CN102323445B - Method for measuring flowing velocity of recycle gas in multiple laser cavity - Google Patents
Method for measuring flowing velocity of recycle gas in multiple laser cavity Download PDFInfo
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Abstract
The invention belongs to the technical field of speed optical measurement, and relates to a method for measuring a flow field speed. A distribution rule of a flow field is shot by combining with an interference method or schlieren method device through providing an intensified charge coupled device (ICCD) imaging device, a generation and evolution process of warm air mass is shot through a delay control function of a controller, acquired images are subjected to digital image processing, a center line of the warm air mass is obtained according to characteristics of the images, the rule that the center line of the warm air mass changes with time is obtained through processing a plurality of frames of images, and data processing and error estimating are carried out by adopting a least square method to obtain speed distribution information of a one-dimensional flow field. The method can be used for measuring the flow field speed in real time by adopting a noncontact measurement method to obtain the whole one-dimensional speed distribution information, overcomes defects and shortcomings in the prior art, and has great progress and practical applicability.
Description
Technical field
The invention belongs to field of optical measuring technologies; What relate to is the method for measuring flow field velocity; Particularly a kind of outfit enhancement mode electric charge coupling (ICCD) image device is taken flow field distribution, utilizes hot gas group that chamber self-energy deposition produces after discharging and the characteristic of drifting about with the flow field thereof, through interferometric method or schlieren method hot gas group is observed; The center line of following the trail of hot gas group moves, thereby realizes the method that flow field velocity is measured.This method is particularly useful for the measurement of gas flowfield speed in the repetition rate pulsed laser.
Background technology
Adopt the pulsed gas laser of pulsed discharge pumping to have repetition rate height, energy and reach the low characteristics of cost greatly and in industry, obtained to use widely, like IC etching, laser medicine and industrial processes etc.The unevenness of laser cavity flow field can have a strong impact on beam quality, output average power, even suppresses the generation of laser generation.High pressure pulse discharge can produce impurity and dump energy in laser cavity deposition can make the gas heating of region of discharge; Thereby the flow field uniformity in the laser cavity is seriously influenced; Directly influence the performance of next pulse discharge, even cause the generation of arc discharge.Therefore need a circulate system to come reset pulse discharge hot gas group and impurity later.Along with to the increasing of the requirement of repetition frequency index, the rate request that stream field circulates is also improving, and this measuring method to laser cavity flow field flow velocity is also had higher requirement.
The measuring method of traditional flow field velocity adopts pitot tube through regular meeting, when this method is measured with pitot tube over against the flow direction, through measuring the pressure differential at tube head and static tube center, and the Bernoulli equation of application streamline calculates flow rate of fluid.Advantages such as it is simple that the pitot tube velocity measurement has equipment, easy to operate are because this method belongs to a kind of contact type measurement; To produce disturbance to the flow field in the laser cavity; And in the discharge excitation direction, difficult to realize accurate location during measurement, its speed that records has suitable error.Therefore general this method only limits in the laboratory flow field velocity of the laser cavity that is not in discharge condition is measured.The pitot tube measuring method also can't realize real-time measurement (M.L.sentis, R.Entropic, 115, the 3-12 (1984) to flow velocity in the laser chamber of discharge work in addition; H.Hatanaka, K.Midorikawa, M.Obara, and H.Tashiro, Review of Scientific Instruments 64,3061-3065 (1993) .).And adopt non-contacting measuring method to can solve the problems referred to above, realize the flow field velocity in the laser cavity is measured in real time.
Non-cpntact measurement is owing to have the artificial interference that causes when avoiding contact measurement; Therefore can measure some impalpable objects, like corrosive gas etc., and the result can be through Digital Image Processing; Computer Recognition; Have advantages such as picking rate is very fast, can well be applicable to the measurement of flow velocity in the laser cavity, the flow velocity and the measurement of chamber flow field speed of using the excimer laser of corrosivity working gas in the laser chamber that is particularly suitable for working.Because pulsed gas laser rapid discharge excitation; In the chamber, have energy deposition; Make main discharge region gas by transient heating and to circumferential expansion, form a hot gas group with regular heat distribution zone, this expansion process is an isentropic expansion process; Its Density Distribution and Temperature Distribution have inverse relation, thereby hot gas group shifts out region of discharge gradually downstream along with gas circulation flows.Because parallel beam when sparing gas through density unevenness deviation can take place, wherein the deflection angle of parallel beam is directly proportional with density gradient, and laser beam is fixed in hot gas group a certain position, downstream, surveys and write down the situation of the out-of-date light beam deviation of whole hot gas bolus flow.People such as Kosugi utilize this single-point deflection of light method come in the gas lasers measured chamber flowing velocity (Kosugi, Maeno and Honma [J] .Jpn.J.Appl.Phys.1993, Vol.32:4980-4986).Shown in Fig. 1 (a); The axially parallel of light 1 direction and laser instrument is surveyed in adjustment; Be positioned at a certain fixed range place, 3 center line downstream, main discharge district, utilize 4 pairs of detection light that see through laser works gas of two quadrant photodiode to receive, and on oscillograph 5, show.At the beginning of the discharge, laser beam is identical in two quadrant light distribution of photodiode, is 0 with its signal subtraction output signal therefore; After hot gas group's process; Light beam generation deviation, the light intensity of two quadrants is no longer equal, changes thereby have corresponding signal; Signal magnitude and positive and negative relevant with the light beam deflection angle, the Density Distribution of hot gas group has determined the size and Orientation of light beam deflection angle.Be depicted as photodiode output signal, the wherein t that obtains like Fig. 1 (b)
0Be that corresponding hot gas cluster centre arrives the moment of surveying light corresponding constantly zero point.Through measure the probing light position apart from discharge centers apart from s, just can measure the flowing velocity in the flow field of this point, that is: v=s/t
0This method is had relatively high expectations to probe source, and for the small deviation amount of energy measurement light, the angle of divergence of light beam is little; And spot radius had relatively high expectations (below 1mm), this method can only be measured in the flow field certain any speed, and flow field velocity is normally uneven; Usually less near the flow velocity of two electrode positions; In order to measure the distribution of flow field velocity, must carry out the light path adjustment to each data point that needs, so this method is to measuring the flow field velocity very trouble that seems that distributes.
Interferometric method and schlieren method also are traditional flow field detection methods.The interferometric method kind that is applied to detect in the flow field is a lot, and commonly used have holographic interference (Clark, Applied Optics 13,1995 (1974) .) and a Mach Zehnder interferometric method (J.T.L.F.Wingate, AIAA Paper 81-1286 (1981) .) etc.Though the experimental provision of distinct methods has a little to change, their principle is roughly the same, all is the measuring technique that is the basis with the optical interference principle.Interference fringe in the interferogram is the information carrier that interferometry obtains, and has reflected the optical path difference of the beam Propagation process in the different paths of two-way.Be illustrated in figure 2 as a typical Mach Zehnder interferometer device synoptic diagram.The Mach Zehnder interference system mainly is made up of three parts, i.e. light path system, light-source system and interferogram receiving system.Light path system is by probe source 11, and beam-expanding system 12 is formed, and the double light path of system partly comprises semi-transparent semi-reflecting lens 13 and 17, and total reflective mirror 14 and 15 constitutes a rectangular configuration.Wherein one road light is through search coverage, and promptly laser cavity 16.The interferogram receiving system generally images in ground glass 18 with interference fringe, is write down or directly interference fringe is directly projected receiver by 19 pairs of images of image device then and carry out record.This method is specially adapted to the vertiginous state of learning gas density.Since the variation of gas refracting index and its density be varied to direct ratio; And change of refractive will make the light through gas that different optical path is arranged; Therefore a plane light wave and the light wave through gas can obtain equal thick interference fringe, and these stripeds can reflect gas refracting index and Density Distribution situation.In the pulsed discharge laser instrument, there is the Density Distribution of certain rule in the hot gas group that produces after discharge takes place, and corresponding to the equal thick interference fringe on the interference image, the symcenter of these interference fringes is the center line of hot gas group.Utilize the record of image device, can obtain the Density Distribution sequential chart of hot gas group difference moment flow field.
