CN103971395A - Mimicry reconstruction and performance computing method of fiber filter medium structure - Google Patents

Abstract

The invention discloses a mimicry reconstruction and performance computing method of a fiber filter medium structure, and belongs to the technical field of fiber structure mimicry reconstruction. The mimicry reconstruction process comprises the steps: first, obtaining fiber filter medium images; second, setting the best threshold value and performing binarization processing; third, performing center line detection on binary images; fourth, performing four-opposite-angle direction comparison on pixel points of the center line and obtaining the gyration radius di and the gyration direction df; fifth, performing three-dimensional gyration and obtaining a fiber filter medium mimicry reconstruction image. According to the mimicry reconstruction and performance computing method, by inputting a series of relevant parameters, filter efficiency curves and pressure loss curves of fiber filter media at different wind speeds are obtained by means of the empirical formula. According to the method, microcosmic single-layer structure images in real fiber filter media are used as the basis, mimicry reconstruction is performed on the obtained images by means of the simple and rapid image processing method, and a mimicry reconstruction model can simulate the real fiber filter medium structure realistically.

Description

A kind of mimicry reconstruction and Calculation Methods for Performance thereof of fiber filter media structure

Technical field

The present invention relates to fibre structure mimicry reconstruction technique field, more particularly, relate to a kind of mimicry reconstruction and Calculation Methods for Performance thereof of fiber filter media structure.

Background technology

Dust can cause injurious effects to atmospheric environment, production and health, and especially pellet can produce harm to the respiratory system of human body.Therefore, reducing suspended particulate substance in air has great importance to protection of the environment and guarantee human health.

In the face of day by day serious atmosphere polluting problem, sack cleaner is high to the arresting efficiency of particulate pollutant, is therefore widely used.Fiber filter media is as one of core component of sack cleaner, the requirement that can it be up to state standards to the filtration of fine particle, closely related with its filtration efficiency and the pressure loss, especially the pressure loss of fiber filter media is the important parameter that characterizes strainability, and its magnitude relationship is to the energy consumption of whole filtering system.And the above-mentioned performance index of filter medium are mainly determined by fiber filter media internal microstructure.Therefore the internal microstructure that, obtains exactly filter medium seems most important.

In early stage research, fiber filter media is reduced to ultimate fibre or isolated fiber, external scientist is on filamentary basis, consider that fiber model is set up in the interference of fiber around, fiber filter media is reduced to desirable filter medium, utilizes computer technology to generate two dimension woven (fiber parallel and cross arrangement) filter medium.But the fiber filter media that said method is set up is two-dimensional structure, larger with actual three-dimensional filter media construction difference, the mimicry model of the two-dimentional filter medium of foundation can not reflect the performance of filter medium really, can only be used for studying simulation.

Also there is researcher to utilize that computer technology is random in space produces three-dimensional fiber filter media, and consider the factor such as diameter, length, direction, bending of fiber.But only consider that model that pars fibrosa factor builds is not taking actual fiber filter media as basis, do not consider the factors such as crimp between fiber.Therefore, the model that structure obtains and actual filter media construction differ still larger, still can only be used for studying simulation, and cannot obtain the structural parameters of true fiber filter medium.

Through retrieval, existing open about the technical scheme of fibrous material performance study, as Chinese Patent Application No. 201210268547.0, the applying date is on July 30th, 2012, and invention and created name is: short fiber reinforced composite fiber alignment degree quantitative evaluating method; This application case relates to a kind of short fiber reinforced composite fiber alignment degree quantitative evaluating method, it is characterized in that: select determine cutting plane and composite sample is dissectd; Obtain microphoto by optical microscope or scanning electron microscope; In graph image software, repaint the oval fibre section in microphoto; Long axis length, minor axis length and the transverse of the each ellipse in the picture after extraction repaints and coordinate axis angle; According to the direction vector of the each oval corresponding fiber of the oval cross section calculation of parameter of having extracted; Calculate the degree of orientation parameter of compound substance along specific direction.This application case has been eliminated due to the corresponding two kinds of errors of calculation that machine direction causes of same elliptic cross-section by choosing suitable cutting plane, is mainly applicable to fiber alignment degree qualitative assessment, and is not suitable for the mimicryization reconstruction of fiber filter media structure.

Summary of the invention

1. the technical matters that invention will solve

The object of the invention is to overcome that existing fiber filter media mimicry method for reconstructing exists: 1) do not rebuild basis taking actual fibers filter medium as mimicry, the fiber model that structure obtains and actual filter media construction differ larger, can only be used for studying simulation, in application, have limitation; 2) deficiency that mimicry process of reconstruction complexity, data processing amount are large, the model construction time is long, provides a kind of mimicry reconstruction and Calculation Methods for Performance thereof of fiber filter media structure; The present invention is taking true fiber filter medium interior microscopic single layer structure image as basis, utilization simply, image processing method carries out mimicry reconstruction to gained image fast, and extract image information, obtain the structural parameters of mimicry reconstruction model, mimicry reconstruction model can realistic simulation true fiber filter medium structure, resulting structures parameter can represent the structural parameters of true fiber filter medium.

