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Research on Detection for Concentration of Methane Gas Based on Lateral Shearing Interferometer

Author: ZhangXueFeng
Tutor: GaoYuBin
School: University of North
Course: Precision instruments and machinery
Keywords: Shearing interferometer the spectral resolution support vector machines themethane gas concentration visual programming platform
CLC: TN247
Type: PhD thesis
Year: 2013
Downloads: 103
Quote: 0
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In China, the mine gas monitoring system is relatively imperfect, so security incidentshappened by the underground gas explosion, the number of deaths accounted for almost halfof all mine; In many of the major natural gas transmission pipeline, natural gas leak causedeconomic losses is an important problem in the process of natural gas supply; In daily life,casualties had occurred by gas leak explosion. Gas, natural gas is a generic term for a varietyof gases, methane (CH4) is the mainly Composition. The traditional equipment for detectingconcentration of methane gas is often difficult to meet the high precision, fast response andgood stability, so research of the method for concentrationm of methane, which is rapid andaccurated is very important. In response to this urgent need, this paper proposes a new type oftransverse shear optical structure, a new lateral shearing interferometer system is designedbased on the optical structure, applied to the detection of methane gas concentration.The main method of the methane gas concentration detector, the domestic an internationalresearch situation, the basic concepts and theory of the infrared absorption measurement wereintroduced. the characteristics of the spectrum analysis method is high-precision, nopoisoning detection,real-time response. Take advantage of the characteristics of the spectrumanalysis method, the interferometer system is designed based on a new type of transverseshear optical structure. Studied the mechanism of the optical path difference distributionfunction and shearing interference fringes by Lateral Shearing terferometer. Based on thespectral data obtained by the discrete Fourier transform, Spectral analysis algorithm wasdesigned, and the corresponding software algorithms was researched and developed.The system is composed of the characteristics of gas corresponding to the infrared laserlight source, Collimated beam expander, gas detection chamber, the double-angle mirrorstructure, CCD detector, signal processors, and visual programming platform structure. Foroptical interferometer system is stable, well-used outdoor, the system uses double-anglemirror optical path to the protection. Meanwhile, using complementary eliminate vibrationdesign, full consideration to the outdoor conditions, vibration interference fringes imagingoptical system. Among them, the double-angle mirror design, the stability of the optical pathwhen the interference of the light path offset, the optical path is only generated in the samedirection displacement offset, and two coherent beams of light to produce the offset will not cause uneven error. The connecting rods are designed to make the beam splitter to generatelinkage effects in the vibration impacts, so that the error introduced by the1mirror of equalsize, in the opposite direction from2mirror in the form of offset, theoretically completelyeliminate the interference of the vibration, in fact, a slight error. This design greatly increasedthe stability of the optical system, it does not affect the flux and the optical path differencescanning range of the interference system.In order to ensure the characteristics of the structure of the high spectral resolution, highflux, the lateral shearing interferometer system characteristics of the basic principles of theinterference fringes, and analyzed using spectroscopic forward and reverse rotation of theoptical path difference limits. Calculated the optical path difference through the connectingrod structure complementary effect to the coherence technique, Fourier optics, photoelectricdetection based on lateral shearing interferometer system to maintain the original opticalcharacteristics on the basis of scanning through a circular pathinstead of the traditional lineartrack scan, to achieve the design ideas of the connecting rod to eliminate vibrationinterference.Visualization platform to develop on the basis of a lateral shearing interferometer systemarchitecture design, the spectral distribution function analyze algorithms and software. Systemuses a support vector machine analysis to complete the solving of the characteristicwavelength, the spectral distribution function and the calculation of the methane gasconcentration, and Microsoft Visual Studio platform data input, Fourier transform, spectralcalibration and analyze of the concentration of methane gas and other functionsto achieve anddisplay.Experiment with indoor vibration environment and outdoor environment to test thedistribution function of the laser spectroscopy, analyzed of the stability and accuracy of theinterferometer system. The experimental results show that, under laboratory conditions,almost non-existent due to interference, Spectral analysis of the two interferometer systemcapacity is close. Traditional interference in the spectral distribution function of theinterference fringes of the system inversion obvious deformation and offset, and Based on thenew lateral shearing interferometer for the spectral distribution function is unchanged,indicating that the system has good stability. On this basis, we completed detectionexperiments for the methane gas concentration. The experiments show that the spectroscopy device of the system compared with indoor applications shows that the interference in theoutdoor case, the detection of stability of this system is much higher.

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CLC: > Industrial Technology > Radio electronics, telecommunications technology > Photonics technology,laser technology > Laser technology, the maser > Optical detection techniques
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