CN103971395B - A kind of mimicry reconstruction of fiber filter media structure and its Calculation Methods for Performance - Google Patents
A kind of mimicry reconstruction of fiber filter media structure and its Calculation Methods for Performance Download PDFInfo
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Abstract
The invention discloses a kind of mimicry reconstruction of fiber filter media structure and its Calculation Methods for Performance, belong to fibre structure mimicry reconstruction technique field.The present invention mimicry process of reconstruction be：First, fiber filter media image is obtained；The 2nd, optimal threshold is set, binary conversion treatment is carried out；3rd, center line detecting is carried out to bianry image；4th, four diagonally opposed contrasts are carried out to pixel on center line, obtains radius of turn di and direction of rotation df；5th, three-dimensional rotation is carried out, fiber filter media mimicry reconstruction image is obtained.The Calculation Methods for Performance of the present invention obtains the filter efficiency curve and pressure loss curve of the different wind speed of fiber filter media using empirical equation by inputting a series of relevant parameters.The present invention carries out mimicry reconstruction, mimicry reconstruction model is capable of the structure of realistic simulation true fiber filter medium using simple, quick image processing method based on true fiber filter medium interior microscopic single layer structure image to gained image.
Description
Technical field
The present invention relates to fibre structure mimicry reconstruction technique field, more specifically to a kind of fiber filter media knot
The mimicry reconstruction of structure and its Calculation Methods for Performance.
Background technology
Dust can cause harmful influence, especially pellet right to atmospheric environment, production and health
The respiratory system of human body produces harm.Therefore, reduce suspended particulate substance in air has to environmental protection and guarantee human health
Important meaning.
In face of increasingly serious atmosphere polluting problem, sack cleaner is high to the arresting efficiency of particulate pollutant, therefore
To being widely applied.Fiber filter media is as one of core component of sack cleaner, its filtering to fine particle
The requirement that can be up to state standards, the especially pressure of fiber filter media closely related with its filter efficiency and the pressure loss
Loss is the important parameter for characterizing strainability, energy expenditure of its magnitude relationship to whole filtration system.And filter medium
Above-mentioned performance indications mainly determined by fiber filter media internal microstructure.Therefore, the interior of filter medium is obtained exactly
Portion's microstructure seems most important.
In the research of early stage, fiber filter media is reduced to single fiber or isolated fiber, and external scientist is in single fiber
On the basis of, it is considered to fiber model is set up in the interference of surrounding annulus, and fiber filter media is reduced into preferable filter medium, profit
With woven (the fibers parallel and cross arrangement) filter medium of computer technology generation two dimension.However, the fiber that the above method is set up
Filter medium is two-dimensional structure, and larger, the plan of the two-dimentional filter medium of foundation is distinguished with actual three dimensional filter dielectric structure
State model can not really reflect the performance of filter medium, be only used for research simulation.
Also there is researcher to randomly generate the fiber filter media of three-dimensional in space using computer technology, and consider fiber
The factor such as diameter, length, direction, bending.But only consider that the model that fiber some factors are built does not have with actual fibre
Based on dimensional filter medium, the factors such as crimp between fiber are not accounted for.Therefore, obtained model and reality are built
Filter media construction difference is still larger, is still only used for research simulation, and can not obtain the structure of true fiber filter medium
Parameter.
Through retrieval, the technical scheme on fibrous material performance study is disclosed, such 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 is determined
To degree quantitative evaluating method；This application case is related to a kind of short fiber reinforced composite fiber alignment degree qualitative assessment side
Method, it is characterized in that：Selection determines cutting plane and carries out cutting to composite sample；Obtained by light microscope or ESEM
Take microphoto；The oval fiber section in microphoto is repainted in graphic image software；After extraction is repainted
Picture in each oval long axis length, minor axis length and transverse and reference axis angle；According to the elliptical cross section extracted
Face parameter calculates the direction vector of each oval corresponding fiber；Calculate degree of orientation parameter of the composite along specific direction.Should
The application case cutting plane appropriate by choosing eliminates the meter caused by same elliptic cross-section two kinds of machine directions of correspondence
Error is calculated, fiber alignment degree qualitative assessment is primarily adapted for use in, the mimicryization for being not particularly suited for fiber filter media structure is rebuild.
