Simultaneous temperature and CO-concentration time-history measurements during the pyrolysis and ultra-fuel-rich oxidation of ethanol, diethyl ether, n-heptane, and isooctane behind reflected shock waves

This article presents a comparative study on the effectiveness of ventilation to mitigate blasting effects on chambers subjected to confined detonations of high explosives. The pressure time-history that acts on the chamber walls is described by three components: (1) the first shock wave, (2) the train of re-reflected shock waves, and (3) the gas pressure. The radial response of spherical chambers is described by the radial breathing mode and modeled by an equivalent single degree of freedom system. The three pressure components are considered for the calculation of the maximum ductility ratio, which is obtained from the numerical solution of the single degree of freedom chamber response. It is assumed that openings reduce the gas pressure but they have an insignificant effect on shock waves. The dynamic response of fully and partially confined chambers are calculated and compared. Results show that intermediate/small openings (less than 10% of the surface of the chamber) are ineffective to mitigate the chamber response and damage. The vibratory response of the chamber is susceptible to elastic or plastic resonance but it is not considerably modified by the long-term gas pressure because of its high radial breathing mode frequency, allowing concluding that ventilation is ineffective to reduce the maximum response of spherical chambers subjected to internal high explosive explosion.

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Time-Resolved Measurements of Intermediate Concentrations in Fuel-Rich n-Heptane Oxidation Behind Reflected Shock Waves

Volume 4A: Combustion, Fuels and Emissions ◽

10.1115/gt2017-63344 ◽

2017 ◽

Cited By ~ 2

Author(s):

Zachary E. Loparo ◽

Joseph G. Lopez ◽

Sneha Neupane ◽

Subith S. Vasu ◽

William P. Partridge ◽

...

Keyword(s):

Shock Waves ◽

Shock Tube ◽

Chemical Kinetics ◽

Continuous Wave ◽

Time Resolved ◽

Ethylene Concentration ◽

Reflected Shock ◽

Concentration Time ◽

Time Histories ◽

Kinetics Of

The chemical kinetics of the oxidation of n-heptane (C7H16) — an important reference compound for real fuels — are well studied at stoichiometric and lean conditions. However, there is only limited information on the chemical kinetics of fuel-rich combustion. In order to improve the accuracy of chemical kinetic models at these conditions, the oxidation of rich n-heptane mixtures has been investigated. Combustion of n-C7H16/O2/Ar mixtures at equivalence ratios, ϕ, of 2.0 behind reflected shock waves has been studied at temperatures ranging from 1075 to 1418K and at pressures ranging from 1.6 to 1.9atm. Reaction progress was monitored by recording ethylene (C2H4) concentration time-histories and initial n-heptane decay rates at a location 2cm from the endwall of a 13.4m long, 14cm inner diameter shock tube. Ethylene and n-heptane concentration time-histories were measured using absorption spectroscopy at 10.532μm from a tunable CO2 laser and at around 3.4μm from a continuous wave distributed feedback interband cascade laser (ICL), respectively. The measured concentration time-histories were compared with modeled predictions from the Lawrence Livermore National Lab (LLNL) detailed n-heptane reaction mechanism. To the best of our knowledge, the current data are the first time-resolved n-heptane and ethylene concentration measurements conducted in a shock tube at these conditions.

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