drum, the structural parameters of the drum are obtained by three-dimensional space perception technology, and the drum silk drying machine is digitally modeled;

[0009] Step (4) geometrically modeling the shoveling plate at the entrance of the drum tobacco drying machine and the shoveling plate inside the drum so that the shoveling plate can fully stir the tobacco;

[0010] Step (5) setting different angles of copying plates, different numbers of copying plates, and different tilt angles of rollers to make the simulation results comparable and facilitate analysis and comparison;

[0011] Step (6) setting different process parameter values ​​to make the simulation results comparable and facilitate analysis and comparison;

[0012] Step (7) fitting the process parameters at different times under various working conditions into dynamic boundary conditions as boundary conditions for CFD simulation to improve the accuracy of simulation results;

[0013] Step (8) performing flow field simulation in CFD, changing various process parameters during the fiber drying process to form different flow fields, which is convenient for comparative analysis;

[0014] Step (9) numerically simulates the field quantity transfer between the temperature field, flow field and discrete element in the tobacco drying process by coupling CFD with DEM, and obtains the temperature and energy variation characteristics of the tobacco in the drying process;

[0015] Step (10) extracts the finite element results in the fluid-heat-solid coupling analysis, studies the temperature field, flow field and tobacco temperature changes in the drum under steady-state conditions, and establishes a relationship model between tobacco temperature and moisture content and process parameters and structural parameters.

[0016] With respect to step (1), the physical characteristics and geometric properties of the tobacco shreds during the drying process include density and thermal conductivity;

[0017] Density (ρ)

[0018] Among them, m is the mass of tobacco, V is the volume of tobacco;

[0019] Thermal conductivity (k)

[0020] Where q is the heat flow, T is the temperature, and x is the spatial coordinate;

[0021] With respect to step (2), the digital model of the columnar flexible tobacco shreds is constructed, including the volume of the columnar tobacco shreds;

[0022] Volume of cylindrical tobacco (V C )

[0023] Among them, d is the diameter of the tobacco, l is the length of the tobacco;

[0024] With respect to step (3), the actual model of the drum includes several main parts such as a drum cover, an outer copying plate, a drum, an inner copying plate, and a rear chamber. The drum, as a key component, plays an important role in tobacco drying. The drum is mainly digitally modeled to make it more consistent with the actual model.

[0025] The structural parameters of the drum include the volume of the drum;

[0026] Roller volume (V d )

[0027] Where D is the roller diameter and L is the roller length;

[0028] For step (7), the moving boundary condition refers to the functional expression of the change of a process parameter value over time. The moving boundary expression of the hot air temperature is:

[0029] Hot air temperature = 273.15[K] + 1[K*s^-10]*(

[0030] +1[s^10]*(111.96569395263201)

[0031] +1[s^9]*(0.0004188627708866421*t)

[0032] +1[s^8]*((-8.371064963974362*10^-7)*t^2)

[0033] +1[s^7]*((2.6830897064978515*10^-7)*t^3)

[0034] +1[s^6]*((-4.0757590047534094*10^-8)*t^4)

[0035] +1[s^5]*((1.206914329667954*10^-9)*t^5)

[0036] +1[s^4]*((-1.6579104528725397*10^-11)*t^6)

[0037] +1[s^3]*((1.2530831389205095*10^-13)*t^7)

[0038] +1[s^2]*((-5.378227406468468*10^-16)*t^8)

[0039] +1[s^1]*((1.2315157295562552*10^-18)*t^9)

[0040] +(-1.1701372171629463*10^-21)*(t^10))

[0041] The moving boundary of the hot air velocity is:

[0042] Hot air speed = 1[ms^-1*s^-10]*(

[0043] +1[s^10]*(3.7964579175071678-1.419)

[0044] +1[s^9]*(0.006129336511330755*t)

[0045] +1[s^8]*((-0.0006362252273160924)*t^2)

[0046] +1[s^7]*((2.838144604329849*10^-5)*t^3)

[0047] +1[s^6]*((-6.859867900257946*10^-7)*t^4)

[0048] +1[s^5]*((1.0005551020404074*10^-8)*t^5)

[0049] +1[s^4]*((-9.224627002150974*10^-11)*t^6)

[0050] +1[s^3]*((5.411624454624429*10^-13)*t^7)