2. technical scheme

For achieving the above object, technical scheme provided by the invention is:

The mimicry method for reconstructing of a kind of fiber filter media structure of the present invention, the steps include:

Step 1, obtain the image of true fiber filter medium;

Step 2, optimal threshold is set, step 1 gained image is carried out to binary conversion treatment, extract the bianry image of fiber filter media and hole, fiber pixel point value is 1, and hole pixel point value is 0;

Step 3, step 2 gained bianry image is carried out to fiber filter media center line detecting, obtain fiber filter media center line ss;

Step 4, carry out the contrast of the four pairs of angular direction taking pixel on step 3 gained center line as basic point, obtain three-dimensional rotation radius di and the three-dimensional rotation direction df of each pixel on center line;

Step 5, taking pixel on step 3 gained center line as rotation basic point, taking step 4 gained three-dimensional rotation radius di and three-dimensional rotation direction df as rotation parameter, carry out three-dimensional rotation, obtain fiber filter media mimicryization and rebuild image.

Further, in step 1, true fiber filter medium is scanned under scanning electron microscope, obtain the scanning electron microscope image of fiber filter media.

Further, described in step 2, the deterministic process of optimal threshold is as follows:

A, fiber filter media scanning electron microscope (SEM) photograph is carried out to gray scale stretching:

K＝255/(b-a)

M＝(-255*a)/(b-a)

Y＝KX+M

In above formula, a is scanning electron microscope image minimum gradation value; B is scanning electron microscope image maximum gradation value; X is any pixel gray-scale value of scanning electron microscope image; Y is the gray scale tension values that pixel X is corresponding;

B, determine optimal threshold:

If the ratio that in target zone, pixel number accounts for entire image in image after step a gray scale stretches is ω 0, in target zone, pixel average gray is μ 0, within the scope of background, to account for the ratio of entire image be ω 1 to pixel number, within the scope of background, pixel average gray is μ 1, and the segmentation threshold of target and background is designated as T _m, the inter-class variance of target and background is designated as g:

g＝ω0ω1(μ0-μ1)^2

Corresponding threshold value T while adopting the method for traversal to obtain making inter-class variance g maximum _m, this threshold value is described optimal threshold.

Further, the method that obtains fiber filter media center line ss in step 3 is: pixel point value 8 directions that stretch out centered by 1 pixel in step 2 gained bianry image, 45 ° of intervals such as 8 described directions, add up the pixel number that in 8 directions, contiguous pixels point value is 1, as as described in the pixel number of any two diagonal angle directional statistics of pixel all equate or to differ be 1, retain this pixel, otherwise give up; The pixel that is 1 to all pixel point values is all carried out aforesaid operations, obtains fiber filter media center line ss.

Further, described in step 4, four pairs of angular direction contrasts are specially: the pixel that step 3 is retained carries out the pixel number contrast that 4 pairs of angular direction contiguous pixels point values are 1 again, using minimum pixel number to angular direction as three-dimensional rotation direction df, this to 1/2nd of pixel number on angular direction as three-dimensional rotation radius di.

The Calculation Methods for Performance of a kind of fiber filter media structure of the present invention, the steps include:

Steps A, obtain the image of true fiber filter medium;

Step B, optimal threshold is set, steps A gained image is carried out to binary conversion treatment, extract the bianry image of fiber filter media and hole, fiber pixel point value is 1, and hole pixel point value is 0;

Step C, step B gained bianry image is carried out to fiber filter media center line detecting, obtain fiber filter media center line ss;

Step D, carry out the contrast of the four pairs of angular direction taking pixel on step C gained center line as basic point, obtain three-dimensional rotation radius di and the three-dimensional rotation direction df of each pixel on center line;

Step e, step B gained bianry image is carried out to anti-phase processing, fiber pixel point value is 0, and hole pixel point value is 1, and the pixel number that statistical pixel point value is 1, is designated as a; The true fiber filter medium image slices vegetarian refreshments number that statistic procedure A obtains, is designated as b, obtains fiber filter media image porosity a/b; Statistical pixel point value is 1 pixel region number, obtains fiber hole histogram;

Step F, step D gained three-dimensional rotation radius di is added up, obtain fibre diameter statistical graph and average fibre diameter d _f;

Step G, substitution step F gained average fibre diameter d _fand filtration fluid absolute temperature T, filtrate thickness t, face velocity V and particle diameter d _p, application experience formula draws filtration efficiency curve and the pressure loss curve of fiber filter media under different wind speed.

