Streamline variable cross-section wind box structure suitable for fabric drying machine

Abstract

The invention relates to a streamline variable cross-section wind box structure suitable for a fabric drying machine, comprising: a wind box main body formed by bending and welding a galvanized sheet or stainless steel; the air box main body is centrosymmetric; the interior of the air box is divided into an upper box body and a lower box body by the partition plate, and the lower box body is a static pressure box; the wind box structure is provided with a streamline variable cross-section contour which is defined by a six-order Bezier curve of seven control points Pi (xi, yi) (i = 0-6); a guide plate is arranged at the inlet of the upper box; the curvilinear equation of the guide plate is consistent with the curvilinear equation of the variable cross-section profile; the lower box body and the partition plate form a two-stage static pressure structure; the air outlet of the air box is a continuous slit type side air outlet and is fully opened in the breadth direction. Compared with the prior art, the device has the advantages that the airflow uniformity is remarkably improved, the energy efficiency is optimized, the space utilization rate and the equipment compactness are high, the adaptability and adjustability are enhanced, and the maintenance convenience is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of fabric hot air drying in the textile printing and dyeing industry, and particularly to a streamlined variable cross-section air box structure applicable to a fabric dryer. Background Art

[0002] Continuous flat fabric processing has become a research hotspot in fabric processing due to its high production efficiency, strong variety adaptability, good process reproducibility, and resistance to wrinkling. Drying is an essential part of the continuous flat fabric processing process. By raising the temperature, the excess moisture inside the fabric after pad dyeing is vaporized to achieve the purpose of dehumidification and color fixation. In hot air drying, the fabric is fixed at the transverse edges by cloth clips or needle plates, and the fabric is suspended in the air. The longitudinal movement of the cloth clips (needle plates) drives the fabric to move forward in the oven. High-temperature dry air impacts the surface of the wet fabric to form forced convection, which has the advantages of gentle heat transfer and less color difference generation. Therefore, it is widely used in the production and processing of various fabrics.

[0003] During hot air drying, an air flow is generated by the high-speed rotation of the blades of the circulation fan. After being heated by the steam heat exchanger, hot air at a certain temperature enters the air supply system of the equipment, and finally, the hot air is evenly and continuously blown onto the surface of the fabric to be processed through the air box. Therefore, as an important air flow distribution component, the air box has an important impact on the drying quality and efficiency of the fabric.

[0004] Currently, the air box structures for fabric drying mostly adopt variable cross-section forms to ensure uniform air outlet in the width direction and meet the production requirements of different types and sizes of fabrics by adjusting the structural parameters.

[0005] Makhsuda Juraeva et al. studied the influence of different pipe end heights and air injection hole shapes on the air flow in the injection pipe system of the dryer and optimized the injection pipe system. However, there are still circulation and collision of the air flow in the pipe, resulting in incomplete uniform air flow distribution and affecting the fabric drying effect. Ahmet Some researchers studied the effects of geometric parameters (porosity, injector angle) and operating parameters (airflow velocity, fabric velocity) on the fabric cooling performance and airflow distribution during the cooling process of a dryer. However, the uneven airflow distribution still exists, affecting the fabric cooling uniformity. John Wilmer Parra Llanos et al. used the finite element method, combined with the standard k-ε turbulence model and the heat and mass transfer model of porous media, to mathematically model and simulate the drying process of cotton fabric in a dryer. By simulating different operating conditions (such as changing the drying air inlet velocity and fabric translation velocity), they analyzed the airflow in the injector, the overall drying process, and related parameters. The results showed that the airflow distribution was uneven along the width direction of the fabric, affecting the fabric drying quality. Although previous studies have improved the airflow distribution uniformity in the dryer system, with the increasing demand for fabric quality, it can no longer meet the production requirements well. In addition, problems such as large equipment footprint also need to be solved urgently.

[0006] Patent CN200720036388.6 discloses an air box for a hot air dryer, which includes an upper side plate, a lower side plate, a left side panel, a right side panel, and an air box inner cavity formed by the above two side plates and two panels. A partition is arranged in the air box inner cavity, and the partition is inclined to divide the air box inner cavity into two independent spaces. The front end and the rear end of the air box are respectively provided with air inlets, and a plurality of air outlets are respectively arranged on the left side panel and the right side panel. A pressure relief hole is arranged on a part of the partition near the front end air inlet of the air box, and a pressure relief hole is arranged on a part of the partition near the rear end air inlet of the air box; wind blocking plates are respectively arranged in the air box inner cavity at the front and rear ends of the air box, and the wind blocking plates are approximately parallel to the partition. However, it still has core disadvantages such as complex structure, insufficient dynamic adjustment ability, and high maintenance cost. Summary of the Invention

[0007] The purpose of the present invention is to overcome the defects of the above-mentioned existing technologies and provide a streamlined variable cross-section air box structure applicable to a fabric dryer, with significantly improved airflow uniformity; optimized energy efficiency; high space utilization rate and equipment compactness; enhanced adaptability and adjustability; and improved maintenance convenience.