The content of the invention
1. the invention technical problem to be solved
Exist it is an object of the invention to overcome existing fiber filter media mimicry method for reconstructing：1) not with actual fibre
Dimensional filter medium is that mimicry rebuilds basis, builds obtained fiber model and differs larger with actual filter media construction, can only
For studying simulation, there is limitation on；2) mimicry process of reconstruction is complicated, data processing amount is big, the model construction time is long
Not enough there is provided a kind of mimicry reconstruction of fiber filter media structure and its Calculation Methods for Performance；The present invention is with true fine
Based on the microcosmic single layer structure image of dimensional filter media interior, gained image is entered using simple, quick image processing method
Row mimicryization is rebuild, and extracts image information, obtains the structural parameters of mimicry reconstruction model, mimicry reconstruction model can be forced
The structure of true simulation true fiber filter medium, resulting structures parameter can represent the structural parameters of true fiber filter medium.
2. technical scheme
To reach above-mentioned purpose, the technical scheme that the present invention is provided is：
A kind of mimicry method for reconstructing of fiber filter media structure of the present invention, its step is：
Step 1: obtaining the image of true fiber filter medium；
Step 2: set optimal threshold, to step one gained image carry out binary conversion treatment, extract fiber filter media with
The bianry image of hole, fiber pixel point value is 1, and hole pixel point value is 0；
Step 3: carrying out fiber filter media center line detecting to bianry image obtained by step 2, obtain fiber filter and be situated between
Matter center line ss；
Step 4: so that pixel carries out four diagonally opposed contrasts as basic point on center line obtained by step 3, obtaining center line
The three-dimensional rotation radius di and three-dimensional rotation direction df of upper each pixel；
Step 5: so that pixel is rotation basic point on center line obtained by step 3, with three-dimensional rotation radius obtained by step 4
Di and three-dimensional rotation direction df is rotation parameter, carries out three-dimensional rotation, obtains fiber filter media mimicry reconstruction image.
Further, true fiber filter medium is scanned under a scanning electron microscope in step one, obtains fiber
The scanning electron microscope image of filter medium.
Further, the determination process of optimal threshold described in step 2 is as follows：
A, by fiber filter media scanning electron microscope (SEM) photograph carry out 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 scanning electricity
Any pixel gray value of mirror image；Y is the corresponding gray scale stretching values of pixel X；
B, determine optimal threshold：
If the ratio that pixel number accounts for entire image in target zone in image after step a gray scale stretchings is ω 0, mesh
Pixel gray level average value is that the ratio that pixel number accounts for entire image in μ 0, background range is ω 1, background model in the range of mark
Interior pixel gray level average value is enclosed for μ 1, and the segmentation threshold of target and background is designated as Tm, the inter-class variance of target and background is designated as
G, then：
G=ω 0 ω 1 (μ 0- μ 1) ^2
Corresponding threshold value T when obtaining making inter-class variance g maximum using the method for traversalm, the threshold value is described optimal
Threshold value.
Further, acquisition fiber filter media center line ss method is in step 3：With two-value obtained by step 2
Pixel point value is stretches out 8 directions in image centered on 1 pixel, and 45 ° of 8 described directions etc. interval counts 8
Contiguous pixels point value is the pixel number of 1 pixel number, the as described diagonally opposed statistics of pixel any two on direction
Equal or difference is 1, then retains the pixel, otherwise give up；Above-mentioned behaviour is performed both by for 1 pixel to all pixels point value
Make, produce fiber filter media center line ss.
Further, four diagonally opposed contrasts are specially described in step 4：4 are carried out again to the pixel that step 3 retains
Diagonally opposed contiguous pixels point value is contrasted for 1 pixel number, and minimum diagonally opposed of pixel number is revolved as three-dimensional
Turn direction df, 1/2nd of the diagonally opposed upper pixel number is used as three-dimensional rotation radius di.
