The transition from deflagration to detonation is studied by focusing on the actual final process, i.e. the onset of detonation itself. The high speed deflagration prior to transition is obtained by suppressing the oscillatory structure of a detonation first. A theoretical model is developed to analyze the resulting deflagration complex which shows that it propagates close to half the CJ detonation velocity with the deflagration slowly separating from the leading shock. These high speed deflagrations thus obtained just prior to transition to detonation as well as the highly turbulent fast deflagrations that have been observed prior to transition in earlier studies are shown to be CJ deflagrations where the propagation velocities are governed by energetics rather than the flow structure. / To understand how the nonsteady behavior of detonations may affect the transition process, the one-dimensional pulsating detonation is analyzed by computational studies. The time averaged solution of the non-overdriven detonation over a cycle is found to recover the steady CJ solution and the independence of the far rearward boundary condition is demonstrated for the activation energies studied. The self-oscillatory nature of the detonation also plays a key role in the maintenance, failure, and re-establishment of the detonation structure. To study the onset of detonation, the high speed deflagration obtained by failing the detonation is subsequently perturbed with periodic disturbances to stimulate transition. The numerical simulations show that the perturbations undergo a frequency selective amplification process to accelerate transition where the optimal frequency is related to the chemical reaction time of the detonation. The existence of optimal perturbation frequencies to stimulate transition is also observed in the experimental investigation carried out, although its value appears to depend on the channel dimension. Based on the oscillatory and frequency selective nature of the detonation phenomena, an oscillator model is proposed. An equation that has the basic features of a mechanical oscillator has been derived for the pulsating detonation. The proposed oscillator concept indicates the need to examine detonation phenomena from the point of view of a resonant oscillator.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.41314 |
| Date | January 1993 |
| Creators | Chue, Randy Shek-Ming |
| Contributors | Lee, John H. (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 Electrical Engineering.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001357574, proquestno: NN91875, Theses scanned by UMI/ProQuest. |
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