Research On CO,C₂H₂ Absorption Spectroscopy In Near Infrared And Measuring Instruments Miniaturization

With the rapid development of world industrialization,people's demand for hydrocarbon fuel energy is increasing,so the emission of carbon monoxide?CO?increases year by year.CO not only causes great pollution to atmospheric environment,but also threats people's health.Hydrocarbon fuel energy acetylene?C₂H₂?is one of the most basic chemical raw materials.It has flammable and explosive properties.It is very dangerous if it leaks out.Therefore,the detection of dangerous gases,such as CO and C₂H₂,with high sensitivity and high-speed is of great significance.Compared to the traditional gas detecting technologies,such as electrochemical and chromatogram,laser spectroscopy has the advantages of high sensitivity,high resolution,fast response and the non-intrusion,so it has been widely used in real-time and on-line monitoring dangerous gases.In this paper,we adopt self-balanced differential technology and wavelength modulation technology to suppress noise and improve signal-to-noise ratio.Spectral parameters is vital for spectroscopic measurement,but the spectroscopic parameter of HITRAN database is partly from theoretical calculation or obtaining from ideal experimental measurement,so it is necessary for driving the spectral parameters before practical measurement under complex conditions.We adopt home-made laser driver,multi-pass absorption cell and digital phase-locked amplifier to study the gas detection system based on TDLAS wavelength modulation technology.The main researches of the dissertation are as follows:?1?We employed tunable diode laser absorption spectroscopy?TDLAS?with self-balancing differential detection technology to suppress common mode noise from laser source and optic-mechanical vibration,and built a CO gas detection system.We are using the system measured the CO spectral lines(spectral line intensity of 2.26*10^-23cm^-1/(molecule×cm^-2))at the 6377.4 cm^-1 were used to analyze the performance of the system.The experimental result indicates that the measurement error of the gas detection system is less than 5%,the optimal detection time is 38s,and the detection limit is 47.8ppm.?2?We set up a C₂H₂ molecular absorption spectroscopy based on TDLAS technology,and used the system to study the spectroscopy line parameter of 6lines for C₂H₂ in the range of 6597-6613cm^-1 band.The deviation between our results and HITRAN database is less than 8%,which is the prerequisite for the instrumentation.?3?We realized the miniaturization of TDLAS instrument based on home-made designing laser driver,multi-pass cell and digital lock phase.Its volume is 60*30*23cm³ after miniaturization.We adopted temperature controller chip WTC3243 and current controller chip WLD3343 to and combined with STM32F103 to control and adjust the output power and central frequency of DFB laser.When the temperature is set at 25?,the accuracy of current is 0.02%.In this paper,the spectra of C₂H₂ were measured by wavelength modulation and multi-pass absorption cell technology.The experimental results indicate that the detection limit of C₂H₂ is estimated at 28ppb.