CN103048112A - Device and method for measuring disturbance of cross flow fan impeller of pulsed gas laser - Google Patents
Device and method for measuring disturbance of cross flow fan impeller of pulsed gas laser Download PDFInfo
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- CN103048112A CN103048112A CN2012105240375A CN201210524037A CN103048112A CN 103048112 A CN103048112 A CN 103048112A CN 2012105240375 A CN2012105240375 A CN 2012105240375A CN 201210524037 A CN201210524037 A CN 201210524037A CN 103048112 A CN103048112 A CN 103048112A
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Abstract
The invention discloses a device and a method for measuring disturbance of a cross flow fan impeller of a pulsed gas laser. The device and the method are mainly used for measuring the disturbance of the fan impeller. The device comprises an exploring laser light source, a beam expanding system, two spectroscopes, two reflecting mirrors, a photoelectric detector, a data acquisition unit and a processor, wherein the two spectroscopes and the two reflecting mirrors form a Mach-Zehnder interferometric system; the two spectroscopes are respectively arranged at both ends of a flow field area to be tested; the exploring laser light source, the beam expanding system and a first spectroscope are located on the same light path in sequence; and the photoelectric detector is located on the emergent light path of a second spectroscope. The method comprises the following steps: performing filtering on a signal, and then performing fast Fourier transform (FFT) treatment on the signal through controlling the data sampling frequency and the number of samples; converting a periodic disturbance signal of a time domain into a signal of a frequency domain to obtain a signal spectrum so as to determine the disturbance of the fan impeller. According to the device and the method disclosed by the invention, the disturbance information of fan rotation is obtained through an optical measurement mode. The device and the method have the characteristics that the measuring device is simple and is high in precision and convenient in operation and the method is very high in practical applicability.
Description
Technical field
The invention belongs to field of optical measuring technologies, what relate to is measurement mechanism and the method for the disturbance of a kind of pulsed gas laser crossflow fan impeller, particularly cooperate the Mach Zehnder interference system to come measurement mechanism and the measuring method thereof of small sample perturbations that the crossflow fan impeller is caused, the method is specially adapted to the measurement of the small sample perturbations of crossflow fan impeller in the paired pulses gas laser chamber.
Background technology
Adopt pulsed gas laser such as the CO of pulsed discharge pumping
2Gas laser and excimer laser etc. industrial processes, integrated circuit (IC) etching and laser medicine and etc. the field obtain a wide range of applications.The homogeneity of main discharge region actuating medium has material impact to Uniform discharge and far field beam quality in the pulsed gas laser, therefore needs the circulation system that the actuating medium of region of discharge is constantly updated, thereby guarantees the homogeneity of actuating medium.Circulating by blower fan of gas drives, and the blower fan kind mainly contains crossflow fan, axial flow blower and centrifugal blower.Be accompanied by the requirement of repetition frequency index is increased, rotating speed to blower fan in the circulation system requires also improving constantly, and under conditions of high flow rate, the cost of axial flow blower and centrifugal blower is higher, and crossflow fan can not only obtain higher flow velocity under hyperbar, and crossflow fan approaches with discharge electrode structure in length and breadth, makes whole laser structure compact.Be illustrated in figure 1 as the gas circulation flow system sectional view of pulsed gas laser, mainly comprise main discharge electrode 101, pre-ionization electrode 102, heat interchanger 103, crossflow fan 104 and impeller 105 thereof.Gas circulation in the pulsed gas laser flows and is mainly finished by crossflow fan 104, and the factors such as structure owing to rotating speed unevenness and impeller thereof after crossflow fan 104 rotates can impact the flow field uniformity of tested flow field regions (being main discharge region) 100.Especially under the high repetition frequency experiment condition, the impact of the efficiency loss that produces during blower fan work can increase, fan leaf is staggered in the flow field can produce periodic disturbance, although these disturbances are less, but in being applied to the excimer laser of photoetching, stability requirement to light source is high, therefore need continuous structure to impeller to be optimized, reduce the disturbance in flow field, homogeneity when equally also needing a kind of measuring method to come blower fan worked is measured, particularly draught fan impeller is staggered in the disturbance that produces in the flow field, this is not only an important parameter of the whole Optical Maser System stability of assessment, and can provide experimental basis to updating of fan impeller structure.Many weeks, Mach Zehnder interferometer is a kind of large-scale optical gauge, is applicable to the vertiginous state of learning gas density, the air eddy that produces during such as experimental aeroplane model in wind-tunnel and the shock wave in the blast process etc.But traditional Mach Zehnder device can not be directly used in the disturbance of blower fan in the ranging pulse gas laser, because the disturbance that the blower fan rotation process produces is the gradual process of gas density, variable density in the whole observation area is little, can't obtain effective information with formation methods such as CCD cameras.
