Analysis of the structure and portion-intermittent movement of the threshed material in the threshing-separating tract

. The article considers a number of models for describing threshing technology, which is associated with a variety of physical and mechanical properties of plants under different threshing conditions. The analysis of determining the position of a site with a relatively high resistance to the movement of plant mass is carried out, which may allow taking constructive measures to increase the speed of stems and reduce their damage for threshing machines of different sizes. The main components of the threshing medium in the threshing space are stems and grains. When studying the regularities of the threshing and separation processes, various models of the components of the threshed mass are used, reflecting to varying degrees the essential aspects of the phenomena under study. The given models of the threshed mass expand our understanding of the picture of what is happening in the threshing space.


Introduction
The main components of the threshing medium in the threshing space are stems and grains.When studying the regularities of the threshing and separation processes, various models of the components of the threshed mass are used, reflecting to varying degrees the essential aspects of the phenomena under study.The given models of the threshed mass expand our understanding of the picture of what is happening in the threshing space.

Research methods
When deriving the basic equation of the drum, V. P. Goryachkin obtained the ratio Р´∆t = ∆m•V, from which it follows that the operation of the drum is reduced to the sum of pulses following one after another and applied to the mass m during ∆t.The model of the threshed mass here represents a set of unrelated material particles.
When studying the movement of plant matter in the threshing space, E.I. Lipkovich identifies as a moving object a portion captured by a single whip.Differential equation mR 2

φˑˑ = NR [(fδfg) -fδ
where: m is the mass of the portion, R is the radius of the arc of the drum, N is the normal compression force, fδ is the coefficient of adhesion of the threshed material to the drum, fg is the coefficient of resistance of the drum, ω is the rotation frequency of the threshing drum, ω1 is the rate of entry of the vegetable mass reflects the movement of the portion as a material point.E.I. Lipkovich uses the dynamics theorem about changing the amount of movement on impact where: m is the mass of the portion, P is the force of the impact, ∆t is the duration of the impact, V is the serving speed, Vp is the serving speed after impact.
In both cases, the very form of writing equations ( 1), (2) indicates that the model of a moving object is a particle or a body whose dimensions are neglected.
N.I.Chursin considers a deformable body to be a portion model, which in the second approximation is replaced by an absolutely solid one based on the principle of solidification, while the movement of the object is studied at the entrance of the threshing space.
V.A. Sakun considers the portion movement inside the threshing space.Depending on the properties of the threshed material, portions can move as a whole, or deform (pull apart) in the process of movement.The model of a moving object here is a body experiencing stresses and shear deformations [1][2][3].
Along with studying the movement of individual portions, the movement of single stems is considered.Thus, E.I. Lipkovich considers a stalk with an ear as an object of influence at the entrance to the threshing space.Writing down the dynamics equation about the change in the amount of motion, the author neglects the mass of the stem, and studies the whole system as a whole as a particle.I.A. Krutikov studies the behavior of a single stem, analytically correlates the speed of the stem layer with the compression stress and some parameters of the threshing apparatus.The equation of motion of the object given by the author mx´´ -P(fbfs) = 0, (3) where: m is the mass of the stem, P is the compression stress of the layer, fb is the coefficient of friction of the scourge on the plant mass, fs is the coefficient of internal friction of the stems, indicating that the material point still serves as the model of the latter.
Taking into account the ratio of linear dimensions of bodies in modeling allows us to explore more complex forms of motion.The impossibility of ignoring the properties of stems related to their length led M.A. Pustygin to the need to consider the stem as a beam on two supports when determining the power spent on bending deformation during threshing [4].
A.I. Getmanov draws attention to the extremity of the stems, highlighting the beginning of the stem and its lumpy part when determining the speed and nature of the movement of the plant mass during threshing.
