The Republic of Uzbekistan is a world leader in cotton production and processing and export. Therefore, cotton fiber and its processing play an important role in the country's economy

§ 1.3 The effect of devices located in the pneumatic transport system on the natural properties of cotton.

One of the main requirements of technological processes in ginneries is to preserve the natural properties of cotton fiber and seeds without damaging them.

While maintaining the quality of cotton, it is necessary to pay attention to the process of transporting cotton by air flow. This is due to the fact that pneumatic transport is used to deliver raw cotton to technological processes throughout the ginnery. For this reason, when transporting cotton from the bales through pipes, its quality indicators are significantly affected when the raw cotton is in contact with pneumatic transport equipment due to the presence of high humidity and contaminants.

That is why scientists who have studied pneumatic transport devices have focused their attention on the study of seed injury. Because it is the condition leads to the formation of defects in the fiber and the consequent deterioration of its properties during the spinning of the fiber. This, in turn, has a significant impact on the quality of the product.

According to the results of a study conducted by H.A. Ziyaev, changes in the angle of impact of cotton have been studied, which affects the damage to seeds. According to him, the mechanical damage of cotton seeds decreases sharply with increasing angle of impact during the impact of cotton. Another study by H.A. Ziyoev studied the effect of airborne movement of raw cotton on seed damage, proposing to increase the angle of impact of a piece of cotton on the pipe wall in order to reduce mechanical damage when moving air through the tube with air [[ 13].

The following formula is proposed to calculate the non-damaging impact angle of the cotton seed.

(1.1)

Here:

- the angle of impact of a piece of cotton on the pipe wall;

- critical speed of cotton in the process of damage, with the speed of impact of a piece of cotton on a metal surface is 15.5 m / s;

- speed of movement of seeds and cotton pieces.

Seed damage occurs mainly in areas where the working surfaces of cotton and equipment interact. The elbows of the air transport system and the working parts of the separator are such zones. Given that the radius of curvature of the air pipe depends on the value of the angle of the cotton to the wall of the pipe, it is recommended that the radius of curvature in the bent parts of the pipe should not be less than R = 3D. In this case, no increase in the degree of mechanical damage to the cotton seed is observed when the air flow velocity reaches 28.4 m / s. Also an author by 3% in the transportation of cotton in single-elbow pipes, and 10% in the transportation of seeds.

Numerous studies have been conducted to study the formation of defects in cotton fiber under the influence of pneumatic transport devices and mechanical damage to seeds.

Burxanov A. found that the greatest damage to seeds was mainly in gin and linters, reaching 2.5–3.0% [49, 59]. At the same time, the surface velocity of cotton seeds varied in the range from 15 m / s to 40 m / s. In the experiments, the moisture content W = 5.6%, 1 variety of hand picking, S 6524 selection cotton seed cotton was used.

The rate of seed damage during transportation from the cotton warehouse to the ginning process increases by 1.5%. Approximately 1.0-1.2% of this is accounted for by the transport process in a pneumatic transport device.

Also, if we look at the results of a similar study by R. Amirov, the higher the speed of movement of cotton and the greater the angle of impact of raw cotton on the pipe wall, the greater the degree of damage to the seed [6].

In addition, in this study, the dependence of the raw cotton material on the impact surface material on the seed was studied.

That is, when the speed of movement of raw cotton is 50 m / s, the degree of mechanical damage to the seed is 70-80%.

In particular, it has been studied that the amount of mechanical damage to the seeds when the cotton raw material hits the rubber surface is less than when it hits the metal surface. That is, according to the results of the study, when the angle of impact of cotton on the surface is 900 and the speed of cotton is up to 50 m / s, the degree of damage to cotton seeds is reduced to 7 times.

U.X. According to Azizkhodjaev's research, cotton is processed from devices connected in series in a pneumatic transport system. as a result of the increase in the number of transfers, the mechanical damage to the cotton seed increases significantly [5]. As a result, during the ginning of raw cotton, it was found that the release of fiber along with the broken seed husk increased by 0.2% in high-grade cotton and up to 0.6 in low-grade cotton.