[0008] The present invention provides a streamlined variable cross-section air box structure applicable to a fabric dryer, including:

[0009] An air box main body, which is bent and welded by galvanized sheet or stainless steel; it has high strength, good sealing performance and airflow guiding performance, can withstand external forces such as wind pressure and airflow impact received by the air box during operation, and ensure the structural stability and service life of the air box; the air box main body is centrosymmetric; it has good stability;

[0010] A partition plate and two upper and lower boxes formed by the partition plate dividing the inside of the air box, and the lower box is a static pressure box;

[0011] The air box structure is provided with a streamline variable cross-section profile, which is defined by a 6th-order Bezier curve with 7 control points P i (x i , y i )(i = 0 to 6); while facilitating profile constraints, it avoids air flow separation, reduces the friction and eddy currents between the air flow and the duct wall surface, ensures stable air flow, and reduces the energy loss of air flow;

[0012] A streamline guide plate is provided at the inlet of the upper box body to guide the air flow to flow along a predetermined path, buffering and suppressing the pressure and speed fluctuations in the air duct; the curve equation of the streamline guide plate is the same as the curve equation of the variable cross-section profile;

[0013] The lower box body and the partition plate form a secondary static pressure structure; the pressure in the lower box body is maintained at a relatively stable level; by adjusting the size and position of the baffle in the secondary static pressure structure, the internal resistance of the air box can be changed to achieve the adjustment of the outlet air volume;

[0014] The air outlet of the air box is a continuous slit-type side air outlet, which is fully open along the width direction. The slit-type outlet makes the air flow more smooth at the air duct outlet, facilitating large-area uniform air supply of the air flow across the entire fabric width, and avoiding the situation of too strong or too weak local air supply; compared with the conventional bottom air outlet, the slit-type side air outlet structure can greatly save the bottom space, improve the space utilization efficiency, and is especially suitable for the elastic fabric drying equipment with a compact space structure; compared with the conventional bottom air outlet, the slit-type side air outlet structure is convenient for daily maintenance, cleaning and overhaul work.

[0015] Furthermore, the parametric equation of the 6th-order Bezier curve is: B(t) = (x(t), y(t));

[0016] Where:

[0017] x(j) = x0(1 - j) 6 + 6x1(1 - j) 5 + 15x2j 2 (1 - j) 4 + 20x3j 3 (1 - j) 3 + 15j 4 x4(1 - j) 2 + 6x5j 5 (1 - j)+ x6j 6 ; y(j) = y0(1 - j) 6 + 6y1(1 - j) 5 + 15y2j 2 (1 - j) 4 + 20y3j 3 (1 - j) 3 + 15j4 y4(1 - j) 2 + 6y5j 5 (1 - j)+ y6j 6 ;

[0018] j is a parameter, 0 ≤ j ≤ 1.

[0019] Furthermore, the control point coordinates of the streamline variable cross - section profile satisfy: the dimension in the total length direction is 2600 mm, the dimension in the height direction is 490 mm, and the center point coordinates are (1300 mm, 245 mm).

[0020] Furthermore, due to the centrosymmetric characteristic of the streamline curve of the air box, two air box structures can be spliced and assembled into a whole. Under the condition of requiring a multi - air - box parallel unit, it reduces the floor area of the equipment and increases the local drying efficiency.

[0021] Furthermore, the length of the deflector can be dynamically adjusted according to the air supply distance of the air duct.

[0022] Furthermore, the secondary static pressure structure includes at least one partition board, and the size and position of the baffle are adjustable to match the requirements of different fabric types.

[0023] Furthermore, the angle between the deflector and the wall surface of the air duct is an obtuse angle.

[0024] Furthermore, the uniformity index C of the air outlet wind speed v ≤ 0.25.

[0025] Furthermore, the upper box body and the lower box body are divided by a partition board (3).

[0026] Furthermore, the deflector is located at the starting end of the variable cross - section profile at the entrance of the upper box body, and its length covers the area from the entrance to the point with the largest cross - sectional area of the air duct.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] (1) The air flow uniformity is significantly improved. Using a 6 - th order Bessel curve to define the streamline variable cross - section profile, combined with the design of the deflector consistent with the profile curve, reduces air flow separation and turbulence; the secondary static pressure structure adjusts the internal resistance through the partition board to stabilize the pressure distribution.

[0029] (2) The energy efficiency is optimized. The streamline profile reduces the friction between the air flow and the wall surface, avoiding energy loss; the arc - shaped transition surface ensures continuous curvature, further reducing the turbulent kinetic energy.

[0030] (3) The space utilization rate and equipment compactness. The slit - type side air outlet structure replaces the traditional bottom air outlet, saving the bottom space; the centrosymmetric splicing design supports the parallel connection of multiple air boxes, reducing the floor area.

[0031] (4) Enhanced adaptability and adjustability. Dynamic adjustment function: the length of the deflector is adjustable, and the position / size of the partition is adjustable to meet the requirements of different fabric types. Process compatibility: the secondary static pressure structure controls the outlet air volume by adjusting the baffle parameters.

[0032] (5) Improved maintenance convenience. The slit-type side air outlet design facilitates cleaning and maintenance, and is easier to maintain compared with the conventional bottom air outlet structure.

[0033] (6) Structural strength and durability. The main body of the air box is made of galvanized sheet or stainless steel, and the bending and welding process ensures high strength and corrosion resistance to withstand the working wind pressure and impact.