Further, described in step B, the deterministic process of optimal threshold is as follows:

A, fiber filter media scanning electron microscope (SEM) photograph is carried out to gray scale stretching:

K＝255/(b-a)

M＝(-255*a)/(b-a)

Y＝KX+M

In above formula, a is scanning electron microscope image minimum gradation value; B is scanning electron microscope image maximum gradation value; X is any pixel gray-scale value of scanning electron microscope image; Y is the gray scale tension values that pixel X is corresponding;

B, determine optimal threshold:

If the ratio that in target zone, pixel number accounts for entire image in image after step a gray scale stretches is ω 0, in target zone, pixel average gray is μ 0, within the scope of background, to account for the ratio of entire image be ω 1 to pixel number, within the scope of background, pixel average gray is μ 1, and the segmentation threshold of target and background is designated as T _m, the inter-class variance of target and background is designated as g:

g＝ω0ω1(μ0-μ1)^2

Corresponding threshold value T while adopting the method for traversal to obtain making inter-class variance g maximum _m, this threshold value is described optimal threshold.

Further, the experimental formula described in step G is:

Pressure loss experimental formula:

$\mathrm{\Δp}=f\left(\mathrm{\α}\right)\frac{\mathrm{\μtV}}{{d_f}^2}$

Wherein: $f\left(\mathrm{\α}\right)=\frac{16\mathrm{\α}}{-0.5\ln \mathrm{\α}-0.5\frac{1-{\mathrm{\α}}^2}{1+{\mathrm{\α}}^2}};$ $f\left(\mathrm{\α}\right)=\frac{16\mathrm{\α}}{\mathrm{Ku}},$ Ku=-0.5ln α-0.75+ α-0.25 α ²; Or f (α)=64 α ^3/2(1+56 α ³), μ is air coefficient of viscosity, for filtering the function of fluid absolute temperature T, α is fractional solid volume;

Filtration efficiency experimental formula:

$E=1-\exp \left(\frac{-4\mathrm{\α}{E}_{\mathrm{\Σ}}t}{\mathrm{\π}{d}_f(1-\mathrm{\α})}\right)$

Wherein, E _Σ=1-(1-E _r) (1-E _i) (1-E _d), $E_D=1.6{\left(\frac{1-\mathrm{\α}}{\mathrm{Ku}}\right)}^{1/3}{\mathrm{Pe}}^{-2/3},$ $E_R=0.6\frac{1-\mathrm{\α}}{\mathrm{Ku}}\frac{R^2}{(1+R)},$ $E_I=\frac{J\×\mathrm{Stk}}{4K{u}^2},$ In above formula, Ku=-0.5ln α-0.75+ α-0.25 α ², $P_e=\frac{{\mathrm{Vd}}_f}{D},$ $D=\frac{\mathrm{\σ}{C}_{c}T}{3\mathrm{\π\μ}{d}_p},$ C _cfor the Cunningham's skink slip correction factor, σ is Boltzmann constant; j=(29.6-28 α ^0.62) R-27.5R ^2.8, $\mathrm{Stk}=\frac{{\mathrm{\ρ}}_p{d}_p^2{C}_{c}V}{18\mathrm{\μ}{d}_f}.$

Further, described in step G, filtering fluid absolute temperature T is 300～1000K, and filtrate thickness t is 0～1000 μ m, and face velocity V1 is that 0～2m/s, V2 are that 0～2m/s, V3 are that 0～2m/s, V4 are that 0～2m/s, V5 are 0～2m/s, particle diameter d _pbe 0～5 μ m.

3. beneficial effect

Adopt technical scheme provided by the invention, compared with existing known technology, there is following remarkable result:

(1) the mimicry method for reconstructing of a kind of fiber filter media structure of the present invention, the scanning electron microscope (SEM) photograph of actual fibers filter medium is carried out to binary conversion treatment, by determining of optimal threshold, fiber pixel and hole pixel are effectively separated, accurately determining and laying a solid foundation for follow-up fiber filter media center line and three-dimensional rotation radius di, three-dimensional rotation direction df, mimicry reconstruction model can realistic simulation true fiber filter medium structure, overcome the application limitation that classic method exists;

(2) Calculation Methods for Performance of a kind of fiber filter media structure of the present invention, based on true fiber filter medium image, input a series of correlation parameters, method by numerical simulation is studied fiber filter media, obtain the performance parameter of true fiber filter medium, do not need to test really, can save plenty of time and manpower and materials, there is very high practical value.

Brief description of the drawings

Fig. 1 is the scanning electron microscope (SEM) photograph of true fiber filter medium of the present invention;

Fig. 2 is that true fiber filter medium of the present invention carries out the image after binary conversion treatment;

Fig. 3 is fibre diameter statistic histogram of the present invention;

Fig. 4 is porosity histogram of the present invention;

Fig. 5 is fiber filter media structure mimicry reconstruction figure of the present invention;

Fig. 6 is the pressure loss curve map under different face velocities in the present invention;

Fig. 7 is the filtration efficiency curve map under different face velocities in the present invention.

Embodiment

For further understanding content of the present invention, the present invention is described in detail in conjunction with the accompanying drawings and embodiments.

