CN104155265B - A kind of droplet detection system - Google Patents
A kind of droplet detection system Download PDFInfo
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- CN104155265B CN104155265B CN201410380817.6A CN201410380817A CN104155265B CN 104155265 B CN104155265 B CN 104155265B CN 201410380817 A CN201410380817 A CN 201410380817A CN 104155265 B CN104155265 B CN 104155265B
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Abstract
The invention discloses a kind of droplet detection system, it is made up of CCD, air pump, conduction optical fiber, breather, imaging fibre, probe, laser instrument, optical cable, laser instrument is connected with probe by conducting optical fiber, air pump is connected with probe by breather, CCD is connected with probe by imaging fibre, and the other end of CCD connects optical cable；Wherein probe includes laser ejecting end, spatial filter, glass enclosure tube, microcobjective, isokinetical sampler, several supports, guide rail；The ageing height of droplet detection system provided by the invention, it is possible to realize online drop and measure；Strong adaptability, accuracy is high.
Description
Technical field
The invention belongs to digital micro-analysis technical field, relate to a kind of droplet detection system.
Technical background
In order to remove the sulfur dioxide in coal-burning power plant's discharge flue gas, coal-burning power plant of current China more than 90% is equipped with wet desulphurization equipment, and more than 90% is wherein limestone-gypsum method flue gas desulfurization device.But flue gas can carry a large amount of droplet after this device, the droplet that demister is difficult to less than 15 microns removes, and the droplet entrance flue therefore having part particle diameter less affects follow-up equipment and enters atmospheric effect environment, can cause very big harm.
The method of existing measurement droplet concentration is mainly to collect method.
Collection method is summarized: drop is acquired by collection method by catcher in flue, catcher is performed twice at weigh after acquisition, contrasts twice heavy result, and both differences are the drop water weight gathered.While sampling, take serosity sample in absorption tower, analyze the Mg in the serosity of absorption tower2Mass concentration and slurry solid content, be modified concentration of liquid drops.In the calculating of droplet concentration, we can according in the concentration of water, absorption tower slurry drops in catcher drop magnesium ion concentration and in catcher drop the densitometer of magnesium ion calculate desired result.
Traditional type gathering method: the external trapping of drop.For preventing slurry drops from condensing in sampling gun and gas path pipe, sampling gun and gas path pipe all must with heaters, and during to ensure to sample, the temperature of sampling gun and gas path pipe is 100-110 DEG C of scope.And demister outlet sampling flue sectional area is often relatively big, will realizing Grid Sampling, need to be equipped with the longer sampling gun with heater and pipeline, this is difficult to.
Before gathering drop with air pump, each point flue gas flow rate, record sampling time, cigarette temperature, humidity of flue gas, suction pressure etc. need to be predicted.Owing to the sampling time is longer, and demister exhaust pass is tortuous, and flue sectional area is big, and flue gas is in turbulence state, and flowed fluctuation is bigger, it was predicted that flow velocity method cannot really realize isokinetic sampling.
Improvement type gathering method:
Tobacco damping-off method measures slurry drops content in demister exiting flue gas, it is exactly utilize the parallel full-automatic smoke dust sampling instrument extremely sampling gun of pitot tube, drop catcher is processed transformation make it to dock with sampling gun, slurry drops is trapped according to smoke dust sampling method, record is converted into mark dry flue gas sampling quantity simultaneously, thus recording slurry drops content in flue gas.Slurry drops similar flue dust in flue gas equally moves, and therefore the point layout of concentration of liquid drops test should adopt lattice method, carries out isokinetic sampling.
The shortcoming that collection method is common:
1, the time of sample-duration is long, it is impossible to monitor in real time.
2, cannot be carried out complete isokinetic sampling, damage accuracy.
3, the degree of accuracy of the requirement of operation, instrument is higher, such as must be complete by the magnesium ion collection adhered on its catcher, otherwise easily cause error, subsequent treatment correction is more complicated.