[0051] +1[s^2]*((-1.9570475680071348*10^-15)*t^8)

[0052] +1[s^1]*((3.973583531338013*10^-18)*t^9)

[0053] +(-3.462499263182982*10^-21)*(t^10))

[0054] Where K represents the Kelvin temperature unit, s is the simple second, and t represents time;

[0055] For step (8), the flow field simulation can be regarded as a turbulent flow model for the air in the cylinder, and the Realizable k-ε model is selected for numerical simulation. The mass conservation equation and momentum equation are expressed as follows:

[0056]

[0057] Where: t is time; ρ is fluid density; u is velocity vector; I is the unit matrix; K is the viscous stress tensor; F is the volume force vector.

[0058] The transport equation of the Realizable k-ε model consists of two equations: the turbulent kinetic energy equation and the turbulent dissipation rate equation, and its expression is:

[0059] Turbulent kinetic energy equation:

[0060] Turbulent dissipation rate equation:

[0061] in

[0062]

[0063] Where: ρ is the fluid density, t is the time, k is the turbulent kinetic energy, ε is the turbulent dissipation rate, μ i is the velocity vector, v is the kinematic viscosity, x is the position vector, μ is the dynamic viscosity, μ i is the turbulent viscosity, G k is the generation term of turbulent kinetic energy k caused by the average velocity gradient, C1 and C2 are empirical constants, σ k , σ ε is the Prandtl number corresponding to the turbulent kinetic energy k and the dissipation rate ε, σ k =1.0,σ ε =1.2, C2=1.9.

[0064] For step (9), the field quantity transfer between the temperature field, flow field and discrete element is numerically simulated, wherein the control equation for the change of the tobacco particle temperature is:

[0065]

[0066] Where c p is the specific heat of the particle; It is the heat transfer between particles or between particles and wall; is the heat transfer between particles and fluid.

[0067] The motion control equations that control the translation and rotation of tobacco particles are as follows:

[0068]

[0069] Where m p is the mass of the particle; F c is the contact force between the particle and the particle wall; ω p is the angular velocity vector; J p is the moment of inertia tensor; M c is the net torque produced by the tangential force that causes the particle to rotate; M f→p is the additional torque due to the fluid phase velocity gradient.

[0070] The flow field information is converted into the fluid drag on the flexible tobacco particles through the drag model, and the flow field data is imported into DEM. At this time, CFD and DEM transfer mass and energy through a certain model to achieve coupling.

[0071] Furthermore, in the steps (1) and (2), the physical characteristics and geometric properties of the tobacco are characterized by parameters, a columnar flexible tobacco model is constructed, the simulation efficiency is improved, and a rapid optimization method is provided to achieve the target value of the moisture content of the tobacco and improve the stability of the moisture content of the tobacco.

[0072] Furthermore, in the step (3), a parallel laser beam is emitted to the drum tofu drying machine entity through three-dimensional space perception technology and reflection information is received to obtain cloud data including information such as the three-dimensional coordinates of the sampling points, thereby realizing the construction of the model.

[0073] Furthermore, in the step (4), the size of the actual copying plate in the drum is enlarged and reconstructed so that the tobacco can be fully stirred and the degree of looseness of the tobacco in the drum is improved.

[0074] Furthermore, in the steps (5) and (6), by changing the structural parameters and process parameters, the optimal structural parameters and process parameters in the silk drying process can be analyzed and compared.

[0075] Furthermore, in the step (7), the process parameters at different times are different. In order to improve the accuracy of the simulation results, the process parameters at each time are fitted into a function form that changes with time.

[0076] Furthermore, in the steps (8) and (9), the flow characteristic parameters of the flow field are directly coupled with the flexible tobacco particle model to construct a fluid-heat-solid coupling system to accurately characterize the temperature and moisture variation of the tobacco in the drum.

[0077] Furthermore, in the step (10), the tobacco temperature and tobacco moisture under different working conditions are compared, the moisture content of the exported tobacco is calculated respectively, and a relationship model between the tobacco temperature and moisture content and the process parameters and structural parameters is obtained; and the process parameters and structural parameters are optimized and adjusted on the premise that the exported tobacco moisture reaches the target value and the stability of the tobacco moisture is improved.