Embodiment 1

By reference to the accompanying drawings, the mimicry method for reconstructing of a kind of fiber filter media structure of the present embodiment, the steps include:

Step 1, true fiber filter medium is scanned under scanning electron microscope, obtain the scanning electron microscope image of fiber filter media, the fiber filter media scanning electron microscope (SEM) photograph that the present embodiment obtains is referring to Fig. 1.

Step 2, optimal threshold is set, step 1 gained image is carried out to binary conversion treatment, extract the bianry image of fiber filter media and hole, fiber pixel point value is 1, and hole pixel point value is 0.The deterministic process of described optimal threshold is as follows:

A, fiber filter media scanning electron microscope (SEM) photograph is carried out to gray scale stretching:

K＝255/(b-a)

M＝(-255*a)/(b-a)

Y＝KX+M

In above formula, a is scanning electron microscope image minimum gradation value; B is scanning electron microscope image maximum gradation value; X is any pixel gray-scale value of scanning electron microscope image; Y is the gray scale tension values that pixel X is corresponding.

B, determine optimal threshold:

Image after stretching is divided into background and target 2 parts, and target is fiber medium, and background is hole between fiber medium.Inter-class variance between background and target is larger, illustrates that the difference of 2 parts of composing images is larger, is divided into target and all can causes 2 part difference to diminish when part target mistake is divided into background or part background mistake.Therefore, make to mean cutting apart of inter-class variance maximum misclassification probability minimum.The resolution that the present embodiment is established image after step a gray scale stretches is M × N, and the segmentation threshold of target and background is designated as T _mthe ratio that the interior pixel number of target zone accounts for entire image is ω 0, in target zone, pixel average gray is μ 0, within the scope of background, to account for the ratio of entire image be ω 1 to pixel number, within the scope of background, pixel average gray is μ 1, the inter-class variance of target and background is designated as g, and total average gray of image is μ.In image, gray-scale value is less than threshold value T _mpixel number be denoted as N0, gray-scale value is greater than threshold value T _mpixel number be denoted as N1, have:

ω0＝N0/M×N (1)

ω1＝N1/M×N (2)

N0+N1＝M×N (3)

ω0+ω1＝1 (4)

μ＝ω0*μ0+ω1*μ1 (5)

g＝ω0(μ0-μ)^2+ω1(μ1-μ)^2 (6)

By formula (5) substitution formula (6), obtain equivalence formula:

g＝ω0ω1(μ0-μ1)^2 (7)

Corresponding threshold value T while adopting the method for traversal to obtain making inter-class variance g maximum _m, this threshold value is described optimal threshold.

What deserves to be explained is, the present embodiment can be described as to the binary conversion treatment of true fiber filter medium image the basis that whole fiber filter media structure mimicryization is rebuild, can binary conversion treatment distinguish fiber pixel and hole pixel accurately, determined the accuracy of mimicry reconstruction model, and the key of binary conversion treatment is just being determining of optimal threshold.The method that the present embodiment obtains optimal threshold is particularly useful for the image that gray scale transformation is level and smooth, because fiber filter media scanning electron microscope (SEM) photograph gray scale transformation is level and smooth, use the method acquired results of the present embodiment can meet after testing the accuracy requirement that mimicryization is rebuild completely, and said method is simple, data processing amount is little, greatly weaken the complexity of mimicry process of reconstruction.After optimal threshold is determined, the pixel gray-scale value and the optimal threshold that extract true filter medium scanning electron microscope (SEM) photograph compare, gray-scale value is classified as hole pixel lower than the pixel of this threshold value, pixel point value is designated as 0, gray-scale value is classified as fiber pixel higher than the pixel of this threshold value, pixel point value is designated as 1, obtains bianry image (referring to Fig. 2).

Step 3, step 2 gained bianry image is carried out to fiber filter media center line detecting, obtain fiber filter media center line ss.Detailed process is: arbitrary pixel point value 8 directions that stretch out centered by 1 pixel in step 2 gained bianry image, 8 directions described in the present embodiment are respectively 0 ° of direction (being parallel to surface level to the right), are rotated counterclockwise 45 ° of directions, 90 ° of directions, 135 ° of directions, 180 ° of directions, 225 ° of directions, 270 ° of directions and 315 ° of directions.Add up pixel point value in 8 directions and be continuously 1 pixel number (for example, from central pixel point, add up pixel point value in 0 ° of direction and be continuously 1 pixel number, meet the pixel that pixel point value is 0 and finish statistics), as as described in the pixel number of any two diagonal angle directional statistics of pixel all equate or to differ be 1, retain this pixel, otherwise give up.The pixel that is 1 to all pixel point values is all carried out aforesaid operations, obtains fiber filter media center line ss.

Step 4, the pixel that step 3 is retained carry out the pixel number contrast that 4 pairs of angular direction contiguous pixels point values are 1 again, using minimum pixel number to angular direction as three-dimensional rotation direction df, this to 1/2nd of pixel number on angular direction as three-dimensional rotation radius di.

