Knotless flexible windproof net with non-uniform porosity and preparation method thereof

Abstract

The invention relates to a knotless flexible windproof net with non-uniform porosity and a preparation method thereof. The knotless flexible windproof net is woven from polymer filament bundles and comprises a lower part and an upper part arranged along the longitudinal direction of the coils; the porosity of the lower part is 31% to 34%, and the porosity of the upper part is 14% to 17%; the preparation method comprises: firstly weaving the tissue structure of the lower part by using a warp knitting machine equipped with an electronic transverse shift device, and then digitally weaving the tissue structure of the upper part by changing the pad yarn to obtain the knotless flexible windproof net with non-uniform porosity; the product of the invention has good windproof and dust suppression effect and has buffer performance; the method of the invention has a simple process.

Description

Technical Field

[0001] The invention belongs to the technical field of windproof structures in stockpile yards and relates to a knotless flexible windproof net with non-uniform porosity and a preparation method thereof. Background Art

[0002] The "Coal Dust Emission Coefficient Table for Coal Loading, Unloading and Stockpiling" states that the coal dust emitted during the loading and unloading process of open-air coal storage is 3.53-6.41Kg / t coal / year, and the coal dust emitted during stockpiling is 1.48-2.02Kg / t coal / year. However, 80% of China's coal resources are distributed in the north, 10% in the southwest, and the nine provinces, cities and districts in the south of the Yangtze River with developed economy and concentrated energy consumption only account for 1.8%. The transportation and open-air stockpiling of coal during the "North Coal to South Transportation" process leads to a large amount of coal dust pollution. According to the annual consumption of raw coal of 500,000 tons, the coal dust emitted during the loading and unloading process is 6.41Kg / t coal / year, and 3,205 tons of coal dust are generated each year. Green waters and green mountains are gold and silver mountains. As the national standards for environmental protection are becoming increasingly stringent, coal yards are also seeking technologies to reduce pollution emissions. The installation of wind and dust suppression nets can not only protect the environment, but also reduce the loss of coal raw materials.

[0003] The wind and dust suppression net is a wind-blocking facility with a certain porosity. The certain porosity can not only attenuate the mechanical energy of the incoming wind to turn it into a low-speed flow, but also break up the larger vortex wind to reduce the pulsation speed of the wind and reduce the dust generation rate of the coal pile. The wind speed of the incoming wind increases exponentially from low to high in the longitudinal direction in front of the net, and the turbulence intensity decreases exponentially from low to high. However, after passing through the windproof net, the flow field of the wind changes. The wind reaches the back of the net in the form of seepage and circumference. The circumference wind is formed in the upper part of the downwind direction. After passing through the windproof net, the seepage wind forms an attached flow that goes up along the material pile. Under the influence of a certain wind speed or porosity, the upper circumferential wind easily generates a longitudinal pressure difference backwards, thus forming a vortex flow. Excessive turbulence intensity and turbulence integral scale vortex flow intensify dust, while the low turbulence intensity and turbulence integral scale vortex flow in the lower part of the protective net are often accompanied by strong seepage wind, which increases the shear force on the pile surface. The greater the shear force on the pile surface, the more obvious the dust effect. Different wind and dust prevention nets have different wind and dust prevention effects, and they need to be reasonably installed and used to achieve the purpose of wind and dust prevention.

[0004] Existing rigid windproof and dust suppression nets (also known as windbreak walls) and uniform porosity flexible windproof net technologies. Rigid windproof and dust suppression nets are made by punching holes on glass fiber reinforced plastics or metal material plates. They are prone to cracks due to poor toughness during long-term use. Steel plates are more likely to break under strong wind impacts, posing a certain threat to human safety. The windproof effect of cracked rigid windproof nets is greatly reduced. Therefore, people try to use flexible filaments to weave flexible windproof nets using warp knitting technology. The filaments are high-density polyethylene or polyester, which has low raw material cost and is easy to transport. The mechanical properties are better than rigid plates, and it is not easy to break. Adding anti-UV agents, anti-aging agents, flame retardants, cross-linking enhancers, etc. can make them flame-retardant and extend their service life. However, the flexible windproof nets currently woven are all uniform nets with a porosity of about 30%. Since the characteristics of the incoming wind are that the wind speed increases with the increase of the height from the ground and the turbulence intensity decreases, they cannot adapt well to the characteristics of the incoming wind.

[0005] For the incoming wind parallel to the ground and perpendicular to the windbreak net, the wind speed increases exponentially from low to high at the upwind side of the net, and the turbulence intensity decreases exponentially. However, the flow field of the wind changes after passing through the windbreak net. The form of change is mainly determined by the speed of the incoming wind, the mesh shape of the windbreak net, and the porosity of the windbreak net.

[0006] When the wind speed is low, the wind mostly flows through the windbreak net in the form of seepage, which has a mild effect on the windbreak net. The wind pressure difference between the front and back of the net is not large, and it is not easy to form a turbulent structure. When the wind speed increases, the wind in the front of the windbreak net gradually accumulates, and the wind pressure difference between the front and back of the net gradually increases. The force on the net begins to increase, and the vortex on the net begins to increase. When the wind speed is extremely high, only a small part of the incoming wind flows to the back of the net in the form of seepage, and most of the wind flows along the windbreak net to the back of the net in the form of vortex. In this case, a vortex with extremely high turbulence intensity will form on the upper part of the back of the net. A vortex that is too large and too strong will increase the dust on the top of the pile behind the net. It can be seen that under different wind speeds, the flow field characteristics along the longitudinal height of the windbreak net after the wind and the windbreak net interact are different.