T.I.Egorova considers the threshed mass as a "flow of fibrous stems" with the physicomechanical properties of a single stem.The author studies the oscillations of a system of material points, and not the accelerated motion of a single particle.A system with distributed parameters (elastic rod) is proposed as a flow model.Such a model allows us to take into account the experimentally observed fact of the propagation of longitudinal and transverse vibrations along the stems while simultaneously moving them in the threshing space [5][6].
I.E.Makarov and B.N. Chetyrkin find a condition under which the drum affects only one "bundle" of stems.However, this condition is formulated without taking into account kinetic factors and is derived from consideration of the kinematics of the motion of a rectangle serving as a "bundle" model in a flat problem.
Using a body of a certain shape as a model gives more opportunities to describe the phenomena occurring in the threshing space, compared with the case of a particle model.
There are works in which the hypothesis of the continuity of the medium filling the threshing space is accepted.I.A. Krutikov considers the equilibrium of the drumming under the action of normal and tangential forces.At the same time, an elementary section of the drumming surface is allocated, which is affected by elementary forces and moment.The resultant of elementary forces and moment is found by integration over the entire girth angle.Thus, the author implies a continuous distribution of these kinetic characteristics along the length of the drum, and hence the continuity of the distribution of the mass of the threshed material in the threshing space [7].Therefore, in this case, the model of the threshed mass is a continuous medium.I.E.Makarov and B.N. Chetyrkin, when determining the mass of one bundle of stems, use the continuity equation of the flow, which reflects the nature of the motion of a continuous medium.
According to N.I.Lenin, the layer of plant mass is a porous medium formed by stems.The author has studied in detail the properties of the layer as an anisotropic continuous medium from the point of view of its stress-strain state under simulated threshing conditions.
It has a location: the model of the object exists, and the patterns of its movement in the specific conditions of the threshing space are not exhaustively disclosed, although the analytical apparatus of the continuum theory has long been developed.
Another model deserves attention, which turned out to be fruitful.It is known that the grain separation process in the threshing space is closely related to the structure of the threshing mass.Its study was carried out on the basis of probabilistic and statistical schemes.Therefore, a model was needed that would take into account the spillage of large masses, and not just single grains.In this regard, E.I. Lipkovich considers grains and straws-the main components of the threshed mass as two statistical ensembles in the nonequilibrium case.In this case, the straws form a lattice of non-interacting stems [8].This model does not reflect the regularities of the movement of the threshed mass in the threshing space, although it allows us to study the separating effect of the threshing apparatus.
The course of threshing and separation processes depends on the distribution of velocities and pressures in the medium filling the threshing space.In Gorbaletov Yu.I., the determination of the portion rate is based on an imperfect measurement method, which is expressed in excessively underestimated results.Krutikov I.A., Sakun V.A. found that at the entrance a portion of the threshed mass moves 5-6 times slower than the drum whips, the measurement was carried out using a rotor in contact with the threshed mass inside the threshing space and beyond.Kheladze A.M. found that under average optimal threshing conditions, the speed of individual stems is 6.5 m/s and can reach 21 m/s.Lipkovich E.I., Polyakov V.N., Chursin N.I.determined the speed using rotors built into the drumming.It is established that the speed reaches the highest value at the output of the threshing machine, not exceeding 10-11 m/s.Polyakov V.N., Chursin N.I.found that the speed of the rotor immediately after the entrance bar of the drumming is almost zero.Researchers were engaged in determining the speed of the threshed mass: Votsky Z.I., Lomakin S.G., Getmanov A.I., Antipin V.G., Korobitsyn V.M. and others.