Step 5, taking pixel on step 3 gained center line as rotation basic point, taking step 4 gained three-dimensional rotation radius di and three-dimensional rotation direction df as rotation parameter, carry out three-dimensional rotation, obtain fiber filter media mimicryization and rebuild image.Detailed process is: select a pixel on center line, centered by this pixel, taking di as radius of turn, carry out three-dimensional rotation taking df as sense of rotation, obtain the disc taking described pixel as the center of circle, all pixels on center line are all carried out to aforesaid operations, can obtain the three-dimensional reconstruction image (referring to Fig. 5) of fiber filter media.

What deserves to be explained is, because above-mentioned three-dimensional reconstruction process computation data are larger, consuming time longer, in order to reduce model construction time and data processing amount, the present embodiment adopts equidistant step-length to carry out disc stack between reconstruction disc, on the fiber filter media center line extracting, uniformly-spaced a pixel of 5～15 pixels extractions carries out three-dimensional disc reconstruction, and rest of pixels point superposes according to rebuilding disc.Roughly process is:

Utilize plane right-angle coordinate on directions X, to be divided into m part to the scanning electron microscope image of fiber filter media, be divided in the Y direction n part, made to be respectively parallel to the straight line of coordinate axis by each division points, scanning electron microscope image is divided into m × n little rectangle, calculate the functional value of site.Again the coordinate information of the three-dimensional rotation radius di obtaining before, three-dimensional rotation direction df, center line pixel is imported in the grid of having finished afterwards, last, by the pixel uniformly-spaced extracting is rebuild and is obtained overall Three-dimension Reconstruction Model.In order to reduce program runtime, to save calculator memory, reduce the configuration requirement to computing machine, it is n/15～n/5 and m/15～m/5 part that optimal mesh is divided umber.The present embodiment is previous n/10 part by grid X interval division, Y interval division is previous m/10 part, the present embodiment passes through test of many times, determine best interval division, by above-mentioned processing, data processing amount had more originally reduced by 100 times, deal with data committed memory and had reduced to 80M by the 5G of classic method, and the model construction time shortens greatly, and built the fiber medium structure obtaining and can meet the requirement that mimicryization is rebuild completely.

The Calculation Methods for Performance of a kind of fiber filter media structure of the present embodiment, its steps A～D is identical with step 1～tetra-in mimicry process of reconstruction, repeats no more herein.

Step e, step B gained bianry image is carried out to anti-phase processing, fiber pixel point value is 0, and hole pixel point value is 1, and the pixel number that statistical pixel point value is 1, is designated as a.The true fiber filter medium image slices vegetarian refreshments number that statistic procedure A obtains, is designated as b, obtains fiber filter media image porosity a/b.The region number of the pixel that statistics is only 1 containing pixel point value, obtain fiber hole histogram, as shown in Figure 4, in Fig. 4, horizontal ordinate represents the pixel number that pixel point value contained in region is 1, ordinate represents the region number that contains x pixel, and this number of regions represents for the logarithm at the end in order to 10.

Step F, step D gained three-dimensional rotation radius di is added up, obtain fibre diameter statistical graph (referring to Fig. 3) and average fibre diameter d _f.

Step G, substitution step F gained average fibre diameter d _fand filtration fluid absolute temperature, filtrate thickness t, face velocity V and particle diameter d _p, application experience formula draws filtration efficiency curve and the pressure loss curve of fiber filter media different wind speed under dust-laden state and clean state.The experimental formula concrete analysis that the present embodiment uses is as follows:

Pressure loss experimental formula:

The pressure loss is an important parameter that is used for characterizing filter capability, and its magnitude relationship is to the energy consumption of whole filtering system, and therefore the pressure loss has great significance for energy-conservation.According to darcy (Darcy) law, it is air coefficient of viscosity μ, filter thickness t, face velocity V, fibre diameter d _fand the function of zero dimension pressure loss f (α):

$\mathrm{\Δp}=f\left(\mathrm{\α}\right)\frac{\mathrm{\μtV}}{{d_f}^2}$

F in formula (α) is the zero dimension pressure loss, only packed density or title fractional solid volume (Solid volume fraction, SVF) function of α, and this zero dimension pressure loss is based upon the different different representations that have in theory.

According to the design feature of fiber filter media, can select the pressure drop according to single cylindrical fibre, calculate the zero dimension resistance expression formula of pressure drop:

$f\left(\mathrm{\α}\right)=\frac{16\mathrm{\α}}{-0.5\ln \mathrm{\α}-0.5\frac{1-{\mathrm{\α}}^2}{1+{\mathrm{\α}}^2}}$

The concentric cylinder that every cylinder outside of this zero dimension pressure loss expression formula hypothesis is b (distance between cylindrical center is 2b) by Radius surrounds, and considered the impact of periphery fiber, and the shear stress of hypothesis periphery is zero.

Meanwhile, provide hypothesis to be enclosed in fiber around and with curl on the coaxial outer cylinder surface of the fiber zero dimension resistance expression formula that is zero:

$f\left(\mathrm{\α}\right)=\frac{16\mathrm{\α}}{\mathrm{Ku}}$

Wherein Ku=-0.5ln α-0.75+ α-0.25 α ²it is the former hydrodynamic contant of mulberry.

