A New Method to Evaluate the Suitability of Ignitor Strength Used in the Tests of Dust Explosions

Abstract:

Based on systematic experiments in the 20-L Siwek sphere, the explosion behaviors of bituminous coal dust were investigated by changing the strength of pyrotechnic ignitor. The effect on the maximum explosion pressure (P_ex) and maximum rate of pressure rise ((dp/dt)_ex) of the ignitor strength is analyzed. Due to the under-or over-driven phenomena, the overly low or high ignitor strength may result in unrealistic P_ex and (dp/dt)_ex, especially for lower dust concentration. To evaluate the suitability of ignitor strength, the time scales (i.e. the effective action time, t_eff, and the induction time, t_i,) of the ignitor combustion and flame kernel development are introduced by analyzing the ignition process of dust cloud. It can be found that the t_eff significantly heightens and the t_i gradually decreases with the rise of ignitor strength. Moreover, when the t_eff is much lower than the t_i, the under-driven phenomenon will occur, which leads to the underestimated P_ex and (dp/dt)_ex. Conversely, when the t_eff is much higher than the t_i, the explosion tests may be over-driven to cause the overestimated P_ex and (dp/dt)_ex. For ideal ignitor strength, the t_eff would be comparable to the t_i. Based on these facts, the under-and over-driven phenomena can be effectively verified by comparing the t_eff and the t_i. As a result, when the dimensionless time ratio t_eff/t_i is 0.52 or 1.42, the explosion tests in the 20-L sphere would be, respectively, under-driven or over-driven. To obtain the realistic test results in the 20-L sphere, it is suggested that the t_eff/t_i value should be in the range of 0.8~1.2 as much as possible.

• Periodical: Applied Mechanics and Materials (Volumes 448-453)
• Pages: 3916-3922
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.448-453.3916
• Online since: October 2013
• Authors: Jing Jie Yuan, Wei Xing Huang*, Bing Du, Nian Sheng Kuai, Jing Yi Tan
• Keywords: Dust Explosion, Effective Action Time, Ignitor Strength, Induction Time

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