In connection with the above, we will single out two main methods for determining the speed.The first method is based on fixing the speed of individual stems, followed by averaging over the flow section [10][11].The second method is based on the registration of the rotations of the rotor rotating under the influence of the threshed mass.Investigating the shape of the moving flow of stems, I.F.Vasilenko believed that the stems move along the surface of the drum without any peculiarities under the influence of the drum.The whips capture, compress and transport the threshed mass, giving it a radial pulsation.The oscillatory nature of the movement of the layer is confirmed by T.I.Egorova.At the same time, A.I. Getmanov came to the conclusion that the wave-like movement is an illusion, which owes its origin to the transverse movements of the ends of the stems, which, under the impact of the scourges, penetrate into the interstitial spaces.In such works, the shape of the moving layer of stems is not considered in comparison with the concave surface of the drumming, primarily on the entrance part of the threshing space.Namely, at the entrance, the discrepancy between the elastic line of the layer (stem) and the piecewise smooth profile outlined by the bottom of the inclined chamber, the surfaces of the receiving flap and the drumming is most pronounced.To understand the essence of threshing by grinding, the latter circumstance changes the generally accepted opinion that the stems in the threshing space copy the surface of the drum throughout its entire length.
Along with the speed, an important characteristic of threshing technology is the pressure distribution of the threshed mass inside the threshing space.The measurement of efforts during threshing is based on the tensioning of the drum, the body of which is mounted on supports-tensioning links or tensioning of individual slats.In the first case, generalized characteristics are obtained-components of the resulting force and the resulting moment applied to the drumming as a whole.In the second case, the forces are determined not in the bar itself, but in the strain gauge located behind the bar, that is, located in conditions significantly different from the real ones.Measuring only the radial load cannot give a complete picture due to the artificiality of the assumption of the connection between the normal and tangential components of the force.
The definition of tangential forces is particularly difficult.The available data on the measurement of tangential loads relate to individual, sometimes not characteristic points of the working surface of the drum, and do not accurately reflect the distribution of pressures in the threshing space.The difficulty of measuring the forces is due to the complexity of the dynamic interaction of the threshed mass with the drumming bars.The pressure on the whip is not an exhaustive characteristic of the stressed state in the elementary volume of the threshed mass.Due to the inability to link the pressure on the whip with the pressure on the bar under it, since other adjacent bars can make the main contribution to the tangential force, due to the finite length of the stems [12].To a certain extent, the value of the torque on the shaft of the threshing drum can serve as an integral measure of tangential forces.According to this characteristic, it is impossible to judge the grinding process in the most important zones of the threshing space, and therefore to control this component of the threshing process.
Measurements and experiments at the micro level were carried out on a special research stand with console working bodies reproducing the scheme of the threshing machine of a combine harvester.The agronomic indicators obtained during the tests are adequate to the real characteristics of threshing.One of the main advantages was the possibility of rapid readjustment of both the scheme and individual elements of the working bodies, which allowed, within the limits of the accepted restrictions, to obtain reliable experimental data based on the planning of multifactor experiments in compliance with the rules of randomization [13].The performed studies made it possible to clarify the general picture of the movement of the threshed mass on the basis of a more complete disclosure of the nature of the interaction of its components with the working surfaces of the threshing space.
At the first stage, the movement of single stems was studied.The next step of the approximation was the consideration of the group movement of the stems, which made it possible to take into account the connections between the stems to a certain extent.The registration of the beach-stem-plank interaction and the beach-stem-plank group allowed a deeper understanding of the internal structure of those complex phenomena that characterize the movement of the flow of the threshed mass as a whole.A single stem entering the threshing space is subject to fluctuations [14].As you progress, the length of the stem console increases, and at some point in time it comes into contact with the drumming bar.Obviously, this contact can take place at different distances from the input bar.The behavior of the stem is quite consistent with the vibrations of an elastic sealed cantilever beam.In the absence of backup from the newly arriving portions of plant mass, there is an instantaneous stop of broken or whole stems.Due to the friction forces, the whips are not able to carry away the stems, thereby overcoming the resistance of the drumming, and there are two cases.In the first case, the further advancement of the stem is hindered by the side face of the bar, against which the free end of the stem rests.In the second case, the resistance is caused by the friction of the stem against the leading edge of the working face of the bar at the point of fracture.The process of fracture formation: under the influence of the whip, the stem deflects with excess of the elastic limit.The stoppage of the stems in the threshing space is temporary.The stem, which is inhibited at the point of fracture, overcomes the resistance of the drumming under the impact of the whip on the end part that has penetrated into the interdigital space.In a different way, the stem overcomes the resistance, resting against the side face of the bar, bulges into the inter-shoulder space, unlike the stem, which comes into contact with the leading edge of the bar at the point of fracture.Under the impact of the whip, the stem enters into an oscillatory motion, which, folding with translational movement, brings the end of the stem from the interplanar space to the working face of the bar.After that, the stem is moved all the way to the next bar, where its release may again become possible.N.I.Chursin and V.N.Polyakov indicate the possibility of stopping the stems at the entrance of the threshing space.