It is therefore seen that, the concentration of emission of the performance of demister and droplet cannot be detected by existing collection method in real time.Therefore it is necessary to adopt a kind of method that can measure droplet concentration in real time.
Summary of the invention
It is an object of the invention to for the deficiencies in the prior art, it is provided that a kind of droplet detection system.
It is an object of the invention to be achieved through the following technical solutions: a kind of droplet detection system, it is made up of CCD, air pump, conduction optical fiber, breather, imaging fibre, probe, laser instrument, optical cable, laser instrument is connected with probe by conducting optical fiber, air pump is connected with probe by breather, CCD is connected with probe by imaging fibre, and the other end of CCD connects computer by optical cable；
Described probe includes laser ejecting end, spatial filter, glass enclosure tube, microcobjective, isokinetical sampler, several supports, guide rail；Support can horizontally slip at guide rail；Laser ejecting end, spatial filter, isokinetical sampler, microcobjective are sequentially arranged on support respectively, and can slide up and down on support；Described spatial filter includes the first convex lens, pinhole diaphragm and the second convex lens, and pinhole diaphragm is arranged between the first convex lens and the second convex lens；The measurement zone pipeline place of isokinetical sampler has two holes, is inserted with two glass enclosure tube in two holes.Wherein, laser ejecting end is connected with conduction optical fiber, and isokinetical sampler is connected with breather；
The work process of described droplet detection system is as follows: isokinetical sampler is under the assistance of air pump, and constant speed collects demister exiting flue gas；Laser instrument sends laser, enters in probe through conduction optical fiber, laser ejecting end penetrates；Laser first passes through the first convex lens in spatial filter, and laser is disperseed, and is then passed through a pinhole diaphragm, filters the part that in the Gauss light that laser instrument sends, edge strength is relatively low, and then through the second convex lens, laser becomes directional light injection spatial filter；It is irradiated to measurement zone by glass enclosure tube from spatial filter laser out；Laser can produce object wave after being irradiated to the droplet of isokinetical sampler, and object wave interferes phenomenon with original reference light wave again；Interference image, after microcobjective amplifies, is transmitted in CCD by imaging fibre, is recorded, optical signal changes into the signal of telecommunication, by, on optical cable transmission to computer, obtaining image information, it is then passed through a series of reconstruction, obtains particle size distribution and the spatial distribution map of droplet.
The method have the advantages that
1, ageing height, it is possible to realize online drop and measure.
The present invention is capable of the real-time measurement to a certain moment point such that it is able to obtain the fluctuation situation of droplet concentration within a period of time.This has great importance for studying the granular size etc. of droplet in the reduction of discharging of droplet and flue, only can accurately measure real-time droplet discharge capacity, and we can be controlled for emission behaviour.
2, realize isokinetic sampling, improve accuracy.
In conjunction with the feature of digital micro-analysis holographic technique, and the practical situation in flue, the present invention applies the first-class system of isokinetic sampling and realizes in site measurement preferably.Regulating air pressure also with air pump, pressure measured by pitot tube such that it is able to makes the identical guarantee flue gas of air pressure before and after sampling flow into measurement zone smoothly.
Accompanying drawing explanation
Fig. 1 is the structural representation of probe system device；
Fig. 2 is probe cut-away view；
Fig. 3 is that CCD shoots the droplet granule interferogram obtained；
Fig. 4 is the droplet particle distribution figure obtained after interferogram Matlab program is rebuild；
Fig. 5 is the droplet spatial distribution map drawn after droplet space coordinates and diameter dimension are imported Tecplot；
In figure, probe 1, conduction optical fiber 2, laser ejecting end the 3, first convex lens 4, pinhole diaphragm the 5, second convex lens 6, glass enclosure tube 7, microcobjective 8, imaging fibre 9, breather 10, isokinetical sampler 11, support 12, laser instrument 13, air pump 14, CCD15, optical cable 16, guide rail 17.
Detailed description of the invention
The technology that digital microscopic holography technology is optical microscopy and Digital Holography blends, the core of its technology derives from traditional principle of holography, namely by diffraction of light characteristic and coherence, records and reproduce strength information and the phase information of original object wave.
