A novel leakage sensing system of hydrogen transportation pipeline based on hybrid UWFBG array

In response to the intrinsic constraints of traditional single-parameter pipeline leakage detection, this paper proposes a hybrid ultra-weak fiber Bragg grating (UWFBG) array with alternating chirped and narrowband gratings of low reflectivity. The microporous Pt/WO₃ sensing material is combined with narrowband gratings to fabricate hydrogen sensors, while adjacent chirped gratings form vibration sensors. The demodulation system incorporates wavelength division multiplexing (WDM) to integrate homodyne coherent detection with tunable laser-based distributed wavelength demodulation, facilitating simultaneous monitoring of pipeline vibrations and ambient hydrogen concentration. This configuration enables multi-parameter sensing of hydrogen concentration and vibration in hydrogen transportation pipelines. Under constant pressure conditions, the experiment designed in the lab simulated hydrogen pipeline leaks with varying hole sizes, resulting in hydrogen accumulation around the leakage site. The hybrid UWFBG array was helically deployed along the pipeline. The findings revealed a quadratic correlation between the time-domain standard deviation of the leakage vibration signal and the leakage hole size, alongside a quartic relationship between the slope of wavelength shift and the leakage hole size. This validates the viability of utilizing the hybrid UWFBG array for leakage detection in hydrogen pipelines. Moreover, the integration of hydrogen concentration and vibration signals offers novel perspectives for subsequent leakage classification and localization.