[0034] (7) Guarantee of drying quality, uniform heat exchange effect, and stability of process parameters. Description of the Drawings

[0035] Figure 1 Schematic diagram of the streamlined variable cross-section air box structure applicable to the fabric dryer in Embodiment 1;

[0036] Figure 2 Variable schematic diagram of the streamlined variable cross-section air box structure applicable to the fabric dryer in Embodiment 1; (a) shows partial parameters of the outer shape; (b) shows partial parameters of the deflector; (c) shows partial parameters of the static pressure box;

[0037] Figure 3 Assembly drawing of the streamlined variable cross-section air box structure applicable to the fabric dryer in Embodiment 1;

[0038] Figure 4 Distribution diagram of the flow field characteristics of the streamlined variable cross-section air box structure applicable to the fabric dryer in Embodiment 1; (a) shows the pressure field distribution; (b) shows the velocity field distribution;

[0039] Figure 5 Distribution diagram of the temperature and moisture content in the fabric area after drying for 70 s in Embodiment 1; (a) shows the temperature distribution; (b) shows the moisture content distribution;

[0040] Figure 6 Schematic diagram of the air supply test experimental environment of the streamlined variable cross-section air box structure applicable to the fabric dryer in Embodiment 1;

[0041] Figure 7 Pressure and velocity distribution curves of the upper air outlet of the streamlined variable cross-section air box structure applicable to the fabric dryer in Embodiment 1; (a) shows the pressure distribution curve; (b) shows the velocity distribution curve;

[0042] Figure 8 Pressure and velocity distribution curves of the lower air outlet of the streamlined variable cross-section air box structure applicable to the fabric dryer in Embodiment 1; (a) shows the pressure distribution curve; (b) shows the velocity distribution curve;

[0043] Figure 9 Schematic diagram of the linear variable cross-section air box structure for Comparative Example 1;

[0044] Figure 10 Distribution diagrams of the temperature and moisture content in the fabric area after drying for 70 s in Comparative Example 1; (a) is the temperature distribution; (b) is the moisture content distribution;

[0045] Figure 11 Pressure and velocity distribution curves at the upper air outlet of the linear variable cross-section air box in Comparative Example 1; (a) is the pressure distribution curve; (b) is the velocity distribution curve;

[0046] Figure 12 Pressure and velocity distribution curves at the lower air outlet of the linear variable cross-section air box in Comparative Example 1; (a) is the pressure distribution curve; (b) is the velocity distribution curve;

[0047] Figure 13 Schematic diagram of the streamlined variable cross-section air box structure with discrete outlets for Comparative Example 2;

[0048] Figure 14 Distribution diagrams of the temperature and moisture content in the fabric area after drying for 70 s in Comparative Example 2; (a) is the temperature distribution; (b) is the moisture content distribution;

[0049] Figure 15 Pressure and velocity distribution curves at the upper air outlet of the streamlined variable cross-section air box with discrete outlets in Comparative Example 2; (a) is the pressure distribution curve; (b) is the velocity distribution curve;

[0050] Figure 16 Pressure and velocity distribution curves at the lower air outlet of the streamlined variable cross-section air box with discrete outlets in Comparative Example 2; (a) is the pressure distribution curve; (b) is the velocity distribution curve;

[0051] Figure 17 Schematic diagram of the streamlined variable cross-section air box structure with slit outlets for Comparative Example 3;

[0052] Figure 18 Distribution diagrams of the temperature and moisture content in the fabric area after drying for 70 s in Comparative Example 3; (a) is the temperature distribution; (b) is the moisture content distribution;

[0053] Figure 19 Velocity and pressure distribution curves at the upper air outlet of the streamlined variable cross-section air box with slit outlets in Comparative Example 3; (a) is the pressure distribution curve; (b) is the velocity distribution curve;

[0054] Figure 20 Velocity and pressure distribution curves at the lower air outlet of the streamlined variable cross-section air box with slit outlets in Comparative Example 3; (a) is the pressure distribution curve; (b) is the velocity distribution curve.

[0055] Reference numerals: 1 - deflector; 2 - upper box body; 3 - partition plate; 4 - lower box body; 5 - upper air outlet; 6 - lower air outlet. Specific embodiments

[0056] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Features such as component models, material names, connection structures, control methods, algorithms, etc. that are not clearly described in this technical solution are regarded as common technical features disclosed in the prior art.

[0057] Embodiment 1

[0058] This embodiment provides a streamlined variable cross - section air box structure applicable to a fabric dryer, as Figure 1 shown, including:

[0059] The air box main body is formed by bending and welding galvanized sheet or stainless steel; it has high strength, good sealing performance and air flow guiding performance, and can withstand external forces such as wind pressure and air flow impact received by the air box during operation, ensuring the structural stability and service life of the air box; the air box main body is centrosymmetric; it has good stability;

[0060] The partition plate 3 and the upper and lower two box bodies formed by the partition plate 3 dividing the interior of the air box, and the lower box body 4 is a static pressure box;

[0061] The air box structure is provided with a streamlined variable cross - section contour, which is defined by a 6 - order Bezier curve with 7 control points P i (x i , y i )(i = 0 - 6); while facilitating contour constraint, it avoids air flow separation, reduces the friction and eddy current between the air flow and the duct wall surface, ensures the stable flow of the air flow, and reduces the energy loss of air flow;

[0062] A streamlined deflector 1 is provided at the inlet of the upper box body 2 to guide the air flow to flow along a predetermined path, buffering and suppressing the pressure and speed fluctuations in the air duct; the curve equation of the streamlined deflector is the same as the curve equation of the variable cross - section contour;

[0063] The lower box body 4 and the partition plate 3 form a secondary static pressure structure; keeping the pressure in the lower box body 4 at a relatively stable level; by adjusting the size and position of the baffle in the secondary static pressure structure, the internal resistance of the air box can be changed to achieve the adjustment of the outlet air volume;

[0064] The air outlet of the air box is a continuous slit-shaped side air outlet, which is fully open along the width direction. The slit-shaped outlet makes the airflow more smooth at the air duct outlet, facilitating large-area uniform air supply of the airflow across the entire fabric width and avoiding the situation of too strong or too weak local air supply; compared with the conventional downward air outlet, the slit-shaped side air outlet structure can greatly save the bottom space, improve the space utilization efficiency, and is especially suitable for the elastic fabric drying equipment with a compact space structure; compared with the conventional downward air outlet, the slit-shaped side air outlet structure is convenient for daily maintenance, cleaning and overhaul work.

[0065] The parametric equation of the 6th-order Bessel curve is: B(t) = (x(t), y(t));

[0066] Where:

[0067] x(j) = x0(1 - j) 6 + 6x1(1 - j) 5 + 15x2j 2 (1 - j) 4 + 20x3j 3 (1 - j) 3 + 15j 4 x4(1 - j) 2 + 6x5j 5 (1 - j)+ x6j 6 ; y(j) = y0(1 - j) 6 + 6y1(1 - j) 5 + 15y2j 2 (1 - j) 4 + 20y3j 3 (1 - j) 3 + 15j 4 y4(1 - j) 2 + 6y5j 5 (1 - j)+ y6j 6 ;

[0068] j is a parameter, 0 ≤ j ≤ 1.

[0069] In the specific implementation manner, the control point coordinates of the streamline variable cross-section profile satisfy: the dimension in the total length direction is 2600 mm, the dimension in the height direction is 490 mm, and the center point coordinates are (1300 mm, 245 mm).

[0070] In the specific implementation manner, the length of the deflector 1 can be dynamically adjusted according to the air supply distance of the air duct.

[0071] In the specific implementation manner, the secondary static pressure structure includes at least one partition plate 3, and the size and position of the baffle are adjustable to match the requirements of different fabric types.

[0072] In a specific embodiment, the included angle between the flow guide plate 1 and the air duct wall surface is an obtuse angle.

[0073] In a specific embodiment, the uniformity index C of the air outlet wind speed v ≤0.25.

[0074] In a specific embodiment, the upper box body 2 and the lower box body 4 are divided by a partition plate (3).

[0075] In a specific embodiment, the flow guide plate 1 is located at the starting end of the variable cross-section contour at the entrance of the upper box body 2, and its length covers the area from the entrance to the point with the largest cross-sectional area of the air duct.

[0076] The main structural parameters include three parts, namely the external shape part, the flow guide plate part, and the static pressure box part, totaling 12. The names and values of each parameter are shown in Table 1, and the schematic diagrams of each parameter are as Figure 2 shown.

[0077] Table 1 Value Table of Structural Parameters of the Streamlined Variable Cross-Section Air Box

[0078]

[0079] In a specific embodiment, due to the central symmetry feature of the streamline curve of the air box, two air box structures can be spliced and assembled into a whole. Under the condition of requiring a multi-air box parallel unit, it reduces the floor area of the equipment and increases the local drying efficiency. The splicing effect is as Figure 3 shown.

[0080] The above air box is simulated and calculated for the flow field and drying process using the commercial software COMSOL Multiphysics 6.2. Among them, the flow field model is expressed by the SST k-ω turbulence model, the energy equation is turned on to express the heat transfer process, and the following thermo-hygroscopic multi-field coupling model is used to describe the fabric area:

[0081] The change of the temperature field inside the fabric with time is calculated by Equation (1):

[0082]

[0083] In the formula, T is the temperature of the fabric (unit: K), t is the drying time (unit: s), ρ e is the equivalent density of the wet fabric (unit: kg·m -3 ), c p,e is the equivalent specific heat capacity of the wet fabric (unit: J·kg -1 ·K -1 ), λ e is the effective thermal conductivity of the wet fabric, Q v is the heat required for the moisture evaporation process inside the wet fabric, and is calculated by Equation (2):

[0084]

[0085] In the formula, is the evaporation rate of liquid water inside the fabric (unit: kg·m -3 ·s -1 ), and this value is calculated by Equation (3). Since the driving force for water evaporation inside the fabric is the difference between the partial pressure of water vapor p* (calculated by the Antoine equation) inside the fabric and the saturated vapor pressure p G in the atmosphere, the evaporation stops when the water content inside the fabric is 0.

[0086]

[0087] In the formula, k vap is the evaporation rate constant (unit: s -1 ), and θ l represents the volume fraction of liquid water.

[0088] The mass transfer process of water inside the fabric can be described as:

[0089]

[0090] In the formula, ρ l represents the density of liquid water (unit: kg·m -3 ), D L is the apparent diffusion rate constant of liquid water between the pores inside the fabric (unit: m 2 ·s -1 ), and is calculated by Equation (5):

[0091]

[0092] In the formula, θ l * represents the volume fraction of the fabric occupied by liquid water when the water content of the fabric reaches the critical saturation point, and α is the proportionality constant of the apparent diffusion coefficient (unit: m 2 ·s -1 ).