Also, the research conducted by A.Davidov and G.Kuznetsova found that the staple length and type of cotton fiber does not change when raw cotton is repeatedly passed through a pneumatic transport device [10,18]. However, the total value of fiber deficiencies and impurities decreases with increasing number of passes of cotton through pneumatic devices. In this case, the lower the moisture content of cotton, the less the amount of fiber defects and impurities. When cotton is transported by air, mineral and organic compounds, fine and coarse contaminants, and the amount of dust can cause fiber defects as a result of repeated transfer of high-moisture cotton raw materials from pneumatic transport equipment. That is, after 8 passes of cotton through pneumatic transport devices, the sum of fiber defects increases by 0.7%. Repeated transportation of raw cotton by pneumatic transport also leads to an increase in seed damage. For example, when raw cotton with a moisture content of 8.2% is passed through a pneumatic device 8 times, the seed damage increases by 0.85%, and when the moisture content of seed cotton increases by 25.0%, the seed damage increases by 1.91%. The authors argue that the increase in seed damage and the increase in fiber defects depend on the performance of the separator.

Also, H.T. In the research work conducted by Akhmedkhodjaev, the number of defects in the fiber and damage to the seed of metal-polymer pipes in pneumatic transport of raw cotton was studied [46]. It found that when cotton was transported through metal-polymer pipes, the fiber seed husk and broken seed were more likely to be used than steel material pipes. the amount of total defects was significantly reduced due to the reduction in the amount of. In the study, the moisture content of cotton was 8.5% and the air speed was 23.7-28.2 m / s, respectively, these figures were 0.09-0.17 and 0.14-0.22%, the humidity of cotton was 24% and at the same rates, these indices were found to decrease by 0.14–0.26 and 0.11–0.30%.

From the results of the above studies, it can be seen that an increase in the number of passes of cotton through a pneumatic device leads to an increase in seed damage with an increase in the air flow rate depending on the moisture content of the cotton. According to the authors, the seeds are mainly damaged in separators and at the bends of the pipes.

Also, S.A. Samandarov and others studied the effect of pneumatic transport on the formation of defects in fine-fiber cotton. The results of the study showed that the length of the pipe distance does not affect the formation of defects in the fiber. Defects in the fiber in the pneumatic transport system occur at the bends of the pipe and in the separators, and worst of all, when transporting raw cotton with high humidity. The results of the study show that all the authors who studied the effect of pneumatic transport equipment on cotton quality came to the same conclusion, that is, raw cotton is damaged at the bends of the pneumatic transport pipeline and in the separator.

The separator is the main unit of this pneumatic transport. The performance of the pneumatic transport is inextricably linked with the performance of the separator. The main requirements for separator devices are to separate the raw cotton transported by this air flow from the air flow without damaging it and to ensure uniform operation of pneumatic transport devices without pressure losses.

Today, the SS-15A cotton separator is widely used in the pneumatic transport system in the process of separating raw cotton from the transport air flow (Figure 1.2).

1.2-raem. General view of SS-15A cotton separator.

This separator device consists of the following parts (Fig. 1.3): inlet pipe 1, working chamber 2, mesh surface 3, nozzle 4, air suction part 5, shaft 6, vacuum valve 7.

1.3-raem. Technological scheme of SS-15A cotton separator.

inlet pipe 1, working chamber 2, mesh surface 3, nozzle 4, air intake section 5, shaft 6, vacuum valve 7.

