The digital twin of the grain cleaning and transportation system of a breeding combine

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Introduction

In accordance with the Food Security Doctrine of the Russian Federation, the levelof self-sufficiency in seeds of the main agricultural crops of domestic selection should be at least 75 %. According to the latest data of the Ministry of Agriculture Россиof the Russian Federation , the availability of domestic seeds for spring, grain and leguminous crops is 70.14 %, taking into account the difficult geopolitical situation, sanctions pressure and international isolation from the largest international suppliers of seed material, the problem of producing domestically selected seeds to ensure food security is more urgent than ever, and the creation of modern high-tech breeding and seed-growing equipment of domestic production, which meets the specific tasks of seed producers and modern requirements, with high indicators of economic efficiency, environmental friendliness, and labor protection is an urgent task. When improving existing equipment, as well as when creating a new one, it is necessary to work out a significant number of ideas and options in order to identify the most promising ones, but to obtain information about the leakageoftechnological processes within systems, it is necessary to produce prototypes, which significantly increases the cost and time of designing and testing hypotheses. Digital twins of individual elements of systems, allow you to simulate technological processes occurring when using the working parts of agricultural machines, while varying the physical and mechanical properties of the processed crops.

In modern breeding and seed production, the key parameter is the technological security of work, as well as the high level of equipment used. According to experts, the level of provision of leading specialized centers with breeding equipment for plot preparation, sowing and crop care does not exceed 33 %, for seed harvesting – 28 %, for post – harvest seed processing-25 %, andfor rovens its wear exceeds 70 %. It is also worth considering the fact that breeding and seed-growing equipment is highly specialized, and in most cases it is created to solve certain problems in the field of mechanization and automation of breeding operations [1]. The shortage of this equipment, its severe wear and tear, lead to the preservation of a high share of manual labor in the industry, a decrease in the speed of work, non-compliance with work deadlines, violation of agrotechnical requirements, increased losses of expensive seed material, high material costs for production. Thus, the low level of technical support is one of the constraining factors for the development of domestic breeding and expanded reproduction of domestic seed material [2]. According to the decree of the Government of the Russian Federation No. 3309-r of November 23, 2023, digital technologies should be implemented at all stages of the production cycle, including the development of self-propelled vehicles and improving approaches to the development and use of digital products.

Selection and seed-growing combines are subject to specific requirements for cleaning the harvested grain: for example, the number of weed impurities should not exceed 0.3% of the grain weight, while damage or crushing of valuable expensive seeds should also not exceed 0.3%. To increase the efficiency of harvesting operations and reduce grain losses, it is advisable to use additional cleaning and transportation systems [3-4]. Designing, debugging, and calibrating such systems is a complex engineering task that also requires significant time and material costs. Inьorder to optimize the development process, in accordance with modern trends, design is carried out in CAD software packages, initial debugging and design optimization – in software packages for modeling physical processes, which include systems that allow modeling the movement of individual particles. The result of such modeling is a digital model, which with a certain degree of probability allows you to obtain the characteristics of the technological process at the design stage, to identify the advantages and disadvantages of the designed machine.

In this paper, the sequence of creating a digital model of the system of pneumatic transportation of seed grain piles through the pipeline to the cyclone is given.

A considerable amount of research has been devoted to the problems of pneumatic transportation, including grain heap components, both in horizontal and vertical pipe sections, as well as to the description of these processes using digital models [15, 16, 19, 23, 24, 29] they allow you to get an idea of the existing level of modeling of this process. At the end of the transportation process, particles are deposited in a cyclone with particle separation [12, 18, 25]. To simulate the process of particle motion under the action of the forces of a moving air flow, it is necessary to determine the velocity and pressure fields at each point of the volume, as well as the kinematic parameters of the motion of all discrete particles and their interaction [13, 14, 19, 21]. It is necessary to take into account the properties of the transported material [17, 20, 22, 26, 27, 28, 38].

The aim of the research is to create a digital twin of the transportation and cleaning system with the ability to simulate the movement of particles in the air stream.

Work objectives:

• construction and optimization of a digital geometric model for possible use in simulation modeling of processes occurring in the system;
• research of grain heap composition and its characteristics;
• creation of digital models of transported particles that have similar characteristics to real grain heap particles;
• conducting simulation modeling of particle motion in an air stream using the discrete-element modeling method.

Materials and methods

This study is based on the discrete element method developed by Cundall and Strack in 1979 [31]. At the beginning of the studyсоставлена , a calculation scheme was drawn up for the mutual arrangement of the main elements of the grain transportation and cyclone cleaning system, the geometric parameters of which corresponded to the designed system for a breeding combine [5-7] (fig.1.)

Fig. 1 - Composition diagram of grain cleaning and transportation system

Using the basic geometric characteristics of the elements and layout scheme, 3D – D models of the main components of the grain cleaning and transportation system were designed- cyclone, centrifugal fan, grain intake diffuser, pipelines, etc., some of these components are presented in figure 2.

