DEVELOPMENT OF AN EFFECTIVE DESIGN AND JUSTIFICATION OF THE PARAMETERS OF THE SCREW CONVEYOR FOR THE TRANSPORTATION AND CLEANING OF COTTON

ABSTRACT

The article presents a new effective structural scheme and the principle of operation of the conveyor with a screw with a zigzag profile. Based on the solution of the problem of system dynamics, taking into account the dynamic mechanical characteristics of the engine, inertial, elastic-dissipative parameters, as well as technological loads from the transported and cleaned cotton lint, regularities of movement of the working body are obtained, the basic parameters of the conveyor are substantiated. Based on production comparative tests of the recommended conveyor, the efficiency of its use in production is substantiated.

АННОТАЦИЯ

В статье приведена новая эффективная конструктивная схема и принцип работы конвейера с винтом с зигзагообразным профилем. На основе решения задачи динамики системы с учетом динамической механической характеристики двигателя, инерционных, упруго-диссипативных параметров, а также технологических нагрузках от транспортируемого и очищаемого хлопкового линта получены закономерности движения рабочего органа, обоснованы основные параметры конвейера. На основе производственных сравнительных испытаний рекомендуемого конвейера обоснована эффективность использования его на производстве.

Keywords: Conveyor, screw, zigzag profile, fibrous material, lint, transportation, cleaning, dynamics, law of motion, moment of inertia, stiffness, dissipation, resistance, swing range.

Ключевые слова: Конвейер, винт, зигзагообразный профиль, волокнистый материал, линт, транспортировка, очистка, динамика, закон движения, момент инерции, жесткость, диссипация, сопротивление, размах колебаний.

Screw conveyors are widely used to transport various materials, in particular bulk and fibrous materials [1,2]. In the technological line of cotton processing there is a cleaning of linters from weeds with a screw cleaner. Known screw conveyor containing a fixed chute, the lower part of which has the form of a half-cylinder, closed on top with a lid, and installed inside the chute along its axis, a drive screw in bearings fixed on the chute. The movement of the load along the chute is carried out by turns of a rotating screw [3]. The disadvantage of this analogue is the high energy consumption and the possibility of slaughtering the load in the chute with an increased supply of material.

The structure of the conveyor of fibrous materials contains a chute, the lower part of which is in the form of a half-cylinder, closed at the top with a cover. Annular bands are attached to the chute in the lower cylindrical part, by means of which the chute is mounted on rollers so that the chute can vibrate around its axis. The rollers abut against the end planes of the annular band on the chute. The chute is suspended on bearings on the propeller shaft for the possibility of oscillation. The cover has an inlet on the left side, and the chute has an outlet on the right side. The disadvantage of this design is the impossibility of removing trash impurities from the total mass of transported cotton seeds, released as a result of the screw movement. As a result, the separated trash impurities enter the technological linter machine and heavily contaminate the resulting lint product [4,5].

It should be noted that in the existing screw conveyors, when transporting fibrous materials, especially cotton ones, due to insufficient loosening of the material, not enough litter is released. In addition, due to insufficient friction between the screw surface and the fibrous material, they lag behind during transportation, which leads to additional mechanical damage to the fibrous material (cotton and their waste). The interaction of the helical surface on the fibrous material occurs monotonously in one direction, with a constant driving force, which does not ensure the effectiveness of their cleaning. In order to ensure sufficient loosening of the transported fibrous material, an increase in the cleaning effect and the required transportation performance, the design of the screw conveyor has been improved by increasing the contact area, increasing the friction force, as well as changing the direction of the force of interaction of the screw with the transported fibrous material.

The screw conveyor contains a chute 1, the lower part of which has the shape of a half-cylinder, closed from above with a cover 2. Inside the chute 1, along its axis, there is a screw 3 transporting material (Fig. 1). On top of the groove 1 there is an inlet 4, and at the end, at the bottom there is an outlet 7. The lower working part of the groove 1 is made in the form of a mesh surface 8. The working surfaces of the screw 3 are made in a zigzag shape 5 with triangular projections and depressions. The height of the triangles 5 of the screw 3 is chosen equal to the average size of the cotton seed, (40 70 mm). The ribs 6 of the triangles 5 of the screw are mutually parallel, and when wound onto the shaft, they are directed along the radius of the screw 3.

scan det. 3

increased

Figure 1. Screw conveyor for conveying and cleaning fibrous material

The screw conveyor works as follows. Fibrous material (raw cotton, fibrous waste) is fed into the chute 1 through the inlet 7 in the lid 2 and, when the screw 3 rotates, slides along the chute 1, pulled by the zigzag (triangular) working surface 5 of the rotating screw 3 to the outlet 8.

