ID#: 172
Abstract Title: The Effect of Nitrates on Deflagration to Detonation Transition
Session Title: DDT
Session Date: 7/31/01
Session Start Time: 8:30 AM
Contributing Author: Pinard, P.F.
Organization: McGill University
Country: Canada
Authors: P. Pinard, A.J. Higgins, J.H.S. Lee, S.B. Murray
Short Abstract: Renewed interest in pulse detonation engines has focused attention on the problem of deflagration to detonation transition (DDT) in fuel-air mixtures. A prohibitively large deposition of energy is required for direct initiation of higher-hydrocarbon fuels in air. Consequently, a method is sought to reduce the run-up distance for DDT. It has been proposed that the addition of nitrate-based sensitizers typically used in diesel fuels could increase the sensitivity of hydrocarbon fuel-air mixtures by increasing the chemical kinetic rates, resulting in a reduction in run-up distance. Experiments were carried out in order to quantify the effect of NO2 addition to propane-O2-N2 mixtures. The run-up distance was established for a baseline C3H8-O2-N2 mixture at 293 K and 1 atm. NO2 was then added to this mixture as a 1% to 10% fuel additive, and finally O2 was added to the baseline mixture in order to achieve the same stoichiometry. The results show a comparable reduction in run-up distance for both NO2 and O2 experiments, indicating that the effect of NO2 is energetic rather than kinetic. It is also found that the propagation in the turbulent flame regime is comparable for both the baseline and the sensitized mixtures. This confirms that the majority of flame acceleration over the run up distance to detonation is dominated by turbulent mixing. It also suggests that a significant reduction in run-up distance would ideally be achieved through a dual approach involving a mechanism for enhancing the turbulent mixing phase, and chemical sensitization for the final onset of detonation.