Experimental characterization of galloping detonations in unstable mixtures
Experimental characterization of galloping detonations in unstable mixtures
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DOI：
10.1016/j.combustflame.2015.02.007
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发表时间：
2015-06
影响因子：
4.4
通讯作者：
Yuan Gao;H. D. Ng;John H. S. Lee
中科院分区：
文献类型：
--
作者：
Yuan Gao;H. D. Ng;John H. S. Lee
本文讨论了爆轰极限附近驰振爆轰的一些特征。Gao等人（2014）先前报道的实验结果，以及本研究中获得的六种具有不同反应灵敏度的爆炸混合物的额外数据，每个混合物在五个不同直径的管中进行了详细分析。它是建立在高度氩气稀释，稳定的混合物中不会发生驰爆。仅适用于不稳定的混合物，易受热化学不稳定性引起的流量波动的影响，当用于小管径时（即，D = 12.7 mm），可观察到驰振爆震。对于最大管径D = 50.8mm的爆轰波，即使对于所有不稳定混合物，当初始压力接近爆轰极限时，爆轰波也完全失效。此外，本研究还表明，发生驰爆的初始压力范围随管径的增加而迅速减小。现有的一组驰振爆轰数据表明，在实验范围内，一个驰振周期的平均波长L约为350 D。尽管如此，随着管直径的增加，似乎存在一些微小的下降趋势（即，D = 12.7 mm），或爆炸混合物的爆轰不稳定性增加。驰振周期的振幅也进行了研究，上部的速度值比下部的波动更大。不同工况下的驰振循环速度的上限值和下限值分别为VCJ ~ 1.5VCJ和0.3VCJ ~ 0.65VCJ。为了说明流动不稳定性对驰振爆轰的作用，进行了实验与螺旋插入到12.7毫米直径的管人工产生扰动。爆轰波通过螺旋后迅速重新启动，并在管的其余部分形成另一个驰振爆轰周期。
Some features of galloping detonations near the detonation limits are discussed in this paper. The experimental results previously reported in Gao et al. (2014), together with additional data obtained in this study for six explosive mixtures with different reaction sensitivities, each in five different diameter tubes, are analyzed in detail. It is established that galloping detonations do not occur in highly argon-diluted, stable mixtures. Only in unstable mixtures, susceptible to flow fluctuations by thermo-chemical instability, when using in small tube diameters (i.e.,D⩽ 12.7 mm), could galloping detonations be observed. For the largest tube diameterD= 50.8 mm, the detonation wave fails completely when the initial pressure approaches the detonation limit even for all unstable mixtures. In addition, the present study shows that the initial pressure range for the occurrence of galloping detonations decreases rapidly with increasing tube diameter. A collection of existing data on galloping detonations indicates that the wavelengthLof one galloping cycle is on average about 350Dwithin experimental variations. Nonetheless, there appears to be some minor decreasing trend with increasing tube diameter (i.e.,D⩾ 12.7 mm), or with increasing detonation instability of the explosive mixture. The amplitude of the galloping cycle is also investigated and the upper velocity values show more fluctuations than the lower ones. The upper and lower values of the velocity in the galloping cycle at different conditions vary fromVCJto 1.5VCJand 0.3VCJto 0.65VCJ, respectively. To illustrate the role of flow instability on galloping detonations, experiments are performed with a spiral inserted into the 12.7-mm diameter tube to generate perturbations artificially. Detonation waves are observed to re-initiate quickly after passing the spiral and another cycle of galloping detonation was formed in the remaining part of the tube.