Measurement and relationship between critical tube diameter and critical energy for direct blast initiation of gaseous detonations

For the explosion safety assessment in industrial setting, detonation dynamic parameters provide important information on the sensitivity and conditions whereby detonations can be favorably occurred. In this study, new measurement of the critical tube diameter and the critical energy for direct initiation of a detonation is reported for a number of hydrocarbon–oxygen mixtures. The simultaneous experimental measurement carried out in this work allows the investigation of the direct scaling between these two dynamic parameter quantities of gaseous detonations. Using the new set of data, this paper also assesses the validity of an existing semi-empirical initiation model, namely, the surface energy model by Lee, and a simplified work done model. Both phenomenological models provide a general relationship between the two dynamic detonation parameters and comparison shows a good agreement between the theoretical results and the experimental measurement. The scaling of critical tube diameter with detonation cell size in this study also confirms the results in the previous literature.     

煤自燃预测气体及活化能变化研究

为了研究煤在低温阶段的自燃活化能及气体产生规律,基于耗氧量与煤温间的计算模型,利用煤氧化动力学测试系统,分析了3种不同自燃性煤的低温氧化表征。结果表明:1)随着煤自燃倾向性增强,煤的耗氧量和耗氧速率逐渐增大,且其耗氧速率急剧增大的拐点温度逐渐升高;2)不同自燃性煤活化能变化规律存在显著差异,利用阶段耗氧量拐点计算出铜川和大同煤样温度分别为203℃、228℃时,活化能快速减小,开始进入自发氧化阶段;晋城煤样活化能经历先减小后增大的过程,其中过渡温度段91~135℃时,活化能最小;同时拟合出活化能(E)与指前因子(A)关系式满足动力补偿效应,验证了机理函数的合理性;3)依据复合气体CO_2/CO、CH_4/C_2H_6、C_2H_4/C_2H_6、C_3H_8/C_2H_6随温度的变化趋势,结合煤低温氧化特性,可预测煤样的氧化进程和煤体温度。     

Relationship between electric spark sensitivity and activation energy of the thermal decomposition of nitramines for safety measures in industrial processes

This study presents a new simple correlation between electric spark sensitivity of nitramines and their activation energies of thermolysis, which are important for safety measures in industrial processes. The new correlation can help to elucidate the mechanism of initiation of energetic materials by electric spark. It can be used to predict the magnitude of electric spark sensitivity of new nitramines, which is difficult to measure. The methodology assumes that electric spark sensitivity of a nitramine with general formula C_aH_bN_cO_d can be expressed as a function of its activation energy of thermal decomposition as well as optimized elemental composition and the contribution of specific molecular structural parameters. The new correlation has the root mean square and the average deviations of 1.37 and 1.09 J, respectively, for 21 nitramines with different molecular structures. The proposed new method is also tested for 16 nitramines so that there is no experimental data of electrostatic sensitivity for them.