Holographic technique is to utilize the record and reproducing technology interfered with diffraction principle record reconstructed object true three dimensional image.From the light that laser instrument shoots out, through spatial filter and be calibrated filter and make an uproar, it is divided into two bundles by spectroscope, a branch of as reference wave, through reflecting mirror to spectroscope, another bundle is reflected mirror and irradiates sample formation light wave, after spectroscope, interference hologram is formed with reference wave, hologram is recorded by photoelectric sensor (CCD), then the hologram recorded by CCD transmitted by capture card and store in computer, realize being recorded the reproduction of object by Computer Numerical Simulation optical diffraction process again, and utilize computer to carry out the technology processed, namely reproduce hologram image with computer and process, physics imaging process is expanded to digital process.
Traditional Digital Holography can only record the granule that particle diameter is relatively larger, the little droplet surveyed for us is difficult to carry out to detect, so we had added a microcobjective before image information enters CCD, amplify image information, in order to the droplet particles that detection particle diameter is little.
And in order to simplify experimental provision, in order to this technology can carry out practical application, and what we adopted is micro-in-line holographic, is the object adopting coherent plane wave to irradiate a highly transparent.The plane wave by force and uniformly of direct projection is as the reference light wave of holographic recording, and weak scattered wave is object wave.Formed and amplify then through microcobjective after interfering hologram.And more weak at scattering light or that do not reach marginal portion, based on the diffraction light wave of object edge.For the ease of field survey, we are on the basis of digital microscopic holography technology, devise a set of droplet detection system, this system is made up of CCD15, air pump 14, conduction optical fiber 2, breather 10, imaging fibre 9, probe 1, laser instrument 13, optical cable 16, laser instrument 13 is connected with probe 1 by conducting optical fiber 2, air pump 14 is connected with probe 1 by breather 10, and CCD15 is connected with probe 1 by imaging fibre 9, and the other end of CCD15 connects computer by optical cable 16；
Described probe 1 includes laser ejecting end 3, spatial filter, glass enclosure tube 7, microcobjective 8, isokinetical sampler 11, several supports 12, guide rail 17；Support 12 can horizontally slip at guide rail 17；Laser ejecting end 3, spatial filter, isokinetical sampler 11, microcobjective 8 are sequentially arranged on support 12 respectively, and can slide up and down on support 12；Wherein, laser ejecting end 3 is connected with conduction optical fiber 2, and isokinetical sampler 11 is connected with breather 10；
Described spatial filter includes the first convex lens 4, pinhole diaphragm 5 and the second convex lens 6, and pinhole diaphragm 5 is arranged between the first convex lens 4 and the second convex lens 6；The laser of fiber optic conduction, by energy filtering clutter after spatial filter, produces parallel laser.
Air pump 14 is for regulating the air pressure of measured zone so that the air pressure of measured zone is identical with ambient pressure；
Isokinetical sampler 11 is when the air pressure of measured zone is identical with ambient pressure, can isokinetic sampling, ensure to enter the speed of droplet in measurement zone consistent with flue with concentration, the measurement zone pipeline place of isokinetical sampler 11 has two holes, two glass enclosure tube 7 are inserted in the two hole, laser light glass enclosure tube 7 injects measurement zone, and measurement zone is closed by glass enclosure tube 7, it is prevented that droplet spills other instruments of pollution from measurement zone.
The effect of microcobjective 8 is laser to be got to produced interference image on drop amplify；The effect of imaging fibre 9 be by amplify after interference image be transferred on CCD15；The effect of air pump 14 is the air pressure adjusting measured zone, it is ensured that the realization of isokinetic sampling；The effect of CCD15 is the optical signal receiving imaging fibre, and the optical signal of interference image is converted to the signal of telecommunication；The signal of telecommunication of CCD15 is transmitted on computer by the effect of optical cable 16 exactly.