The schlieren method principle is similar with single-point deviation method, all is to have utilized light beam that the character of deviation takes place in the uneven medium of index distribution.In schlieren method is measured, probe source 31 is expanded bundle, make the size of whole hot spot greater than search coverage.Utilize lens 34 that outgoing beam is focused on, and an aperture diaphragm 35 is set at lens back focal plane place.Place a frosted glass 36 with interferometric method is the same at the back at aperture, utilize 37 pairs of images that obtained of image device to carry out record.In schlieren method is measured; The effect of aperture is extremely important, if through certain any light generation deviation in the density field, can make corresponding light source image displacement; This moving part branch is blocked by aperture; Reduced the illumination of this light beam corresponding specific picture point on film viewing screen, promptly the size of the last illumination of screen and the deflection angle of relevant position can be mapped, thereby obtain the density gradient distributed intelligence in the whole chamber.When hot gas group density gradient was big, light beam can produce very big deflection angle through hot gas group, makes light beam depart from aperture fully, on screen, can obtain a dark space completely especially, and the center line of this dark space is corresponding to the center of hot gas group.Utilize the record of image device, can obtain the density gradient sequential chart picture of hot gas group difference moment flow field.
These two kinds of methods are commonly used to observe the homogeneity and the influence factors such as sound wave and shock-wave disturbance of laser chamber flow field.The present invention just is being based on the rule of above-mentioned sniffer and chamber flow field and is carrying out basic Analysis of Flow Field, and the differentiation through following the trail of hot gas group and along with the moving of flow field obtains the speed that intracavity gas circulates.
Summary of the invention
The object of the invention provides the mobile method of velocity of recyclegas in a kind of measurement Repetition Frequency Laser device chamber, and this method can simply and exactly be measured the gas flowfield speed of high Repetition Frequency Laser device.
The mobile method of velocity of recyclegas is characterized in that this method comprises the steps: in a kind of measurement Repetition Frequency Laser device provided by the invention chamber
(1) acquisition and the collection of the distribution of laser chamber flow field
Based on the duty of testing laser device, select the distributed image in interferometric method or schlieren method acquisition flow field, and the image that obtains is gathered with image device, obtain the sequential chart picture that the laser chamber flow field distributes;
(2) sequential chart is as pre-service
Through the sequential chart that obtains is looked like to carry out level and smooth and denoising, obtain striped and distribute, carry out binaryzation and micronization processes then, obtain the center line of stripeds at different levels;
(3) obtain the center that hot gas is rolled into a ball
Image after the micronization processes is carried out center line extract, obtain the position of center line of hot gas group;
(4) data analysis is handled
The position of center line that adopts least square method that hot gas is rolled into a ball carries out data analysis to be handled;
(5) distribution plan of acquisition flow field velocity
With the discharge excitation direction is horizontal ordinate; With the flow field flow direction is ordinate; Adopt identical first-order linear fit equation that the corresponding ordinate in each horizontal ordinate position is calculated; Obtain the corresponding flow field average velocity of different horizontal ordinates, thereby to obtain with the discharge excitation direction be the velocity distribution of flow field of horizontal ordinate.
The present invention is through being equipped with enhancement mode electric charge coupling (ICCD) image device; In conjunction with the density distributing law that interferometric method or schlieren method apparatus system are taken the flow field,, take the generation and the evolutionary process that obtain hot gas group through the time-delay control function of controller; The image that obtains is carried out Digital Image Processing; Extract hot gas cluster centre line and positional information in each two field picture, multiple image is handled, obtain hot gas cluster centre line rule over time; Adopt least square method to carry out data processing and estimation of error, obtain the one dimension velocity information in whole flow field.
