Research On Gas Concentration Measurements Under Conditions Of Weak Absorption Based On TDLAS

With the continuous development of industrialization and advanced science, for the requirements of economy, security and cleanness, gas concentration in the production and living of real-time monitoring put forward higher requirements. Relevant test technology have developed rapidly in recent years, Absorption spectrum technology, with its fast response, high sensitivity, easy operation and harsh conditions applicability, has become a key technology in measurement field. Tunable Diode Laser Absorption Spectroscopy technique has become the focus of many studies. It has been widely used in such as, ammonia in the process of power plant denitration escape rate measurement, air pollutants monitoring and extremely low concentration of gas in the aerospace industry measurement research and other fields, also have achieved good results.Based on the absorption spectrum and harmonic detection theory, we made the detailed description for TDLAS system, through numerical simulation and experimental validation of the way completed the following work. First, we designed the TDLAS experimental program for laboratory conditions, and then build the experimental platform to prove the superiority of this method, introduce the traditional direct absorption method briefly. Also, compare the measurement range and the measurement accuracy by experiment. Then, on the basis of previous studies add the Wight pool device, making effective optical path extended to 12 times the initial value, and applied directly to the experiment. Meanwhile, through improved the data processing method, the center frequency accuracy 6982.0678cm-1 measured at low concentrations of CO2 technique has been significantly improved. The experimental results show that, when the test gas concentrations as low as 100 ppm, TDLAS technique is still able to accurately measure. The measurement relative error is only about 2%. Finally, this paper introduced the continuous-wave ring-down spectroscopy, and made a preliminary study of its theory, This method has the advantages of multi-path length measurement, while its result is not affected by fluctuations in intensity. So, it has a better performance in the field of gas detection under conditions of weak absorption. The fifth chapter conducted a simulation of its superiority measure. At the same time we set up a preliminary experiment platform, through the experimental study, we got the same results with the previously simulation. This article is expected to be able to effectively promote the research and application of gas concentration measurements under conditions of weak absorption.