The zigzag (triangular protrusions and depressions) 5 shape of the working surfaces of the screw 3 acts on the cotton seeds and flies with a force of different size and direction, which leads to an additional release of cotton, this allows the effective separation of litter from the fibrous material (cotton). The impurities released from the fibrous material fall out through the openings of the mesh surface 8 of the chute 1 and are discharged into a self-draining through the opening [6,7].

The recommended design of the screw conveyor allows efficient transportation of fibrous materials, increased productivity, and provides the necessary cleaning effect.

The design diagram of the screw conveyor water is adopted in the form of a three-mass system: 1-mass consists of an engine rotor, a driving belt drive pulley; 2-mass from the driven pulley and the reduced masses of the gears of the reducer, as well as the leading part of the coupling; 3-mass includes the leading part of the coupling and the screw. The design scheme is shown in Fig. 2.

Figure 2. Design diagram of a machine unit with a conveyor screw drive mechanism for transporting and cleaning cotton linters

The system of differential equations describing the movement of the elements of the screw conveyor has the form [8, 9]:

                  (1)

, , - reduced moments of inertia of masses on the motors haft, on the input shaft of the gearbox, on the propellers haft; , , , - coefficients of circular stiffness and coefficients of dissipation of the belt drive and clutch;, - components of technological load from transported and cleaned cotton linters, - frictional moment on the screw shaft, - engine torque;- motor rotor angular speed;  - number of pole pairs; - rotor slip and its critical value; - electromagnetic time constant;- auxiliary variable;- network circular frequency, с, - circular stiffness coefficient and dissipation coefficient; а- factor taking into account the effect of pre-tension; R- pulley radius; Е- elastic modulus; F- cross-sectional area; - belt length; T- oscillation period[10,11].

The numerical solution of system (1) was carried out on a PC using standard programs with the following parameter values: asynchronous motor Y132S-8, P = 2.2 kW; n = 710 rpm;= 1,27; = 20; = 1,12 kgm²;=2,89 kgm²; =7,14 kgm²; = (200÷250) Nm/rad; =(5,0÷5,5) Nms/rad; = (400÷420) Nm/rad; = (9,5÷10,5) Nms/rad; = (46÷65) Nm; = (5.5÷10) Nm; = (0,05÷0,07); = (35÷45) Nm;

Based on the solution of the system of differential equations (1) with the following initial conditions, t = 0; = 0; = 0; = 0; = 0; = 0. the regularities of changes in the angular speeds of the rotor of an induction motor, screw conveyor, as well as the torque on the motor shaft are obtained.

The obtained patterns of change in  and  are shown in Fig. 3. The analysis shows that with an increase in the load M_1 from the transported and cleaned linters within (4565) Nm, the angular speed of the engine rotor actually remains unchanged, its decrease is insignificant. In addition, the range of fluctuations in the angular speed of the rotor of the engine also varies within insignificant limits. But, the decrease in the angular speed of the screw with a zigzag profile will be noticeable.

So, at M₁ = 45Nm φ ̇_b decreases to 27.2 s^-1, and at a load of 65 Nm, decreases to 25,9 s^-1. In this case, the swing of oscillations increases from (1.2 ÷ 1.4) s^-1 to (3.0 ÷ 3.8) s^-1. An increase in the amplitude of oscillations  has a positive effect on the effect of transportation and cleaning of the linters due to their additional shaking

at 

at 

Figure 3. Regularities of changes in the angular speeds of the rotor of the engine, the propeller shaft, as well as the torque on the motor shaft

Based on the substantiated parameters of the working elements of the screw conveyor, a prototype was designed and manufactured.

Tests of the recommended conveyor design with a zigzag screw surface were carried out in comparison with the existing version in a cotton mill. Analysis of the test results shows that when using a screw with a zigzag profile, the emitted fluff decreases by (3 ÷ 3.5) times, and damage to the seeds (skin) of cotton is also reduced. The release of fine litter is increased (2.0 ÷ 2.5) times compared to the existing conveyor. The overall cleaning effect of cotton linters increases by (6.0 ÷ 10.5) % in the recommended conveyor relative to the serial machine.

Conclusions. Offers efficient conveyor with zigzag screw. On the basis of theoretical studies, the laws of motion of the rotor of the engine and the screw of the conveyor were obtained, the parameters and modes of movement of the system were substantiated. Experiments have shown that the recommended conveyor allows a significant increase in the effect of cleaning and transportation of linters.

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