[0093] The hexahedron + tetrahedron hybrid honeycomb grid is used to spatially discretize the solution domain, and the number of grids is about 8.9 million; the variable step transient simulation technology is used to discretize time, and the drying process of 70 s is calculated. The time step in the first 1 s is set to 0.1 s, and the time step after that is set to 1 s. The initial values of the process parameters are set as: hot air temperature 81.5 °C, wind speed 13.3 m / s, and fabric bottom surface temperature 75.5 °C. After calculation, the pressure field distribution in the air box is extracted as shown in Figure 4 (a), and the velocity field is shown in Figure 4 (b).

[0094] The surface temperature and moisture content distribution of the fabric area after 70 s of extraction drying are as follows Figure 5 shown

[0095] Relevant quality indicators of the fabric drying process are established to evaluate the air supply performance of the air box, mainly considering three aspects: surface temperature uniformity, surface evaporation rate uniformity, and turbulent kinetic energy inside the air box

[0096] 1) Surface temperature uniformity index CVT

[0097]

[0098] In the formula, T i is the temperature at a certain point on the fabric surface is the average temperature on the fabric surface, and n is the number of divisions of the fabric surface

[0099] 2) Surface evaporation rate uniformity index CVE

[0100]

[0101] In the formula, E i is the evaporation rate at a certain point on the fabric surface is the average evaporation rate on the fabric surface

[0102] 3) Overall turbulent energy consumption index

[0103]

[0104] In the formula, k i is the turbulent kinetic energy in a certain area of the air box, V is the volume of the air box fluid domain, and N is the number of divisions of the internal space of the air box

[0105] Based on the simulation results, the three evaluation indicators are calculated as shown in Table 2

[0106] Table 2 Evaluation results of the air supply performance of the streamlined variable cross-section air box

[0107]

[0108] According to the definitions of the three indicators, the smaller the CVT, the smaller the discreteness of the fabric surface temperature distribution, that is, the better the uniformity. The same applies to CVE; _k represents the average turbulence degree in the flow field calculation domain. The smaller its value, the smaller the turbulent loss in the flow field and the higher the energy utilization rate. Therefore, it can be seen from Table 2 that the levels of the three indicators are all < 1, indicating that the air box takes into account the problem of turbulent energy loss while effectively improving the drying quality

[0109] The designed air box is tested for wind speed and wind pressure. The test environment is as follows Figure 6As shown in the figure. The test platform includes 2 circulation fans, 2 curved main air ducts, and 2 air boxes to be tested; according to the positional relationship, the 2 air boxes to be tested are divided into an upper air box and a lower air box, and each air box is also divided into an upper air outlet 5 and a lower air outlet 6; the experimental instrument uses a Pitot tube anemometer (pressure range 600 Pa, resolution 1 Pa, accuracy ±1 Pa, Pitot tube coefficient 1.0); before the test starts, the L-shaped Pitot tube probe is fixed by a guide rail slider device so that it can only slide in the width direction, the probe is perpendicular to the air outlet (i.e., parallel to the air outlet direction) and is 2 mm away from the air outlet; use a high-precision caliper to mark measurement points every 120 mm at the air outlet position and number them from left to right, and there are a total of 21 measurement points for a single-row air outlet. During the test process, the motor power is divided into groups at intervals of 10% from 30% to 100%, measure the air velocity and air pressure at the upper and lower air outlets at different motor powers, and fit the distribution curves, as Figure 7 , 8 shown.

[0110] Observation Figure 7 and Figure 8 show that:

[0111] 1. Whether it is the upper air outlet 5 or the lower air outlet 6, the pressure and speed both show a trend of "low at the inlet and high at the end". This is because the air flow at the inlet part is not stable when it just blows out from the main air duct, and most of the air flow direction is parallel to the width direction of the air box; since the end of the air box is closed, part of the air flow accumulates here, resulting in a relatively large pressure (for the upper air outlet 5, number 1 is the end and number 21 is the inlet end; for the lower air outlet 6, it is the opposite).

[0112] 2. The pressure and speed levels at the upper air outlet 5 are significantly higher than those at the lower air outlet 6, indicating that the energy loss in the lower half of the air box is greater than that in the upper half. Considering that it is due to the angle between the streamlined baffle and the main air duct wall. For the upper half of the air box, the angle between the baffle and the main air duct wall is relatively large and obtuse, which is more friendly to the air flow channel. For the lower half of the air box, the angle between the baffle and the main air duct wall is relatively small and acute, forcing the air flow to change the flow direction, resulting in a large energy loss.

[0113] Establish an index to evaluate the uniformity of the pressure at the test point, that is, the pressure singularity coefficient c p :

[0114]

[0115] In the formula: c p is the pressure singularity coefficient, indicating the relative dispersion degree of the pressure on the air outlet section; σ p is the standard deviation of the pressure on the air outlet section, indicating the absolute dispersion degree of the pressure value; μ p is the average value of the pressure on the air outlet section; M is the number of pressure samples; p iis the pressure at the i-th measurement point. c p The smaller the value, the better the pressure uniformity on the air outlet section; conversely, it indicates poor pressure uniformity.

[0116] Similarly, an index for evaluating the uniformity of the velocity at the test point is established, that is, the velocity singularity coefficient c v :

[0117]

[0118] In the formula: c v is the velocity singularity coefficient, representing the relative dispersion degree of the velocity on the air outlet section; σ v is the standard deviation of the velocity on the air outlet section, representing the absolute dispersion degree of the velocity values; μ v is the average value of the velocity on the air outlet section; M is the number of velocity samples; v i is the velocity at the i-th measurement point. c v The smaller the value, the better the velocity uniformity on the air outlet section; conversely, it indicates poor velocity uniformity.

