On the measure of the relative detonation hazards of gaseous fuel-oxygen and air mixtures

The critical energy for direct initiation of spherical detonation for eight gaseous fuels (C 2 H 2 , C 2 H 4 , C 2 H 4 O, C 3 H 6 , C 2 H 6 , C 3 H 8 , CH 4 and H 2 ) have been measured using a planar detonation from a linear tube for initiation. On the basis of the minimum value of the critical energy (corresponding to about the stoichiometric composition) a dimensionless parameter D H is defined by the ratio of the minimum energy of the fuel to that of acetylene-oxygen mixture. The magnitude of D H is then used for comparing the relative detonation sensitivity of the various fuels. Based on the values of D H for fuel-oxygen mixtures, it is found that ethylene oxide with a value of D H ⋍10 is about 10 times less sensitive than acetylene (D H =1). The olefins (i.e., ethylene and propylene) having values of D H ⋍10 2 are about 100 times less sensitive than acetylene. The alkanes (i.e., propane, ethane, etc.) have values of D H ⋍10 3 with the exception of methane which is particularly insensitive with a value of D H ⋍10 5 . Hydrogen is found to be similar to the normal alkanes with a value of D H ⋍10 3 . Fuel-air mixtures in general have values of D H about 10 6 times larger than the corresponding values for the same fuel with pure oxygen. The relative sensitivities of the various fuels remain the same for fuel-air mixtures as in the case of fuel-oxygen mixtures.