Effect of initial pressure and temperature on hydrogen-air detonations with ignition promoters

Emerging detonation-based engines like rotating detonation engines (RDE) encourage the study of detonation stability and propagation limits. Operating these combustors at wide operating conditions like different initial pressures, temperatures, and equivalence ratios is a challenging task since the stability and detonability limits in such cases are significantly affected. In the present study, ZND calculations are performed to study the effects of varying equivalence ratios, initial pressures, temperatures, and ignition promoters like ozone and hydrogen peroxide on detonation parameters. The role played by the ignition promoters in widening the detonability limits at lower equivalence ratios for hydrogen-air gaseous detonations is also investigated. Our results show that ignition promoters, when added in trace amounts, significantly reduces the induction length/time for hydrogen-air gaseous detonations. However, they do not seem to affect the reaction length and time scales (radical generation and recombination zone) significantly. Present calculations show that ignition promoters do not affect the gas dynamics and thermodynamic states of the gaseous mixtures when added in trace amounts. Fuel-sensitization also affects various detonation dynamic parameters where it lowers the activation energy parameter, stability parameter and enhances the energy release rates, which can be used for widening the detonability limits and hence the operating temperature limits of detonation-based engines. The results also suggest similar detonability for H2-air mixtures at very low initial pressures and elevated initial temperatures for a broader range of equivalence ratios. The detonation dynamics were found to be sensitive to initial pressure and temperature over a range of equivalence ratios.