[0119] Extract the pressure and velocity at the air outlet test points, and the statistical results are shown in Table 3. It can be seen from Table 3 that for the upper air outlet 5, its pressure singularity coefficient c p is about 0.26, and c v the velocity singularity coefficient is below 0.26, indicating good consistency; for the lower air outlet 6, there is only a slightly larger pressure distribution deviation at higher powers (90%, 100%), and the velocity distribution uniformity is less affected by the fan power. Overall, the velocity and pressure distribution characteristics of this air box are not affected by the fan power, and both have a relatively uniform distribution characteristic, only with differences in magnitude.

[0120] Table 3 Statistical quantities of the air outlet pressure and velocity uniformity of the streamlined variable cross-section air box

[0121]

[0122]

[0123] Comparative Example 1

[0124] A spliced linear variable cross-section air box structure applicable to a fabric dryer has the following characteristics:

[0125] 1) The outline of the air box changes linearly and is spliced into a whole by two linear variable cross-section air boxes;

[0126] 2) There is no deflector at the air box inlet;

[0127] 3) The air box outlet is a continuous slit-type outlet;

[0128] 4) At the air outlet of the air box, 51 flow rectifiers are evenly distributed in the radial direction, with each interval being approximately 50 mm and no deflection angle.

[0129] 5) The distance between the first (last) flow rectifier and the air box inlet (end) is approximately 18 mm.

[0130] The basic structure of the linearly variable cross-section air box is as Figure 9 shown.

[0131] Carry out drying simulation and air pressure and air velocity experimental tests on the air box described in Comparative Example 1. The simulation process, test platform, test equipment, and test method are all the same as those described above; after the simulation is completed, extract the surface temperature and moisture content distribution of the fabric area after drying for 70 s as Figure 10 shown; after the test is completed, draw the pressure and velocity distribution curves of the upper and lower air outlets respectively as Figure 11 、 12 shown.

[0132] Based on the simulation results, calculate the same three evaluation indexes as in Table 2, as shown in Table 4.

[0133] Table 4 Evaluation results of the air supply performance of the linearly variable cross-section air box

[0134]

[0135] Comparing Table 4 with Table 2, it can be obtained that the CVT, CVE, and k values of Comparative Example 1 are all significantly higher than those of the aforementioned air box, which indicates that its performance in fabric drying uniformity is significantly inferior to the aforementioned air box design scheme; comparing Figure 11 、 12 with Figure 7 、 8 it can be obtained that the air pressure and velocity level of the air box described in Comparative Example 1 is higher than that of the aforementioned air box, with a relatively large overall fluctuation range and poor overall uniformity, especially being more obvious at the upper air outlet 5, and there is almost no velocity at the lower air outlet 6 near the inlet end. The uneven air outlet performance will lead to uneven and unstable heat flow field on the upper surface of the fabric during the drying process, resulting in inconsistent heat transfer intensity in the width direction, causing temperature differences, and further leading to different moisture evaporation rates, ultimately resulting in the problem of dye "migration" and affecting product quality.

[0136] Extract the air pressure and velocity at the air outlet test points, and the statistical results are shown in Table 5. It can be seen from Table 5 that for the upper air outlet 5, the pressure singularity coefficient c p fluctuates in the range of 0.34 to 0.41, with a relatively significant fluctuation range. This phenomenon indicates that the upper air outlet 5 is extremely vulnerable to changes in the fan power. At the same time, the velocity singularity coefficient c vThe distribution also shows an obvious non-uniform state. Generally speaking, the pressure and velocity distribution characteristics of the upper air box are not only greatly affected by the fan power, but also the distribution state is not uniform enough. On the contrary, for the lower air outlet 6, the pressure singularity coefficient c p stabilizes at about 0.38. Compared with the upper air box, it is relatively less affected by the fan power. However, the velocity singularity coefficient c v of the lower air outlet 6 remains at a relatively high level under different fan power conditions. This means that regardless of the power state of the fan, the pressure and velocity distributions in the lower air box show relatively chaotic characteristics. Generally speaking, the velocity and pressure distribution characteristics of this air box are extremely sensitive to the change of fan power, and its distribution characteristics show an obvious chaotic trend, and the distribution uniformity is poor, which may lead to uneven evaporation rate of the fabric surface during the fabric drying process, and thus cause local dye "migration" problems, affecting the fabric drying quality.

[0137] Table 5 Statistics of the air outlet pressure and velocity uniformity of the linear variable cross-section air box

[0138]

[0139]

[0140] Comparing Table 4 with Table 3, it can be obtained that: the statistical results of the air outlet pressure and velocity uniformity of the air box described in Comparative Example 1 are quite different from those of the previous air box. Whether it is pressure or velocity, its singularity coefficient is higher than that of the previous one, indicating that the air outlet uniformity is poor, and the pressure and velocity levels are relatively high, which may lead to too fast evaporation rate of the fabric surface during the drying process, exacerbating quality defects such as dye "migration" problems and fabric damage.

