The effect of activation-to-energy release on near limit detonations

• Detonation regularity is experimentally explored through activation energy and heat release rate. • Data shows regular detonations with low activation energies and high heat release. • The results are independent of gas dynamic effects. • This is validated using nine mixtures that are statistically significant with over 600 tests. The regularity of cellular detonation has been studied canonically to have a strong dependence on the effective activation energy (ε i ) of the mixture. Other chemical properties, such as heat release rate (HRR), have also been identified as possible influences on detonation regularity. Activation energy and heat release rate are experimentally investigated to resolve a relationship between chemical properties to predict cellular regularity. To examine these parameters, nine mixtures were selected that isolated each constraint over a range of heat capacity ratios to incorporate the underlying gas dynamic effects. To determine statistically significant regularity, each mixture had over 30 realizations in an automated high aspect ratio linear detonation facility. The resulting data showed similar dependences on ε i and HRR, with mixtures of low ε i and high HRR yielding the most regular detonations. A ratio of activation energy to heat release rate that definitively compares the amount of energy required to initiate a reaction to the amount of heat emitted by that reaction, is established as an experimentally derived indicator of detonation cell regularity.