1. a) b) c)

Fig.2. Main assemblies of the transportation and cleaning system, where

1. a) cyclone, b) centrifugal fan, c) grain intake diffuser

To optimize the design and conduct discrete-element modeling of the transportation process , a model of the internal space of the grain transportation and cleaning system filled with air was obtained [8], which is actually a component of a digital twin. The general viewof the model is shown in figure 3.

Fig.3 - Model of the internal space of the grain transportation and cleaning system

For modeling, it is necessary to determine the characteristics of the air flow in each discrete volume of the system and set the characteristics of the particles transported by it. For this purpose, the physical parameters of grain and impurities entering the transportation and cleaning system were analyzed. As impurities in the grain heap, therewere polova, awns, straw particles, small fragments of grain, as well as dust with a particle size of about 50 microns. To determine the average size characteristics of grains and impurities, 10 samples of grains of the Anfisa variety and each of the groups of weeds in the grain pile were used. Particle masses were measured on an OHAUSEX224/AD analytical balance, and the weighing process is shown in figure 4.

1. a) b)

Fig.4 - Weighing on analytical scales of grain and weed impurities,

where a) grain, b) osti

Geometric parameters were measured using an electronic caliper with an accuracy of 0.01 mm.. The average values of the particle parameters and their models are shown in Table 1.

Table 1 - Parameters of particles and their models

The obtained data were usedas initial data in further modeling in the Ansys environment with additional add-ons. The range of particle generation in thegrain intake, their mass and size, and the air flow velocity are set.

When modeling the digital system of grain transportation and cleaning, and modeling the process of pneumatic transportation of grain mass with its subsequent deposition in a cyclone , a one-sided problem statement was used, when the obtained characteristics of the air flow are transmitted for subsequent modeling of particle movement, while the change in the air flow due to the presence of particles in the air environment is It should be noted that the one-sided formulation of the problem requires many times less computing power and adequately allows modeling the motion of particles with their low density relative to the volume occupied by them, which as a result do not significantly change the parameters of the air flow.

When particles collide with the system walls and with each other, the forces of gravity, friction, normal and tangential forces were taken into account [33-37-37]. Normal forces described by the law Waltonof Walton O. R. and Braun R. L. [32] by an elastic hysteresis model, the normal component of which to the contact plane is equal to:

                                                   (1)

where and is the value of the load and discharge contact stiffness;

 and - normal elastic-plastic contact forces at the current time; - modeling step; - change in the normal overlap of particle contacts during the current time (positive when the particles approach each other, and negative when they move away);  and - the value of the normal overlap at the current and previous time;                              - constant, =0.001.

The elastic-friction tangential component is calculated using theLinear spring Coulomb limit model):

                      ;                                                   (2)

                    ,                                             (3)

where is the value of the tangential force at the previous moment of time; - tangential relative displacement of particles during the time interval; - tangential stiffness, - coefficient of friction.

The initial geometry of the pneumatic conveyingsystem isис.5shown in Figure 5.

Fig.5 - Geometry of pneumatic conveying system

The composition of the grain pile and its characteristics were set with parameters identical to the natural ones presented in Table 1. Examples of setting the material characteristics are presented in fig.6.

Windows for entering physical parameters of particles on the example of grain and straware shown in Figure 6.

Fig.6 - Particle characteristics data entry windows

When modeling air flows, the velocity at the entrance to транспортирующеthe transport-separation system was 30 m / s [9].. In the visualization of air flow velocities and directions, they are presented in figure 7..

1. a) b)

c)

Fig.7 - Visualization of velocities and directions of air flow:

1. a) general view, b) in the cyclone, c) in the grain collector

Particle generation was performed according to the above parameters in the rectangular area above the grain intake, indicated by the red rectangle in figure 8.

Fig.8 - Area of grain pile particle generation

To determine the correctness of the geometric parameters of the model and determine the ability of a group of particles to overcome the distance from the generation site to the end point along a given trajectory, the process of movement of primitive particles in the air flow was simulated. The particle motion trajectories are shown in Figure 9.

1. a) b)

Fig. 9 – Visualization of particle trajectories in an air stream:

1. a) in a cyclone, b) general appearance.

Simulation of the movement of a grain pile through the grain transportation and cleaning system is presented in Figure 10.

1. a) b)

c)

Fig.10 - Visualization of grain pile particle movement in the conveying and cleaning system:

1. a) in the grain intake, b) in the pipeline bend, c) in the cyclone

Experimental andinvestigation of air flow parameters in the system of pneumatic transportation and grain cleaning of a breeding combine

The parameters of the speed and flow rate of the air flow in the system of pneumatic transportation and cleaning of grain of a selection combine with electric drive of working bodies were measured Figure 11 shows the grain transportation and cleaning system of a breeding combine.