Сепаратор қурилмасининг ишлаш жараёни қуйидагичадир: ҳаво оқими билан ҳаракатланиб келаётган пахта хом ашёси кириш қисми (1) орқали ажратиш ишчи камера (2)га киради. Ишчи камера (2) хажми қувур диаметридан анча катта бўлганлиги сабабли унга кирган оқим тезлиги кескин пасаяди. Пахта хом ашёсининг асосий қисми инерция кучи таъсирида ҳаракатланишни давом эттириб, ишчи камеранинг орқа деворга урилади ва унинг юзасидан сирпаниб вакуум – клапани (7)нинг парраклари орасига тушади. Вакуум – клапани (7)нинг айланиши даврида унга тушган пахта хом ашёси қурилмадан ташқарига чиқиб кетади. ишчи камера (2)га кирган пахта хом ашёсининг қолган қисми ҳаво оқими билан ишчи камера (2)нинг икки четида жойлашган тўрли юза (3)ларга бориб ёпишади. Тўрли юза (3)ларга ёпишган пахтани айланиб турувчи вал (6)га бириктирилган эластик материал қопланган қирғич (4)лар ёрдамида ажратиб олинади ва ажратиб олинган пахта хом ашёси ҳам вакуум-клапан (7)га тушириб юборилади. Тўрли юза (3) тирқишларидан ўтган ҳаво оқими эса ҳаво сўрувчи қисм орқали қурилмададан сепаратордан ўтиб, қувурлар ёрдамида вентиляторга боради.

Ушбу СС-15А маркали пахта сепараторида камерага кираётган пахтанинг бироз миқдори қурилманинг икки ён томонидан ҳавони сўриш жараёнида турли сиртларга бориб ёпишиб, сўнгра қиғичлар ёрдамида сидириб олинади.

Бунинг натижасида ишчи камерада пахта зом ашёсининг вакуум - клапан узунлик кесими буйича тенг тақсимланмаслигига сабаб бўлади. Бу эса ўз навбатида вакуум - клапаннинг резинали парракларини нотекис ҳолатда ейилишига сабаб бўлади.

Тадқиқот натижларига кўра, сепаратор қурилмасида пахта ҳом ашёсини ҳаво оқимидан ажратиб олиш вақтида толанинг йўқолиши юқори навларда ўртача 0,0285 % ҳамда паст навларда ўртача 0,052 % ни ташкил қилади. Сепаратордан ўтишлар сонининг ошиши билан толанинг йуқолиши яъна шунча миқдорга ошади. Шуни алоҳида такидлаб ўтиш зарурки, агар фоиз кўрсаткичларига эмас аксинча оғирлик кўрсаткичларига ўтадиган бўлсак, у

without U.X. According to a study conducted by Azizkhodjaev, when the efficiency of pneumatic transport is 15 t / h, the loss of fiber is 4.14 kg / h [5].

Cotton raw material is also separated from the mesh surface using elastic scrapers (Figure 1.4).

Figure 1.4. Clean the surface of the separator mesh using a cotton scraper.

In the process of separating cotton from the surface of the separator net, as a result of compression of the raw cotton between the gin and the surface of the net, the seed is broken and the cotton fiber is separated from the seed, that is, "fake" madness. The fibers that pass through the mesh surface cracks are blown out of the separator by the air stream. This results in the formation of free fiber and loss of fiber content.

Thus, in the technological process of separation of raw cotton from the air stream in the SS-15A separator is observed deterioration of the natural properties of uiing and loss of fiber content.

During the highest performance of pneumatic transport or when transporting cotton raw material by air in high humidity conditions, also a small amount of cotton pieces will stick to the mesh surface and the elastic scraper will not be able to completely clean the mesh surface. As a result, the cotton in the separator becomes clogged. Cotton in the separator clogging can cause the elastic part of the scraper to wear out quickly and the structure to bend, rendering it unusable.

Muradov R. The problems of seed damage and the formation of various defects as a result of exposure to the working parts of the mechanisms, in particular the separator, during the air transportation of raw cotton. studied in depth by [6,7].

R. In Fayziev's research, the critical velocity of a cotton seed in mechanical damage as a result of a direct impact of a cotton ball on a metal surface during air movement was determined to be 15.5 m / s (Figure 1.5) [25].

Figure 1.5. Interaction of cotton with the front wall of the SS-15A cotton separator.

R. In his research, Azbadalov tested a rubber-coated separator on the surface of the front wall in a system of air-transporting cotton. In this case, the author experimented with the selection variety S-6524 cotton. Then cotton based on experimental results developed an improved design of the SS-15A separator, which is part of the device for air transportation of raw materials, with a rubber coating on the surface of the front wall, where the seed cotton is beaten [23].