[0078] Compared with the prior art, the above technical solution has the following beneficial effects:

[0079] Compared with the existing technology, the present invention uses a columnar flexible particle structure to construct a tobacco cut model. Under the premise of ensuring that the tobacco cut drying process can proceed normally, the complexity of the tobacco cut shape is reduced, the calculation speed is greatly improved, and the tobacco cut drying process can be simulated more efficiently, and various process parameters and structural parameters can be further optimized. Directly importing CFD data into DEM for coupling simulation can directly couple the flow field flow characteristic parameters with the tobacco cut particle model, construct a flow-heat-solid three-field coupling system, and accurately simulate the entire tobacco cut drying process.

[0080] By enlarging and reconstructing the copy board model, the tobacco can be fully stirred, the loose field of tobacco in the drum is improved, and the temperature and moisture of tobacco cannot reach the target value due to the agglomeration of some tobacco. By setting up control tests with different structural parameters and process parameters, the optimal structural parameters and process parameters suitable for the thin plate drying process can be analyzed. In the DEM environment, a cube can be created to divide the tobacco in the drum after drying into 32 partitions, and the detailed data of the average temperature and average moisture content of tobacco in each partition can be directly counted, which is convenient for intuitively analyzing the change law of tobacco temperature and moisture content and the mutual influence relationship between the two. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] Figure 1 It is a graphic flow chart of the present invention;

[0082] Figure 2 A flow chart illustrating the present invention;

[0083] Figure 3 Schematic diagram of the columnar flexible tobacco particle model constructed by the present invention;

[0084] Figure 4 This is a schematic diagram of the structure of a drum wire drying machine used in the present invention;

[0085] Figure 5A schematic diagram of the structure of the inlet copying group and the internal copying group used in the present invention;

[0086] Figure 6 A schematic diagram showing the comparison of copy boards with different angles provided in the present invention;

[0087] Figure 7 A schematic diagram showing the comparison of different roller inclination angles provided in the present invention;

[0088] Figure 8 A schematic diagram for comparing different numbers of copy boards provided in the present invention. DETAILED DESCRIPTION

[0089] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention, wherein the implementation examples are only part of the embodiments of the present invention, not all. Based on the embodiments in the embodiments, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0090] See also Figure 1 and Figure 2 , which is a simulation analysis method for drying columnar flexible tobacco based on CFD-DEM numerical simulation provided in an embodiment of the present invention, specifically comprises the following steps:

[0091] Step (1) parameterizing the characteristics of the tobacco shreds according to the physical characteristics and geometric properties of the tobacco shreds during the drying process;

[0092] Step (2) constructing a digital model of the columnar flexible tobacco according to the physical properties and geometric attribute parameters obtained in step (1);

[0093] Step (3) according to the actual model of the drum, the structural parameters of the drum are obtained by three-dimensional space perception technology, and the drum silk drying machine is digitally modeled;

[0094] Step (4) geometrically modeling the shoveling plate at the entrance of the drum tobacco drying machine and the shoveling plate inside the drum so that the shoveling plate can fully stir the tobacco;

[0095] Step (5) setting different angles of copying plates, different numbers of copying plates, and different tilt angles of rollers to make the simulation results comparable and facilitate analysis and comparison;

[0096] Step (6) setting different process parameter values ​​to make the simulation results comparable and facilitate analysis and comparison;

[0097] Step (7) fitting the process parameters at different times under various working conditions into dynamic boundary conditions as boundary conditions for CFD simulation to improve the accuracy of simulation results;

[0098] Step (8) performing flow field simulation in CFD, changing various process parameters during the fiber drying process to form different flow fields, which is convenient for comparative analysis;

[0099] Step (9) numerically simulates the field quantity transfer between the temperature field, flow field and discrete element in the tobacco drying process by coupling CFD with DEM, and obtains the temperature and energy variation characteristics of the tobacco in the drying process;

[0100] Step (10) extracts the finite element results in the fluid-heat-solid coupling analysis, studies the temperature field, flow field and tobacco temperature changes in the drum under steady-state conditions, and establishes a relationship model between tobacco temperature and moisture content and process parameters and structural parameters.

