为快速地、 大范围地对天然气管道进行泄漏监测, 设计了基于静态傅里叶变换干涉系统的甲烷气体浓度遥测系统。 采用对准甲烷分子吸收峰的红外光源照射被测区域, 再由聚光准直系统和干涉模块完成干涉条纹的获取。 最后, 通过多特征波长光谱分析算法计算被测区域的浓度程长积, 进而反演相应的甲烷浓度。 通过HITRAN光谱数据库选择了1.65 μm的主特征吸收峰, 从而光源使用1.65 μm的DFB激光器。 为了在不增加系统硬件结构的基础上提高检测精度及稳定性, 引入辅助波长求解吸光度比值, 进而通过多特征波长比例运算的方法获得被测气体的浓度程长积。 实验针对泄漏速度恒定的标准甲烷液化气罐检测, 采用PN1000型便携式甲烷检测仪的检测数据作为标准数据与本系统的测试数据进行对比, 测试距离分别为100, 200和500 m。 实验结果显示, 甲烷浓度检测值在泄漏一段时间稳定后, 系统检测值也基本保持稳定。 对100 m的检测距离而言, 浓度程长积的检测误差小于1.0%。 随着测试距离的增大, 检测误差也相应的增大, 距离500 m的检测误差小于4.5%。 总之, 在气体泄露稳定后系统检测误差均小于5.0%, 满足野外天然气泄漏遥测要求, 该方法采用差分思想, 在求解吸光度比率的过程中将误差消除, 降低了外界干扰造成的误差, 从而提高系统的检测精度及稳定性。

In order to be able to quickly, to a wide range of natural gas pipeline leakage monitoring, the remote detection system for concentration of methane gas was designed based on static Fourier transform interferometer. The system used infrared light, which the center wavelength was calibrated to absorption peaks of methane molecules, to irradiated tested area, and then got the interference fringes by converging collimation system and interference module. Finally, the system calculated the concentration-path-length product in tested area by multi-wavelength characteristics spectrum analysis algorithm, furthermore the inversion of the corresponding concentration of methane. By HITRAN spectrum database, Selected wavelength position of 1.65 μm as the main characteristic absorption peaks, thereby using 1.65 μm DFB laser as the light source. In order to improve the detection accuracy and stability without increasing the hardware configuration of the system, solved absorbance ratio by the auxiliary wavelength, and then get concentration-path-length product of measured gas by the method of the calculation proportion of multi-wavelength characteristics. The measurement error from external disturbance is caused by this innovative approach, and it is more similar to a differential measurement. It will eliminate errors in the process of solving the ratio of multi-wavelength characteristics, and can improve accuracy and stability of the system. The infrared absorption spectrum of methane is constant, the ratio of absorbance of any two wavelengths by methane is also constant. The error coefficients produced by the system is the same when it received the same external interference, so the measured noise of the system can be effectively reduced by the ratio method. Experimental tested standards methane gas tank with leaking rate constant. Using the tested data of PN1000 type portable methane detector as the standard data, and were compared to the tested data of the system, while tested distance of the system were 100, 200 and 500 m. Experimental results show that the methane concentration detected value was stable after a certain time leakage, the concentration-path-length product value of the system was stable. For detection distance of 100 m, the detection error of the concentration-path-length product was less than 1.0%. With increasing distance from tested area, the detection error is increased correspondingly. When the distance was 500 m, the detection error was less than 4.5%. In short, the detected error of the system is less than 5.0% after the gas leakage stable, to meet the requirements of the field of natural gas leakage remote sensing.