Detection of Acetylene by Photoacoustic Spectroscopy with Near-infrared Fiber Laser
|School||Dalian University of Technology|
|Keywords||Acetylene Photoacoustic spectroscopy Tunable erbium-doped fiber laser Harmonic Detection|
With the vigorous development of China's power industry, industrial and mining electrification and power consumption continues to improve, all kinds of transformers increasingly wide range of applications. During operation may result in breakdown characteristics of gases in the transformer oil. Acetylene as the fault feature one of the gases in the transformer oil is an important symbol of the transformer internal fault category and severity. Therefore, accurate monitoring of the concentration of acetylene gas production and to ensure the safety of life has a very important significance. With the development of optical fiber sensing technology and laser spectroscopy detection technology, optical gas detection technology has been widely Research and Application. On this basis, we propose a the acetylene gas photoacoustic spectroscopy detection method based on near-infrared light source - tunable erbium-doped fiber laser (TEDFL). This application of quantum mechanics and molecular spectra theoretical analysis the acetylene molecule near-infrared 1.5 m absorption band energy level transitions of the mechanism system discussed the intensity of the absorption band distribution of the fine structure and absorption broadening, to carry out spectral detection of acetylene gas a theoretical basis. Designed and implemented means of a near-infrared gas absorption spectroscopy experiments, theoretical analysis to be verified from the experiments, gives the exact position of the absorption lines in the near-infrared acetylene gas 1.5 m absorption band and absorption intensity of broadening variation , provides an important reference data for the next photoacoustic detection system. While the apparatus can be used to detect the concentration of acetylene gas, the maximum detection sensitivity of up to 36ppm. Designed and implemented a set of near-infrared photoacoustic spectroscopy of acetylene gas detection system. The first use of a low cost tunable erbium-doped fiber laser as a light source to replace the relatively expensive cost of the tunable semiconductor laser. Select acetylene molecules near infrared 1.5 m pan-frequency absorption band P9 peak as a test absorption peak, combined with the second harmonic of wavelength modulation and lock-in amplifier technology, to improve the signal-to-noise ratio of the photoacoustic detection at a relatively low The excitation light source power to obtain a higher limit detection sensitivity. The experimental results show that, under atmospheric pressure, the second harmonic signal with the true concentration of acetylene gas showed a good linear relationship, the maximum detection sensitivity of up to 15 ppm. This study trace gas spectral detection equipment, low-cost and industrial applications research laid the foundation.