Image credit: F. Veiga-Lopez et al.Abstract
The influence of ozone on quasi-steady curved detonations was numerically studied in stoichiometric H 2-air and DME-O 2 (-CO 2) mixtures with 0%, 0.1% and 1% O 3 addition. Detonation speed-curvature (D-κ) relations were determined for both fuels. The H 2-air mixture has one critical point related to high-temperature chemistry whereas the DME-O 2 (-CO 2) mixture has two critical points, one sustained by high-temperature chemistry, and the other supported by low-temperature chemistry. O 3 addition significantly increases the curvature at all the critical points by speeding up both high-and low-temperature chemistry. Two mechanisms were found to be responsible for the results. First, O 3 addition increases the rate of reaction initiation by fast decomposition to provide O radical via O 3 (+M) = O 2 + O (+M). The dominant reaction with fuel therefore changes from a chain propagation reaction to a fuel + O radical chain branching reaction during the initial stage, which establishes the radical pool more rapidly. Second, O 3 influences the reaction pathways. For H 2-air with 1% O 3 , H + O 3 = O 2 + OH becomes the most important reaction for OH radical and heat generation during the initial stage. For DME-O 2-CO 2 , O 3 changes the respective contributions of competing low-temperature chemistry reactions, i.e. CH 3 OCH 2 = CH 2 O + CH 3 vs. CH 3 OCH 2 + O 2 = CH 3 OCH 2 O 2 and CH 2 OCH 2 O 2 H = 2CH 2 O + OH vs. CH 2 OCH 2 O 2 H + O 2 = O 2 CH 2 OCH 2 O 2 H. The change of dominant reactions either enhances (0.1% of O 3) or eliminates (1% O 3) the negative temperature coefficient behavior. Our study contributes to the detailed understanding of the thermo-chemical impact of ozone on detonation limits.
Fernando Veiga López
Assistant professor of Fluid Mechanics
Passionate researcher on hydrogen combustion for safety and power generation.