乙炔气体浓度的TDLAS在线监测

Acetylene gas concentration on-line monitoring using TDLAS

介绍了利用可调谐半导体激光吸收光谱(TDLAS)技术实现乙炔浓度在线监测的研究。该系统通过复合调制信号调制近红外分布反馈式二极管激光器(DFB LD)作为光源,光纤耦合器将激光分为两束,分别通过0.5 m封闭短光程气体吸收池和参考光路,双路接收采集含有气体浓度信息的测量光信号和参考光信号送后级处理,应用快速傅里叶变换(FFT)得到含有气体浓度信号的各次谐波检测分量,实现乙炔浓度信息反演,其中多次平均、数字滤波及背景扣除等数字信号处理技术被用于提高系统信噪比。通过理论分析和试验系统实验证明,该系统在软、硬件上的设计可以满足乙炔气体的在线监测,且系统体积小,光路调试和标定简单,便于实际应用。

A novel acetylene concentration on-line monitoring system using the tunable diode laser absorption spectroscopy（TDLAS） technology was introduced. Near infrared （MR）distribute feedback laser diode （DFB LD） was used as light source, 0.5 m short path absorption cell, 16-bit analog-to-digital data- acquisition card obtains four channels data which should be processed by a personal computer, four channels obtain separately by varying the laser wavelength using different temperature and different light paths （signal light path and reference light path）. Wavelength modulation spectroscopy（WMS） technique is slowly ramping the wavelength by scaning weak absorption lines of acetylene. Fast Fourier transform （FFT） analysis obtains the harmonic signal of absorption spectrum in the harmonic detection （HD）. Because interfered by residual amplitude modulation and the laser small dc drift, some digital signal processing techniques such as mean value, digital filtering and background correction are implemented to improve the signal-to-noise ratio. Both theory analysis and experimental results show that the sensitivity of this system can meet the needs of transformer incipient fault diagnosis, which structure is compact and its calibration and adjustment of lightl path are easy.