[0101] With respect to step (1), the physical characteristics and geometric properties of the tobacco shreds during the drying process include density and thermal conductivity;

[0102] Density (ρ)

[0103] Among them, m is the mass of tobacco, V is the volume of tobacco;

[0104] Thermal conductivity (k)

[0105] Where q is the heat flow, T is the temperature, and x is the spatial coordinate;

[0106] With respect to step (2), the digital model of the columnar flexible tobacco shreds is constructed, including the volume of the columnar tobacco shreds;

[0107] Volume of cylindrical tobacco (V C )

[0108] Among them, d is the diameter of the tobacco, l is the length of the tobacco;

[0109] With respect to step (3), the actual model of the drum includes several main parts such as a drum cover, an outer copying plate, a drum, an inner copying plate, and a rear chamber. The drum, as a key component, plays an important role in tobacco drying. The drum is mainly digitally modeled to make it more consistent with the actual model.

[0110] The structural parameters of the drum include the volume of the drum;

[0111] Roller volume (V d )

[0112] Where D is the roller diameter and L is the roller length;

[0113] For step (7), the moving boundary condition refers to the functional expression of the change of a process parameter value over time. The moving boundary expression of the hot air temperature is:

[0114] Hot air temperature = 273.15[K] + 1[K*s^-10]*(

[0115] +1[s^10]*(111.96569395263201)

[0116] +1[s^9]*(0.0004188627708866421*t)

[0117] +1[s^8]*((-8.371064963974362*10^-7)*t^2)

[0118] +1[s^7]*((2.6830897064978515*10^-7)*t^3)

[0119] +1[s^6]*((-4.0757590047534094*10^-8)*t^4)

[0120] +1[s^5]*((1.206914329667954*10^-9)*t^5)

[0121] +1[s^4]*((-1.6579104528725397*10^-11)*t^6)

[0122] +1[s^3]*((1.2530831389205095*10^-13)*t^7)

[0123] +1[s^2]*((-5.378227406468468*10^-16)*t^8)

[0124] +1[s^1]*((1.2315157295562552*10^-18)*t^9)

[0125] +(-1.1701372171629463*10^-21)*(t^10))

[0126] The moving boundary of the hot air velocity is:

[0127] Hot air speed = 1[ms^-1*s^-10]*(

[0128] +1[s^10]*(3.7964579175071678-1.419)

[0129] +1[s^9]*(0.006129336511330755*t)

[0130] +1[s^8]*((-0.0006362252273160924)*t^2)

[0131] +1[s^7]*((2.838144604329849*10^-5)*t^3)

[0132] +1[s^6]*((-6.859867900257946*10^-7)*t^4)

[0133] +1[s^5]*((1.0005551020404074*10^-8)*t^5)

[0134] +1[s^4]*((-9.224627002150974*10^-11)*t^6)

[0135] +1[s^3]*((5.411624454624429*10^-13)*t^7)

[0136] +1[s^2]*((-1.9570475680071348*10^-15)*t^8)

[0137] +1[s^1]*((3.973583531338013*10^-18)*t^9)

[0138] +(-3.462499263182982*10^-21)*(t^10))

[0139] Where K represents the Kelvin temperature unit, s is the simple second, and t represents time;

[0140] For step (8), the flow field simulation can be regarded as a turbulent flow model for the air in the cylinder, and the Realizable k-ε model is selected for numerical simulation. The mass conservation equation and momentum equation are expressed as follows:

[0141]

[0142]

[0143] Where: t is time; ρ is fluid density; u is velocity vector; I is the unit matrix; K is the viscous stress tensor; F is the volume force vector.

[0144] The transport equation of the Realizable k-ε model consists of two equations: the turbulent kinetic energy equation and the turbulent dissipation rate equation, and its expression is:

[0145] Turbulent kinetic energy equation:

[0146] Turbulent dissipation rate equation:

[0147] in

[0148]

[0149] Where: ρ is the fluid density, t is the time, k is the turbulent kinetic energy, ε is the turbulent dissipation rate, μ i is the velocity vector, v is the kinematic viscosity, x is the position vector, μ is the dynamic viscosity, μ i is the turbulent viscosity, G k is the generation term of turbulent kinetic energy k caused by the average velocity gradient, C1 and C2 are empirical constants, σ k , σ ε is the Prandtl number corresponding to the turbulent kinetic energy k and the dissipation rate ε, σ k =1.0,σ ε =1.2, C2=1.9.

