An acoustic framework for quantifying hydrogen leakage flow rates in next-generation liquid-hydrogen-cooled superconducting cables

Liquid-hydrogen-cooled superconducting cables, owing to their high power density, near-zero-resistance power transmission capability, and deep integration with hydrogen energy systems, are regarded as a promising direction for future power grids. However, unavoidable liquid hydrogen leakage —which rapidly undergoes flash boiling and transitions into a high-speed gaseous hydrogen jet after release into the ambient environment—still lacks effective quantitative assessment methods. In this study, a systematic acoustic framework is developed to remotely and quantitatively estimate hydrogen leakage flow rates. Controlled leakage experiments are conducted, first revealing an approximately linear frequency shift of the dominant spectral line at low flow rates, associated with shear-layer instabilities of the gaseous hydrogen jet and governed by jet velocity and leak geometry, as well as a linear increase in integrated acoustic energy within the 20–52 kHz band at higher flow rates. Second, a spectral line–background subtraction method is proposed, enabling robust extraction of narrowband dominant leakage components from broadband turbulent backgrounds. Third, a quantitative mapping between leakage flow rate and multidimensional acoustic features is established: in the low-flow regime (3–8 slm), the characteristic spectral-line frequency enables flow-rate estimation with a maximum relative error of ±2.65%, while in the higher-flow regime (8–10 slm), the integrated acoustic energy in the 20–52 kHz band provides a linear mapping with a maximum relative deviation of ±0.47%. This work provides a new technical pathway for early identification and remote, non-contact quantitative estimation of hydrogen leakage in liquid-hydrogen superconducting cables, which is of significant importance for promoting the safe and reliable operation of liquid-hydrogen superconducting power transmission systems. • A linear shift of characteristic spectral lines at low leakage flow rates is identified. • A quasi-linear increase in band-integrated acoustic energy at higher flow rates is observed. • A spectral line–background subtraction method is proposed to extract narrowband components. • A mapping between leakage flow rate and multidimensional acoustic features is established.