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Others
Modeling of deflagration of Unconfined Propane
We modeled the fast deflagration of unconfined propane vapor clouds of pancake shape. We used linear acoustic theory and a Taylor-type constant-velocity flame-piston formulation to estiĀmate bounds on
the overpressure. We showed that the results differ significantly from those obtained with the assumption of a spherically symmetric cloud or with a standard TNT analysis.
Explosions of Accidentally Released Fuels ā TNT Yields
For NASA, we compiled TNT yields reported for major explosions of accidentally released fuels such as propane and ethelyne oxide. To interpret a large scatter in the data, we delineated two factors: the
fraction of chemical energy released in the explosion; and the fraction of released energy transĀmitted to the blast. The later factor varied little and placed a theoretical upper limit on yield (which was
consistent with the data). The former factor was accident specific and varied significantly, thus contributing to the scatter in the data.
Hydrogen Safety -
After the Three Mile Island accident, EPRI invited Dr. Moussa along with a few selected experts to help them plan a program on hydrogen safety. The burning character of the hydrogen bubble inside the
reactor was discussed -- including the potential for deflagration and detonation. A quarter scale model of a reactor sector was selected to test fires under simulated conditions.
Design of Gas Spill Test Fires-
For the Coast Guard, we participated in the design of the (then) world's largest liquefied natural gas spill test fires (10,000 gallons). Both pool and vapor fires were tested. We calculated the
emissive power of LNG flames based on measurements of flame shapes and sizes and spectral and total radiation fields. Also, we identified and interpreted new and salient features of the dynamics of vapor fires.
Fires in Rapid Transit Systems-
For a major US transit authority, we modeled the growth of an undercar fire. The burning rate was assumed to follow a power law involved initially the polyurethane insulation in the wall cavity,
then the melamine panels, then the remaining combustible materials in the car. Two flow fields were analyzed. First, a fire-induced two-layer system with products of combustion moving away from the fire at the
top layer, and fresh. air moving towards the fire at the bottom. Second, a ventilation fan-induced (forced convection) flow field consisting of a single plug flow-type gas layer which contained initially fresh
air, but then, as it passed over the fire zone, it carried along the products of combustion. For each flow field, the build-up of smoke and heat was estimated as a function of time at various locations inside
the tunnel--until lethal conditions were reached.
Safety Evaluation of Fires in Tunnels -
We conducted a quick review of the proposed fire safety practices for the Eurotunnel train and tunnel system, and attended related hearings at the House of Lords. We suggested a number of improved
safety practices, as well as an innovative method to screen cars before boarding the train to prevent leaking fuel car from entering the tunnel.
Fire Safety in Rail Transit Vehicles-
We assisted the US Department of Transportation in a study to identify practical means to improve fire safety in existing and new rail transit vehicles and buses. We used fault and event tree analyses
and engineering judgment to evaluate car design, operations and training. We identified practices that would prevent ignition, contain a fire, or facilitate passenger evacuation.
Mining Fires-
For the Bureau of Mines, we assessed explosion and fire hazards associated with coal and metal mining. Mine disaster case histories were reviewed to identify typical chronology of events and
dynamics of explosions, fires, miners and emergency crews. We analyzed gob, rib and electrical fires, coal pile self-heating and methane/coal dust explosions. We also evaluated various safety measures
such as rock dusting, oxygen masks and fire curtains
Accidental Scenarios in Petrochemical Plants-
For several petrochemical plants, we modeled a variety of accident scenarios, including the venting of gases, spills of liquids, and two-phase flow releases. These releases may be followed by the
formation of pool, trench or vapor cloud fires or by fireballs, BLEVEs, and explosions. In the case of fire, we calculated the thermal radiation field around the fire to estimate the hazard zones for burn
injury or wood ignition. In the case of explosion, we calculated the pressure field around the explosion point to estimate the hazard zones using damage criteria for building collapse, ear drum rupture, window
breakage, etc.
Risk Analysis Studies-
For a number of commercial clients, we carried out risk analysis studies covering oil/LNG/LPG operations, and shipments of hazardous materials by various transportation systems. These studies consisted
of four elements. First, we identified the major types of accidents and their qualitative features. Second, we estimated the probability of these accidents using fault-tree analysis. Third,
we quantified the consequences of the accidents in terms of fire, BLEVEs, explosion, dispersion and the hazard distance in each case. Forth, we developed risk profiles that integrated probability and severity
and allowed us to evaluate various mitigation options.
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