A kind of Calculation Methods for Performance of fiber filter media structure of the present invention, its step is：
Step A, the image for obtaining true fiber filter medium；
Step B, setting optimal threshold, carry out binary conversion treatment to image obtained by step A, extract fiber filter media and hole
The bianry image of gap, fiber pixel point value is 1, and hole pixel point value is 0；
Step C, fiber filter media center line detecting is carried out to bianry image obtained by step B, obtain fiber filter media
Center line ss；
Step D, using pixel on center line obtained by step C it is that basic point is carried out on four diagonally opposed contrasts, acquisition center line
The three-dimensional rotation radius di and three-dimensional rotation direction df of each pixel；
Step E, anti-phase processing is carried out to bianry image obtained by step B, fiber pixel point value is 0, and hole pixel point value is
1, statistical pixel point value is 1 pixel number, is designated as a；The true fiber filter medium image slices vegetarian refreshments that statistic procedure A is obtained
Number, is designated as b, obtains fiber filter media image porosity a/b；Statistical pixel point value is 1 pixel areal, obtains fine
Tie up hole histogram；
Step F, three-dimensional rotation radius di obtained by step D is counted, obtain fibre diameter statistical chart and fiber is put down
Equal diameter df；
Average fibre diameter d obtained by step G, substitution step FfAnd filter fluid absolute temperature T, filtrate thickness t, head on
Wind speed V and particulate matter diameter dp, application experience formula draws filter efficiency curve of the fiber filter media under different wind speed
With pressure loss curve.
Further, the determination process of optimal threshold is as follows described in step B：
A, by fiber filter media scanning electron microscope (SEM) photograph carry out 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 scanning electricity
Any pixel gray value of mirror image；Y is the corresponding gray scale stretching values of pixel X；
B, determine optimal threshold：
If the ratio that pixel number accounts for entire image in target zone in image after step a gray scale stretchings is ω 0, mesh
Pixel gray level average value is that the ratio that pixel number accounts for entire image in μ 0, background range is ω 1, background model in the range of mark
Interior pixel gray level average value is enclosed for μ 1, and the segmentation threshold of target and background is designated as Tm, the inter-class variance of target and background is designated as
G, then：
G=ω 0 ω 1 (μ 0- μ 1) ^2
Corresponding threshold value T when obtaining making inter-class variance g maximum using the method for traversalm, the threshold value is described optimal
Threshold value.
Further, the empirical equation described in step G is：
Pressure loss empirical equation：
Wherein： Ku=-0.5ln α -0.75+ α -0.25 α2；Or
F (α)=64 α3/2(1+56α3), μ is air viscosity coefficient, and to filter the function of fluid absolute temperature T, α is solid volume point
Number；
Filter efficiency empirical equation：
Wherein, EΣ=1- (1-ER)(1-EI)(1-ED), In above formula, Ku=-0.5ln α -0.75+ α -0.25 α2, CcSlided for Cunningham's skink
Modifying factor is moved, σ is Boltzmann constants；J=(29.6-28 α0.62)R-27.5R2.8,
Further, it is 300~1000K that fluid absolute temperature T is filtered described in step G, filtrate thickness t is 0~
1000 μm, 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,
Grain thing diameter dpFor 0~5 μm.
3. beneficial effect
The technical scheme provided using the present invention, compared with existing known technology, with following remarkable result：
(1) the mimicry method for reconstructing of a kind of fiber filter media structure of the invention, to actual fibers filter medium
Scanning electron microscope (SEM) photograph carries out binary conversion treatment, by the determination of optimal threshold, fiber pixel and hole pixel by effectively separated,
It is that subsequent fiber filter medium center line and three-dimensional rotation radius di, three-dimensional rotation direction df accurate determination have laid solid
Basis, mimicry reconstruction model is capable of the structure of realistic simulation true fiber filter medium, overcomes conventional method presence
Application limitation；
(2) Calculation Methods for Performance of a kind of fiber filter media structure of the invention, based on true fiber filter medium figure
Picture, inputs a series of relevant parameters, fiber filter media is studied by the method for numerical simulation, true fiber mistake is obtained
The performance parameter of filter medium, it is not necessary to really tested, can be saved plenty of time and manpower and materials, with very high reality
With 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 the fibre diameter statistic histogram of the present invention；
Fig. 4 is the porosity histogram of the present invention；
Fig. 5 is the 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 filter efficiency curve map under different face velocities in the present invention.
Embodiment
To further appreciate that present disclosure, the present invention is described in detail in conjunction with the accompanying drawings and embodiments.
Embodiment 1
With reference to accompanying drawing, a kind of mimicry method for reconstructing of fiber filter media structure of the present embodiment, its step is：
Step 1: true fiber filter medium is scanned under a scanning electron microscope, sweeping for fiber filter media is obtained
Sem image is retouched, the fiber filter media scanning electron microscope (SEM) photograph that the present embodiment is obtained is referring to Fig. 1.
