Venting dynamics of compressed natural gas from vehicle pressure relief devices: Experiments and computational fluid dynamics modeling

This study investigates the venting behavior of compressed natural gas from passenger vehicle fuel tanks through temperature-triggered pressure relief devices at full capacity (200 bar). Experimentally measured mass loss rates were calculated to provide gas source boundary conditions for compressed natural gas dispersion modeling and to support evaluation of methods for predicting gas flow from pressurized systems in accidental releases. Using air as a venting gas, near-field flow patterns were qualitatively analyzed, revealing four characteristic regimes: (1) air entrainment from behind the vehicle, (2) left rear wheel recirculation, (3) forward-directed flow under the car, and (4) right rear wheel free jet. These regimes were confirmed in a full-scale vehicle fire test, demonstrating the relevance of the observed flow patterns for real fire scenarios and providing an experimentally supported framework for hazard assessment and risk evaluation of accidental compressed natural gas release.