Blast Mitigation Using Water Mist

Abstract

Approved for public release; distribution is unlimited. REPORT DOCUMENTATION PAGE Form Approved RTGOMB Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR / MONITOR'S ACRONYM(S)Office of Naval Research One Liberty Center 875 North Randolph Street 11. SPONSOR( MONITOR'S REPORT Arlington, VA 22217-1995 NUMBER(S) DISTRIBUTION I AVAILABILITY STATEMENTApproved for public release; distribution is unlimited.13. SUPPLEMENTARY NOTES *Marioff, Inc., Linthicum, Maryland ABSTRACTA series of experiments demonstrating the mitigation of water mist on the over-pressure effects of a TNT detonation have been conducted. A series of TNT charges, 0.9 kg (2 lb), 2.2 kg (5 lb) and 3.2 kg (7 lb), were detonated both with and without employing a water mist system. The TNT detonations were characterized by five measurements: initial blast over-pressure start time, peak, and impulse, as well as quasi-static pressure and start time. The initial blast over-pressure peak and impulse, as well as quasi-static pressure were reduced by the presence of water. These experiments show that the use of water mist to mitigate the over-pressure effects of a high explosive detonation is an extremely promising concept.

Blast Mitigation Using Water Mist: Test Series II

“…The size and magnitude of the charges detonated specified the chamber size and dimensions used for the test series. The previous test series [13]. That chamber was rated for overpressures associated with 4.5 kg (10 lbs) detonations of TNT.…”

“…The pump provides the capability of delivering water at a constant flow and pressure (maximum 194 lpm at 120 bars). As a result, a steady state water mist composition inside the chamber was achieved and maintained, unlike the previous test series [13,14]. Figure 3 shows the pump configuration (please note only two of the pumps were required for these tests) and Table 3 provides the pump motor specifications and capacity.…”

“…Emphasis was placed on comparing and determining the mitigating efficiency of the water mist on explosives whose chemical composition and reaction process were different than that of TNT. [13].…”

“…Studies indicate an explosion, in such an environment, would create reflecting shock waves that could cause additional increases in overpressures, thus causing even further damage to the ship [12]. The other concern is the amount of time and water mist needed to effectively achieve blast mitigation in the event of an attack [13].…”

“…The objective of the studies was to utilize lower charge density explosions of 0.9 kg, 2.2 kg, and 3.2 kg (2 lbs, 5 lbs, and 7 lbs) TNT to establish the ability of water mist to mitigate the overpressures associated with detonations in a confined space. The studies showed that quasi-static overpressures were reduced by as much as 47%, and both the start of the initial blast overpressure and quasi-static pressures were delayed [13]. The water mist characterization studies indicated that mitigation was achieved with droplet sizes ranging from 35 -550 μm with a Sauter Mean Diameter (SMD) greater than 50 μm [14].…”