The present invention has overcome the limitation influence of spot measurement, and measurement range is bigger, need not repeatedly to measure the one dimension velocity distribution that just can access the flow field, promptly obtains along the average velocity in the flow field of each position of discharge excitation direction.Interferometric method can be surveyed the small sample perturbations in flow field, and precision is higher.This invention have measure be easy to realize, the measuring speed scope is big, precision is high and convenience operation, has very strong practicality.
Description of drawings
Fig. 1 is a single-point deflection of light synoptic diagram, and wherein (a) is single-point deflection of light subtraction unit synoptic diagram, (b) is two quadrant photodetector output signal;
Fig. 2 is the interferometric method structural representation;
Fig. 3 is the schlieren method structural representation;
Fig. 4 is a flow field velocity measuring method process flow diagram;
Fig. 5 is the interference pattern that adopts one group of flow field that interferometric method obtains; Wherein (a) is discharge initial time interference image; (b) for the interference image behind the 100us takes place in discharge, the interference image behind the 300us takes place for discharge in the interference image (d) that (c) takes place behind the 200us for discharge;
Fig. 6 is the different position distribution of center line constantly that adopt interferometric method to obtain;
Fig. 7 is the velocity profile that adopts interferometric method to obtain.
Embodiment
The electro-optical efficiency of pulsed gas laser is lower; After the pulsed gas discharge excitation; Superfluous injection energy can deposit in the chamber; Make transient heating of main discharge region gas and isentropic expansion, be formed with the hot gas group of regular heat distribution, thereby hot gas group shifts out region of discharge gradually downstream along with gas circulation flows.In moving process, the essential characteristic of hot gas group remains unchanged, particularly near the structure the hot gas cluster centre line.The present invention just is being based on said process, in conjunction with interfering or schlieren method experimental provision system, is equipped with high speed imaging device, and it is moving to observe the hot gas bolus flow, has proposed a kind of new flow field velocity measuring method.Flow field velocity measuring method flow process is as shown in Figure 4, below introduces respectively:
(1) acquisition and the collection of the distribution of laser chamber flow field
According to the duty of testing laser device, selection interferometric method or schlieren method obtain the distributed image in flow field, and with image device the image that obtains are gathered.If the energy density of laser instrument deposition is big, then density distribution gradient is big in the hot gas group, should obtain the Flow Field Distribution in the chamber with schlieren method.Otherwise, then can adopt the Mach Zehnder interferometric method to come Density Distribution image in the chamber is carried out record.The collection of image can be accomplished through being equipped with enhancement type charge coupling imaging spare (ICCD), and the image that images on the frosted glass is carried out record.Wherein the electromagnetic pulse interference of ICCD employing discharge moment generation is as synchronous triggering signal; Carry out the trigger pip time-delay through the ICCD controller; Obtain one group of sequence signal of delaying time accurately; Through this time-delay sequence control ICCD different constantly collection after discharge, obtain the sequential chart picture that the laser chamber flow field distributes.
(2) utilize digital image processing method to carry out the image pre-service:
Because light beam is inhomogeneous, reach factors such as external interference, can make the image of acquisition that certain ground unrest is arranged.Through the image that obtains is carried out level and smooth and denoising, striped distribution comparatively uniformly be can obtain, and then binaryzation and micronization processes adopted, obtain the center line of each bright fringes.
