Deflagrations

Explosions initiated by sparks, heated surfaces, frictional sparks (molten metal fragments) and hot jets are studied in the explosion test vessels located in the explosion dynamics facility. Issues examined in these facilities include the initiation of flames and detonations by high-speed jets, the ignition of aviation fuel (Jet A) vapor-air mixtures by electrical sparks and the limits of flammability of mixtures containing multiple components, including nitrous oxide and ammonia.

A facility to simulate explosion events during nuclear power plant accidents was built around two pressure vessels: (1) the driver, a 6-inch diam. tube 4-ft. long; (2) the receiver, a 36-inch diam., 64-inch long pressure vessel. The driver and pressure vessel are connected with a special hydraulic closure of a design similar to that used in the 6-inch GALCIT shock tube.

A typical experiment begins with both the driver and receiver evacuated to less than 1 millibar. The driver is then filled to 1 bar with a rich mixture of hydrogen and oxygen, and the receiver is filled to 1 bar with a mixture of 50/50 air/diluent (nitrogen or steam), and some small percentage (0 to 10%) of hydrogen. The driver mixture is ignited by the discharge of 15 kV pulse from an EG&G TM-11 trigger generator through a commercial spark plug. The diaphragm separating the driver and receiver is ruptured by the pressure rise, and a hot jet of hydrogen and steam enters into the receiver. If critical conditions (sufficiently large jet diameter/or high enough hydrogen concentration in receiver) for jet combustion or deflagration exist, a combustion event will occur in the driver.

Transient high-temperature jet of steam and hydrogen in a nitrogen atmosphere.

Initiation of a propagating diffusion flame by transient jet into a hydrogen(10%)-air mixture.

We have studied flammability and flame propagation in multicomponent mixtures. The investigated fuels, oxidizers and inert components are hydrogen, methane, propane, ammonia, nitrous oxide, oxygen, nitrogen and fuels containing various higher hydrocarbons, such as Jet A. This experimental work is being carried out in 1.8, 11 and 400 liter explosin test vessels. Measurements of ignition energy, flammability limits, flame speeds, quenching behavior, pressure- and temperature histories are being carried out for a variety of reactants at different initial conditions.