[0150] For step (9), the field quantity transfer between the temperature field, flow field and discrete element is numerically simulated, wherein the control equation for the change of the tobacco particle temperature is:

[0151]

[0152] Where c p is the specific heat of the particle; It is the heat transfer between particles or between particles and wall; is the heat transfer between particles and fluid.

[0153] The motion control equations that control the translation and rotation of tobacco particles are as follows:

[0154]

[0155] Where m p is the mass of the particle; F c is the contact force between the particle and the particle wall; ω p is the angular velocity vector; J p is the moment of inertia tensor; M c is the net torque produced by the tangential force that causes the particle to rotate; M f→p is the additional torque due to the fluid phase velocity gradient.

[0156] The flow field information is converted into the fluid drag on the flexible tobacco particles through the drag model, and the flow field data is imported into DEM. At this time, CFD and DEM transfer mass and energy through a certain model to achieve coupling.

[0157] Furthermore, in the steps (1) and (2), the physical characteristics and geometric properties of the tobacco are characterized by parameters, a columnar flexible tobacco model is constructed, the simulation efficiency is improved, and a rapid optimization method is provided to achieve the target value of the moisture content of the tobacco and improve the stability of the moisture content of the tobacco.

[0158] Furthermore, in the step (3), a parallel laser beam is emitted to the drum tofu drying machine entity through three-dimensional space perception technology and reflection information is received to obtain cloud data including information such as the three-dimensional coordinates of the sampling points, thereby realizing the construction of the model.

[0159] Furthermore, in the step (4), the size of the actual copying plate in the drum is enlarged and reconstructed so that the tobacco can be fully stirred and the degree of looseness of the tobacco in the drum is improved.

[0160] Furthermore, in the steps (5) and (6), by changing the structural parameters and process parameters, the optimal structural parameters and process parameters in the silk drying process can be analyzed and compared.

[0161] Furthermore, in the step (7), the process parameters at different times are different. In order to improve the accuracy of the simulation results, the process parameters at each time are fitted into a function form that changes with time.

[0162] Furthermore, in the steps (8) and (9), the flow characteristic parameters of the flow field are directly coupled with the flexible tobacco particle model to construct a fluid-heat-solid coupling system to accurately characterize the temperature and moisture variation of the tobacco in the drum.

[0163] Furthermore, in the step (10), the tobacco temperature and tobacco moisture under different working conditions are compared, the moisture content of the exported tobacco is calculated respectively, and a relationship model between the tobacco temperature and moisture content and the process parameters and structural parameters is obtained; and the process parameters and structural parameters are optimized and adjusted on the premise that the exported tobacco moisture reaches the target value and the stability of the tobacco moisture is improved.

[0164] See also Figure 3, which is a simulation analysis method for drying columnar flexible tobacco based on CFD-DEM numerical simulation of the present invention, and a schematic diagram of columnar flexible tobacco particles; by obtaining the physical parameters of tobacco samples in the cigarette processing process, the shape of the tobacco is sheet-like, the length is in the range of 20mm to 100mm, the width is between 2mm and 3mm, and the thickness is between 1mm and 2mm; by controlling the length and cross-sectional area to be equal to the actual tobacco stick, a columnar flexible tobacco model is constructed, and the structural parameters of the columnar tobacco are input into the DEM for model construction, including the starting point coordinates, the end point coordinates and the diameter of the tobacco particles of the columnar tobacco, wherein the geometric center line of the particle is the coordinate axis Z axis, the starting point coordinates are the origin coordinates, and the length of the end point coordinates in the Z direction is the actual length of the tobacco particles; in order to improve the simulation efficiency, the diameter of the columnar flexible tobacco is constructed to be 2mm, which provides a rapid optimization means for making the moisture content of the tobacco reach the target value and improving the stability of the moisture content of the tobacco.

[0165] See also Figure 4 , which is a simulation analysis method for drying columnar flexible tobacco based on CFD-DEM numerical simulation of the present invention, and a schematic diagram of the structure of a drum tobacco drying machine; through the three-dimensional space perception technology, a parallel laser beam is emitted to the entity of the drum tobacco drying machine and the reflection information is received to obtain cloud data containing information such as the 3D coordinates of the sampling points, and the original STL model of the drum is converted into a solid model through operations such as hole filling, noise reduction, and surface smoothing to be used for finite element analysis. The main structures of the drum tobacco drying machine include drum wall, drum cover, rear chamber, inlet shoveling plate group and inner shoveling plate group; the drum wall size is 5961mm×1342mm×1342mm, the drum cover size is 445mm×1110×mm 1110mm, the rear chamber size is 1388mm×1970mm×2980mm, the shoveling plate group and the inner shoveling plate group are both composed of 8 shoveling plates and are close to the inner side of the drum wall to realize the construction of the model; the drum model is set at an inclination angle of 2.5 degrees, so that the tobacco can move smoothly to the drum outlet during the drying process without being blocked in the drum.

