VIUALIZATION OF FLAME ACCELERATION AND DDT IN AN OBSTRUCTED TUBE
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Authors
Hashemi Mehr, Shervin
Date
Type
thesis
Language
eng
Keyword
Flame acceleration , Detonation propagation , DDT , DDT run-up distance
Alternative Title
Abstract
Self-luminous high-speed photography was used to study flame acceleration and DDT inside a fully transparent round tube filled with equally distanced orifice plates. The combustion tube was 288 cm long with an inner diameter of 7.6 cm. Two sets of orifice plates (50% BR and 75% BR) were used. Stoichiometric ethylene-oxygen diluted with nitrogen or argon was used primarily in this study. The reactivity of mixtures was controlled by the initial pressures. Stoichiometric hydrogen-oxygen with 70% and 80% argon dilution were also used to check the effect of cell structure regularity on DDT. The average combustion velocity was measured using high-speed video data. Soot foils were used to determine detonation propagation mechanism, as well as for detonation cell size measurement.
The DDT criterion based on the ratio of the orifice plate opening diameter and the detonation cell size (d/λ≥1) was verified for the 50% BR but was conservative for higher blockage ratios. For 75% BR a galloping detonation mode that travels at an average velocity below the product's speed of sound influences the determination of the DDT limit in the traditional manner based on the velocity. The use of large argon dilution was found to not influence the propagation mechanism and flame acceleration behavior. Also, 70% argon dilution had no noticeable effect on the critical d/λfor 50% BR, and a very small effect for 80% argon dilution, however, the effect was more noticeable for 75% BR. Generally, large argon dilution increases the cell structure's regularity. Soot foil records obtained for 70% and 80% argon dilution show that the structure is very regular but not significantly more than for the nitrogen diluted ethylene mixtures.
DDT run-up distance was obtained using high-speed videos and soot foils. It was determined that the Silvestrini correlation predicts the DDT run-up distance successfully for reactive mixtures. However, for mixtures near the limit, the DDT run-up distance was significantly larger. A basic correlation for the DDT run-up distance was proposed based on the concept of flame acceleration to fast-flame followed by DDT induction distance that depends on the detonation cell size and activation energy.
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ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
CC0 1.0 Universal