Study on the dynamics of the process of dust lifting by propagating shock wale and with constant flow of air

Aim of project
The aim of the project was to investigate the process of dust lifting from the layer behind a propagating shock wave. In a number of industrial facilities and factory buildings, dust layers cover fl oors, walls, ceilings and various installations. Dust can be easily dispersed by pressure waves generated by weak explosions or as a result of damage of compressed gas systems. Situations like these could be very hazardous because a weak primary explosion can initiate a strong one in the whole area where there is dust deposit. A typical example of such a situation is a coal mine with a high risk of methane explosion. A weak explosion of methane/air mixture can generate a pressure wave which may disperse the deposited dust. Combustion of methane can cause ignition of the dust/air mixture and then a strong pressure wave can be generated which intensifies the dust dispersion process and finally causes a powerful explosion. As a result, a fully developed explosion can propagate in the whole area where dust was deposited in the layer. To obtain the explosive dust/air mixture in a big volume, it is enough to have a relatively thin dust layer. If a coal dust layer (1 mm thick and of bulk density equal to 450 kg/m3) is deposited only on the floor, the height of the space where stoichiometric dust/air mixture can be formed is equal to about 3.5 m. However, the height of the space where explosive dust/air mixture can be obtained is in this case equal to about 12.5 m.

Expected results
The influence of layer thickness of selected organic dusts and the velocity of shock wave upon the dispersing process dynamics will be determined. Using special laser facilities will enable the determination of the vertical component of the velocity of the dispersed dust and also its concentration along duct heights. The speed of dust lifting will be verified by means of fast electronics camera. On the basis of streak pictures technique with simultaneous use of the Schlieren system, the delay in lifting of the dust behind the shock wave will be precisely determined. Elaboration of a reliable code, based on the new concept and experimentally verified, enabling numerical simulation of the investigated processes will make it possible to test several industrial installations in terms of feasibility of dust explosion propagation. However, the main task of the above code will be to be used in further research as the principal element of the final program enabling numerical simulation of the dust explosion propagation process in case where dust is not initially dispersed but deposited in a layer.