It should be noted that the aerodynamic resistance of the SS-15A separator is very high. In this case, when the flow rate of the carrier air flow is 5-6 m3 / s, the loss of air pressure is 1180-1370 Pa.

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Connection of SS-15A cotton separators to the system of pneumatic transport equipment in ginneries, air extraction devices are connected to the collector and then to the air pipe through pipes. In this case, according to experimental results, when the air flow is 6.1 m3 / s, the aerodynamic resistance of the separator is around 1600 Pa. Therefore, most of the pressure transmitted by the fan is used to overcome the resistance of the SS-15A cotton separator, which in turn leads to a reduction in the operating radius of the pneumatic transport. For this reason, additional equipment will be installed in the pneumatic transport system for the delivery of raw cotton from long-distance cotton gins to technological processes at ginneries. This, in turn, leads to an increase in the level of damage to cotton, as well as an increase in energy consumption and, as a result, an increase in costs.

Transportation of raw cotton by pneumatic transport with additional connections leads to changes in its natural properties and increased fiber loss.

Z.O. According to a study conducted by Shodiev, during the separation of cotton from the air stream in the SS-15A cotton separator, the state of distribution of the cotton flow along the working length of the vacuum-valve of the separated cotton raw material was studied [36]. In the analysis of the results of experiments conducted by the researcher in the I, II and 1U-industrial varieties of selection variety S 65-24, the distribution of the flow of cotton along the working length of the vacuum valve was studied.

Also, on the basis of Hertz's theory of contact, AA Ismailov conducted research on the impact process of cotton seeds in air transportation. The author took the shape of a seed for calculations in the form of a sphere with a radius of 0.3 cm and a weight of 12 • 104 N. He derived the formula (1.2) for the calculation of the shock parameters (impact force, maximum approximation, impact time). In these calculations, the coefficient of viscosity plays an important role, and it is determined as follows:

, N • m-3 (1.2)

Where: R - normal load, N;

Deformation of the seed under the influence of U - R load, m;

S is the contact surface of the seed with the surface, m2.

Equipment for air transport of raw cotton has separators that serve to separate the cotton from the air.

Separators separating raw cotton from air in the technological process were first created in 1900 in connection with the introduction of air transportation of cotton. They also clean a certain amount of cotton from minor contaminants. When the separators are running, fine contaminants are released with the exhaust air.

Baydyuk P.V. [9], Muradov R. [53, 57] have established a number of laws as a result of experimental-theoretical studies of the properties of cotton during the separation of cotton from the transmitted air flow. For example the loss of air in the separator the dependence of the mesh surface on the cutting surface, which is evaluated by the total consumption and the experimental coefficient S, was determined.

For SS-15A separator, the magnitude of the coefficient S is S = 3.0. Since the pressure drop at the separation point of the cotton air transport device is one of the main parameters, a number of studies have been carried out to determine it.

N.A. Based on the results of a study conducted by Ortikov, he developed a method of calculation that is easy to imagine [27],

That is, according to him, the sum of the pressure drop during the separation process, the pressure drop in the air movement without concentration, and the pressure drop from the presence of the transported material is as follows:

(1.2)

Here: Nsep.o. - loss of pressure in the movement of fresh air;

Nsep.m. - additional pressure losses due to the presence of transported material.

In the system of air-transported cotton, as the speed of movement of cotton increases, its carrying capacity increases, but at the same time the degree of damage to the seeds, which are reflected as fiber and seed, increases. Defects in the fiber content, that is, the amount of fibrous shells increases.

Several researchers on the process of separating cotton from the mesh surface of the SS-15A cotton separator have proposed effective methods of the separation process by changing the design of the device.