Step 2: set optimal threshold, to step one gained image carry out binary conversion treatment, extract fiber filter media with
The bianry image of hole, fiber pixel point value is 1, and hole pixel point value is 0.The determination process of the optimal threshold is as follows：
A, by fiber filter media scanning electron microscope (SEM) photograph carry out 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 scanning electricity
Any pixel gray value of mirror image；Y is the corresponding gray scale stretching values of pixel X.
B, determine optimal threshold：
Image after stretching is divided into background and the part of target 2, target is fiber medium, and background is hole between fiber medium.
Inter-class variance between background and target is bigger, illustrates that the difference of 2 parts of pie graph picture is bigger, when partial target mistake is divided into the back of the body
Scape or part background mistake, which are divided into target, can all cause 2 part difference to diminish.Therefore, the segmentation for making inter-class variance maximum means mistake
Divide probability minimum.The present embodiment sets the resolution ratio of the image after step a gray scale stretchings as M × N, the segmentation threshold of target and background
It is designated as Tm, the ratio that pixel number accounts for entire image in target zone is that pixel gray level average value is in ω 0, target zone
The ratio that pixel number accounts for entire image in μ 0, background range is that pixel gray level average value is μ 1 in ω 1, background range,
The inter-class variance of target and background is designated as g, and total average gray of image is μ.Gray value is less than threshold value T in imagemPixel
Point number is denoted as N0, and gray value is more than threshold value TmPixel number be denoted as N1, then have：
ω 0=N0/M × N (1)
ω 1=N1/M × N (2)
N0+N1=M × N (3)
ω 0+ ω 1=1 (4)
μ=ω 0* μ 0+ ω 1* μ 1 (5)
G=ω 0 (μ 0- μ) ^2+ ω 1 (μ 1- μ) ^2 (6)
Formula (5) is substituted into formula (6), equivalence formula is obtained：
G=ω 0 ω 1 (μ 0- μ 1) ^2 (7)
Corresponding threshold value T when obtaining making inter-class variance g maximum using the method for traversalm, the threshold value is described optimal
Threshold value.
What deserves to be explained is, the present embodiment can be described as whole fibre to the binary conversion treatment of true fiber filter medium image
Can the basis that dimensional filter dielectric structure mimicryization is rebuild, binary conversion treatment accurately distinguish fiber pixel and hole pixel
Point, determines the degree of accuracy of mimicry reconstruction model, and the key of binary conversion treatment is just being the determination of optimal threshold.This implementation
The method that example obtains optimal threshold is particularly suitable for use in the smooth image of gray scale transformation, due to fiber filter media scanning electron microscope (SEM) photograph
Gray scale transformation is smooth, and the precision for being fully able to meet mimicryization reconstruction after testing using the method acquired results of the present embodiment will
Ask, and the above method is simple, data processing amount is small, and the complexity of mimicry process of reconstruction is reduced significantly.After optimal threshold is determined,
The pixel gray value for extracting true filter medium scanning electron microscope (SEM) photograph is compared with optimal threshold, and gray value is less than the threshold value
Pixel is classified as hole pixel, and pixel point value is designated as 0, and gray value is classified as fiber pixel higher than the pixel of the threshold value, as
Vegetarian refreshments value is designated as 1, produces bianry image (referring to Fig. 2).
Step 3: carrying out fiber filter media center line detecting to bianry image obtained by step 2, obtain fiber filter and be situated between
Matter center line ss.Detailed process is：It is outside centered on 1 pixel by any pixel point value in bianry image obtained by step 2
Extend 8 directions, 8 directions described in the present embodiment are respectively 0 ° of direction (), 45 ° of rotate counterclockwise parallel to horizontal plane to the right
Direction, 90 ° of directions, 135 ° of directions, 180 ° of directions, 225 ° of directions, 270 ° of directions and 315 ° of directions.Count pixel on 8 directions
Point value continuously (such as, from central pixel point, counts the picture that pixel point value on 0 ° of direction is continuously 1 for 1 pixel number
Vegetarian refreshments number, meets pixel point value and then terminates statistics for 0 pixel), the picture of the diagonally opposed statistics of pixel any two as described
Vegetarian refreshments number is equal or difference is 1, then retains the pixel, otherwise give up.All pixels point value is held for 1 pixel
Row aforesaid operations, produce fiber filter media center line ss.