[0007] The windbreak net mesh shapes were compared with typical trapezoidal, square and circular windbreak effects. Under the same incoming wind conditions, the wind speed, pressure and turbulent kinetic energy on the surface of the pile behind the circular mesh windbreak net were smaller than those of the other two mesh shapes, that is, the dust-raising effect on the pile was weaker and it could effectively suppress dust.

[0008] The porosity of the windbreak net affects the mechanics and windproof effect of the windbreak net. In the study of windbreak nets, the resistance coefficient is usually used to measure the resistance of the windbreak net to the wind. Under the condition of constant wind speed, the resistance coefficient decreases with the increase of the opening rate. Since the resistance is proportional to the resistance coefficient and the wind speed of the incoming wind, the greater the resistance coefficient and the wind speed of the incoming wind, the greater the wind resistance of the windbreak net, which is extremely challenging for the toughness of the windbreak net. Under the condition of constant wind speed, the uniform porosity increases from 0 to 1, and the comprehensive windproof effect behind the net first increases and then decreases. A vortex flow is easily formed between the upper part of the net and the pile, and the height gradually decreases but still appears in the upper part. The vortex flow usually disappears when it increases to about 30%. It can be seen that when the porosity of the windbreak net is less than 30%, the impact on the wind field in the upper part of the windbreak net is more obvious.

[0009] In order to overcome the problems existing in the above technologies, there is an urgent need for a flexible windproof net that can well balance mechanics and windproof performance, has a certain toughness and conforms to the characteristics of the incoming wind, so as to improve the wind and dust suppression effect of the flexible windproof net. Summary of the invention

[0010] The purpose of the present invention is to solve the problems existing in the prior art and to provide a knotless flexible windproof net with non-uniform porosity and a preparation method thereof.

[0011] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0012] A knotless flexible windproof net with non-uniform porosity is woven from polymer filament bundles, including a lower part and an upper part arranged along the longitudinal direction of the coils; the porosity of the lower part is 31% to 34%, and the porosity of the upper part is 14% to 17%; the tension of the windproof and dust suppression net is released after it is taken off the machine, and different positions of the windproof and dust suppression net will shrink to different degrees. When the windproof net is installed on a windproof frame, different positions will also produce different tensions. Tension is the main factor affecting the mesh size, so the porosity is a range value.

[0013] As the preferred technical solution:

[0014] The knotless flexible windproof net with non-uniform porosity as described above is an integrally formed part.

[0015] The knotless flexible windproof net with non-uniform porosity as described above is a knotless flexible windproof net with non-uniform porosity; the knotless flexible windproof net with non-uniform porosity is a knotless net; the knotless net has greater ductility than the knotted net, and can effectively buffer the impact of wind pressure when facing strong winds. Under the same Reynolds number in the flow field, the knotless net has a smaller resistance coefficient than the knotted net, that is, when strong winds come, the flexible knotless net with the same height, width and mesh distribution is less stressed than the flexible knotted net, and the safety factor is improved. In addition, the knots of the knotted net are dead knots, and the nodes bend under the action of external forces, which makes the extrusion at the nodes more intense and the force more concentrated, that is, the breaking strength of the knots of the knotted net is lower than that of the knots of the knotless net. The knotless net used in the present invention has a greater breaking strength at the knots.

[0016] As described above, a knotless flexible windproof net with non-uniform porosity is obtained by weaving high-density polyethylene filament bundles (including but not limited to 4 high-density polyethylene filaments) through a warp knitting machine. Considering that high-density polyethylene filaments are strong and low in cost and are suitable for making flexible windproof nets, and considering that a small number of filaments may have insufficient bearing capacity and a large number may be inconvenient to weave, the present invention preferably comprises a knotless flexible windproof net with non-uniform porosity that is obtained by weaving high-density polyethylene filament bundles through a warp knitting machine.

[0017] The knotless flexible windproof net with non-uniform porosity as described above has a fineness of high-density polyethylene filaments of 290 to 400 deniers.

[0018] The knotless flexible windproof net with non-uniform porosity as described above, the ideal forming model of the warp knitted net is: the mesh of the lower part is a regular hexagonal hexagonal mesh, the mesh of the upper part is a flat hexagonal hexagonal mesh, the flat hexagon is a hexagon with an inscribed ellipse, and the height of the upper mesh is less than the height of the lower mesh; the present invention installs the regular hexagonal hexagonal mesh part with larger porosity below the windproof grid frame, and the flat hexagonal hexagonal mesh part with smaller porosity above the windproof grid frame, thereby enhancing the wind and dust suppression effect of the windproof and dust suppression net; due to the use of warp knitting technology to weave small The technical limitations make it impossible for the mesh to be completely circular. The hexagonal mesh weaving structure adopted in the present invention can fit the circular hole as closely as possible, and can improve the wind and dust suppression effect compared with other shapes of mesh such as square mesh. Taking into account the convenience of the weaving process and the uniformity of the load-bearing of the mesh feet, a combination of hexagonal meshes of different shapes and sizes is adopted for weaving design. Without additional warp drawing and warping work, the weaving can be continuously switched between one hexagonal mesh structure and another hexagonal mesh structure, which reduces manpower consumption and saves production time.