(3) obtain the center that hot gas is rolled into a ball:
The image striped of gathering keeps essential characteristic constant after refinement, still has a symcenter, is the center line that whole hot gas is rolled into a ball.Image to above-mentioned refinement carries out the center line extraction, obtains the position of center line of hot gas group.After the image that interferometric method obtains carried out the image pre-service, the hot gas cluster centre line position that obtains can not directly extract, and can pass through the center line of the striped of the contiguous center line of extraction, and they are averaged, thereby obtained the center line of hot gas group.After the image that schlieren method obtains carried out the image pre-service, the center line that can directly hot gas be rolled into a ball extracted.Adopt said method, the multiframe sequential chart is looked like to handle, can obtain discharge different hot gas cluster centre constantly position, back takes place.The position of center line of hot gas group is made up of pixel, and the coordinate of each pixel can directly obtain from image, and according to the actual size of each pixel, can itself and physical size be mapped.Coordinate system is an initial point with a certain electrode summit; With the discharge excitation direction is the direction of horizontal ordinate; The value representation of horizontal ordinate is from the distance on this electrode summit; With the flow field flow direction is the ordinate direction, and flow direction departs from the distance of two electrode summit lines to the value representation hot gas cluster centre line of ordinate along the flow field.
(4) adopting least square method to carry out data analysis handles
Owing to hot gas cluster centre line position changes along with the flow field circulates, promptly to the point of same horizontal ordinate, the time changes Δ t, and the value of ordinate changes Δ y, then the corresponding flow field movement speed v=Δ y/ Δ t in this horizontal ordinate position.Here adopt first-order linear fit equation y=y
0+ vt comes the corresponding flow field velocity of each horizontal ordinate is estimated, utilizes least square method to find the solution speed v, wherein t be the time (with discharge moment as time zero), y be the ordinate position of the center line of t correspondence constantly, v is a flow field velocity, y
0Ordinate value (y for initial time (t=0) hot gas cluster centre line position
0Be calculated value, because t=0 formation of hot gas group constantly).The above-mentioned equation of coordinate substitution of the center of the many groups of different hot gas groups constantly that previous processed is obtained can obtain the corresponding unknown parameter y in any horizontal ordinate position
0And v.In order to obtain accurate result, measuring number of times should be greater than 10 group, thereby reduces the error that factors such as noise and speed is inhomogeneous produce.
(5) distribution plan of acquisition flow field velocity
The ordinate corresponding to each horizontal ordinate position all adopts above-mentioned first-order linear fit equation; Obtain the flow field average velocity of different horizontal ordinates position; Thereby obtain the velocity distribution of flow field between the two electrode summits; This velocity distribution has reflected that the one dimension of the speed of gas circulation in the laser chamber distributes, and utilizes computing machine can the whole flow field velocity information that obtain be presented on the computer screen with image format.
Instance:
Below in conjunction with in pulsed gas laser; Gas mixing ratio is N2: He=1: 115; Total gas pressure 500mbar; Discharge excitation voltage is under the 20KV condition of work, utilizes the Mach Zehnder interference device system that is equipped with enhancement type charge coupling imaging spare (ICCD) that above-mentioned flow field velocity is distributed and measures.Through this embodiment technical scheme of the present invention is described in further detail:
(1) in above-mentioned condition of work, because main gas componant is He, its heat transmissibility is better, therefore in the forming process of hot gas group, because the density gradient that the heat deposition effect causes is not too large, therefore can adopt the Mach Zehnder interference device to measure.The image imaging that two-beam interference is produced utilizes ICCD that the interference image that images on the frosted glass plate is carried out record in frosted glass.Because parallel beam sees through the protection window of image device, is easy to generate the background interference striped, and become scattered light through the light after the frosted glass imaging, light beam just can not interfere after seeing through the protection window of this image device like this.Way through imaging is gathered the interference fringe on the frosted glass plate, can eliminate the influence of background interference striped, improves the contrast of interference fringe.Before laser works, the position of eyeglass in the adjustment Mach Zehnder device, make image in frosted glass have only the one-level interference fringe, obtain uniform hot spot.After discharge took place, wherein the light path of one road light changed, and on frosted glass, can obtain a series of interference fringes, and these interference fringes distribute corresponding one by one with the intracavity gas Density Distribution.Through sequential record, just can obtain the evolution and the evolution of chamber flow field to these interference images.
(2) this instance utilizes ICCD to come interference fringe is carried out record.The time shutter of ICCD has determined the brightness of the interference fringe of acquisition, and its minimum exposure time can reach several nanoseconds.Because the use of frosted glass can reduce the brightness of light intensity, so the time shutter is longer in this instance, is made as 1 μ s.But this can not influence the result of measured average velocity.ICCD passes through the electromagnetic pulse of discharge moment generation as synchronous triggering signal, and the ICCD controller can carry out accurate sequential time-delay with trigger pip.The ICCD controller can be regulated the sequential time-delay accurately, because this laser instrument flow field velocity is less, therefore gets the increment (time interval that is adjacent two frames is 50 μ s) that 50 μ s are the sequential time-delay here.Through this time-delay sequence control ICCD different constantly collection after discharge, obtain the image of Density Distribution in the different flow fields constantly, discharge back.Because the reading speed of ICCD is slower; The piece image time for reading needs about 1s; Therefore can not in same pulse, the difference to image carry out records constantly; Each pulse can only obtain a width of cloth interference image, through the combination of a plurality of pulses, can the flow field change procedure of a pulse be reappeared out.Fig. 5 is the part in the sequential interference pattern in one group of flow field of intercepting, wherein (a) (b) (c) (d) be four different interference images constantly of intercepting, they are respectively 0us after the pulsed discharge, 100us, 200us, the image that 300us is collected constantly.
(3) because the interference image that obtains has stronger ground unrest, make that certain one-level bright fringes is not very even, this can influence follow-up thinning process, therefore earlier the image that obtains is carried out level and smooth and denoising, and obtaining comparatively uniformly, striped distributes.And then image carried out the center line that binaryzation and micronization processes obtain each grade interference fringe.
(4) shown in Fig. 5 (b), the symcenter of this interference fringe is relatively disorderly, thus the center of hot gas group can not be directly refinement through striped obtain.But can see that striped is symmetrically distributed with the central area.In order to obtain the center line of hot gas group; Can with among the figure+1 grade of center line with-1 grade of interference fringe averages; And+1 grade of center line with-1 grade of interference fringe can extract through digital image processing method, though hot gas group has a process that expands outwardly flowing with the flow field, thermal diffusion is symmetrically distributed; Its essential characteristic remains unchanged, Gu adopt average+1 grade of method with the center line of-1 grade of interference fringe to obtain the center line that whole hot gas is rolled into a ball.The method through Digital Image Processing of being illustrated in figure 6 as obtain the discharging center line of the different hot gas groups constantly in back; Wherein abscissa value is the pixel coordinate of transverse axis among Fig. 5; Ordinate value is corresponding hot gas cluster centre line position pixel coordinate, can these pixel coordinates be converted into the volume coordinate among Fig. 7 through the potential electrode spacing.Be respectively discharge excitation among Fig. 6 and back 100us take place, therefrom can be clearly seen that the drift of stripe centerline to the different positions of center line constantly between 500us.
(5) because flowing of speed is not evenly to flow, but certain disturbance is arranged, the influence of the systematic error brought of factor such as air turbulence is inevitable in addition, and these factors all can cause the non-homogeneous of center line to move up.In order to improve the precision of measurement, take least square method that these data that measure are carried out the first-order linear match, thereby reduce the influence of systematic error.Through first-order linear equation y=y
0+ vt carries out linear fit, wherein y
0Be the position of center line of the initial time set, v is the speed that center line moves.The above-mentioned equation of center position coordinates substitution with many groups that obtain different hot gas groups constantly utilizes least square method to obtain the normal equations group, thereby solves unknown parameter y
0And v.Because what utilize that image processing method obtains is that the center line of whole hot gas group distributes, the speed v that therefore solves is the one dimension velocity distribution between the whole region of discharge two electrode summits.
(6) can calculate their corresponding speed through linear fit to each pixel on the above-mentioned center line; Thereby obtain along the one dimension velocity distribution in discharge excitation direction flow field, and the whole flow field velocity information that will obtain is presented on the computer screen with image format.Be illustrated in figure 7 as the velocity distribution of flow field figure that experiment obtains, wherein the value of horizontal ordinate is the distance between data point and the cathode electrode summit, and the value of ordinate is corresponding flow field velocity.Owing near two electrodes, can produce disorderly flow field during discharge, can not produce interference fringe, therefore can't measure their speed, but this does not influence the measurement of main discharge region center flow field velocity.This method of experiment proof can access comparatively accurate data, makes error control within tolerance interval.