Step 4: carrying out the pixel number that 4 diagonally opposed contiguous pixels point values are 1 again to the pixel that step 3 retains
Contrast, regard minimum diagonally opposed of pixel number as three-dimensional rotation direction df, the two of the diagonally opposed upper pixel number
/ mono- is used as three-dimensional rotation radius di.
Step 5: so that pixel is rotation basic point on center line obtained by step 3, with three-dimensional rotation radius obtained by step 4
Di and three-dimensional rotation direction df is rotation parameter, carries out three-dimensional rotation, obtains fiber filter media mimicry reconstruction image.Specifically
Process is：A pixel on center line is selected, centered on the pixel, using di as radius of turn, is entered by direction of rotation of df
Row three-dimensional rotation, obtains the disc using the pixel as the center of circle, is performed both by aforesaid operations to all pixels point on center line, i.e.,
It can obtain the three-dimensional reconstruction image of fiber filter media (referring to Fig. 5).
What deserves to be explained is, it is time-consuming longer because above-mentioned three-dimensional reconstruction process calculating data are larger, in order to reduce model structure
Time and data processing amount are built, the present embodiment carries out disc superposition using equidistant step-length between disc is rebuild, that is, carried
5~15 pixels extract a pixel and carry out three-dimensional disc reconstruction at equal intervals on the fiber filter media center line taken, its
After image vegetarian refreshments is overlapped according to disc is rebuild.Substantially process is：
M parts are divided into the X direction to the scanning electron microscope image of fiber filter media using plane right-angle coordinate, in Y side
It is divided into n parts upwards, the straight line parallel to reference axis is made respectively by each division points, scanning electron microscope image is divided into m × n small squares
Shape, calculates the functional value of site.Afterwards again by the three-dimensional rotation radius di obtained before, three-dimensional rotation direction df, center line
The coordinate information of pixel is imported into the grid finished, finally, by being rebuild to the pixel extracted at equal intervals
Obtain overall Three-dimension Reconstruction Model.In order to reduce program runtime, save calculator memory, the configuration reduced to computer will
Ask, it is n/15~n/5 and m/15~m/5 parts that optimal mesh, which divides number,.The present embodiment be by grid X interval divisions before n/
10 parts, Y interval divisions be before m/10 parts, the present embodiment passes through test of many times, it is determined that optimal interval is divided, by upper
State processing, data processing amount reduced more originally 100 times, processing data committed memory 80M, mould are reduced to by the 5G of conventional method
The type structure time greatly shortens, and builds the requirement that obtained fiber medium structure is fully able to meet mimicryization reconstruction.
A kind of Calculation Methods for Performance of fiber filter media structure of the present embodiment, its step A~D was rebuild with mimicry
Step one~tetra- in journey are identical, and here is omitted.
Step E, anti-phase processing is carried out to bianry image obtained by step B, fiber pixel point value is 0, and hole pixel point value is
1, statistical pixel point value is 1 pixel number, is designated as a.The true fiber filter medium image slices vegetarian refreshments that statistic procedure A is obtained
Number, is designated as b, obtains fiber filter media image porosity a/b.The areal for 1 pixel containing only pixel point value is counted,
Fiber hole histogram is obtained, as shown in figure 4, abscissa represents that pixel point value contained in region is individual for 1 pixel in Fig. 4
Number, ordinate represents the areal containing x pixel, and the number of regions is represented to 10 for the logarithm at bottom.
Step F, three-dimensional rotation radius di obtained by step D is counted, acquisition fibre diameter statistical chart (referring to Fig. 3) with
And average fibre diameter df。
Average fibre diameter d obtained by step G, substitution step FfAnd filter fluid absolute temperature, filtrate thickness t, head on
Wind speed V and particulate matter diameter dp, application experience formula show that fiber filter media is different under dust-laden state and clean state
The filter efficiency curve and pressure loss curve of wind speed.Empirical equation concrete analysis is as follows used in the present embodiment：
Pressure loss empirical equation：
The pressure loss is an important parameter for being used for characterizing filter capability, its magnitude relationship to whole filtration system
Energy expenditure, therefore the pressure loss for energy-conservation have great significance.According to darcy (Darcy) law, it is that air glues
Property coefficient μ, filter thickness t, face velocity V, fibre diameter dfAnd zero dimension pressure loss f (α) function：
F (α) is the zero dimension pressure loss in formula, only packed density or fractional solid volume (Solid volume
Fraction, SVF) α function, and the zero dimension pressure loss set up have different representations in theory in different.