[0141] Comparative Example 2

[0142] A streamlined variable cross-section air box structure with discrete outlets applicable to a fabric dryer has the following characteristics:

[0143] 1) The air box profile adopts a cubic polynomial spline curve with a central symmetry point, and is spliced into a whole by two streamlined variable cross-section air boxes;

[0144] 2) There are two guide vane structures at the air box inlet, and the guide vanes are designed with cubic polynomial spline curves;

[0145] 3) The outlet is a single-row discrete uniformly distributed rectangular outlet, the size of a single outlet is 20mm×20mm, the spacing is 20mm, and there are 66 in total distributed radially;

[0146] The basic structure of the streamlined variable cross-section air box with discrete outlets is as Figure 13 shown.

[0147] Perform drying simulation and wind pressure and wind speed experimental tests on the air box described in Comparative Example 2. The simulation process, test platform, test equipment, and test method are the same as those described above. After the simulation, extract the surface temperature and moisture content distribution of the fabric area after 70 s of drying as shown in Figure 14 ; after the test is completed, draw the pressure and velocity distribution curves of the upper and lower air outlets respectively as shown in Figure 15 、 16 .

[0148] Based on the simulation results, calculate the same three evaluation indexes as in Table 2, as shown in Table 6.

[0149] Table 6 Evaluation results of the air supply performance of the discrete outlet streamlined variable cross-section air box

[0150]

[0151] Comparing Table 6, Table 4, and Table 2, it can be obtained that the CVT, CVE, and k values of Comparative Example 2 are improved compared with those of Comparative Example 1, but they are still inferior to the performance of the aforementioned air box. In particular, its k value is significantly higher, indicating that there are still obvious energy loss problems in the design of this air box.

[0152] Comparing Figure 15 、 16 it can be obtained that the pressure and velocity levels of the air box described in Comparative Example 2 are also higher than those of the aforementioned air box, and the overall fluctuation range is larger, and the uniformity is poor, which is more obvious at the upper and lower air outlets 6. The uneven air outlet condition will cause the air flow field on the surface of the fabric to be unbalanced and unstable during the drying process, resulting in different air flow impact intensities in the width direction, causing a wind force difference, and then causing different wind forces on the fabric, and finally resulting in fiber displacement, affecting the product quality.

[0153] Extract the pressure and velocity at the air outlet test points, and the statistical results are shown in Table 7. It can be seen from Table 7 that for the upper air outlet 5, its pressure singularity coefficient c p is between 0.38 and 0.59, and the velocity singularity coefficient c v is between 0.25 and 0.41, indicating that the air outlet uniformity is not ideal at each power; for the lower air outlet 6, its pressure singularity coefficient c p is between 0.28 and 0.43, which is improved compared with the upper air outlet 5, but the velocity singularity coefficient still varies between 0.21 and 0.33 under different powers, indicating that the pressure and velocity distribution characteristics are greatly affected by the fan power. Generally speaking, the structural design of this air box has defects, the pressure and velocity distribution characteristics are greatly affected by the fan power, the air outlet is uneven, and then it affects the moisture evaporation rate of the fabric in the width direction, and finally leads to uneven fabric color.

[0154] Table 7 Statistics of the air outlet pressure and velocity uniformity of the streamlined variable cross-section air box with discrete outlets

[0155]

[0156] Comparing Table 7 with Table 3, it can be obtained that: the statistical results of the air outlet pressure and velocity uniformity in Comparative Example 2 have significant differences compared with the previous air box. Whether it is pressure or velocity, its singular coefficient is higher than the previous one, indicating that the air outlet uniformity is poor. In addition, the discontinuous opening structure may cause a discontinuous distribution pattern of the cloth surface temperature and moisture content during the drying process, affecting the drying quality.

[0157] Comparative Example 3

[0158] A streamlined variable cross-section air box structure with a slit-shaped outlet applicable to a fabric dryer has the following characteristics:

[0159] 1) The air box contour adopts a cubic polynomial spline curve with a central symmetry point and is spliced into an integral body by two streamlined variable cross-section air boxes;

[0160] 2) The air box air outlet is a continuous slit-shaped outlet, and the outlet size is 2596 mm × 10 mm;

[0161] 3) There are two deflector structures at the air box inlet, and the deflectors are designed with cubic polynomial spline curves;

[0162] Its basic structure is as Figure 17 shown.

[0163] Carry out drying simulation and air pressure and air velocity experimental tests on the air box described in Comparative Example 3. The simulation process, test platform, test equipment, and test method are the same as those described above; after the simulation, extract the surface temperature and moisture content distribution of the fabric area after 70 s of drying as Figure 18 shown. After the test is completed, draw the pressure and velocity distribution curves of the upper and lower air outlets respectively as Figure 19 、 20 shown.

[0164] Based on the simulation results, calculate the same three evaluation indexes as in Table 2 as shown in Table 8.

[0165] Table 8 Evaluation results of the air supply performance of the streamlined variable cross-section air box with a slit outlet

[0166]

[0167] Comparing Table 8, Table 6, Table 4, and Table 2, it can be obtained that: compared with Comparative Example 1 and Comparative Example 2, this air box shows different characteristics in performance: its temperature uniformity is better than that of Comparative Example 1 but worse than that of Comparative Example 2, while the surface evaporation rate uniformity is better than that of Comparative Example 2. However, compared with the previous air box, there are still certain gaps in the evaluation indexes of this air box, indicating that there is still significant room for optimization in its overall performance. ComparingFigure 19 , 20 It can be obtained that the pressure fluctuations at the upper and lower outlets of the air box described in Comparative Example 3 are relatively significant, indicating that the pressure distribution characteristics of the air box are greatly affected by the fan power and the uniformity is poor; although the air outlet speed at the lower air outlet 6 shows an increasing trend with the increase of the fan power, the speed is still relatively stable at different powers.

