Design Of A Miniaturized Acetylene Gas Detection System Based On TDLAS Technology

Acetylene is a kind of flammable and explosive gas which is mainly used in the field of metal welding.At present,conventional methods for acetylene detection include catalytic combustion method,electrochemical method and gas chromatography,but these methods have disadvantages such as poor selectivity,large sensor drift and long pretreatment time.The application of TDLAS technology in the detection of acetylene gas concentration has the advantages of high selectivity,short response time,high detection accuracy and strong stability,which can make up for the shortcomings of other detection methods.This thesis Based on TDLAS technology developing a gas detection system for acetylene.Based on the analysis of the molecular absorption spectroscopy of gas,the infrared absorption line used for the determination of acetylene concentration was selected.The theory analysis and theoretical derivation of the basic theory of TDLAS technology--Bill Lambert's law,and the key technology--wavelength modulation technology and harmonic detection technology are completed,providing theoretical support for the design of acetylene gas concentration detection system.Completed the overall design of TDLAS acetylene gas detection system,including the main control module,laser current drive module,laser temperature control module,photoelectric signal acquisition and processing module and communication module.In particular,this thesis fully consider the advantages and disadvantages of the single and double optical path in gas detection method,this thesis proposes a way for TDLAS technology of single photon time-division multiplexing background noise removal laser modulation scheme,this scheme can be from two aspects of the effects of dc and ac factors to remove background noise,and simplify the system complexity,reduce the size of our system;In addition,an adjustable optical path gas chamber is designed.Controlling the optical path adjusting rod can effectively change the optical path of the laser passing through the gas in the gas chamber,and increase the optical path by means of multiple reflections,so as to achieve the purpose of small volume and long optical path.Finally,this thesis completed the calibration of the designed acetylene detection system,and carried out experiments from the system detection error,detection accuracy,detection stability and Detecting Uniformity.The experimental data show that when the acetylene gas in the concentration range of 10-1000 ppm,the detection accuracy of the system is 10 ppm,the detection error decreases with the increase of the detection concentration,and the system has good stability and uniformity for the detection of acetylene gas concentration.