[0166] See also Figure 5 , which is a simulation analysis method for drying columnar flexible tobacco based on CFD-DEM numerical simulation of the present invention, and a schematic diagram of an inlet copying plate group and an internal copying plate; in order to increase the contact area between the copying plate and the tobacco, so that the tobacco can be fully stirred, improve the loose field degree of the tobacco in the drum, and prevent the tobacco temperature and moisture from failing to reach the target value due to the agglomeration of some tobacco, the size of the copying plate in the actual drum is enlarged and reconstructed, wherein the size of the inlet copying plate group is 258mm×353mm×123mm, and the size of the internal copying plate group is 5127mm×283mm×307mm, and both groups of copying plates are composed of 8 copying plates and are close to the inner wall of the drum.

[0167] See also Figure 6 , Figure 7and Figure 8 , which is a simulation analysis method for drying columnar flexible tobacco based on CFD-DEM numerical simulation of the present invention, schematic diagrams of copying plates with different angles, schematic diagrams of rollers with different inclination angles, and schematic diagrams of different numbers of copying plates; in order to compare the effects of structural parameters on tobacco temperature and moisture content and find the optimal structural parameters, the copying plate angles are set to 50°, 60°, and 70° respectively; the number of copying plates is set to 6, 8, and 10 respectively; the roller inclination angles are set to 2.5°, 4°, and 5.5° respectively; the effects of different structural parameters on tobacco characteristics are further analyzed and compared.

[0168] In order to compare the effects of process parameters on tobacco temperature and moisture content and find the optimal process parameters, the hot air temperature (103°, 111°, 119°), hot air speed (1.42m / s, 2.37m / s, 2.77m / s), drum wall temperature (109°, 117°, 125°), drum speed (8rev / min, 11rev / min, 14rev / min), dehumidification air temperature (81°, 89°, 97°), dehumidification air speed (-6.09m / s, -6.49m / s, -6.89m / s), rear chamber wind speed (3.39m / s, 3.79m / s, 4.19m / s) and discharge port temperature (90°, 98°, 106°) were set to different values, and the effects of different process parameters on tobacco characteristics were further analyzed and compared.

[0169] Since the process parameters at different times are different, in order to improve the accuracy of the simulation results, the process parameters at each time are fitted into a function form that changes with time through the custom expression in Fluent; these mainly include inlet hot air velocity, inlet hot air temperature, cylinder wall temperature, exhaust air temperature, exhaust air velocity and rear chamber hot air inlet.

[0170] The fiber resistance model proposed by Marheineke and Wegener in turbulent flow is used to analyze the columnar tobacco fiber particles; the flow field flow characteristic parameters are directly coupled with the flexible tobacco particle model to construct a fluid-heat-solid coupling system to accurately characterize the temperature and moisture changes of tobacco in the drum; the temperature field, flow field and tobacco temperature changes in the drum under steady-state conditions of different working conditions are studied, and when the material input of the drying process reaches a balanced state and the output no longer changes, the tobacco temperature and outlet tobacco moisture content are analyzed. A cube is created in the DEM environment to directly calculate the detailed data of the temperature and moisture content of the tobacco in the entire drum after the drying is completed, and the change law of the tobacco temperature and moisture content and the mutual influence between the two are further analyzed, and the relationship model between the tobacco temperature and moisture content and the process parameters and structural parameters is obtained.