M.N. According to Salohiddinova's research, the laws of motion of cotton falling into the valve were studied, the cases of cotton damage when cotton pieces falling on the ends of the vacuum valve blade interact with the body were analyzed, and it was proposed to change the trajectory of cotton falling into the vacuum valve. [62]. Also, in this study, the SS-15A cotton separator working chamber was proposed to have a mesh surface structure on the front wall to clean the raw cotton from passive contaminants (Figure 1.6).

However, in this study, tasks such as regular cleaning to prevent the formation of clogs as a result of the ingress of cotton fiber and various compounds into the holes of the sloping mesh surface mounted on the front wall have not been studied in depth.

Figure 1.6. small cleaning chamber separator.

1 inlet pipe; 2 working cameras; 3 mesh surface; 4 pins; 5 air outlet pipe; 6 oblique mesh surface; Cover 7; 8-vacuum valve

Another researcher, O. Mamatkulov, summarized the results of the study and made graphs (Figure 1.7). In the study, defects in the seed were studied in relation to the number of passes through the separator. It has also been studied that the increase in the number of transitions in the separator results in the loss of fiber in the device. To reduce fiber loss and seed damage in the SS-15 A cotton separator by the researcher proposed a modification of the separator design [63]. The author also studied the effect of increase in the number of passes, seed damage and fiber loss on the SS-15A separator device and analyzed the results obtained (Figure 1.8).

Figure 1.7. Effect of separator device on cotton quality

Figure 1.8. Cotton separator with mesh drum.

1 inlet pipe, 2 separation chamber, 3 net drum, 4 net drum suction, 5 net disc, 6 suction, 7 suction shaft, 8 vacuum-valve, 9 air discharge pipe.

In this separator, the dirty compounds in the cotton are effectively separated and the fiber is eliminated by dusty air. However, the condition of replacement and operation of the device's pins during repair was not taken into account.

Previous studies have examined the extent to which seeds are damaged and the amount of defects in the composition of cotton transported by air flow depends on the effect of transport standards. However, the effects of impact process parameters and the percentage of damage to ginned cotton seeds on the quality performance of the cotton fibers being developed have not been studied in depth.

When we conducted research on the existing SS-15A cotton separator at the ginnery to analyze the results of the study, it was found that the front wall of the separator was damaged by cotton and the cotton seed was mechanically damaged. This shows how accurate the research work on the above seed injury is shown in Figure 1.9.

Figure 1.9. Front wall section of SS-15A separator.

The results of the study showed that 60-70% of the cotton entering the working chamber hit the separator wall and fall into the vacuum valve, and the remaining 25-30% of the raw cotton went to the surface of the net. Increases the rate of mechanical damage to the seed and fiber when the worker hits the chamber wall. The wall of the working chamber, on the other hand, collapses after a certain period of time as a result of the continuous impact of the raw material. When cotton raw material moving towards the two edges of the working chamber is notxed to the surface of the mesh, it increases the load on the scraper, which cleans the surface of the mesh, and this causes the rubber coatings to be unevenly eroded. As a result, the mesh surface cleaning efficiency of the scraper is reduced, which reduces the air permeability by quickly clogging the hole, which has a negative effect on the work efficiency. In addition, the cotton, which tends to the mesh surface at both ends of the working chamber, is not evenly distributed over the vacuum valve. This in turn causes further damage to the seed and fiber, as well as rapid wear of the rubber part on both ends of the vacuum valve due to friction. To overcome the above shortcomings, it is also necessary to make changes to the working chamber and distribute the raw material evenly to the working chamber without damaging it.

Scientific research by the authors shows that the exact causes of fiber loss by industrial varieties of cotton have not been fully explored. Also, the laws of motion of cotton between different surfaces and scrapers, including the factors that negatively affect the natural properties of cotton, have not been studied in depth.

In particular, during the transportation of cotton by air, the system is constantly interacting with the working surfaces.

It was also found that the air-carrying device of the cotton was exposed to impact on the working surfaces of the turning parts of the pipes, the front wall at the entrance to the separating chamber of the separator and other working elements.

In addition, the nature of the interaction of seed cotton with the working surfaces of the system of air transport device depends on the mode of operation of the system, construction, material of the working surfaces and the angle of inclination.