[0019] The knotless flexible windproof net with non-uniform porosity as described above has a diameter of the inscribed circle of the regular hexagon of 3.5 to 4.5 mm; the horizontal axis length of the inscribed ellipse of the flat hexagon is 3.5 to 4.5 mm, and the vertical axis length is 1.5 to 2 mm; the spacing of the mesh of the lower part is 2.5 to 3.5 mm, the spacing of the mesh of the upper part along the horizontal direction of the coil is 2.5 to 3.5 mm, and the spacing along the longitudinal direction of the coil is 4 to 5 mm; the number of mesh holes per 2 inches in the horizontal direction of the coil of the lower part is 6 to 8, and the number of mesh holes per 2 inches in the longitudinal direction of the coil is 7 to 9; the number of mesh holes per 2 inches in the horizontal direction of the coil of the upper part is The number of mesh holes is 6 to 8, and the number of mesh holes per 2 inches along the longitudinal direction of the coil is 7 to 9; these values ​​are the results of weaving according to the designed padding yarn numbers, which can ensure that the porosity of the lower part of the flexible windproof net is 31% to 34%, and the porosity of the upper part is 14% to 17% when it is used; this is also the reason why "the height of the upper mesh is smaller than the height of the lower mesh", and the density is the same because among the five combs of the upper and lower tissues, only changing the padding yarn numbers of two of the combs can successfully change the mesh size and shape, that is, since the padding yarn numbers of the remaining three combs have not changed, the mesh distribution density has not changed.

[0020] As described above, a knotless flexible windproof net with non-uniform porosity has a height ratio of 1:1 between the lower and upper parts along the longitudinal direction of the coils. The height ratio of the two parts in the present invention is determined based on the longitudinal influence range of the circumferential wind at the downwind direction of the knotless flexible windproof net.

[0021] A knotless flexible windproof net with non-uniform porosity as described in any of the above items, the longitudinal breaking strength × breaking elongation of the knotless flexible windproof net with non-uniform porosity detected under the close-mesh safety vertical net test standard of "GB5725-2009 Safety Net" is 200~240KN·mm, and the transverse breaking strength × breaking elongation is 45~65KN·mm. It can be seen that its mechanical properties are good and meet the impact resistance assessment requirements of this standard. It will not be damaged or torn under strong wind conditions; the dust suppression rate of the knotless flexible windproof net with non-uniform porosity (calculated by dividing the area of ​​the surface of the material pile behind the net below a certain wind speed value by the total surface area of ​​the material pile) is above 85%.

[0022] The present invention also provides a method for preparing a knotless flexible windproof net with non-uniform porosity as described in any of the above items, using a warp knitting machine equipped with an electronic transverse shift device to first weave the lower tissue structure, and then weave the upper tissue structure by changing the padding yarn number (only the transverse shift needle pitch of the padding yarn number needs to be changed without changing the warp threading method), so as to obtain a knotless flexible windproof net with non-uniform porosity.

[0023] The present invention adopts continuous sheet weaving. Compared with weaving meshes with different uniform porosities separately and then suturing and installing them, the different uniform porosities of the continuously woven flexible windproof net are connected when subjected to stress, that is, part of the yarns of the filaments between adjacent mesh nodes and mesh feet will be mutually transformed when subjected to stress, which is conducive to balancing the stress between each node and the mesh foot. The larger the continuously woven mesh is, the more conducive it is to balancing and easing the stress, so that the buffering capacity of the flexible windproof net to wind is improved. Moreover, the continuous sheet weaving does not need to install the corresponding facilities for suturing and splicing, and only needs to fix and connect the longitudinal columns on both sides of the mesh, which reduces the expenditure of manpower, material and financial resources, and also saves time costs.

[0024] As the preferred technical solution:

[0025] According to the method described above, the lower part and the upper part both have five combs involved in weaving, the warp drawing method of GB1 is full drawing, and the warp drawing methods of the other combs are 1 drawing and 1 empty, wherein the yarn laying numbers of the lower part are:

[0026] GB1: 1-0 / 0-1 / 1-0 / 0-1 / / ; GB2: 0-0 / 2-2 / 3-3 / 1-1 / / ;

[0027] GB3: 3-3 / 1-1 / 0-0 / 2-2 / / ; GB4: 0-0 / 1-1 / 3-3 / 2-2 / / ; GB5: 3-3 / 2-2 / 0-0 / 1-1 / / ;

[0028] The upper inlay yarn number is:

[0029] GB1: 1-0 / 0-1 / 1-0 / 0-1 / / ; GB2: 0-0 / 2-2 / 3-3 / 1-1 / / ;

[0030] GB3: 3-3 / 1-1 / 0-0 / 2-2 / / ; GB4: 0-0 / 2-2 / 5-5 / 3-3 / / ; GB5: 5-5 / 3-3 / 0-0 / 2-2 / / ;

[0031] The shape of the mesh of the knotless flexible windproof net with non-uniform porosity is formed by pulling the warp knitted chain structure with four yarn guide bars, and the weft yarn bundles woven by the four yarn guide bars form a reinforcement structure to connect the adjacent warp knitted chain structures.