In the second case, when the terminal part of the stem penetrates into the interbeam and interplanetary space, the group movement of the stems is studied.In this case, by analogy with the previous one, we followed the overcoming of the "fracture resistance", but already with the active coupling of interconnected and broken stems with the corrugated surface of the scourges.At the entrance of the drumming, part of the stems bulges into the zone of the interbeam windows and does not touch the working surface of the drumming, and the other part, penetrating further into the threshing space, is adjacent to the slats with lumpy sections.
Based on the consideration of the behavior of individual stems and their groups, it is possible to imagine the formation at the entrance and the passage of a bulging wave in the threshing space in the flow of the threshed mass.Part of the stems at the entrance faces the bulge to the threshing drum, while the other part is adjacent to the entrance surface of the drumming.We also note the bulging of the mass in front of the scourge, which is located inside the threshing space in the central part of the surface of the drumming.Moreover, this zone, "driven" by the scourge, seems to move along with the plant flow.Figure 1 shows the characteristic configurations of the threshed mass depending on the position of the scourges.The diagram (Fig. 1 a, b) shows that the compression conditions of the mass are not the same in time, which indicates the heterogeneity of the threshing conditions.It has been experimentally established that the stems, both single and in the flow, do not have a clearly defined permanent contact with the input part of the working surface of the drum.Entering the threshing space, the stems in the layer of the threshed mass, while maintaining an elastic line, meet with slats that slow down their progress.Under the conditions of continued support from the newly arriving portions of plant mass, the stems bend, bulging into the interstitial windows.Following this, under the influence of whips, the stems bend to the surface of the drumming.The end sections gain freedom in radial movement and, under the influence of the scourges, deviate into the interstitial spaces, creating, together with the phenomena of buckling, the illusion of undulating movement of the layer.
When bending, a fracture of the stems is possible.As we move towards the exit from the threshing space, new fractures appear on the stem due to repeated bending deformations beyond the limits of elasticity (at the entrance).The movement of the stems with the successive occurrence of fractures and the sliding of the fracture points along the working surface of the drum is observed both for single (group) stems and stems in the flow of plant mass.
After sufficient penetration of the stems into the threshing space, the bonds imposed on them by the falling working organs weaken, the bulging of the stems into the interstitial spaces increases their adhesion to the threshing drum.The combined effect of these factors leads to an increase in the flow rate of stems in the output part of the threshing space.It is established that the coordinate of the initial contact of the stems with the input surface of the drum is a random variable subject to the normal distribution law.The length of the contact zone is determined by the angle β = 26 °, and the center of this zone is separated from the input bar by an angle γ = 31 °.It is obvious that with a steady flow of the threshed mass, the probability of meeting and the intensity of the interaction of the stems with the lateral faces of the slats should decrease somewhat due to an increase in the connectedness of the layer.The same can be said about the probability of penetration of the end sections of the stems into the interstitial spaces [15].
Based on the above, it can be argued that in the threshing space there is a zone commensurate in length with twice the length of the undeformed section.In the specified zone, the stems do not come into contact with the surface of the drumming until the fracture.The parameters of the zone obviously depend on the physics of the process of deformation of the stems, which is difficult to explain only on the basis of the idea of "pressing" the threshed mass into the interplanar spaces.