For SVF within the scope of 0.6%-30%, the situation of fibre diameter df between 1.6-80 μ m, zero dimension pressure loss expression formula can adopt:

f(α)＝64α ^3/2(1+56α ³)。

Optionally one of above-mentioned zero dimension pressure loss function when calculating.

Filtration efficiency experimental formula:

Be based upon on Kuwabara born of the same parents' shell model basis, if liquid form and fibrillar meshwork structure are known, filtrator filtration efficiency E can be calculated by ultimate fibre media filtration efficiency (Single Fiber Efficiency, SFE, E Σ).Filter clogging effect:

$E=1-\exp \left(\frac{-4\mathrm{\α}{E}_{\mathrm{\Σ}}t}{\mathrm{\π}{d}_f(1-\mathrm{\α})}\right)$

In formula, α is fractional solid volume (SVF), and t is fibrolaminar thickness, d _ffor fibre diameter.

Total SFE can be combined and be tried to achieve by the SFE of each mechanism independent role:

E _Σ＝1-(1-E _R)(1-E _I)(1-E _D)

E in formula _dfor because Blang is spread the SFE causing, E _rfor the SFE causing due to interception, E _ifor by the caused SFE of inertial collision.

(1) spread caused SFE by Blang

Diffusion motion has vital role to short grained capture rate, and fluid has the ability of the thermal energy distribution of equalization gas.When there is the particle suspending in gas, they just can be balanced.Therefore, the particle of suspension also can obtain airborne heat energy.Brownian movement is because the thermal equilibrium exchange of gas molecule and suspended particulate substance causes.Based on this fact, particle does STOCHASTIC DIFFUSION (Blang's diffusion), and due to this motion, the chance of particle and fiber collision increases, thereby causes catching.The coefficient of diffusion that this motion quantizes has just shown that ultimate fibre arresting efficiency is relevant with Brownian movement.

The present embodiment spreads caused SFE by Blang:

$E_D=1.6{\left(\frac{1-\mathrm{\α}}{\mathrm{Ku}}\right)}^{1/3}{\mathrm{Pe}}^{-2/3}$

In above formula, Ku=-0.5ln α-0.75+ α-0.25 α ²,

Wherein:

D _pfor particle diameter

T is the absolute temperature of fluid

μ is air viscosity

V is face velocity

C _cfor the Cunningham's skink slip correction factor can be expressed as $C_c=1+{\mathrm{Kn}}_p(1.257+0.4e^{-1.1/{\mathrm{Kn}}_p})$

σ is Boltzmann constant σ=1.38 × 10-23 (m2kg s-2k-1)

(2) SFE being caused by interception

When particle particle enough can make greatly Blang spread to ignore but when ambassador's inertial collision occurs not, by this machine-processed trapped particle.In this case, it is feasible particle being done to simplification.Therefore, can be interpreted as by air-flow caused by interception trapped particle.

The SFE causing due to interception is:

$E_R=0.6\frac{1-\mathrm{\α}}{\mathrm{Ku}}\frac{R^2}{(1+R)}$

In formula, for the ratio of particle diameter and fibre diameter.

(3) SFE being caused by inertial collision

If the particle diameter of particle is greater than 1 μ m in dust-contained airflow, granular mass is larger, and in the time of airflow passes fibrage, due to the effect of inertia, some particles can depart from streamline and collide on fiber and be captured.

Due to the SFE that inertial collision causes, E _iexpression formula determined by the value of Stk, the present embodiment by the caused SFE of inertial collision is:

$E_I=\frac{J\×\mathrm{Stk}}{4{\mathrm{Ku}}^2}$

The present embodiment is based on true fiber filter medium image, input a series of correlation parameters, method by numerical simulation is studied fiber filter media, it is 400K that the present embodiment input parameter filters fluid absolute temperature T, air coefficient of viscosity μ is the function of filter fluid absolute temperature T, μ=[2.3 × 10 ^-6(T-273.15) ²+ 0.00485 (T-273.15)+1.72] × 10 ^-5, filtrate thickness t is 3 μ m, face velocity V1 is that 0.1m/s, V2 are that 0.2m/s, V3 are that 0.5m/s, V4 are that 1.0m/s, V5 are 2.0m/s, particle diameter d _pbe 2 μ m.Bring above-mentioned parameter into pressure loss experimental formula and filtration efficiency experimental formula, both filtration efficiency value and the pressure loss value of the fiber filter media under different face velocities can have been obtained, taking face velocity as horizontal ordinate, the pressure loss is that ordinate is drawn fiber filter media pressure loss curve, as shown in Figure 6.Taking filtration of particulate matters diameter as horizontal ordinate, filtration efficiency is that ordinate is drawn fiber filter media filtration efficiency curve, as shown in Figure 7.

