| dc.description.abstract | Dust explosions threaten people, assets, and the environment across a wide range of industries. To identify hazards and manage risks, dust materials must be tested with standard methods and equipment like the MIKE3 minimum ignition energy (MIE) testing device. The MIKE3 device, while important for safety testing, is also appealing for the scientific investigation of dust cloud ignitability. Dust explosion conditions in the MIKE3 device can be easily controlled, and the resulting MIE data is easily interpreted within the context of industrial safety. However, conventional MIE measurements are not sufficient to resolve the multi-scale physics and chemistry of dust explosions, and advanced methods must be developed to probe the dust cloud dispersion, ignition, and flame propagation processes that evolve inside the MIKE3 device. Optical diagnostics offer promising pathways to new experimental investigations with the MIKE3 device through in-situ, non-intrusive, multi-scale, and multi-dimensional measurement capabilities. Therefore, the objective of this research is to develop advanced optical diagnostics for novel dust cloud particle, flow, and combustion measurements that are compatible with the MIKE3 device over a wide range of relevant material types and testing conditions.
Firstly, particle and flow diagnostics were implemented to investigate the dynamics of dust clouds prior to ignition. Digital in-line holography (DIH) was implemented during the dust cloud dispersion process for micro-scale particle detection and tracking in three-dimensional (3D) space. Quantitative particle size, concentration, and velocity measurements revealed how different dust sample properties can influence the observed characteristics of the dust cloud in the ignition zone. Next, particle image velocimetry (PIV) was combined with DIH in the MIKE3 glass tube for micro-scale particle diagnostics, macro-scale flow visualizations, and two-dimensional (2D) flow velocity and vorticity field measurements. Multiple experimental runs were repeated to accommodate the stochastic dust cloud dispersion process, and key particle and flow statistics were assessed.
Secondly, combustion diagnostics were implemented to investigate the ignition and flame propagation behaviors of combustible dusts. Broadband imaging and excited-state hydroxyl (OH*) and methylidyne (CH*) chemiluminescence imaging were implemented to obtain quantitative size, position, and velocity measurements during the early flame kernel development process. An asymmetric motion of the flame kernel away from the central ignition zone was discovered, and differences between organic and metal dust cloud ignition were identified. Finally, hydroxyl planar laser-induced fluorescence (OH-PLIF) imaging was implemented to analyze the 2D flame structure of burning dust clouds. OH-PLIF images were used to visualize the flame structure and categorize flames based on their qualitative features. Quantitative flame area and curvature measurements were then used to characterize the expanding flame surface.
Overall, the completed research represents significant forward progress for dust explosion diagnostics research. The developed methods leverage the capabilities of advanced imaging devices, lasers, and instrumentation while remaining compatible with the geometry and operation of the MIKE3 device. This research has enhanced our fundamental understanding of dust explosions, produced valuable validation data for numerical dust explosion models, and provided dust cloud ignitability insights that are relevant to industrial safety. | |