Analysis of the movement of the grain flow in the threshing space, which was obtained when the whip hit the ears, shows that a group of free grains formed above the second bar from the entrance forms a point field that reaches the surface of the drum and creates a spectrum of initial trajectories by hitting the ear with the whip, as shown in Figure 1.Part of the grains reaches the surface of the drum and is reflected from its elements or sifted, since the vegetable mass is permeable.In real conditions of threshing, grains move in the flow of stems and can penetrate the layer of the threshed mass.With a sufficiently high permeability and a significant grain velocity reaching 37 m/s, in order to simplify, we neglected the interference from the stems and considered the movement of free grain material in the threshing space.At the same time, the fate of individual grains depended on the interaction with the working surfaces of the threshing space.

Conclusions
Based on the analysis of models of the threshing medium, its main characteristics and methods of measuring them, as well as the results of special experiments, it is possible to draw a conclusion about the state and patterns of movement of threshing products in the threshing space.
1.A number of models are used to describe the threshing technology, which is due to the variety of physical and mechanical properties of plants under different threshing conditions.Such an important characteristic as the trajectory of the layer is not the subject of study.The position at which the model of a moving object is known, the regularities of its movement are established, can take place in the case when the latter is also known: the flow of stems in the threshing space copies the surface of the drumming.But such a representation is consistent with all discrete physical models, except for the model in the form of a system with distributed parameters, which primarily has elastic properties.2. The speed of the threshed mass has no real physical content in relation to the flow of stems.Conventionally, the speed of the threshed mass can be considered as the average speed of the stems in a given flow section, obtained by mathematically averaging the speeds of individual elements.The unstable nature or even the absence of rotation of the rotor when measuring the flow velocity of the threshed mass at the entrance part of the threshing space indicates a possible loss of contact between the stems and the working surface of the drum in the zone under consideration.
3. The flow of plant mass in the threshing space is a set of stems connected by coupling forces, deformed to varying degrees, communicating their own elastic properties to the layer.The most common type of deformation is bending, generated by a constantly acting factor -the curvature of the surface of the drum.The penetration of the end sections of the stems into interplanetary spaces is a consequence of the finite length of the stems, the sparsity of the layer and the action of elastic and centrifugal forces.
4. The resistance of the films causes instantaneous braking of the stems and their damage or bulging into the interstitial spaces.Under the influence of the threshing drum, buckling is replaced by a deflection towards the drumming and is accompanied by a fracture of the stem.By origin, the primary is buckling, and the secondary is the penetration of the end sections of the stems into the interstitial spaces.The resistance of the drumming is formed by the friction of the stems on the slats and the penetration of the broken and terminal sections of the stems into the interplanar spaces.
5. Due to the elastic properties, the layer of plant mass does not copy the surface of the drum at the entrance, but moves with the preservation of the elastic line, forming a dead zone immediately behind the entrance bar.Only clumps of stems leaving the threshing space can be in the dead zone.At the entrance part of the drumming, the process of grinding the ears is weakened.
6.The final length of the stems plays a decisive role in their movement in the threshing space.Due to the discrete length and the presence of a ribbed surface of the stems in the threshing space, they move intermittently, with momentary stops and bulging towards the drum under the destructive effect of whips.The consequence of the weakening of the contacts of the plant mass at the entrance of the drum may be an increase in the stress concentration in the layer of stems in the vicinity of the input bar, which in this case should make the greatest contribution to the overall compressive force during threshing.
7. On the working surface of the drum there is an area of relatively high resistance to the movement of plant mass.Determining the position of the specified area may allow taking constructive measures to increase the speed of the stems and reduce their damage for threshing machines of different sizes.

Fig. 1 .
Fig. 1.Configuration of the layer of the threshed mass depending on the location of the scourges.

Fig. 2 .
Fig. 2. Spectrum of initial grain trajectories in the threshing space.

Fig. 3 .
Fig. 3. Classification of grain trajectories in the threshing space.