Unified theory of ignition limits for unconfined and confined releases of hydrogen and gas dilutions into atmospheric air

A unified theory is presented for predicting hydrogen jet ignition limits for unconfined and confined releases for any driven-section tube shape. Experimental data for ignition limits are obtained from the literature and used for calculating the minimum shock strength required for ignition as a function of the ratio between tube length and effective diameter (L/D_eff). It is found that the minimum shock strength required for ignition is independent of the driver-gas composition and driven-section tube shape when using the effective diameter. Furthermore, conservative correlations are proposed for the minimum shock strength required for ignition. The minimum shock strength required for ignition becomes constant at the value of 12.3 at L/D_eff=7.0. Our new approach can conservatively estimate all existing experimental results for the ignition limits. Finally, ignition limits under arbitrary conditions for hydrogen dilutions are predicted for the first time. The theory presented in this work can be used for hydrogen safety purposes.