According to the design feature of fiber filter media, the pressure drop according to single cylindrical fibre may be selected, filter is calculated
The zero dimension resistance expression formula of the pressure loss：
It is that (distance between cylindrical center is b that the zero dimension pressure loss expression formula, which is assumed outside every cylinder by Radius,
Concentric cylinder 2b) is surrounded, that is, take into account the influence of peripheral fiber, and the shear stress of hypothesis periphery is zero.
The nothing for being enclosed in fiber peripheral there is provided hypothesis simultaneously and being zero with the curl on the outer cylinder surface of fiber-coax
Dimension resistance expression formula：
Wherein Ku=-0.5ln α -0.75+ α -0.25 α2It is the former hydrodynamic contant of mulberry.
For SVF in the range of 0.6%-30%, situations of the fibre diameter df between 1.6-80 μm, then zero dimension pressure
Loss expression formula can be used：
F (α)=64 α3/2(1+56α3)。
Above-mentioned zero dimension pressure loss function can optional one during calculating.
Filter efficiency empirical equation：
Set up on the basis of Kuwabara born of the same parents' shell model, if liquid form and fibrillar meshwork structure are, it is known that filter mistake
Filter efficiency E can be calculated by single fiber media filtration efficiency (Single Fiber Efficiency, SFE, E Σ) and obtained.Filtering
Device efficiency：
α is fractional solid volume (SVF) in formula, and t is the thickness of fibrous layer, dfFor fibre diameter.
Total SFE can be combined by the SFE of each mechanism independent role to try to achieve：
EΣ=1- (1-ER)(1-EI)(1-ED)
E in formulaDSFE, E caused by be spread BlangRFor the SFE caused by interception, EIFor by inertial collision
Caused SFE.
(1) caused SFE is spread by Blang
Diffusion motion plays an important roll to short grained capture rate, and fluid has the thermal energy distribution of equalization gas
Ability.When the particle that there is suspension in gas, they just can be balanced.Therefore, the particle of suspension can also obtain the heat energy in air.
Brownian movement is due to caused by gas molecule is exchanged with the thermal balance of suspended particulate substance.Based on the fact that, particulate matter do with
Machine spreads (Blang's diffusion), due to this motion, and particulate matter increases with the chance that fiber is collided, so as to cause capture.This fortune
The diffusion coefficient of momentum has indicated that single fiber arresting efficiency is relevant with Brownian movement.
The present embodiment spreads caused SFE by Blang：
In above formula, Ku=-0.5ln α -0.75+ α -0.25 α2,
Wherein：
dpFor particulate matter diameter
T is the absolute temperature of fluid
μ is air viscosity
V is face velocity
CcIt is represented by for the Cunningham's skink slip correction factor
σ is Boltzmann constants σ=1.38 × 10-23 (m2kg s-2k-1)
(2) SFE caused by interception
When particulate matter particle is sufficiently large make Blang diffusion ignore but inadequate ambassador's inertial collision generation when, pass through
This mechanism trapped particle.In this case, it is feasible particle to be done into simplification.Therefore, it can be solved by interception trapped particle
It is interpreted as caused by air-flow.
SFE caused by interception is：
In formula,For the ratio of particulate matter diameter and fibre diameter.
(3) SFE caused by inertial collision
If the particle diameter of particle is more than 1 μm in dust-contained airflow, granular mass is larger, when airflow passes fibrous layer, due to used
The effect of property, some particles can deviate streamline and collide on fiber and be captured.
SFE caused by inertial collision, EIExpression formula determined by Stk value,The present embodiment
It is as the SFE caused by inertial collision：
The present embodiment is based on true fiber filter medium image, inputs a series of relevant parameters, passes through the side of numerical simulation
Method is studied fiber filter media, and the present embodiment input parameter filtering fluid absolute temperature T is 400K, air viscosity coefficient
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 μm, and 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, particulate matter diameter dpFor 2 μm.Bring above-mentioned parameter into pressure loss empirical equation and filter efficiency empirical equation, both
The filter efficiency value and pressure loss value of the fiber filter media under different face velocities can be obtained, is sat using face velocity to be horizontal
Mark, the pressure loss is that ordinate draws fiber filter media pressure loss curve, as shown in Figure 6.It is a diameter of with filtration of particulate matters
Abscissa, filter efficiency is that ordinate draws fiber filter media filter efficiency curve, as shown in Figure 7.
