Airblast Attenuation and Flow Loss Performance of Passive Attenuators

摘要

An analytical/experimental program was conducted for Waterways Experiment Station (WES) to develop a passive airblast attenuator to protect hardened shelters from conventional weapon attack. The role of a passive attenuator is to provide protection through attenuation of air shock, which would otherwise enter air ducts, damaging sensitive air filtration and decontamination equipment, electronic and mechanical systems, and injuring building occupants. The design constraints placed on the passive attenuator were that it have no moving parts, be inexpensive, and require no maintenance. Further, air flow loss under normal operating conditions was not to exceed 2.0 in.-H(2)O at 500 ft/min. The goal was 99% attenuation of both pressure and impulse. A Phase I analytical study evaluated the feasibility of using Suppressive Shields concepts for passive attenuators. A series of orifice plates was found to offer less resistance to normal air flow, yet equal or exceed the attenuation levels of any of the Suppressive Shields concepts. The Phase II experimental work included both airblast attenuation and flow loss measurements, and evaluated six concepts, three of which were orifice plate designs. The flow loss requirement proved to be very stringent, and measured losses were greater than analytical predictions. Airblast attenuation levels of 86 to 92% were measured with several orifice plate designs, but with 10 to 14 in.-H(2)O pressure drop. Two orifice plate concepts achieved 80 to 85% attenuation of both pressure and impulse at the 2.4 in.-H(2)O requirement. Departing from orifice plate designs in an attempt to improve performance, three concepts were evaluated that directed the shock wave into holding chambers. The best of these designs achieved 87-9596 attenuation, with a flow loss of 2.6 in.-H(2)O at 500 ft/min.