[0032] The principle of the present invention is as follows:

[0033] Compared with the existing flexible windproof net with uniform porosity, the knotless flexible windproof net with non-uniform porosity adopted by the present invention has different porosities in the upper and lower parts of the net, and the porosity of the upper part is 14%-17%. The porosity is less than 30%, which can raise the height of the vortex flow that may be formed in the upper part behind the windproof net when subjected to strong winds. The raised vortex flow has a smaller range of influence of the wind on the flat top of the pile. The porosity of the lower part is 31%-34%. The porosity slightly greater than 30% reasonably controls the seepage rate of the incoming wind, reduces the shear force of the incoming wind on the windward surface of the pile, and also weakens the pressure difference between the front and rear wind pressures of the knotless flexible windproof net, that is, the force on the lower part of the windproof net can be reduced. The windproof effect of this porosity is better and can adapt to most application scenarios. The knotless flexible windproof net with non-uniform porosity cooperates with different porosities in the upper and lower parts to reasonably control the ratio of the circumferential wind and the infiltration wind in the air flow field, thereby effectively suppressing dust. In addition, due to the different organizational structures, the upper part of the windproof and dust-suppressing net has two combs with weft yarns spanning 5 needles, making the upper part more solid and less prone to deformation, that is, the upper part of the net has better stability, firmness, and tensile strength than the lower part, and the upper part of the net has better wind resistance than the lower part when strong winds come. The characteristics of the incoming wind are that the higher the wind speed is from the ground, the greater the wind speed is. The greater the wind speed and the larger the area of ​​the windproof net, the greater the force on the windproof net. This organizational structure meets the situation that the upper part needs to bear more force than the lower part due to the characteristics of the incoming wind. However, the prior art flexible windproof net with uniform porosity is a net with a single structure throughout the whole piece, and the porosity is uniformly 30%. The windproof and dust suppression net with uniform porosity cannot take into account the on-site airflow movement laws and turbulent structure problems well. The wind speed increases exponentially with the height from the ground, which will cause the knotless flexible windproof net to bear more load at high places than at the ground. The mechanical properties of the upper half of the windproof net are relatively weak under strong winds, and the center height of the vortex flow that may be formed under strong winds is lower than that of the knotless flexible windproof net with non-uniform porosity of the present invention. It has weak wind and dust suppression effect on the flat top of the pile, that is, it often cannot take into account the force and dust suppression effect of the upper and lower parts of the pile at the same time, resulting in unsatisfactory dust prevention effect of the windproof and dust suppression net.

[0034] Compared with the existing rigid windproof and dust suppression net, the knotless flexible windproof net with non-uniform porosity adopted by the present invention is woven from polymer filaments. In terms of mechanics, polymer filaments have higher toughness and better shear resistance than glass fiber reinforced plastic plates and metal plates. The woven net is also more flexible, tough and lighter than glass fiber reinforced plastic plates or metal plate punching nets. When strong winds come, the woven net can use its flexibility to buffer the pressure applied by strong winds. When it is subjected to uneven wind flow, it can also use the stress transmission between the net feet and the mesh to balance the forces in various parts. The rigid windproof net material of the prior art is bulky in itself, which tests the bearing capacity of the steel frame of the windproof net when strong winds come. In order to increase the safety factor, the installation of the steel frame will also increase the cost. Moreover, due to the weak shear resistance and weak toughness of the material itself, the windproof board is prone to cracking or even breaking after a period of use. While the windproof capacity is weakened under strong winds, it also poses a great threat to human life safety. When a rigid windbreak is subjected to uneven wind force, it cannot balance the force through stress transfer between the meshes because it is made of mesh pieces. The unbalanced force of the entire rigid windbreak will also increase the burden on the mesh and steel frame, and the risk factor will increase. Compared with the existing rigid wind and dust suppression nets, the knotless flexible windbreak net with non-uniform porosity has lower cost, better toughness, and is safer in strong winds. Under the same porosity, the impact on the flow field is not much different, and the mechanical properties are better. In terms of windproof mechanism, since the windproof and dust suppression net of the present invention is woven from filament bundles, the mesh feet and meshes in the woven net will have a certain relaxation effect due to the decrease in tension after being taken off the machine, that is, there are tiny gaps between the filaments. Under weak wind conditions, there is a certain degree of looseness between the filament bundles in the knotless flexible windproof net, which slightly reduces the porosity of the flexible net, and due to the tiny gaps between the filaments, part of the incoming wind from the filaments through the net to the back of the net impacts each other, thereby weakening the kinetic energy; under strong wind conditions, there is tension in the filament bundles in the knotless flexible windproof net, and the tension makes the filaments The wire bundles are only fitted together, and the porosity of the flexible windproof net increases slightly at this time, which is consistent with the scientific research results that within a certain porosity range, the greater the wind speed of the incoming wind, the better the dust suppression effect of the windproof net with a larger porosity is. The rigid windproof and dust suppression net is made of punched steel plates, and its porosity is fixed, so its wind blocking effect cannot be improved with the size of the wind. In addition, the flexible windproof net that fits the wire bundles tightly under strong winds has a greater surface roughness than the rigid windproof and dust suppression net with the same porosity, which weakens the wind kinetic energy at the windproof net to a certain extent, which is beneficial to suppressing dust near the pile; finally, Figure 1 As shown, the knotless flexible windproof net 2 with non-uniform porosity is supported by a steel frame 3 and installed in the upwind direction. Such a position relationship can also weaken the effect of the incoming wind 1 on the material pile 4 in the downwind direction.