What deserves to be explained is, in actual experiment, it is 300～1000 DEG C that input parameter numerical value filters fluid absolute temperature T, and filtrate thickness t is 0～1000 μ m, face velocity V1 is that 0～2m/s, V2 are that 0～2m/s, V3 are that 0～2m/s, V4 are that 0～2m/s, V5 are 0～2m/s, particle diameter d _pbe 0～5 μ m.Input different numerical value and can obtain different pressures loss curve and filtration efficiency curve, repeat no more herein.

Mimicry reconstruction and the Calculation Methods for Performance thereof of a kind of fiber filter media structure described in embodiment 1, the scanning electron microscope (SEM) photograph of actual fibers filter medium is carried out to binary conversion treatment, by determining of optimal threshold, fiber pixel and hole pixel are effectively separated, accurately determining and laying a solid foundation for follow-up fiber filter media center line and three-dimensional rotation radius di, three-dimensional rotation direction df, mimicry reconstruction model can realistic simulation true fiber filter medium structure, overcome the application limitation that classic method exists.Simultaneously, based on true fiber filter medium image, input a series of correlation parameters, method by numerical simulation is studied fiber filter media, obtain the performance parameter of true fiber filter medium, do not need to test really, can save plenty of time and manpower and materials, there is very high practical value.

Below schematically the present invention and embodiment thereof are described, this description does not have restricted, and also one of the embodiments of the present invention just shown in accompanying drawing are actually not limited to this.So, if those of ordinary skill in the art is enlightened by it, in the situation that not departing from the invention aim, without the creationary scheme similar to this technical scheme and the embodiment of designing, all should belong to protection scope of the present invention.

Claims (9)

1. a mimicry method for reconstructing for fiber filter media structure, the steps include:

Step 1, obtain the image of true fiber filter medium;

Step 2, optimal threshold is set, step 1 gained image is carried out to binary conversion treatment, extract the bianry image of fiber filter media and hole, fiber pixel point value is 1, and hole pixel point value is 0;

Step 3, step 2 gained bianry image is carried out to fiber filter media center line detecting, obtain fiber filter media center line ss;

Step 4, carry out the contrast of the four pairs of angular direction taking pixel on step 3 gained center line as basic point, obtain three-dimensional rotation radius di and the three-dimensional rotation direction df of each pixel on center line;

Step 5, taking pixel on step 3 gained center line as rotation basic point, taking step 4 gained three-dimensional rotation radius di and three-dimensional rotation direction df as rotation parameter, carry out three-dimensional rotation, obtain fiber filter media mimicryization and rebuild image.

2. the mimicry method for reconstructing of a kind of fiber filter media structure according to claim 1, is characterized in that: in step 1, true fiber filter medium is scanned under scanning electron microscope, obtain the scanning electron microscope image of fiber filter media.

3. the mimicry method for reconstructing of a kind of fiber filter media structure according to claim 2, is characterized in that: described in step 2, the deterministic process of optimal threshold is as follows:

A, fiber filter media scanning electron microscope (SEM) photograph is carried out to gray scale stretching:

K＝255/(b-a)

M＝(-255*a)/(b-a)

Y＝KX+M

In above formula, a is scanning electron microscope image minimum gradation value; B is scanning electron microscope image maximum gradation value; X is any pixel gray-scale value of scanning electron microscope image; Y is the gray scale tension values that pixel X is corresponding;

B, determine optimal threshold:

If the ratio that in target zone, pixel number accounts for entire image in image after step a gray scale stretches is ω 0, in target zone, pixel average gray is μ 0, within the scope of background, to account for the ratio of entire image be ω 1 to pixel number, within the scope of background, pixel average gray is μ 1, and the segmentation threshold of target and background is designated as T _m, the inter-class variance of target and background is designated as g:

g＝ω0ω1(μ0-μ1)^2

Corresponding threshold value T while adopting the method for traversal to obtain making inter-class variance g maximum _m, this threshold value is described optimal threshold.

4. according to the mimicry method for reconstructing of a kind of fiber filter media structure described in claim 2 or 3, it is characterized in that: the method that obtains fiber filter media center line ss in step 3 is: pixel point value 8 directions that stretch out centered by 1 pixel in step 2 gained bianry image, 45 ° of intervals such as 8 described directions, add up the pixel number that in 8 directions, contiguous pixels point value is 1, as as described in the pixel number of any two diagonal angle directional statistics of pixel all equate or to differ be 1, retain this pixel, otherwise give up; The pixel that is 1 to all pixel point values is all carried out aforesaid operations, obtains fiber filter media center line ss.

5. the mimicry method for reconstructing of a kind of fiber filter media structure according to claim 4, it is characterized in that: described in step 4, four pairs of angular direction contrasts are specially: the pixel that step 3 is retained carries out the pixel number contrast that 4 pairs of angular direction contiguous pixels point values are 1 again, using minimum pixel number to angular direction as three-dimensional rotation direction df, this to 1/2nd of pixel number on angular direction as three-dimensional rotation radius di.

