Oblique detonation wave stability around a spherical projectile by a high time resolution optical observation
Oblique detonation wave stability around a spherical projectile by a high time resolution optical observation
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DOI：
10.1016/j.combustflame.2011.09.001
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发表时间：
2012-02
影响因子：
4.4
通讯作者：
S. Maeda;J. Kasahara;A. Matsuo
中科院分区：
文献类型：
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作者：
S. Maeda;J. Kasahara;A. Matsuo
球形弹丸以接近查普曼-朱盖(Chapman-Jouguet，C-J)速度的大范围弹丸速度发射到可爆混合物中。利用纹影技术和1-μS帧速度的高速摄像机，以高时间和高空间分辨率显示了稳定在弹丸周围的斜爆轰波(ODW)和激波诱导燃烧(SIC)。在C-J奇数波的稳定临界点附近观察到了由碳化硅区域和C-J奇数波组成的称为草帽型结构的非定常波结构，并根据C-J奇数波能否稳定而分为两种传播类型[11，12，14]。在本研究中，我们基于对数十幅连续图像的检查，提出了稻草帽类型的波结构。当弹丸速度略高于C-J速度时，在弓形激波、C-J奇数波和横向爆轰波或激波的交汇处观察到三重点。已有报道在碳化硅区域发生局部爆炸，以稳定草帽型结构中的奇数波[14]。当弹丸速度远高于C-J速度时，我们通过可视化周期性局部爆炸及其向球面爆轰波的转变来观察这种稳定机制。我们还使用化学计量比的乙炔-氧气混合物，分别在50%或75%的体积分数中用Ar或氪稀释，确定了稳定临界。我们发现稳定临界不仅仅取决于弹丸直径和混合物的泡孔大小之比。
Spherical projectiles were launched into detonable mixtures over a wide range of projectile velocities from near to about 1.8 times the Chapman–Jouguet (C–J) velocity. Oblique detonation waves (ODWs) and shock-induced combustions (SICs) stabilized around the projectiles were visualized with high time and high spatial resolutions using the Schlieren technique and a high-speed camera with a 1-μs frame speed. Unsteady wave structures called Straw Hat type structures consisting of a SIC region followed by a C–J ODW were observed near stabilizing criticalities of a C–J ODW, and they were divided into two propagation types, depending on whether the C–J ODW could be stabilized [11,12,14]. In the present study, we suggested wave structures of the Straw Hat types based on our examination of dozens of continuous images. Triple points were observed at the intersection of a bow shock, a C–J ODW and a transverse detonation or shock wave when projectile velocities were slightly higher than C–J velocities. Onsets of local explosions in the SIC region for stabilizing the ODW in the Straw Hat type structures have been reported [14]. We observed this stabilizing mechanism by visualizing onsets of periodical local explosions and their transition to spherical detonation waves when the projectile velocity was much higher than the C–J velocity. We also determined stabilizing criticalities using a stoichiometric acetylene-oxygen mixture diluted with argon or krypton in 50% or 75% volumetric fractions, respectively. We found that the stabilizing criticalities did not depend only on the ratio of the projectile diameter and the cell size of the mixture.