The work process of this system is as follows:
Isokinetical sampler 11 is under the assistance of air pump 14, and constant speed collects demister exiting flue gas；Laser instrument 13 sends laser, enters in probe 1 through conduction optical fiber 2, laser ejecting end 3 penetrates；Laser first passes through the first convex lens 4 in spatial filter, and laser is disperseed, and is then passed through a pinhole diaphragm 5, filters the part that in the Gauss light that laser instrument sends, edge strength is relatively low, and then through the second convex lens 6, laser becomes directional light injection spatial filter；Being irradiated to measurement zone from spatial filter laser out by glass enclosure tube 7, laser can produce object wave after being irradiated to the droplet in isokinetical sampler 11, and object wave interferes phenomenon with original reference light wave again；Interference image is after microcobjective 8 amplifies, it is transmitted in CCD15 by imaging fibre 9, it is recorded, and optical signal is changed into the signal of telecommunication, the signal of telecommunication is transferred on computer by optical cable 16, obtain image information, be then passed through a series of reconstruction, obtain particle size distribution and the spatial distribution map of droplet.
Embodiment 1
The probe 1 of native system device is stretched in flue, opens air pump 14；Flue gas containing droplet will pass through isokinetical sampler 11 and enter the measurement zone of probe；Isokinetical sampler 11 under the assistance of air pump 14, isokinetic sampling；Meanwhile, laser instrument 13 is internal to probe 1 by laser conduction by conducting optical fiber 2, first pass through spatial filter and produce parallel laser, then laser can be irradiated in the droplet of measurement zone isokinetical sampler 11, produce interference image signal, interference image signal first passes through microcobjective and amplifies, then through imaging fibre, signal is transferred on the CCD being placed on outside, CCD can show original image after photographing image on computers, by adjusting the first convex lens 4, pinhole diaphragm 5, second convex lens 6, glass enclosure tube 7, microcobjective 8, the height of imaging fibre 9 and distance each other, make computer presents droplet interference image clearly, as shown in Figure 3.
Fig. 3 inverting of matlab program is rebuild, finally can obtain roughly the space coordinates of each granule of passable spatial distribution map (as shown in Figure 4) and measurement zone and the Pixel Dimensions (as shown in table 1) of particle diameter.By Pixel Dimensions after formula scales, obtain the actual size of space coordinates and particle diameter, as shown in table 2.Then more accurate particle distribution figure is obtained after the actual size after conversion being imported Tecplot, as shown in Figure 5.
Table 1CCD image program inverting initial data
| x/pix | y/pix | z/pix | d/pix |
| 87.5 | 1 | 90 | 4 |
| 434 | 1 | 279 | 3 |
| 124.5 | 1.4 | 97 | 20 |
| 111.6667 | 1.7778 | 86 | 9 |
| 154.5 | 3 | 382 | 2 |
| 1202 | 7 | 451 | 3 |
| 413 | 35.5 | 198 | 2 |
| 160.5 | 36 | 573 | 2 |
| 325.5 | 57 | 28 | 2 |
| 163.125 | 58 | 505 | 8 |
| 164.5 | 73 | 576 | 2 |
| 334.3158 | 101.2632 | 29 | 19 |
| 741.5 | 155 | 28 | 2 |
| … | … | … | … |
Scaled data
Assume that droplet is spherical.The mean diameter D of droplet granule can be obtained, thus calculating the average external volume V of every droplet by particle size distribution.The density p of droplet calculates according to the density of slurry pool, and granule number N calculates according to measuring the number obtained, measured zone V0It is region during reconstruction.According to data above, the real-time mass concentration C obtaining droplet can be calculatedm。
Computing formula: Cm=NV ρ/V0
With the one group of data instance adopting microcobjective that amplification is 10 times, the pixel adopting CCD is 4.5 microns, actual demarcate after the amplification that obtains be 9.4 times.