[0171] The specific implementation methods described above further illustrate the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A simulation analysis method for drying columnar flexible tobacco based on CFD-DEM numerical simulation, characterized in that: The specific steps include: Step (1) parameterizing the characteristics of the tobacco shreds according to the physical characteristics and geometric properties of the tobacco shreds during the drying process; Step (2) constructing a digital model of the columnar flexible tobacco according to the physical properties and geometric attribute parameters obtained in step (1); Step (3) according to the actual model of the drum, the structural parameters of the drum are obtained by three-dimensional space perception technology, and the drum silk drying machine is digitally modeled; Step (4) geometrically modeling the shoveling plate at the entrance of the drum tobacco drying machine and the shoveling plate inside the drum so that the shoveling plate can fully stir the tobacco; Step (5) setting different angles of copying plates, different numbers of copying plates, and different tilt angles of rollers to make the simulation results comparable and facilitate analysis and comparison; Step (6) setting different process parameter values ​​to make the simulation results comparable and facilitate analysis and comparison; Step (7) fitting the process parameters at different times under various working conditions into dynamic boundary conditions as boundary conditions for CFD simulation to improve the accuracy of simulation results; Step (8) performing flow field simulation in CFD, changing various process parameters during the fiber drying process to form different flow fields, which is convenient for comparative analysis; Step (9) by coupling CFD with DEM, numerical simulation is performed on the field quantity transfer between the temperature field, flow field and discrete element in the tobacco drying process to obtain the temperature and energy change characteristics of the tobacco in the drying process; Step (10) extracts the finite element results in the fluid-heat-solid coupling analysis, studies the temperature field, flow field and tobacco temperature changes in the drum under steady-state conditions, and establishes a relationship model between tobacco temperature and moisture content and process parameters and structural parameters.

2. The simulation analysis method for drying columnar flexible tobacco based on CFD-DEM numerical simulation according to claim 1 is characterized in that: CFD-DEM is used for fluid-heat-solid coupling, which has high simulation efficiency, is easy to extract key data, is conducive to intuitive analysis of the impact of various process parameters and structural parameters on temperature and moisture content, and has a high degree of automation.

3. The simulation analysis method for drying columnar flexible tobacco based on CFD-DEM numerical simulation according to claim 1 is characterized in that: In the steps (1) and (2), the physical characteristics and geometric properties of the tobacco are characterized by parameters, a columnar flexible tobacco model is constructed, the simulation efficiency is improved, and a rapid optimization method is provided to achieve the target value of the moisture content of the tobacco and improve the stability of the moisture content of the tobacco.

4. The simulation analysis method for drying columnar flexible tobacco based on CFD-DEM numerical simulation according to claim 1 is characterized in that: In the step (3), a parallel laser beam is emitted to the drum torrefaction machine entity and reflected information is received through three-dimensional space perception technology to obtain cloud data including information such as the three-dimensional coordinates of the sampling points, thereby realizing the construction of the model.

5. The simulation analysis method for drying columnar flexible tobacco based on CFD-DEM numerical simulation according to claim 1 is characterized in that: In the step (4), the size of the actual lifting plate in the drum is enlarged and reconstructed so that the tobacco can be fully stirred and the degree of loosening of the tobacco in the drum is improved.

6. The simulation analysis method for drying columnar flexible tobacco based on CFD-DEM numerical simulation according to claim 1, characterized in that: In the steps (5) and (6), the structural parameters and process parameters of the roller are different, and the drying efficiency of the tobacco shreds is also different.

7. The simulation analysis method for drying columnar flexible tobacco based on CFD-DEM numerical simulation according to claim 1 is characterized in that: In the step (7), the process parameters at different times are different. In order to improve the accuracy of the simulation results, the process parameters at each time are fitted into a function form that changes with time.

8. The simulation analysis method for drying columnar flexible tobacco based on CFD-DEM numerical simulation according to claim 1 is characterized in that: In the steps (8) and (9), the flow characteristic parameters of the flow field are directly coupled with the flexible tobacco particle model to construct a fluid-heat-solid coupling system to accurately characterize the temperature and moisture variation of the tobacco in the drum.

9. The simulation analysis method for drying columnar flexible tobacco based on CFD-DEM numerical simulation according to claim 1, characterized in that: In the step (10), the tobacco cut temperature and tobacco cut moisture under different working conditions are compared, the moisture content of the exported tobacco cut is statistically analyzed, and a relationship model between the tobacco cut temperature and moisture content and the process parameters and structural parameters is obtained; and the process parameters and structural parameters are optimized and adjusted on the premise that the exported tobacco cut moisture reaches the target value and the stability of the tobacco cut moisture is improved.

Images