Summary of the invention
The object of the invention provides measurement mechanism and the measuring method thereof of a kind of pulsed gas laser crossflow fan impeller disturbance, the disturbance that brings when this device and measuring method thereof can simply and exactly be measured blower fan work.
The measurement mechanism of a kind of pulsed gas laser crossflow fan impeller provided by the invention disturbance, it is characterized in that, it comprises exploring laser light light source, beam-expanding system, the first spectroscope, the second spectroscope, the first catoptron, the second catoptron, photodetector, data acquisition unit and processor;
The first spectroscope, the second spectroscope, the first catoptron and the second catoptron consist of the Mach Zehnder interference system jointly, and the first catoptron and the second spectroscope are respectively applied to be placed on the two ends of tested flow field regions; Exploring laser light light source, beam-expanding system and the first spectroscope are positioned on the same light path successively, and photodetector is positioned on second spectroscopical emitting light path, and data acquisition unit is electrically connected with photodetector, and processor is electrically connected with data acquisition unit.
Utilize the method for above-mentioned measurement mechanism ranging pulse gas laser crossflow fan impeller disturbance, it is characterized in that:
The 1st step made detecting light beam cover the whole observation window of laser instrument, adjusted the Mach Zehnder interference device, obtained a uniform light spots on the surface of photodetector;
The 2nd step control data sampling frequency f
sCount N with sample, make sample frequency f
sGreater than the tested disturbing signal frequency of twice, the signal that photodetector is produced carries out record;
The 3rd step processor carries out filtering to the signal that receives to be processed, carrying out Fast Fourier Transform (FFT) processes again, the periodic disturbance signal of time domain is converted to the signal of frequency domain, obtain the signal collection of illustrative plates, horizontal ordinate is the frequency of corresponding periodic perturbation signal, and ordinate is the amplitude size of disturbing signal under the respective frequencies;
The 4th step was determined the disturbance of draught fan impeller, and the frequency of deterministic disturbances and size by the peak value of frequency-region signal in the signal collection of illustrative plates, the amplitude of this disturbance and the ratio of the amplitude of initial point are the relative size of the disturbance of tested draught fan impeller.
The present invention measures for the small sample perturbations of the key factor that affects pulsed gas laser crossflow fan impeller, it realizes paired pulses gas laser blower fan disturbance measurement based on the Mach Zehnder principle of interference, it obtains the light spot of unlimited equal thick interference fringe by the Mach Zehnder interference system, adopt the detector of limited photosurface size to come the light intensity that obtains is carried out record; Because the disturbance that different flabellums alternately bring during blower fan work is to have periodically, the variation of the refractive index that causes also is periodic, this periodic disturbance meeting makes the fluctuation of the detection light light intensity generating period in experience flow field, the function of photodetector real-time detection can obtain this disturbance information, sample frequency and the hits of control data acquisition card control data carry out real time record to information, processor is processed these data and is shown, the information after process can be easy to obtain the information of pulsed gas laser draught fan impeller disturbance.
The present invention obtains the disturbance information that blower fan rotates by the mode of optical measurement, has the advantages that measurement mechanism is simple, precision is high, easy to operate, has very strong practicality.
Description of drawings
Fig. 1 is the gas circulation flow system sectional view of pulsed gas laser;
Fig. 2 is the installation drawing that the draught fan impeller disturbance is measured in the pulsed gas laser;
Fig. 3 is the installation drawing of the spot size that receives of aperture control photodetector photosurface;
The hot spot that Fig. 4 obtains for the unlimited equal thickness fringes of Mach Zehnder device furnishing the time, wherein the center solid area is the spot area that is incident upon on the detector photosurface;
Fig. 5 is the live signal that photodetector detects, and wherein (a) is before the work of pulsed gas laser blower fan; (b) be the work of pulsed gas laser blower fan after;
Fig. 6 (a) is for carrying out the signal behind the High frequency filter to live signal; (b) frequency-region signal for carrying out obtaining after the Fast Fourier Transform (FFT) (FFT), wherein horizontal ordinate is frequency, ordinate is the amplitude size of disturbing signal under the respective frequencies.
