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Title: The Enhancement of Gas Pressure Diagnostics in the P-ODTX System

Abstract

The One Dimensional Time to Explosion (ODTX) system at the Lawrence Livermore National Laboratory is a useful tool for thermal safety assessment of energetic material. It has been used since 1970s to measure times to explosion, threshold thermal explosion temperature, thermal explosion violence, and determine decomposition kinetic parameters of energetic materials. ODTX data obtained for the last 40 years can be found elsewhere.

Authors:
 [1];  [1];  [1];  [1];  [1]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1305893
Report Number(s):
LLNL-TR-700708
DOE Contract Number:
AC52-07NA27344
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY

Citation Formats

Hsu, Peter C., Jones, Aaron, Tesillo, Lynda, Strout, Steven, and Ellsworth, Fred. The Enhancement of Gas Pressure Diagnostics in the P-ODTX System. United States: N. p., 2016. Web. doi:10.2172/1305893.
Hsu, Peter C., Jones, Aaron, Tesillo, Lynda, Strout, Steven, & Ellsworth, Fred. The Enhancement of Gas Pressure Diagnostics in the P-ODTX System. United States. doi:10.2172/1305893.
Hsu, Peter C., Jones, Aaron, Tesillo, Lynda, Strout, Steven, and Ellsworth, Fred. 2016. "The Enhancement of Gas Pressure Diagnostics in the P-ODTX System". United States. doi:10.2172/1305893. https://www.osti.gov/servlets/purl/1305893.
@article{osti_1305893,
title = {The Enhancement of Gas Pressure Diagnostics in the P-ODTX System},
author = {Hsu, Peter C. and Jones, Aaron and Tesillo, Lynda and Strout, Steven and Ellsworth, Fred},
abstractNote = {The One Dimensional Time to Explosion (ODTX) system at the Lawrence Livermore National Laboratory is a useful tool for thermal safety assessment of energetic material. It has been used since 1970s to measure times to explosion, threshold thermal explosion temperature, thermal explosion violence, and determine decomposition kinetic parameters of energetic materials. ODTX data obtained for the last 40 years can be found elsewhere.},
doi = {10.2172/1305893},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2016,
month = 8
}

Technical Report:

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  • Incidents caused by fire and other thermal events can heat energetic materials that may lead to thermal explosion and result in structural damage and casualty. Thus, it is important to understand the response of energetic materials to thermal insults. The One-Dimensional-Time to Explosion (ODTX) system at the Lawrence Livermore National Laboratory (LLNL) has been used for decades to characterize thermal safety of energetic materials. In this study, an integration of a pressure monitoring element has been added into the ODTX system (P-ODTX) to perform thermal explosion (cook-off) experiments (thermal runaway) on PETN powder, PBX-9407, LX-10-2, LX-17-1, and detonator samples (cupmore » tests). The P-ODTX testing generates useful data (thermal explosion temperature, thermal explosion time, and gas pressures) to assist with the thermal safety assessment of relevant energetic materials and components. This report summarizes the results of P-ODTX experiments that were performed from May 2015 to July 2017. Recent upgrades to the data acquisition system allows for rapid pressure monitoring in microsecond intervals during thermal explosion. These pressure data are also included in the report.« less
  • A standard ODTX test configuration was designed and proven for 12.7 mm dia. x 50.8 mm long and 25.4 mm dia. x 76.2 mm long test samples. The results from plastic-bonded explosives (LX-10, PBX 9501, X-0298, PBX 9502, RX-26-AF and PBX 9502) suggest a shortened sample and larger heater contributed to achieving a near isothermal test environment. The ODTX test is used to establish safe pressing temperatures for large explosive parts.
  • In a series of papers researchers at Lawrence Livermore National Laboratory (LLNL) have reported measurements of the time to explosion in spheres of various high explosives following a rapid, uniform increase in the surface temperature of the sphere. Due to the spherical symmetry, the time-dependent properties of the explosive (temperature, chemical composition, etc.) are functions of the radial spatial coordinate only; thus the name one-dimensional time-to-explosion (ODTX). The LLNL researchers also report an evolving series of computational modeling results for the ODTX experiments, culminating in those obtained using a sophisticated heat transfer code incorporating accurate descriptions of chemical reaction. Althoughmore » the chemical reaction mechanism used to describe HMX decomposition is quite simple, the computational results agree very well with the experimental data. In addition to reproducing the magnitude and temperature dependence of the measured times to explosion, the computational results also agree with the results of post reaction visual inspection. The ODTX experiments offer a near-ideal example of a transport process (heat transfer in this case) tightly coupled with chemical reaction. The LLNL computational model clearly captures the important features of the ODTX experiments. An obvious question of interest is to what extent the model and/or its individual components (specifically the chemical reaction mechanism) are applicable to other experimental scenarios. Valid exploration of this question requires accurate understanding of (1) the experimental scenario addressed by the LLNL model and (2) details of the application of the model. The author reports here recent work addressing points (1) and (2).« less
  • What will be discussed in this report represents a framework upon which multiphase and other real physical effects can be built. Chemical models of increasing complexity are envisioned and this methodology can provide a tool for evaluating new ideas against known experimental data. The recent work to be reported here addresses the multiphase issue of temperature deviation between phases undergoing chemical and heat transport processes. Modeling of the LLNL ODTX experiment will be performed with FLUENT, a commercially available computational fluid dynamics (CFD) code. FLUENT solves flows in 2D or 3D in Cartesian, cylindrical, or general curvilinear coordinates, with steady-statemore » of fully time-dependent analysis. Multiphase flows in which two or more continuous phases are present can be solved with arbitrary volumetric sources of heat, mass, momentum, and chemical species applied through user-defined FORTRAN subroutines. FLUENT models these of phenomena by solving the conservation equations for mass, momentum, energy, phasic volume fraction, and chemical species for each phase using a control volume based finite difference method. The equations are solved using SIMPLE-like algorithms with an iterative line-by-line matrix solver and multigrid acceleration. Before considering the temperature deviation issue and its dependence upon gaseous bubble diameter in a multiphase system, the author discusses the use of FLUENT for modeling the basic constant and uniform density LLNL ODTX problem. Following the discussion of the temperature deviation in the multiphase treatment, the author discusses possible extensions of this work to include more advanced multiphase effects such as surface reactions within bubbles and gas phase transport out of the HE sample.« less
  • Cross-comparison of the results of two computer codes for the same problem provides a mutual validation of their computational methods. This cross-validation exercise was performed for LLNL's ALE3D code and AKTS's Thermal Safety code, using the thermal ignition of HMX in two standard LLNL cookoff experiments: the One-Dimensional Time to Explosion (ODTX) test and the Scaled Thermal Explosion (STEX) test. The chemical kinetics model used in both codes was the extended Prout-Tompkins model, a relatively new addition to ALE3D. This model was applied using ALE3D's new pseudospecies feature. In addition, an advanced isoconversional kinetic approach was used in the AKTSmore » code. The mathematical constants in the Prout-Tompkins code were calibrated using DSC data from hermetically sealed vessels and the LLNL optimization code Kinetics05. The isoconversional kinetic parameters were optimized using the AKTS Thermokinetics code. We found that the Prout-Tompkins model calculations agree fairly well between the two codes, and the isoconversional kinetic model gives very similar results as the Prout-Tompkins model. We also found that an autocatalytic approach in the beta-delta phase transition model does affect the times to explosion for some conditions, especially STEX-like simulations at ramp rates above 100 C/hr, and further exploration of that effect is warranted.« less