The present invention not only is confined to above-mentioned embodiment; Persons skilled in the art are according to content disclosed by the invention; Can adopt other multiple embodiment embodiment of the present invention, therefore, every employing project organization of the present invention and thinking; Do some simple designs that change or change, all fall into the scope of the present invention's protection.
Claims (1)
1. measure the mobile method of velocity of recyclegas in the Repetition Frequency Laser device chamber for one kind, it is characterized in that this method comprises the steps:
(1) acquisition and the collection of the distribution of laser chamber flow field:
Based on the duty of testing laser device, select the distributed image in interferometric method or schlieren method acquisition flow field, and the image that obtains is gathered with image device, obtain the sequential chart picture that the laser chamber flow field distributes;
(2) sequential chart is as pre-service:
Through the sequential chart that obtains is looked like to carry out level and smooth and denoising, obtain striped and distribute, carry out binaryzation and micronization processes then, obtain the center line of each grade striped;
(3) image after the micronization processes is carried out center line and extracts, obtain the position of center line of hot gas group:
For the image that interferometric method obtains, extract the center line of the striped of contiguous center line, and they are averaged, obtain the center line of hot gas group; For the image that schlieren method obtains, directly extract the center line of hot gas group; Adopt aforesaid way, the multiframe sequential chart is looked like to handle, obtain discharge different hot gas cluster centre constantly position, back takes place;
(4) position of center line that adopts least square method that hot gas is rolled into a ball carries out data analysis to be handled:
The translational speed in corresponding flow field, horizontal ordinate position adopts first-order linear fit equation y=y
0+ vt comes the corresponding flow field velocity of each horizontal ordinate is estimated that wherein, t is the time, and y be the ordinate position of the center line of t correspondence constantly, and v is a flow field velocity, y
0Be the ordinate value of initial time hot gas cluster centre line position, the 3rd step was handled the coordinate substitution first-order linear fit equation of the center of the different hot gas groups constantly that obtain, find the solution and obtain unknown parameter y
0And v;
(5) distribution plan of acquisition flow field velocity:
With the discharge excitation direction is horizontal ordinate; With the flow field flow direction is ordinate; Adopt identical first-order linear fit equation that the corresponding ordinate in each horizontal ordinate position is calculated; Obtain the corresponding flow field average velocity of different horizontal ordinates, thereby to obtain with the discharge excitation direction be the velocity distribution of flow field of horizontal ordinate.
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| IT1244170B (en) * | 1990-12-04 | 1994-07-08 | Cise Spa | LASER EQUIPMENT FOR MEASURING THE SPEED OF A FLUID. |
| CN2186398Y (en) * | 1993-11-01 | 1994-12-28 | 胡传镛 | Laser interference harmful gas monitoring end instrument |
| CN1333258C (en) * | 2004-06-25 | 2007-08-22 | 清华大学 | Self-mixed intervention Doppler velometer based on two-frequency laser |
| CN100541204C (en) * | 2006-08-11 | 2009-09-16 | 中国科学院力学研究所 | A kind of measurement mechanism of fluid channel velocity distribution and measuring method |
| DE102006039489B3 (en) * | 2006-08-21 | 2008-01-31 | B.R. Deutschland, vertr. d. d. Bundesministerium f. Wirtschaft u.Technologie, dieses vertr. d. d. Präs. d. Phys.-Techn. Bundesanstalt | Method for measurement of speed distributions of fluid flown through tubing cross section and spreading light, involves measuring multiple predetermined measuring points arranged over tubing cross section |
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2011
- 2011-06-14 CN CN2011101600979A patent/CN102323445B/en not_active Expired - Fee Related
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