What deserves to be explained is, in actual experiment, input parameter numerical value filtering fluid absolute temperature T is 300~1000 DEG C,
Filtrate thickness t be 0~1000 μm, face velocity V1 be 0~2m/s, V2 be 0~2m/s, V3 be 0~2m/s, V4 be 0~2m/s,
V5 is 0~2m/s, particulate matter diameter dpFor 0~5 μm.Different pressures loss curve and filter efficiency can be obtained by inputting different numerical value
Curve, here is omitted.
A kind of mimicry reconstruction of fiber filter media structure described in embodiment 1 and its Calculation Methods for Performance, to reality
The scanning electron microscope (SEM) photograph of fiber filter media carries out binary conversion treatment, by the determination of optimal threshold, fiber pixel and hole picture
Vegetarian refreshments is subsequent fiber filter medium center line and three-dimensional rotation radius di, three-dimensional rotation direction df standard by effectively separated
Determine to lay a solid foundation, mimicry reconstruction model is capable of the structure of realistic simulation true fiber filter medium, overcomes
The application limitation that conventional method is present.Meanwhile, based on true fiber filter medium image, a series of relevant parameters are inputted,
Fiber filter media is studied by the method for numerical simulation, the performance parameter of true fiber filter medium is obtained, is not required to
Really tested, can be saved plenty of time and manpower and materials, with very high practical value.
Schematical above that the present invention and embodiments thereof are described, the description does not have restricted, institute in accompanying drawing
What is shown is also one of embodiments of the present invention, is actually not limited thereto.So, if one of ordinary skill in the art
Enlightened by it, it is without departing from the spirit of the invention, similar to the technical scheme without designing for creativeness
Scheme and embodiment, all should belong to protection scope of the present invention.
Claims (7)
1. a kind of mimicry method for reconstructing of fiber filter media structure, its step is：
Step 1: true fiber filter medium is scanned under a scanning electron microscope, the scanning electricity of fiber filter media is obtained
Mirror image；
Step 2: determining optimal threshold, binary conversion treatment is carried out to step one gained image, fiber filter media and hole is extracted
Bianry image, fiber pixel point value be 1, hole pixel point value be 0；Wherein, the determination process of optimal threshold is as follows：
A, by fiber filter media scanning electron microscope image carry out 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 scanning electron microscope (SEM) photograph
As any pixel gray value；Y is the corresponding gray scale stretching values of pixel X；
B, determine optimal threshold：
If the ratio that pixel number accounts for entire image in target zone in image after step a gray scale stretchings is ω 0, target model
Interior pixel gray level average value is enclosed for μ 0, and the ratio that pixel number accounts for entire image in background range is in ω 1, background range
Pixel gray level average value is μ 1, and the segmentation threshold of target and background is designated as Tm, the inter-class variance of target and background is designated as g, then：
G=ω 0 ω 1 (μ 0- μ 1) ^2
Corresponding threshold value T when obtaining making inter-class variance g maximum using the method for traversalm, the threshold value is described optimal threshold；
Step 3: carrying out fiber filter media center line detecting to bianry image obtained by step 2, obtain in fiber filter media
Heart line ss；
Step 4: so that pixel carries out four diagonally opposed contrasts as basic point on center line obtained by step 3, obtaining each on center line
The three-dimensional rotation radius di and three-dimensional rotation direction df of pixel；
Step 5: using pixel on center line obtained by step 3 for rotation basic point, with three-dimensional rotation radius di obtained by step 4 with
Three-dimensional rotation direction df is rotation parameter, carries out three-dimensional rotation, obtains fiber filter media mimicry reconstruction image.
2. a kind of mimicry method for reconstructing of fiber filter media structure according to claim 1, it is characterised in that：Step
Acquisition fiber filter media center line ss method is in three：Pixel using pixel point value in bianry image obtained by step 2 as 1
Stretch out 8 directions centered on point, 45 ° of 8 described directions etc. interval, and contiguous pixels point value is 1 on 8 directions of statistics
Pixel number, the pixel number of the diagonally opposed statistics of pixel any two is equal as described or difference is 1, then retaining should
Pixel, otherwise gives up；Aforesaid operations are performed both by for 1 pixel to all pixels point value, fiber filter media center is produced
Line ss.
