Dynamic Vivacity and Its Application to Conventional and Electrothermal-Chemical (ETC) Closed Chamber Results

Report No. ARL-TR-2631
Authors: William F. Oberle
Date/Pages: December 2001; 57 pages
Abstract: Historically, dynamic vivacity has been used extensively in propellant lot acceptance. More recently, dynamic vivacity has been used in the analysis of closed chamber experimental data to assess propellant grain surface area behavior during combustion. The objective of this report is to (a) examine the physical meaning of dynamic vivacity; (b) theoretically explore the behavior of dynamic vivacity for conventionally ignited charges of various geometries, including layered propellant charges; and (c) determine the appropriate method for applying dynamic vivacity to electrothermal-chemical (ETC) closed chamber data. The results presented indicate that dynamic vivacity is a robust statistic for assessing grain surface area behavior during combustion as long as the burn rate exponent in Vielle's Law is between approximately 0.7 and 1.0. If the burn rate exponent is greater than 1.0, the nature of the propellant surface area deduced from the dynamic vivacity appears to be distorted. In these cases, the dynamic vivacity always indicates a progressive grain geometry. From the cases studied, it appears that grain fracture during combustion will not significantly change the dynamic vivacity results unless the original grain possess a progressive grain geometry and the fractured grain pieces are relatively large. Finally, it appears that ETC ignition does not impact the shape of the dynamic vivacity curve but only affects the magnitude of the curve.
Distribution: Approved for public release
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Last Update / Reviewed: December 1, 2001