Experimental study on hydrogen pipeline leakage: Negative pressure wave characteristics and inline detection method

This paper presents an experimental study on a potential safety system for hydrogen fuel cells. It focuses on early leakage detection and localization. This would enable effective system response to avoid the effects of catastrophic loss of containment. Experimental results are presented from a pipeline setup wherein the leak is identified utilizing inline pressure sensors and flowmeters. The investigations involve recorded data at two leak locations at different initial pressures, mass flow rates, and leak diameters. The leak detection technique is based on analysis of the negative pressure wave (NPW) intensity and propagation duration, denoted as peak-to-peak amplitude (Δh) and oscillation period (Δτ). They are extracted from filtered pressure records' first derivative (dp/dt). Δh and Δτ increase as the initial mass flow rate and leak diameter decrease. Therefore, this approach is advantageous for detecting leaks from tiny cross-sections. Δh and Δτ measured at two leak positions at different lengths from the system inlet increase at a higher initial flow rate of 1.0 g/s, but they exhibit opposite behavior at a lower rate (0.42 g/s). Increasing the sampling rate in the dp/dt-time graphs enhances the precision of leak localization. Calculation results show an effective leakage localization with an accuracy of 15 mm (2.5%). The leak flow rate during nitrogen leakage tests is about three times that of hydrogen, and it has higher Δh (about two times at 10 bar).