[0035] Beneficial Effects

[0036] (1) The knotless flexible windproof net with non-uniform porosity of the present invention has better wind and dust suppression effect, is easy to install, is light and thin, has cushioning performance and is easy to transport;

[0037] (2) The method of the present invention is simple and convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the relationship between a knotless flexible windbreak net with non-uniform porosity, incoming wind and a pile of materials according to the present invention;

[0039] Figure 2 It is a motion diagram of the warp knitting yarn inlay yarn of the lower part of a knotless flexible windproof net with non-uniform porosity of the present invention;

[0040] Figure 3 It is a motion diagram of the warp knitting yarn inlay yarn of the upper part of a knotless flexible windproof net with non-uniform porosity of the present invention;

[0041] Among them, 1-incoming wind, 2-knotless flexible windbreak net with non-uniform porosity, 3-steel frame of windbreak net, 4-material pile. DETAILED DESCRIPTION

[0042] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0043] A method for preparing a knotless flexible windproof net with non-uniform porosity, such as Figures 2-3 As shown, the specific steps are as follows:

[0044] (1) Preparation of raw materials;

[0045] High-density polyethylene filament with a fineness of 290 to 400 denier;

[0046] (2) A knotless flexible windproof net with non-uniform porosity is prepared by first weaving the lower structure of a high-density polyethylene filament bundle and then changing the upper structure of the digital weaving of the pad yarn;

[0047] There are five bars in the lower and upper parts for weaving. The threading method of GB1 is full threading, and the threading methods of the other bars are 1 threading and 1 empty. The yarn numbers of the lower part are:

[0048] GB1: 1-0 / 0-1 / 1-0 / 0-1 / / ; GB2: 0-0 / 2-2 / 3-3 / 1-1 / / ;

[0049] GB3: 3-3 / 1-1 / 0-0 / 2-2 / / ; GB4: 0-0 / 1-1 / 3-3 / 2-2 / / ; GB5: 3-3 / 2-2 / 0-0 / 1-1 / / ;

[0050] The upper yarn numbers are:

[0051] GB1: 1-0 / 0-1 / 1-0 / 0-1 / / ; GB2: 0-0 / 2-2 / 3-3 / 1-1 / / ;

[0052] GB3: 3-3 / 1-1 / 0-0 / 2-2 / / ; GB4: 0-0 / 2-2 / 5-5 / 3-3 / / ; GB5: 5-5 / 3-3 / 0-0 / 2-2 / / .

[0053] The finally obtained knotless flexible windproof net with non-uniform porosity is an integrally formed part and a knotless net, woven from polymer filament bundles, and consists of a lower part and an upper part arranged along the longitudinal direction of the coil; under ideal conditions, the mesh of the lower part is a regular hexagonal hexagonal mesh, and the mesh of the upper part is a flat hexagonal hexagonal mesh, and the flat hexagon is a hexagon with an inscribed ellipse; the diameter of the inscribed circle of the regular hexagon is 3.5-4.5mm; the horizontal axis length of the inscribed ellipse of the flat hexagon is 3.5-4.5mm, and the vertical axis length is 1.5-2mm; the spacing of the mesh of the lower part is 2.5-3.5mm, the spacing of the mesh of the upper part along the horizontal direction of the coil is 2.5-3.5mm, and the spacing along the longitudinal direction of the coil is 4-5mm; the number of mesh holes per 2 inches in the horizontal direction of the coil of the lower part is 6-8, and the spacing along the longitudinal direction of the coil is 4-5mm. The number of mesh holes per 2 inches in the vertical direction is 7 to 9; the number of mesh holes per 2 inches in the upper part along the horizontal row direction of the coil is 6 to 8, and the number of mesh holes per 2 inches in the vertical row direction of the coil is 7 to 9; in the vertical direction, the height ratio of the lower and upper parts along the vertical row direction of the coil is 1:1; the porosity of the lower part is 31% to 34%, and the porosity of the upper part is 14% to 17%; the longitudinal breaking strength × breaking elongation of the knotless flexible windproof net with non-uniform porosity detected under the dense-mesh safety vertical net test standard of "GB5725-2009 Safety Net" is 200 to 240KN·mm, and the transverse breaking strength × breaking elongation is 45 to 65KN·mm, and it meets the impact resistance assessment requirements of this standard; the dust suppression rate of the knotless flexible windproof net with non-uniform porosity is above 85%.

[0054] Example 1

[0055] A method for preparing a knotless flexible windproof net with non-uniform porosity, the specific steps are as follows:

[0056] (1) Preparation of raw materials;

[0057] High-density polyethylene filament with a fineness of 290 denier;

[0058] (2) After merging four high-density polyethylene filaments, a warp knitting machine with a machine number of E12 is used to first weave the lower structure, and then the upper structure is digitally woven by changing the pad yarn to obtain a knotless flexible windproof net with non-uniform porosity;

[0059] There are five bars in the lower and upper parts for weaving. The threading method of GB1 is full threading, and the threading methods of the other bars are 1 threading and 1 empty. The yarn numbers of the lower part are:

[0060] GB1: 1-0 / 0-1 / 1-0 / 0-1 / / ; GB2: 0-0 / 2-2 / 3-3 / 1-1 / / ;

[0061] GB3: 3-3 / 1-1 / 0-0 / 2-2 / / ; GB4: 0-0 / 1-1 / 3-3 / 2-2 / / ; GB5: 3-3 / 2-2 / 0-0 / 1-1 / / ;

[0062] The upper yarn numbers are:

[0063] GB1: 1-0 / 0-1 / 1-0 / 0-1 / / ; GB2: 0-0 / 2-2 / 3-3 / 1-1 / / ;

[0064] GB3: 3-3 / 1-1 / 0-0 / 2-2 / / ; GB4: 0-0 / 2-2 / 5-5 / 3-3 / / ; GB5: 5-5 / 3-3 / 0-0 / 2-2 / / .

[0065] The finally obtained knotless flexible windproof net with non-uniform porosity is an integrally formed part and a knotless net, woven from polymer filament bundles, and consists of a lower part and an upper part arranged along the longitudinal direction of the coil; under ideal conditions, the mesh of the lower part is a regular hexagonal hexagonal mesh, and the mesh of the upper part is a flat hexagonal hexagonal mesh, and the flat hexagon is a hexagon with an inscribed ellipse; the diameter of the inscribed circle of the regular hexagon is 3.5-4.5mm; the horizontal axis length of the inscribed ellipse of the flat hexagon is 3.5-4.5mm, and the vertical axis length is 1.5-2mm; the spacing of the mesh of the lower part is 2.5-3.5mm, the spacing of the mesh of the upper part along the horizontal direction of the coil is 2.5-3.5mm, and the spacing along the longitudinal direction of the coil is 4-5mm; the number of mesh holes per 2 inches in the horizontal direction of the coil in the lower part is 6-8, and the number of mesh holes per 2 inches in the longitudinal direction of the coil is 6-8. The number of mesh holes is 7 to 9; the number of mesh holes per 2 inches along the horizontal row direction of the coil on the upper part is 6 to 8, and the number of mesh holes per 2 inches along the vertical row direction of the coil is 7 to 9; in the vertical direction, the height ratio of the lower part and the upper part along the vertical row direction of the coil is 1:1; the porosity of the lower part is 31% to 34%, and the porosity of the upper part is 14% to 17%; the longitudinal breaking strength × breaking elongation of the knotless flexible windproof net with non-uniform porosity is 200KN·mm and the transverse breaking strength × breaking elongation is 45KN·mm under the close-mesh safety vertical net test standard of "GB5725-2009 Safety Net", and it meets the impact resistance assessment requirements of this standard; the knotless flexible windproof net with non-uniform porosity is combined with the velocity measurement on the surface of the coal pile and the calculation formula for the dust generation of the coal pile to obtain a dust suppression rate of 85%.

[0066] Comparative Example 1

[0067] A flexible windproof net with uniform porosity is basically the same as the knotless flexible windproof net with non-uniform porosity in Example 1, the only difference being the lower part. The lower and upper parts of the flexible windproof net with uniform porosity in Example 1 are the same as the upper part of the knotless flexible windproof net with non-uniform porosity in Example 1.

[0068] The flexible windproof net with uniform porosity is combined with the velocity measurement on the coal pile surface and the calculation formula for the dust generation amount of the coal pile to obtain a dust suppression rate of 60% (the test method and test conditions are the same as those in Example 1).

[0069] By comparing Example 1 with Comparative Example 1, it can be seen that the windproof effect of the knotless flexible windproof net of Comparative Example 1 is not as good as that of the knotless flexible windproof net of Example 1. This is because the porosity of the entire windproof net is too low, resulting in most of the infiltration wind in the middle and lower parts of the knotless flexible windproof net being blocked in front of the net, causing more wind in front of the net to pass through the back of the net in the form of disturbed wind, thereby increasing the speed of the bypass wind. In addition, since the wind pressure in the middle and lower parts behind the net is too low and the wind pressure above the net is too high, the vertical airflow disturbance behind the net is enhanced and the turbulence intensity is too large, thereby forming a vortex flow wind with high wind speed and large area, which will greatly aggravate the dust level of the flat top of the pile behind the net.

[0070] Comparative Example 2

[0071] A flexible windproof net with uniform porosity is basically the same as the knotless flexible windproof net with non-uniform porosity in Example 1, the only difference being the upper part. The upper and lower parts of the flexible windproof net with uniform porosity in Comparative Example 2 are the same as the lower part of the knotless flexible windproof net with non-uniform porosity in Example 1.

[0072] The flexible windproof net with uniform porosity, combined with the velocity measurement on the coal pile surface and the calculation formula for the amount of dust generated by the coal pile, obtained a dust suppression rate of 75% (the test method and test conditions were the same as those in Example 1).

[0073] By comparing Example 1 with Comparative Example 2, it can be seen that the windproof effect of the knotless flexible windproof net of Comparative Example 2 is not as good as that of the knotless flexible windproof net of Example 1. This is because the porosity of the upper half of the windproof net is increased, which lowers the center of the vortex flow, so that a larger area of ​​the surface of the material pile is affected by the vortex flow, thereby increasing the dust effect on the surface of the material pile.

[0074] Comparative Example 3

[0075] A metal plate perforated mesh, having the same structure as the knotless flexible windproof mesh with non-uniform porosity as that of Example 1.

[0076] The metal plate punching mesh cooperates with the velocity measurement on the coal pile surface and the calculation formula of the dust generation amount of the coal pile to obtain a dust suppression rate (the test method and test conditions are the same as those in Example 1) of 80%.

