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Project WP-2612 sought to develop and test measurement technology that would support the characterization of airborne particulate and gas-phase emissions generated from the use of metal-based energetics and pyrotechnic formulations.
The two technical objectives were to:
A sampling platform was designed and constructed with enough flexibility that it could be adapted to contain detonation or combustion test facility, as well as to take ground-level ambient samples of plumes from OB/OD activities or live-fire tests.
The main distinguishing features of the platform were: 1) the use of multiple mass flow controllers to precisely distribute particle laden air that has been routed from one sample port through a single PM10 (particulate matter with aerodynamic diameter smaller than 10 micrometers) selective inlet through to multiple filter collection and other measurement devices; 2) a relatively high flow rate of 113.5 liter per minute that enables collection of PM10 material on filter media in a relatively short period of time; 3) flexibility in adding or removing instrumentation with minimal impact; and 4) a rapid sample-air to clean-air port switching mechanism which provided the ability to instantly collect plume samples without any startup time or delays in achieving designed flowrates during sample platform operation.
The sampler filter ports were equipped with three types of filter media: Teflon™, quartz fiber, and Teflon-impregnated glass fiber followed by a selective resin column. A multi-stage impactor device was connected to a sampling port and used to collect size-segregated particle samples. Product gases including carbon dioxide, carbon monoxide, and oxides of nitrogen were sampled in real-time through a sample port using a gas analyzer. Particle concentration by light scattering was also measured in real-time. All real-time data were logged by a remote computer that also controlled the functions of the sampling apparatus. Filter media were analyzed with multiple techniques including gravimetric weighing to determine loading levels, X-ray fluorescence spectroscopy, ion chromatography, liquid chromatography, gas chromatography, and thermal optical reflectance/ transmittance.
Testing consisted of the detonation of thirteen test articles and one blank in a confined detonation test chamber (DTC), followed by sampling of the plume with the measurement platform. Twelve of the test articles consisted of combinations of two energetics (PBXN-113 and PBXN-114) and two casing materials for the article (brass and stainless steel with tin insert). The thirteenth test article was a booster-only device.
The main result of the test effort was the successful implementation of the sampling platform and the proof of its use in conjunction with the DTC. Overall, the platform performed as expected and the magnitude of the sample flowrate and ability to distribute the sample air to multiple filters and instruments made for very efficient and flexible sample collection. This experience also provided areas where improvement can be sought and enabled assessment of the testing platform for use in other configurations and for other energetic formulations.
Additional results specific to the testing conducted included:
In all, the platform used for measurements in this SEED project was flexible enough to be used in future DTC-based testing of explosives (< 200 grams) and propellants (small arms). In-situ testing in an outdoor setting expands the list of test article to include large energetic devices, pyrotechnics, large device propellants, and rocket motors. One caveat is that the plume must have a portion that is at or near ground level (i.e., can be reached by elevated ground-based sample line) for at least a short period of time, so that sample materials could be channeled through an inlet line. Other than pyrotechnics all of these test articles are available at NAWCWD China Lake along with personnel and facilities to conduct both indoor and outdoor testing.