Tunable diode laser absorption spectroscopy (TDLAS), owing to its high selectivity, sensitivity, and fast response, has been widely employed for monitoring methane leakage in urban natural gas pipelines. However, variations in ambient temperature and pressure can alter the absorption spectral lines, thereby reducing the accuracy of concentration measurements. To address this issue and improve measurement reliability, a 1654 nm DFB laser was adopted as the light source, and methane (CH4) at different concentrations was used as the target gas for testing under conditions of 263–323 K and 0.6–1.1 atm. To handle temperature effects, we developed two corrections: one for direct absorption spectroscopy (DAS) that integrates line-strength variation with a system-error compensation coefficient, and another for wavelength modulation spectroscopy (WMS) based on dual-peak combined intensity, while pressure effects were mitigated via a least-squares correction. The temperature correction reduced the maximum relative errors of DAS and WMS from about 30 % and 20 % to around 2 %, respectively, while the pressure correction decreased the maximum relative error from 3.69 % to 1.05 %. Allan deviation analysis indicated that the sensor achieved a minimum detection limit (MDL) of 4.41 ppm at an integration time of 30 s. In a 24-hour continuous monitoring test conducted under fluctuating temperature conditions, the maximum relative errors for measuring 1 × 104 ppm CH4, after applying the correction formulas, were reduced to 1.92 % for DAS and 0.84 % for WMS. This study provides a novel and effective approach to enhancing gas concentration measurement accuracy in urban natural gas pipeline leakage detection and related industrial applications.
扫码关注我们
求助内容:
应助结果提醒方式:
