(47g) Shock Interaction with Dust Layers for Different Mach Numbers and Dust Layer Depths

Secondary dust explosion is a serious industrial issue because it occurs under conditions corresponding to an increased quantity and concentration of dispersed, combustible dust when compared with the primary explosion. The problems of lifting and dispersing of a dust layer behind a propagating shock wave must therefore be understood to ensure safety regarding secondary dust explosion hazards. A new facility was developed recently by the authors for the study of shock waves over dust layers. A shock tube and high-speed (15,000 fps) shadowgraph system were used to film shock waves over limestone dust layers. New data were collected for image analyses over longer periods than found in prior works, where the longer observation time and higher frame rates led to the discovery of trends not previously observed by earlier studies. Further investigation is needed to aid the development of predictive models for shock wave/dust layer interaction.

Data were collected for various Mach numbers and different limestone dust layer depths. Within the current data, it was observed that the rate of dust rise increases linearly with increasing shock Mach number. This trend does not appear to hold true above Mach number 1.32 as the rise rate and overall rise height of Mach 1.32 and 1.40 are nearly identical. However, an increase in rise rate is observed as Mach number increases between 1.10 and 1.32. Further experiments at higher Mach numbers above 1.40 are required to fully observe the effects of shock Mach number on the dust layer rise rate and raise height. When comparing the effects of the dust layer depth, it was observed that increasing the dust layer depth resulted in an increased dust layer rise height but a slight decrease in the rate of the dust layer rise.