[0077] By comparing Example 1 with Comparative Example 3, it can be seen that the windproof effect of the knotless flexible windproof net of Comparative Example 3 is not as good as that of the knotless flexible windproof net of Example 1. This is because the porosity of the metal plate punching net is fixed and its wind-blocking effect cannot be improved with the size of the wind, while the porosity of the knotless flexible windproof net increases slightly under the action of wind, which is consistent with the scientific research results that within a certain porosity range, the greater the wind speed of the incoming wind, the better the dust suppression effect of the windproof net with a larger porosity. The surface roughness of the windproof net is greater than that of the rigid windproof and dust suppression net, which weakens the wind kinetic energy at the windproof net to a certain extent, which is beneficial to suppressing dust near the pile.

[0078] Example 2

[0079] A method for preparing a knotless flexible windproof net with non-uniform porosity, the specific steps are as follows:

[0080] (1) Preparation of raw materials;

[0081] High-density polyethylene filament with a fineness of 340 denier;

[0082] (2) After merging four high-density polyethylene filaments, a warp knitting machine with a machine number of E12 is used to first weave the lower structure, and then the upper structure is digitally woven by changing the pad yarn to obtain a knotless flexible windproof net with non-uniform porosity;

[0083] There are five bars in the lower and upper parts for weaving. The threading method of GB1 is full threading, and the threading methods of the other bars are 1 threading and 1 empty. The yarn numbers of the lower part are:

[0084] GB1: 1-0 / 0-1 / 1-0 / 0-1 / / ; GB2: 0-0 / 2-2 / 3-3 / 1-1 / / ;

[0085] GB3: 3-3 / 1-1 / 0-0 / 2-2 / / ; GB4: 0-0 / 1-1 / 3-3 / 2-2 / / ; GB5: 3-3 / 2-2 / 0-0 / 1-1 / / ;

[0086] The upper yarn numbers are:

[0087] GB1: 1-0 / 0-1 / 1-0 / 0-1 / / ; GB2: 0-0 / 2-2 / 3-3 / 1-1 / / ;

[0088] GB3: 3-3 / 1-1 / 0-0 / 2-2 / / ; GB4: 0-0 / 2-2 / 5-5 / 3-3 / / ; GB5: 5-5 / 3-3 / 0-0 / 2-2 / / .

[0089] The finally obtained knotless flexible windproof net with non-uniform porosity is an integrally formed part and a knotless net, woven from polymer filament bundles, and consists of a lower part and an upper part arranged along the longitudinal direction of the coil; under ideal conditions, the mesh of the lower part is a regular hexagonal hexagonal mesh, and the mesh of the upper part is a flat hexagonal hexagonal mesh, and the flat hexagon is a hexagon with an inscribed ellipse; the diameter of the inscribed circle of the regular hexagon is 3.5-4.5mm; the horizontal axis length of the inscribed ellipse of the flat hexagon is 3.5-4.5mm, and the vertical axis length is 1.5-2mm; the spacing of the mesh of the lower part is 2.5-3.5mm, the spacing of the mesh of the upper part along the horizontal direction of the coil is 2.5-3.5mm, and the spacing along the longitudinal direction of the coil is 4-5mm; the number of mesh holes per 2 inches in the horizontal direction of the coil in the lower part is 6-8, and the number of mesh holes per 2 inches in the longitudinal direction of the coil is 6-8. The number of mesh holes is 7 to 9; the number of mesh holes per 2 inches along the horizontal row direction of the coil in the upper part is 6 to 8, and the number of mesh holes per 2 inches along the vertical row direction of the coil is 7 to 9; in the vertical direction, the height ratio of the lower part and the upper part along the vertical row direction of the coil is 1:1; the porosity of the lower part is 31% to 34%, and the porosity of the upper part is 14% to 17%; the longitudinal breaking strength × breaking elongation of the knotless flexible windproof net with non-uniform porosity is 225KN·mm and the transverse breaking strength × breaking elongation is 53KN·mm under the close-mesh safety vertical net test standard of "GB5725-2009 Safety Net", and it meets the impact resistance assessment requirements of this standard; the dust suppression rate of the knotless flexible windproof net with non-uniform porosity is 85% in combination with the velocity measurement on the surface of the coal pile and the calculation formula for the dust generation of the coal pile.

[0090] Example 3

[0091] A method for preparing a knotless flexible windproof net with non-uniform porosity, the specific steps are as follows:

[0092] (1) Preparation of raw materials;

[0093] High-density polyethylene filament with a fineness of 400 denier;

[0094] (2) After merging four high-density polyethylene filaments, a warp knitting machine with a machine number of E12 is used to first weave the lower structure, and then the upper structure is digitally woven by changing the pad yarn to obtain a knotless flexible windproof net with non-uniform porosity;

[0095] There are five bars in the lower and upper parts for weaving. The threading method of GB1 is full threading, and the threading methods of the other bars are 1 threading and 1 empty. The yarn numbers of the lower part are:

[0096] GB1: 1-0 / 0-1 / 1-0 / 0-1 / / ; GB2: 0-0 / 2-2 / 3-3 / 1-1 / / ;

[0097] GB3: 3-3 / 1-1 / 0-0 / 2-2 / / ; GB4: 0-0 / 1-1 / 3-3 / 2-2 / / ; GB5: 3-3 / 2-2 / 0-0 / 1-1 / / ;

[0098] The upper yarn numbers are:

[0099] GB1: 1-0 / 0-1 / 1-0 / 0-1 / / ; GB2: 0-0 / 2-2 / 3-3 / 1-1 / / ;

[0100] GB3: 3-3 / 1-1 / 0-0 / 2-2 / / ; GB4: 0-0 / 2-2 / 5-5 / 3-3 / / ; GB5: 5-5 / 3-3 / 0-0 / 2-2 / / .

