In order to elucidate the propagation mechanism of detonations, the failure mechanism of detonations propagating in tubes with porous walls is investigated experimentally. Two distinct failure mechanisms were identified depending on the type of detonating mixture. Experiments in mixtures characterized by piecewise laminar reaction zone structures with weak three-dimensional effects revealed that the attenuation and failure is caused by the global mass divergence to the porous, permeable walls. The limits observed in these mixtures agreed very well with the theoretical limiting conditions for the existence of curved ZND detonations subjected to lateral expansions. / Experiments were also conducted in a second class of mixtures, characterized by irregular cellular structures and turbulent reactions zones. When detonations in this class of mixtures are attenuated, transverse waves re-amplify from local instabilities in the reaction zone. This re-amplification permits the detonation wave to continue to propagate and overcome the effects of global mass divergence and transverse wave attenuation at the porous walls. Ultimately, when the rate of transverse wave re-generation is surpassed by the rate of transverse wave damping at the walls, the detonation can no longer be self-sustained and fails. The limits obtained in these irregular structure mixtures were found significantly wider than predicted by the ZND formulation, thus further confirming the important role of the three-dimensional turbulent structure in these detonations in providing a more efficient mechanism of gas ignition and propagation than detonations that exhibit a regular structure. / The implications of the present study are that the ZND model is not valid in describing the reaction zone structure, the ignition mechanism and thus the propagation mechanism in these turbulent detonations. In these mixtures, the ignition mechanism is a combination of the classical mechanism of adiabatic shock compression leading to ignition as well as the intense turbulent mechanism usually attributed to deflagrations only.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.84420 |
| Date | January 2003 |
| Creators | Radulescu, Matei Ioan |
| Contributors | Lee, John (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Mechanical Engineering.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001983831, proquestno: AAINQ88563, Theses scanned by UMI/ProQuest. |
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