Explosions of vapor/aerosol clouds
In deflagration, the combustion process propagates outward at speeds slower than that of sound (subsonic speeds). However, typically flame accelerates because of turbulence generation of the moving gas ahead of the flame. Flame can start at speeds as low as m/s order of magnitude and accelerates up to 600 m/s. Factors that increase turbulence are blockage ratio and congestion. Blast strength and hence damage increases with flame speed. In detonation, the speed is faster than the local speed of sound (supersonic speed), causing explosion, resulting in shattering of objects in the path. For a long time, occurrence of detonation in vapor clouds have been denied or at least doubted, but only the last few years evidence has been found that it is possible. Detonation occurs only in massive clouds under near wind still conditions.
Deflagration to Detonation
Deflagration to detonation (DDT) refers to the phenomena whereby the propagation of the combustion process of a flammable gas and air mixture suddenly transitions to an explosion. Energy is released during combustion. DDT incidents can be particularly dangerous in congested spaces such as offshore oil and gas production platforms.
Currently, MKOPSC is validating the likelihood to obtain Deflagration-to-Detonation Transition (DDT) on different scenarios by using the CFD model in FLACS. So far, the validation has been carried out with data found in the literature. Moreover, the current facilities available at the Turbomachinery Laboratory of Texas A&M University are being used to run, experiments that will provide data to help validating this CFD model.
Dust Explosion Research
Every process involving combustible finely divided solids or dusts is associated with explosion hazards. Although detailed statistical records of dust explosion are not generally available, it is known that approximately 70% of the dusts or powders processed in the chemical process industry are combustible and ignitable. Data from the Health and Safety Executive indicate one dust explosion every day in Europe, with damages from each incident in the range of millions of dollars, not including the damage and loss caused by injuries, fatalities, production stoppages, and marketing losses. In the United States, some recent incidents where dust explosions were most likely the root cause include incidents in Indiana (October 2003), Kentucky (February 2003), and North Carolina (January 2003). As stated by the U.S. Chemical Safety Board in regard to the June 18, 2003, dust explosion in Kinston, NC, there is a critical need for research to characterize the explosion behavior of dusts to make possible strategies for handling dusts safely and to minimize the possibility and severity and therefore the risk of industrial dust explosions.
Fundamental research in the field of dust explosions has been classified into dust cloud formation process, dust cloud ignition process, flame propagation in dust clouds, and blast waves generation by burning dust clouds. Preliminary results seem encouraging but there are still a lot unresolved issues that need to be investigated further. On the experimental front, large-scale tests need to be conducted on dusts that are able to mimic typical industrial explosion scenarios.