Initial data is (the droplet granule number obtained in this example is 145):
Pixel Dimensions is scaled actual size, and wherein X-axis reduction formula is: x*4.5/1000；Y-axis reduction formula is: y*4.5/1000；Z axis reduction formula determines according to concrete reconstruction regions, and in this example, the Z axis interval of reconstruction regions is 0.01mm to 0.2mm, reconstruction be spaced apart 0.01mm, so Z axis reduction formula is: 0.01+0.01*z；The reduction formula of particle diameter d is: (d*4.5*4.5*4/ π) ^0.5/9.4.
According to spherical volume computing formula V=π d3/ 6, calculate after the volume of each droplet is converted and be of a size of:
According to the size after conversion, granule obtains the measured zone V of this example0=△ x △ y △ z=(7.2522-0.2805) * (5.4873-0.012) * (0.21-0.02)=7.25mm3。
The cumulative volume V obtaining 145 droplets it is added by the volume of each dropleta=566.25um3。
The average external volume V=V of each droplet is obtained by droplet cumulative volumea/ 145=3.91um3.Obtain droplet mean diameter D=1.95um.
The serum density assuming slurry pool is 1.05g/cm3
By computing formula: Cm=NV ρ/V0: Cm=145*3.91*1.05/7.25=82.11mg/m3
Droplet concentration after current national Specification demister needs at below 75mg/m3, but owing to the demister frequency that breaks down is higher, actual discharge droplet concentration there will be fluctuation, and using the droplet concentration that this invention records is 82.11mg/m3, meet actual droplet concentration of emission.
Claims (1)
1. a droplet detection system, it is characterized in that, this system is by CCD(15), air pump (14), conduction optical fiber (2), breather (10), imaging fibre (9), probe (1), laser instrument (13), optical cable (16) form, laser instrument (13) is connected with probe (1) by conducting optical fiber (2), air pump (14) is connected with probe (1) by breather (10), CCD(15) by imaging fibre (9) with probe (1) be connected, CCD(15) the other end by optical cable (16) connection computer；
Described probe (1) includes laser ejecting end (3), spatial filter, glass enclosure tube (7), microcobjective (8), isokinetical sampler (11), several supports (12), guide rail (17)；Wherein, laser ejecting end (3) is connected with conduction optical fiber (2), and isokinetical sampler (11) is connected with breather (10)；Support (12) can horizontally slip in guide rail (17)；Laser ejecting end (3), spatial filter, isokinetical sampler (11), microcobjective (8) are sequentially arranged on support (12) respectively, and can slide up and down on support (12)；Described spatial filter includes the first convex lens (4), pinhole diaphragm (5) and the second convex lens (6), and pinhole diaphragm (5) is arranged between the first convex lens (4) and the second convex lens (6)；The measurement zone pipeline place of isokinetical sampler (11) has two holes, is inserted with two glass enclosure tube (7) in two holes；
Air pump (14) regulates the air pressure of measured zone so that the air pressure of measured zone is identical with ambient pressure；Isokinetical sampler (11) is under the assistance of air pump (14), and constant speed collects demister exiting flue gas；Laser instrument (13) sends laser, enters in probe (1) through conduction optical fiber (2), laser ejecting end (3) penetrates；Laser first passes through the first convex lens (4) in spatial filter, and laser is disperseed, and is then passed through pinhole diaphragm (5), and then through the second convex lens (6), laser becomes directional light injection spatial filter；It is irradiated to measurement zone by glass enclosure tube (7) from spatial filter laser out；Laser produces object wave after being irradiated to the droplet in isokinetical sampler (11), and object wave interferes phenomenon with original reference light wave again；Interference image is after microcobjective (8) amplifies, it is transmitted to CCD(15 by imaging fibre (9)) in, it is recorded, optical signal changes into the signal of telecommunication, it is transferred on computer by optical cable (16), obtaining image information, the inverting being then passed through matlab program is rebuild, and obtains particle size distribution and the spatial distribution map of droplet.
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| CN201673116U (en) * | 2010-04-30 | 2010-12-15 | 中国科学技术大学 | Experiment device used for measuring spaying characteristics under condition of low atmospheric pressure |
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