Critical Evaluation and Modeling of Solid Propellant Dark Zone Experiments
ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
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The dark zone DZ region is a curious phenomenon in low pressure approximately 5 - 100 atm flames of combusting solid propellants. The chemistry controlling low pressure DZ structure has recently been shown to be crucial to combustion properties of these propellants at higher pressures, as in guns. The present work focuses on quantitative testing of a model of DZ structure based on a detailed chemical mechanism. A critical survey of the literature was performed to find sufficiently complete experimental datasets. Modeling then was performed, comparing predicted DZ ignition delay times, tauDZ, from the model with experimental results obtained by converting the DZ lengths to corresponding times for convective flow. Predictions were mostly within a factor of two of experiment. Most can be made to agree by changes of initial DZ temperature input to the model within the error limits of measured temperature values. The model captures the proper trends with pressure and DZ mixture ratio. However, many of the predicted tauDZ results were too long, and few too short, a concern that is discussed. Work which could elucidate whether there might be an important mechanism error and key reactions within the DZ are briefly discussed.
- Physical Chemistry
- Combustion and Ignition