Influence of pyrolysis failure thresholds on burst pressure prediction of 70 MPa type III hydrogen tanks under fire exposure

Accurately predicting the burst time and pressure of hydrogen storage tanks (HSTs) is critical for the safety of hydrogen fuel cell vehicles. This study investigated how pyrolysis failure thresholds influence burst pressure predictions for high-pressure HSTs in fires. The burst pressure of a 48L-70 MPa tank under fire conditions was 112.3 MPa, a 46.5 % decrease from its room-temperature hydraulic burst pressure (209.77 MPa). The failure temperatures and decomposition heat of the carbon fiber composite were analyzed under nitrogen and air atmospheres at different mass loss ratios. Using thermal flux from a standard bonfire test for simulation, the burst time and pressure were predicted. The most accurate predictions, closely matching experimental results (burst time: 1322 s, pressure: 112.30 MPa), occurred under a 12 % mass loss ratio in an air atmosphere (burst time error ≤3.1 %, pressure error ≤12.5 %) and 12 %–14 % ratios in nitrogen (time error ≤3.4 %, pressure error ≤13.5 %). • Critically pyrolysis failure threshold influence on prediction accuracy. • Proposes a standard failure prediction procedure for tanks under fire scenarios. • Conducted hydraulic burst tests and fire-induced burst test on a 70 MPa tank. • Effects of atmosphere and mass loss ratio on tank burst pressure and time. • Recommends a 12–14 % mass loss failure threshold under nitrogen atmosphere.