Embodiment
Before the blower fan work, the Mach Zehnder interference device is adjusted to the thick striped of unlimited equal thickness interference, namely the optical path difference of Mach Zehnder interference system two-way light beam is the integral multiple of wavelength, and this moment, light intensity I size was as can be known by the two-beam interference principle:
I＝4I
0cos
2(kΔ)＝4I
0 (1)
Wherein k is wave vector, and Δ is the optical path difference of two-beam, I
0Light intensity magnitude for each road light beam.The size of light intensity is definite value before the blower fan work as can be seen from the above equation.When working, blower fan can cause the optical path difference Δ of two-way light beam in the Mach Zehnder interference system to change, and the variation of optical path difference Δ mainly to be the gas refracting index that causes when being worked by blower fan change produces, so the staggered disturbance meeting of fan leaf makes output intensity also produce the one-period disturbance.Photodetector can carry out real time record to light intensity magnitude, obtains the variation relation of light intensity time.Because it is periodic that the light intensity that causes of draught fan impeller disturbance changes, it is relevant that the cycle T of this fluctuation and the sheet of the rotation speed n of blower fan and impeller are counted N, can be expressed from the next:
T＝1/Nn (2)
Because the impact of air turbulence and other environmental factor, can in the signal that photodetector real-time detects, produce ambient noise signal, need to adopt the way of digital signal processing that the live signal that measures is processed, change time-domain signal into frequency-region signal, cyclical signal is extracted from ground unrest, thereby obtain the information of draught fan impeller disturbance.The present invention is based on above-mentioned principle design and form, the present invention is further detailed explanation below in conjunction with accompanying drawing and example.
As shown in Figure 2, pulsed gas laser blower fan disturbance measurement mechanism provided by the invention, it mainly comprises exploring laser light light source 201, beam-expanding system 202, the first spectroscope 203, the second spectroscope 206, the first catoptron 204, the second catoptron 205, photodetector 207, data acquisition unit 208 and processor 209.
Spectroscope 203 and 206, catoptron 204 and 205 consists of the Mach Zehnder interference system, and catoptron 204 and spectroscope 206 lay respectively at the two ends of tested flow field regions 100.Exploring laser light light source 201, beam-expanding system 202 and the first spectroscope 203 are positioned on the same light path successively, photodetector 207 is positioned on the emitting light path of the second spectroscope 206, data acquisition unit 208 is electrically connected with photodetector 207, and processor 209 is electrically connected with data acquisition unit 208.
During work, the light beam of exploring laser light light source 201 emissions is divided into two-way light by spectroscope 203 after beam-expanding system 202 expands, wherein one road light is successively through catoptron 205 and spectroscope 206 reflections, after another road light reflects through catoptron 204, successively by tested flow field regions 100 and spectroscope 206, the dot projection of two-way light after spectroscope 206 overlaps is on photodetector 207 surfaces, by the sample frequency f of data acquisition unit 208 control signals
sCount N with sample, and the data that obtain are transferred to processor 208 carry out digital signal processing and shown.The photosurface size of described photodetector is 1～3mm
2, the spot size after expand (decide according to the observation window size of measured pulse gas laser), thus the sensitivity of measurement increased; If the area of detector is larger, can by method as shown in Figure 3, by between spectroscope 206 and photodetector 207, adding aperture 301, control the size of the hot spot that projects photodetector 207 surfaces by the size of control aperture 301.
The laser of exploring laser light light source 201 emission after beam-expanding system 202 expands by tested flow field regions 100, described exploring laser light light source 201 can be the Nd of frequency multiplication: the YAG laser instrument, beam-expanding system 202 is the beam-expanding system that is comprised of lens, and its multiplying power that expands is decided according to the observation window size.
