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 significant. 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 effectiveness 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 S 2 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/m3. 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/m3 cases, respectively. Flame speeds measured for the 280 g/m3 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.
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机译：由于粉尘火焰在工业安全和事故预防中的重要性，因此已经进行了数十年的研究。最近，尘埃姆斯已成为对抗生物战的有前途的候选人。特别是硫是令人感兴趣的元素之一，但是对硫粉尘的危害还不太清楚。这项研究调查了涉及硫粉尘燃烧的物理和化学机理。设计并建造了一个31 L的等体积粉尘云燃烧设施，以开发一种方法来确定粉末分散的有效性，以及使用压力时间数据测量粉尘爆炸中弹药速度的有效性。将这些结果用于基本燃烧量的测量，例如原子温度和速度，以确定硫粉尘的燃烧状态。;采用二维激光消光技术通过测量颗粒来表征粉末的分散性和均匀性专注于时空分辨率。二维测量提供了一种方法，可以增加视线测量的数量（即样品数量），从而使平均浓度在统计学上显着。该方法用于确定平均颗粒浓度达到预期值的时间。观察到那时，云是最均匀的，如颗粒浓度的标准偏差降低所表明的。然后将该测量结果用于确定抗结块剂辅助硫分散的有效性。甚至在更高浓度下添加1质量％的亚微米级气相二氧化硅颗粒比添加硬脂酸钙和硬脂酸镁更有效。在恒定体积的粉尘爆炸中使用压力-时间数据测量层流速度的有效性为同时使用电离探针进行检查。电离探针ii测得的ame速度表明，系统内显着的湍流使得将计算出的ame速度称为层流是不合适的。然而，在两种测量技术之间观察到有限的一致性。得出的结论是，压力时间数据可用于估算等体积粉尘爆炸的弹速。结合以上结果，研究了硫粉尘（〜325目）弹药。光谱测量表明在气相中存在S 2，这表明硫至少在气相中燃烧。测量了颗粒浓度分别为280和560 g / m3的硫磺粉的火焰温度和Ame速度。氧气浓度在10％至42％（体积）之间变化。随氧气浓度的升高，顶峰温度从10％氧气情况下的约900 K升高到富氧条件下超过2000 K的温度。还观察到温度随颗粒浓度而略微升高。降低的温度（与绝热阿米温度相比）可能是由于燃烧不完全所致。据信未燃烧的硫颗粒起着散热器的作用，从而降低了室内的温度。在280 g / m3和560 g / m3的情况下，观察到的ame速度分别从含10％氧气的约10 cm / s增加到57和81 cm / s含42％氧气。在21％的氧气中以280 g / m3的粉末负载量测得的火焰速度大于文献报道的值，这可能是由于在此使用的实验装置中湍流增加和热损失较小的结合。缩放分析确定在21％和42％的氧气中燃烧的阿姆斯烟扩散受到限制。
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