3. a kind of mimicry method for reconstructing of fiber filter media structure according to claim 2, it is characterised in that：Step
Four diagonally opposed contrast are specially described in four：It is 1 to carry out 4 diagonally opposed contiguous pixels point values again to the pixel that step 3 retains
The contrast of pixel number, regard minimum diagonally opposed of pixel number as three-dimensional rotation direction df, the diagonally opposed upper picture
/ 2nd of vegetarian refreshments number are used as three-dimensional rotation radius di.
4. a kind of Calculation Methods for Performance of fiber filter media structure, its step is：
Step A, the scanning electron microscope image for obtaining true fiber filter medium；
Step B, optimal threshold is determined, binary conversion treatment is carried out to image obtained by step A, extract fiber filter media and hole
Bianry image, fiber pixel point value is 1, and hole pixel point value is 0；
Step C, fiber filter media center line detecting is carried out to bianry image obtained by step B, obtain fiber filter media center
Line ss；
Step D, using pixel on center line obtained by step C it is that basic point carries out each picture on four diagonally opposed contrasts, acquisition center line
The three-dimensional rotation radius di and three-dimensional rotation direction df of vegetarian refreshments；
Step E, anti-phase processing is carried out to bianry image obtained by step B, fiber pixel point value is 0, and hole pixel point value is 1, is united
The pixel number that pixel point value is 1 is counted, a is designated as；The true fiber filter medium image slices vegetarian refreshments that statistic procedure A is obtained
Number, is designated as b, obtains fiber filter media image porosity a/b；Statistical pixel point value is 1 pixel areal, obtains fiber
Hole histogram；
Step F, three-dimensional rotation radius di obtained by step D is counted, acquisition fibre diameter statistical chart and fiber are averagely straight
Footpath df；
Average fibre diameter d obtained by step G, substitution step FfAnd filtering fluid absolute temperature T, filtrate thickness t, face velocity V
And particulate matter diameter dp, application experience formula draws filter efficiency curve and pressure of the fiber filter media under different wind speed
Lose curve.
5. a kind of Calculation Methods for Performance of fiber filter media structure according to claim 4, it is characterised in that：Step B
The determination process of the optimal threshold is as follows：
A, by fiber filter media scanning electron microscope image carry out 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 scanning electron microscope (SEM) photograph
As any pixel gray value；Y is the corresponding gray scale stretching values of pixel X；
B, determine optimal threshold：
If the ratio that pixel number accounts for entire image in target zone in image after step a gray scale stretchings is ω 0, target model
Interior pixel gray level average value is enclosed for μ 0, and the ratio that pixel number accounts for entire image in background range is in ω 1, background range
Pixel gray level average value is μ 1, and the segmentation threshold of target and background is designated as Tm, the inter-class variance of target and background is designated as g, then：
G=ω 0 ω 1 (μ 0- μ 1) ^2
Corresponding threshold value T when obtaining making inter-class variance g maximum using the method for traversalm, the threshold value is described optimal threshold.
6. a kind of Calculation Methods for Performance of fiber filter media structure according to claim 5, it is characterised in that：Step G
Described empirical equation is：
Pressure loss empirical equation：
Wherein：Ku is the former hydrodynamic contant of mulberry, Ku=-0.5ln
α-0.75+α-0.25α2；Or f (α)=64 α3/2(1+56α3), μ is air viscosity coefficient, to filter the letter of fluid absolute temperature T
Number, α is fractional solid volume；
Filter efficiency empirical equation：
Wherein, E∑=1- (1-ER)(1-EI)(1-ED), EDSingle fiber media filtration efficiency caused by be spread Blang, ER
For the single fiber media filtration efficiency caused by interception, EIFor as the single fiber media filtration effect caused by inertial collision
Rate,In above formula, Ku=-
0.5lnα-0.75+α-0.25α2,CcFor the Cunningham's skink slip correction factor, σ is Boltzmann
Constant；R is the ratio of particulate matter diameter and fibre diameter,J=(29.6-28 α0.62)R-27.5R2.8,
7. a kind of Calculation Methods for Performance of fiber filter media structure according to claim 6, it is characterised in that：Step G
Described in filtering fluid absolute temperature T be 300~1000K, filtrate thickness t is 0~1000 μm, face velocity V1 be 0~2m/s,
V2 is that 0~2m/s, V3 are that 0~2m/s, V4 are that 0~2m/s, V5 are 0~2m/s, particulate matter diameter dpFor 0~5 μm.
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