Distribution Statement A/Unlimited
Characterizing the Pressure Gain of Magazines due to Convective Combustion of M1 Gun Propellant
Brian T. Bojko; Naval Air Warfare Center Weapons Division; China Lake, CA, USA
Nathaniel Davis; Naval Air Warfare Center Weapons Division; China Lake, CA, USA
Cynthia Romo; Naval Air Warfare Center Weapons Division; China Lake, CA, USA
Ephraim Washburn; Naval Air Warfare Center Weapons Division; China Lake, CA, USA
Alice I. Atwood; Naval Systems Integrated; Ridgecrest, CA, USA
Josephine Covino; Department of Defense Explosives Safety Board; Alexandria, VA, USA
Keywords: Convective Combustion, CFD, Modeling, H1.3, M1, Pressurization
Abstract
Experimental results of the deflagration of M1 gun propellant, an HD1.3 material, are used to develop
a burning-rate versus pressure model to be used in large scale simulations. The burning-rate model of
the M1 is used as the boundary condition for a propellant within a magazine after it has been ignited.
To validate the approach and determine the effects of combustion temperature on magazine
pressurization, detailed two-dimensional simulations are conducted and compared to the small-scale
experiments. The pressure gain in the simulations were within 5% of the experimental data for
combustion temperatures of 2800 − 3000K. After validation of the model at small scales, a three-
dimensional large-scale combustion simulation of a vented magazine was conducted for varying
loading densities and venting areas. Results are presented showing the effects of Mach number and
internal pressure as a function of the vent-area-ratio at different loading densities.
Introduction
Safe storage of energetic material is currently determined by a safety distance function that is proportional
to the weight of the hazardous material. However, weight-based methods are insufficient in determining safe
distances when HD1.3 systems ignite and deflagrate within a structure, increasing the internal pressure and inducing
choked flow at the exit resulting in violent ejections of energetic materials. To increase the safety of such systems, it
is critical to explore the loading densities and venting areas of the storage facilities to evaluate risks of propellant
deflagration.
The rest of this study is organized as follows. First, a brief description of the experimental setup that was
used to develop and validate the numerical models is presented. Then, the mathematical formulation of the burning-
rate versus pressure model is developed from the small-scale experimental data. The multi-dimensional,
compressible Navier-Stokes equations with Large Eddy Simulations (LES) to account for combustion and
turbulence effects is presented. This model is used for both the 2D and 3D detailed and large-scale combustion
simulations, respectively. Results of a two-dimensional detailed simulation of the combustion of M1 propellant in a
poly-carbonate tube are presented for different combustion temperatures and compared to experimental data for
model validation. The burning-rate model and combustion temperature are then combined and used to simulate a
large-scale magazine structure at varying loading densities (LD) and vent-area-ratios (VAR). Simulation results of
the magazine structure are presented and discussion on effects of LD and VAR are presented. Conclusions are drawn
regarding the burning-rate model and its validation in the 2D simulations, along with the results of the large-scale 3D
simulations. Finally, Appendix A offers an example of the collaboration between experimentalists and modelers, and
how the two approaches can compliment one another to answer important scientific questions.