Utilize the method for above-mentioned measurement mechanism ranging pulse gas laser crossflow fan disturbance, it mainly comprises following step:
(1) adjustment of experimental provision
Determine the size of pulsed gas laser observation window, and then the enlargement ratio of definite beam-expanding system, the detecting light beam after guaranteeing to expand can cover whole observation window, obtains large measured zone; Be projeced into the surface of photodetector 207 behind the light beam process Mach Zehnder interference device after expanding.
(2) data acquisition
Data sampling frequency f by control collector 208
sCount N with sample, the signal that photodetector 207 is produced carries out record.For fear of aliasing, should guarantee sample frequency f
sTested disturbing signal frequency greater than twice.For fast digital signal being carried out Fourier transform, sample is counted N=2
γ, γ is integer.Carry out after the digital signal processing getable minimum frequency space on the frequency axle, namely frequency resolution F satisfies F=f
s/ N, under the certain condition of sample frequency, the size that can control N obtains the resolution sizes of needs.
(3) processing of time-domain signal
The noise signal that can comprise some high frequencies in the signal, processor 209 take first the data processing method of filtering that signal is carried out pre-service, filter out high-frequency signal; And then adopt Fast Fourier Transform (FFT) (FFT) that the signal that gathers is processed, the periodic disturbance signal of time domain is converted to the signal of frequency domain, and obtains the signal collection of illustrative plates.
(4) size of deterministic disturbances
In the signal collection of illustrative plates after FFT processes, horizontal ordinate is the frequency of corresponding periodic perturbation signal, and ordinate is the amplitude size of disturbing signal under the respective frequencies, and what wherein true origin was corresponding is the mean value size of signal.Determine the disturbance of draught fan impeller by the peak value of frequency-region signal, and the frequency of deterministic disturbances and size, the amplitude of this disturbance and the ratio of the amplitude of initial point are the relative size of tested draught fan impeller disturbance.
Below in conjunction with being example at pulsed gas laser, wherein rotation speed of fan is 1400rpm, and the draught fan impeller number is 24, and the observation window zone is 24mm * 16mm.Adopt the disturbance of the draught fan impeller of apparatus of the present invention system paired pulses gas laser to measure, by this embodiment technical scheme of the present invention be described in further detail:
(1) before blower fan rotates, the laser beam that the spot size of exploring laser light light source 201 emission is about 1.5mm after beam-expanding system 202 expands 20 times by tested flow field regions, regulate the Mach Zehnder interference system, make its acquisition light spot shape as shown in Figure 4, because the photosurface area of photodetector 207 is 4.8mm
2, therefore placed aperture 301 in its front, be incident upon spot area on 207 of the photodetectors shown in solid black zone among the figure.
(2) in conjunction with above-mentioned experiment condition, by formula (2) the forcing frequency 588Hz of draught fan impeller as can be known, the sample frequency of data acquisition unit 208 should greater than this frequency, be made as 10 in the experiment
5Hz.Output under this sample frequency size is shown in Fig. 5 (a), and the disturbance among the figure mainly is that the disturbance by air causes, and this disturbance makes output intensity at I
MaxNear disturbance, these all are the ground unrests of signal.During blower fan work, the light intensity that photodetector 207 receives has corresponding strong and weak the variation, and its output signal is shown in Fig. 5 (b).
(3) data of blower fan work postscript record are carried out filtering shown in Fig. 6 (a) after the filtering, partial data (the sample number size is 1024) among Fig. 6 (a) is carried out image after Fast Fourier Transform (FFT) is processed shown in Fig. 6 (b), wherein horizontal ordinate is the frequency of corresponding periodic perturbation signal, and ordinate is the amplitude size of disturbing signal under the respective frequencies.
(4) second peak value among Fig. 6 (b) is corresponding with the disturbance that draught fan impeller causes, and its frequency and size are respectively 586Hz and 0.034.Convenient it has carried out normalized with the signal of real time record in order to process in the experiment, and the direct current output before being undisturbed is normalized to 1, and the amplitude that obtains after then processing through data-signal is the size of Relative Perturbation.
In sum, the present invention well small sample perturbations of paired pulses gas laser draught fan impeller measures, and has preferably accuracy and higher precision, and method is easy, has very strong operability.