[0101] The finally obtained knotless flexible windproof net with non-uniform porosity is an integrally formed part and a knotless net, woven from polymer filament bundles, and consists of a lower part and an upper part arranged along the longitudinal direction of the coil; under ideal conditions, the mesh of the lower part is a regular hexagonal hexagonal mesh, and the mesh of the upper part is a flat hexagonal hexagonal mesh, and the flat hexagon is a hexagon with an inscribed ellipse; the diameter of the inscribed circle of the regular hexagon is 3.5-4.5mm; the horizontal axis length of the inscribed ellipse of the flat hexagon is 3.5-4.5mm, and the vertical axis length is 1.5-2mm; the spacing of the mesh of the lower part is 2.5-3.5mm, the spacing of the mesh of the upper part along the horizontal direction of the coil is 2.5-3.5mm, and the spacing along the longitudinal direction of the coil is 4-5mm; the number of mesh holes per 2 inches in the horizontal direction of the coil in the lower part is 6-8, and the number of mesh holes per 2 inches in the longitudinal direction of the coil is 6-8. The number of mesh holes is 7 to 9; the number of mesh holes per 2 inches along the horizontal row direction of the coil in the upper part is 6 to 8, and the number of mesh holes per 2 inches along the vertical row direction of the coil is 7 to 9; in the vertical direction, the height ratio of the lower part and the upper part along the vertical row direction of the coil is 1:1; the porosity of the lower part is 31% to 34%, and the porosity of the upper part is 14% to 17%; the longitudinal breaking strength × breaking elongation of the knotless flexible windproof net with non-uniform porosity is 240KN·mm and the transverse breaking strength × breaking elongation is 65KN·mm under the close-mesh safety vertical net test standard of "GB5725-2009 Safety Net", and it meets the impact resistance assessment requirements of this standard; the dust suppression rate of the knotless flexible windproof net with non-uniform porosity combined with the velocity measurement on the surface of the coal pile and the calculation formula for the dust generation of the coal pile is 85%.

Claims

1. A knotless flexible windproof net with non-uniform porosity, which is woven by a polymer filament bundle through a warp knitting machine, characterized in that: It comprises a lower part and an upper part arranged along the longitudinal direction of the coils; the porosity of the lower part is 31% to 34%, and the porosity of the upper part is 14% to 17%; the dust suppression rate of the knotless flexible windproof net with non-uniform porosity is above 85%.

2. The knotless flexible windbreak net with non-uniform porosity according to claim 1, characterized in that: The knotless flexible windproof net with non-uniform porosity is a one-piece molded part.

3. The knotless flexible windbreak net with non-uniform porosity according to claim 2, characterized in that: The knotless flexible windbreak net with non-uniform porosity is a knotless net.

4. The knotless flexible windbreak net with non-uniform porosity according to claim 3, characterized in that: The knotless flexible windproof net with non-uniform porosity is obtained by weaving high-density polyethylene filament bundles through a warp knitting machine; the fineness of the high-density polyethylene filaments is 290-400 deniers.

5. The knotless flexible windbreak net with non-uniform porosity according to claim 1, characterized in that: The mesh of the lower part is a regular hexagonal hexagonal mesh, and the mesh of the upper part is a flat hexagonal hexagonal mesh. The flat hexagon is a hexagon with an inscribed ellipse, and the height of the mesh of the upper part is less than the height of the mesh of the lower part.

6. The knotless flexible windbreak net with non-uniform porosity according to claim 1, characterized in that: In the longitudinal direction, the height ratio between the lower part and the upper part along the longitudinal direction of the coil is 1:

1.

7. A knotless flexible windbreak net with non-uniform porosity according to any one of claims 1 to 6, characterized in that: The knotless flexible windbreak net with non-uniform porosity was tested under the close-mesh safety vertical net test standard of "GB5725-2009 Safety Net" with a longitudinal breaking strength × breaking elongation of 200~240KN·mm and a transverse breaking strength × breaking elongation of 45~65KN·mm, and met the impact resistance assessment requirements of this standard.

8. A method for preparing a knotless flexible windbreak net with non-uniform porosity as claimed in any one of claims 1 to 7, characterized in that: The lower structure is firstly knitted by a warp knitting machine equipped with an electronic transverse shifting device, and then the upper structure is digitally knitted by changing the pad yarn to obtain a knotless flexible windproof net with non-uniform porosity.

9. The method according to claim 8, characterized in that The lower part and the upper part both have five combs involved in weaving, GB1 is drawn in with full warp, and the other combs are drawn in with 1 through and 1 empty, wherein the yarn numbers of the lower part are: GB1: 1-0 / 0-1 / 1-0 / 0-1 / / ; GB2: 0-0 / 2-2 / 3-3 / 1-1 / / ; GB3: 3-3 / 1-1 / 0-0 / 2-2 / / ; GB4: 0-0 / 1-1 / 3-3 / 2-2 / / ; GB5: 3-3 / 2-2 / 0-0 / 1-1 / / ; The upper inlay yarn number is: GB1: 1-0 / 0-1 / 1-0 / 0-1 / / ; GB2: 0-0 / 2-2 / 3-3 / 1-1 / / ; GB3: 3-3 / 1-1 / 0-0 / 2-2 / / ; GB4: 0-0 / 2-2 / 5-5 / 3-3 / / ; GB5: 5-5 / 3-3 / 0-0 / 2-2 / / .

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