6. a Calculation Methods for Performance for fiber filter media structure, the steps include:

Steps A, obtain the image of true fiber filter medium;

Step B, optimal threshold is set, steps A gained image is carried out to binary conversion treatment, extract the bianry image of fiber filter media and hole, fiber pixel point value is 1, and hole pixel point value is 0;

Step C, step B gained bianry image is carried out to fiber filter media center line detecting, obtain fiber filter media center line ss;

Step D, carry out the contrast of the four pairs of angular direction taking pixel on step C gained center line as basic point, obtain three-dimensional rotation radius di and the three-dimensional rotation direction df of each pixel on center line;

Step e, step B gained bianry image is carried out to anti-phase processing, fiber pixel point value is 0, and hole pixel point value is 1, and the pixel number that statistical pixel point value is 1, is designated as a; The true fiber filter medium image slices vegetarian refreshments number that statistic procedure A obtains, is designated as b, obtains fiber filter media image porosity a/b; Statistical pixel point value is 1 pixel region number, obtains fiber hole histogram;

Step F, step D gained three-dimensional rotation radius di is added up, obtain fibre diameter statistical graph and average fibre diameter d _f;

Step G, substitution step F gained average fibre diameter d _fand filtration fluid absolute temperature T, filtrate thickness t, face velocity V and particle diameter d _p, application experience formula draws filtration efficiency curve and the pressure loss curve of fiber filter media under different wind speed.

7. the Calculation Methods for Performance of a kind of fiber filter media structure according to claim 6, is characterized in that: described in step B, the deterministic process of optimal threshold is as follows:

A, fiber filter media scanning electron microscope (SEM) photograph is carried out to gray scale stretching:

K＝255/(b-a)

M＝(-255*a)/(b-a)

Y＝KX+M

In above formula, a is scanning electron microscope image minimum gradation value; B is scanning electron microscope image maximum gradation value; X is any pixel gray-scale value of scanning electron microscope image; Y is the gray scale tension values that pixel X is corresponding;

B, determine optimal threshold:

If the ratio that in target zone, pixel number accounts for entire image in image after step a gray scale stretches is ω 0, in target zone, pixel average gray is μ 0, within the scope of background, to account for the ratio of entire image be ω 1 to pixel number, within the scope of background, pixel average gray is μ 1, and the segmentation threshold of target and background is designated as T _m, the inter-class variance of target and background is designated as g:

g＝ω0ω1(μ0-μ1)^2

Corresponding threshold value T while adopting the method for traversal to obtain making inter-class variance g maximum _m, this threshold value is described optimal threshold.

8. the Calculation Methods for Performance of a kind of fiber filter media structure according to claim 7, is characterized in that: the experimental formula described in step G is:

Pressure loss experimental formula:

$\mathrm{\Δp}=f\left(\mathrm{\α}\right)\frac{\mathrm{\μtV}}{{d_f}^2}$

Wherein: $f\left(\mathrm{\α}\right)=\frac{16\mathrm{\α}}{-0.5\ln \mathrm{\α}-0.5\frac{1-{\mathrm{\α}}^2}{1+{\mathrm{\α}}^2}};$ $f\left(\mathrm{\α}\right)=\frac{16\mathrm{\α}}{\mathrm{Ku}},$ Ku=-0.5ln α-0.75+ α-0.25 α ²; Or f (α)=64 α ^3/2(1+56 α ³), μ is air coefficient of viscosity, for filtering the function of fluid absolute temperature T, α is fractional solid volume;

Filtration efficiency experimental formula:

$E=1-\exp \left(\frac{-4\mathrm{\α}{E}_{\mathrm{\Σ}}t}{\mathrm{\π}{d}_f(1-\mathrm{\α})}\right)$

Wherein, E _Σ=1-(1-E _r) (1-E _i) (1-E _d), $E_D=1.6{\left(\frac{1-\mathrm{\α}}{\mathrm{Ku}}\right)}^{1/3}{\mathrm{Pe}}^{-2/3},$ $E_R=0.6\frac{1-\mathrm{\α}}{\mathrm{Ku}}\frac{R^2}{(1+R)},$ in above formula, Ku=-0.5ln α-0.75+ α-0.25 α ², c _cfor the Cunningham's skink slip correction factor, σ is Boltzmann constant; j=(29.6-28 α ^0.62) R-27.5R ^2.8, $\mathrm{Stk}=\frac{{\mathrm{\ρ}}_p{d}_p^2{C}_{c}V}{18\mathrm{\μ}{d}_f}.$

9. the Calculation Methods for Performance of a kind of fiber filter media structure according to claim 8, it is characterized in that: described in step G, filtering fluid absolute temperature T is 300～1000K, filtrate thickness t is 0～1000 μ m, face velocity V1 is that 0～2m/s, V2 are that 0～2m/s, V3 are that 0～2m/s, V4 are that 0～2m/s, V5 are 0～2m/s, particle diameter d _pbe 0～5 μ m.