Claims (4)
1. the measurement mechanism of pulsed gas laser crossflow fan impeller disturbance, it is characterized in that, it comprises exploring laser light light source, beam-expanding system, the first spectroscope, the second spectroscope, the first catoptron, the second catoptron, photodetector, data acquisition unit and processor;
The first spectroscope, the second spectroscope, the first catoptron and the second catoptron consist of the Mach Zehnder interference system jointly, and the first catoptron and the second spectroscope are respectively applied to be placed on the two ends of tested flow field regions; Exploring laser light light source, beam-expanding system and the first spectroscope are positioned on the same light path successively, and photodetector is positioned on second spectroscopical emitting light path, and data acquisition unit is electrically connected with photodetector, and processor is electrically connected with data acquisition unit.
2. the measurement mechanism of described pulsed gas laser crossflow fan impeller disturbance according to claim 1 is characterized in that, the photosurface size of described photodetector is 1mm
2～3mm
2
3. the measurement mechanism of described pulsed gas laser crossflow fan impeller disturbance according to claim 1 is characterized in that, the exploring laser light light source is the Nd:YAG laser instrument of frequency multiplication.
4. method of utilizing the disturbance of the described measurement mechanism ranging pulse of claim 1 gas laser crossflow fan impeller is characterized in that:
The 1st step made detecting light beam cover the whole observation window of laser instrument, adjusted the Mach Zehnder interference device, obtained a uniform light spots on the surface of photodetector;
The 2nd step control data sampling frequency f
sCount N with sample, make sample frequency f
sGreater than the tested disturbing signal frequency of twice, the signal that photodetector is produced carries out record;
The 3rd step processor carries out filtering to the signal that receives to be processed; Again signal is carried out Fast Fourier Transform (FFT) and process, the periodic disturbance signal of time domain is converted to the signal of frequency domain, obtain the signal collection of illustrative plates, horizontal ordinate is the frequency of corresponding periodic perturbation signal, and ordinate is the amplitude size of disturbing signal under the respective frequencies;
The 4th step was determined the disturbance of draught fan impeller, and the frequency of deterministic disturbances and size by the peak value of frequency-region signal in the signal collection of illustrative plates, the amplitude of this disturbance and the ratio of the amplitude of initial point are the relative size of the disturbance of tested draught fan impeller.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103674471A (en) * | 2013-12-02 | 2014-03-26 | 中国农业大学 | Intelligent acquisition device for material suspension location parameters |
| CN107870160A (en) * | 2017-11-13 | 2018-04-03 | 西安工业大学 | A kind of measuring method of optical material face refractive index |
| CN110530923A (en) * | 2019-08-05 | 2019-12-03 | 西安交通大学 | A kind of the film cooling flowing and Experimental Study of Heat Transfer Characteristics test macro of band crossing current |
| CN113074902A (en) * | 2021-03-15 | 2021-07-06 | 华中科技大学 | Quantitative release test device for throwing object |
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| CN102323445A (en) * | 2011-06-14 | 2012-01-18 | 华中科技大学 | Method for measuring flowing velocity of recycle gas in multiple laser cavity |
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Patent Citations (2)
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| CN1844873A (en) * | 2006-05-22 | 2006-10-11 | 中国科学院光电技术研究所 | Supersonic speed flow field detection system based on H-S wave front sensor and detection method thereof |
| CN102323445A (en) * | 2011-06-14 | 2012-01-18 | 华中科技大学 | Method for measuring flowing velocity of recycle gas in multiple laser cavity |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103674471A (en) * | 2013-12-02 | 2014-03-26 | 中国农业大学 | Intelligent acquisition device for material suspension location parameters |
| CN103674471B (en) * | 2013-12-02 | 2015-12-09 | 中国农业大学 | Material suspended location parameter intelligent acquisition device |
| CN107870160A (en) * | 2017-11-13 | 2018-04-03 | 西安工业大学 | A kind of measuring method of optical material face refractive index |
| CN110530923A (en) * | 2019-08-05 | 2019-12-03 | 西安交通大学 | A kind of the film cooling flowing and Experimental Study of Heat Transfer Characteristics test macro of band crossing current |
| CN113074902A (en) * | 2021-03-15 | 2021-07-06 | 华中科技大学 | Quantitative release test device for throwing object |
| CN113074902B (en) * | 2021-03-15 | 2022-01-11 | 华中科技大学 | Quantitative release test device for throwing object |
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