1. a) b)

Fig.11 - combine harvester with electric drive of working bodies:

a - centrifugal fan; b - grain intake device

The test program and methodology are prepared in accordance with GOST 12.3.018-79 " System of occupational safety standards. Ventilation systems. Methods of aerodynamic testing". Sampling of parameters was carried out in five dimensional sections: fan inlet, diffuser outlet, cyclone inlet, 1st cyclone outlet, 2nd cyclone outlet (fig. 12).

Fig.12 - Scheme of the system of transportation and cleaning of combine grain, measured sections of sampling:

1 - fan (inlet); 2 - outlet after grain intake; 3 - entrance to cyclone; 4 - upper outlet from cyclone; 5 - lower outlet from cyclone

The sections are cylindrical in shape, with a diameter of D up to 300 mm. In sections 1-3 and 5, the cross – section diameter was 120 mm, in section 4-300 mm. The coordinates of the velocity measurement points were determined as 0.12D with an error of deviations of no more than ±10% of the coordinate value (Fig. 13).

Fig.13 - Coordinates of velocity measurement in cylindrical ducts at D≤300 mm

Each pointеhas 6 dimensions. The measurements were carried out with a digital anemometer Testo405-v1 with a measurement range of air flow velocity 0 ... 10 m/s (Fig. 14). The results of cross-section measurements are shown in Table 2.

Fig.14 - Measuring fan shaft speed and airflow rate

Shaft speed measurements were performed with a digital contact tachometer DT 6236B. However, due to the limited measuring range of the Testo405-v1 anemometer, it was possible to perform measurements only at a fan shaft rotation speed of 1300 min^-1, with a further increase in the speed of the air flow significantly exceeding 10 m/s.

Table 2 - Air flow velocity , m/s at the cross-section points and average cross-section values at fan shaft speed = 1300 rpm

The nature of the speed change at one point, as well as the average values relative to different cross-sections, allows us to conclude about the degree of uniformity of the air flow in the system of a breeding combine with an electric drive [10].

The uniformity of the air flow velocity was estimated by the coefficient of variation of the intervals between adjacent ears, determined by the formula:

where is the standard deviation

where  current value of measuring the air flow velocity, m/s.

 – arithmetic mean of measurements, cm.

 – number of dimensions

To calculate the coefficient of variation, the values of the velocity measurement determined by the three sigma rule are taken

According to formula 3 and the table data, all values can be used in calculations.

The air flow can be considered uniform if the uniformity coefficient does not exceed 33%.

In accordance with formulas 1, 2 and the table data, it is established that the coefficient of variation in section 1 is 11%, in section 2-27%, in section 3-10%, in section 4-57%, in section 5-56%. The values of the uniformity coefficient in sections 4 and 5 indicate uneven flows, however, they do not affect the quality of the grain transportation and cleaning system.

The air consumption was determined by the formula:

where ,^m2 is the cross-sectional area.

For a circle.

Then the air flow rate according to the average values of the air flow rate will be for the cross sections 1-5: 332,8; 320,8; 305,3; 162,8; 98,9^m3/h, respectively.

Results and discussion

A digital twin of the transport and cleaning system was created with the ability to simulate the movementof particles in the air stream, for which 3D models were builtfor visualization and simulation of processes. Thecomposition частиц of grain heap particleswas studied, their masses and geometrical dimensions were measured, and 3D-modelsand typical particles were constructed.Simulation modeling of the movement and separation of particles in the air flowis carried out, which makes it possible to more deeply assess the system's performance.

Such virtual studies allow simulating the operation of various combine systems, varying various parameters and characteristics of the system-geometrically,the size of individual nodes, the speedью of air flow, the compositionof om and the size of particles. Thus, it is possible to obtain preliminary data for machines of different productivity, different crops and their varieties, and the current level of development of modeling methods and the amount of computing power ensures a fairly high accuracy of the results obtained. Creating digital doubles significantly optimizes the development process, reducing time and economic costs, allowing you to reduce the necessary number of expensive and complex experimentalsamples, long-term tests tied to the time of year, and the digital models used serve as the basis for production documentation.

Conclusions

The possibility of conducting research in a digital environment for a design that needs to optimize many parameters is considered, using the example of a grain transportation and cleaning system in a selection combine harvester.

About the authors

Mikhail E. Chaplygin

Email: misha_2728@yandex.ru
Russian Federation

Andrey V. Butovchenko

Email: ButovchenkoAV@yandex.ru
Russian Federation

Kirill A. Stepanov

Author for correspondence.
Email: 89999878895@mail.ru

Sergey V. Belousov

Email: sergey_belousov_87@mail.ru
Russian Federation

Aleksander S. Овчаренко

Email: peterbilt@list.ru
Russian Federation

References

Supplementary files