Pathological detonations in mono-disperse spray media Articles uri icon

publication date

  • July 2024

start page

  • 1

end page

  • 7

issue

  • 1-4, 105505

volume

  • 30

International Standard Serial Number (ISSN)

  • 1540-7489

Electronic International Standard Serial Number (EISSN)

  • 1873-2704

abstract

  • Detonation waves differ from deflagration fronts in several distinct properties, with perhaps the most significant distinction being the supersonic propagation and pressure variations of the former. In the absence of additional supporting mechanisms and non-ideal effects, the supersonic speed can be accurately predicted by considering the global properties associated with the state of the fresh mixture. Specifically, at the Chapman-Jouguet (CJ) speed, the velocity is determined by the maximum expansion that the hot products can undergo associated with the attainment of the sonic condition at the end of the reaction zone. However, there is a specific mode of propagation known as pathological (or eigenvalue) detonation when the sonic condition is not achieved at the end of the reaction zone but occurs at an intermediate finite distance from the shock. This type of detonation can occur when endothermic effects are present in the system, resulting in the formation of an internal frozen sonic point, where the local thermicity becomes negligible. This condition is typically associated with the presence of two or more irreversible steps describing the overall chemical reaction that ends with a final endothermic process. The propagation speed of the detonation is then determined by the placement of the sonic locus at the neutrally thermal zone, which depends on the internal profiles. Then, this kind of detonation resembles a deflagration as it is influenced by its inner structure to determine its speed. In turn, the subsequent supersonic region uncouples part of the endothermic effects from the detonation driving mechanism, resulting in greater propagation speeds. In this study, we find that pathological detonations can also occur when the fuel exists in multi-phase state, so endothermic fuel vaporization dominates at the end of the non-equilibrium region. The range of occurrence of pathological detonations increases with the Stokes number and the fuel equivalence ratio of the fuel liquid phase.

subjects

  • Chemistry
  • Industrial Engineering
  • Renewable Energies

keywords

  • sprays; detonations; chapman-jouguet; pathological detonations