[0168] Extract the pressure and speed at the test points of the air outlet, and the statistical results are shown in Table 6. As can be seen from Table 6, for the upper air outlet 5, the pressure singularity coefficient c p fluctuates within the range of 0.36 - 0.62, and the speed singularity coefficient c v fluctuates within the range of 0.21 - 0.38. The fluctuation ranges of both are relatively large, indicating that the distribution characteristics of pressure and speed are greatly affected by the fan power. At the same time, the values of the two evaluation indexes are relatively large at some powers, indicating that the structural defects of this air box are relatively large; for the lower air outlet 6, its pressure singularity coefficient is about 0.25, and the singularity coefficient is relatively large only when the power is 70%. The singularity coefficients at other powers are within the acceptable range. Generally speaking, the structural design of this air box has relatively large defects, the distribution characteristics of pressure and speed are greatly affected by the fan power, and the air outlet is uneven.

[0169] The relevant mathematical statistical indexes of the test data are extracted as shown in Table 6.

[0170] Table 6 Statistics of the air outlet pressure and speed uniformity of the streamlined variable cross-section air box with slit-shaped outlets

[0171]

[0172] By comparing Table 6 with Table 3, it can be obtained that the statistical indexes of the air outlet speed and pressure of the air box described in Comparative Example 3 are very different from those of the previous air box. Whether it is pressure or speed, its coefficient of variation is higher than that of the previous one, indicating that the air outlet uniformity is poor. In addition, it is difficult to control the air outlet direction during the drying process for the slit-shaped opening structure, resulting in uneven distribution of the moisture content on the cloth surface, which in turn affects the drying quality of the fabric.

[0173] The components not described in detail in this embodiment are all existing components that can be purchased from public channels.

[0174] The above description of the embodiments is for the convenience of those of ordinary skill in the art to understand and use the invention. Obviously, those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A streamlined variable cross-section wind box structure suitable for a fabric drying machine, characterized in that: include: The main body of the wind box is made of galvanized sheet or stainless steel by bending and welding; The main body of the wind box is centrally symmetrical; A partition plate (3) and an upper and lower box body into which the interior of the wind box is divided by the partition plate (3), the upper box body (2) being an air duct and the lower box body (4) being a static pressure box; The wind box structure has a streamlined variable cross-section profile and uses 7 control points P i (x i ,y i )(i=0~6) 6th order Bezier curve definition; The inlet of the upper box body (2) is provided with a guide plate (1); the curve equation of the guide plate (1) is consistent with the curve equation of the variable cross-section profile; The lower box body (4) and the partition plate (3) form a secondary static pressure structure; The air outlet of the wind box is a continuous slit-type side outlet, fully open along the width direction.

2. A streamlined variable cross-section wind box structure suitable for a fabric drying machine according to claim 1, characterized in that: The parametric equation of the 6th order Bezier curve is: B(t)=(x(t), y(t)); in: x(j)=x0(1-j) 6 +6x1(1-j) 5 +15x2j 2 (1-j) 4 +20x3j 3 (1-j) 3 +15j 4 x4(1-j) 2 +6x5j 5 (1-j)+x6j 6 ;y(j)=y0(1-j) 6 +6y1(1-j) 5 +15y2j 2 (1-j) 4 +20y3j 3 (1-j) 3 +15j 4 y4(1-j) 2 +6y5j 5 (1-j)+y6j 6 4 j is a parameter, 0≤j≤1.

3. The streamlined variable cross-section wind box structure suitable for a fabric drying machine according to claim 1, characterized in that: The control point coordinates of the streamlined variable-section profile satisfy the following requirements: the total length dimension is 2600 mm, the height dimension is 490 mm, and the center point coordinates are (1300 mm, 245 mm).

4. The streamlined variable cross-section wind box structure suitable for a fabric drying machine according to claim 1, characterized in that: The two wind box structures can be spliced ​​and assembled into a whole.

5. The streamlined variable cross-section wind box structure suitable for a fabric drying machine according to claim 1, characterized in that: The length of the guide plate (1) can be dynamically adjusted according to the air supply distance of the air duct.

6. The streamlined variable cross-section wind box structure suitable for a fabric drying machine according to claim 1, characterized in that: The secondary static pressure structure comprises at least one partition plate (3), and the size and position of the partition plate are adjustable to match the requirements of different fabric types.

7. The streamlined variable cross-section wind box structure suitable for a fabric drying machine according to claim 1, characterized in that: The included angle between the guide plate (1) and the wall surface of the air duct is an obtuse angle.

8. The streamlined variable cross-section wind box structure suitable for a fabric drying machine according to claim 1, characterized in that: Air outlet wind speed uniformity index C v ≤0.

25.

9. The streamlined variable cross-section wind box structure suitable for a fabric drying machine according to claim 1, characterized in that: The upper box body (2) and the lower box body (4) are divided by a partition plate (3).

10. The streamlined variable cross-section wind box structure suitable for a fabric drying machine according to claim 1, characterized in that: The guide plate (1) is located at the starting end of the variable cross-section profile of the inlet of the upper box body (2), and its length covers the area from the inlet to the point with the largest cross-sectional area of ​​the air duct.

Images