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Title:Experimental investigation of constant volume sulfur dust explosions
Author(s):Kalman, Joseph
Director of Research:Glumac, Nick G.
Doctoral Committee Chair(s):Glumac, Nick G.; Krier, Herman
Doctoral Committee Member(s):Dlott, Dana D.; Brewster, M. Quinn
Department / Program:Mechanical Sci & Engineering
Discipline:Mechanical Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
dust explosion
constant volume
dust flame
Abstract:Dust flames have been studied for decades because of their importance in industrial safety and accident prevention. Recently, dust ames have become a promising candidate to counter biological warfare. Sulfur in particular is one of the elements that is of interest, but sulfur dust ames are not well understood. This research investigates the physical and chemical mechanisms involved in sulfur dust combustion. A 31 L constant volume dust cloud combustion facility was designed and built to develop a methodology to determine both the e ectiveness of powder dispersion, and also the validity of using pressure-time data to measure ame speed in dust explosions. These results were applied to measurements of the fundamental combustion quantities, such as ame temperature and speed, to ascertain the burning regime of sulfur dust ames. A two-dimensional laser extinction technique was used to characterize the powder dispersion and uniformity by measuring the particle concentration with spatial and temporal resolution. The two-dimensional measurement provided a methodology to increase the number of line-of-sight measurements (i.e. number of samples) such that the mean concentration was statistically signi cant. This approach was used to determine the time at which the mean particle concentration approached the expected value. It was observed that at that time, the cloud was most uniform, as indicated by a decrease in the standard deviation of particle concentration. The measurement was then used to determine the e ectiveness of anti-caking agents to assist with the dispersion of sulfur. The addition of 1% by mass of submicron fumed silica particles was more effective then the addition of calcium stearate and magneisum stearate even at greater concentrations. The validity of using pressure-time data within a constant volume dust explosion to measure laminar ame speed was examined by using ionization probes simultaneously. The ame speeds measured by the ionization probes ii indicated that the significant amount of turbulence within the system makes it inappropriate to call the calculated ame speeds laminar. Nevertheless, limited agreement was observed between the two measurement techniques. It was concluded that pressure-time data can be used to estimate the ame speed of constant volume dust explosions. Sulfur dust (-325 mesh) ames were investigated in conjunction with the above results. Spectroscopic measurements indicated the presence of S2 in the gas-phase, suggesting that sulfur burns at least partially in the gas-phase. Flame temperature and ame speed were measured for sulfur ames with particle concentrations of 280 and 560 g=m 3 . The oxygen concentration varied between 10% and 42% by volume. The ame temperature increased with oxygen concentration from approximately 900 K for the 10% oxygen cases to temperatures exceeding 2000 K under oxygen enriched conditions. The temperature was also observed to increase slightly with particle concentration. The reduced temperatures (compared to the adiabatic ame temperature) might be due to incomplete combustion. The unburnt sulfur particles are believed to act as heat sinks, thus decreasing the temperature within the chamber. The ame speed was observed to increase from approximately 10 cm=s with 10% oxygen to 57 and 81 cm=s with 42% oxygen for the 280 and 560 g=m 3 cases, respectively. Flame speeds measured for the 280 g=m 3 powder loading in 21% oxygen were greater than the values reported in the literature, which is likely due to a combination of increased turbulence and smaller heat losses in the experimental setup used here. A scaling analysis determined that ames burning in 21% and 42% oxygen are diffusion limited.
Issue Date:2014-09-16
Rights Information:Copyright 2014 Joseph Kalman
Date Available in IDEALS:2014-09-16
Date Deposited:2014-08

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