Response of critical tube diameter phenomenon to small perturbations for gaseous detonations
Response of critical tube diameter phenomenon to small perturbations for gaseous detonations
复制标题
DOI：
10.1007/s00193-013-0491-2
复制
发表时间：
2014-03
期刊：
影响因子：
2.2
通讯作者：
N. Mehrjoo;Bo Zhang;R. Portaro;H. D. Ng;John H. S. Lee
中科院分区：
文献类型：
--
作者：
N. Mehrjoo;Bo Zhang;R. Portaro;H. D. Ng;John H. S. Lee
在本实验研究中，研究了稳定和不稳定混合物中气体爆轰的临界管径现象，并着重探讨了其破坏机理。有人以前假设，在不稳定的混合物，其中的细胞爆轰前是非常不规则的，失败是由抑制本地重新启动中心链接到动态的不稳定性。在稳定的混合物中，通常具有高氩气稀释度，爆轰结构是非常规则的，故障模式是由于全球前的过度曲率。为了区分这两种故障机制，通过放置障碍物引入流动扰动，从而使最小堵塞率约为8%。障碍物放置在管出口处，在爆轰衍射之前。结果表明，由障碍物引起的扰动仅对未稀释的（即，不稳定）的混合物，导致成功传爆所需的最小初始压力降低。因此，这表明，当地的流体动力学不稳定性发挥了重要作用的临界管径现象在未稀释的，不稳定的混合物。与此相反，稳定的，氩气稀释的混合物的结果表现出小的变化之间的扰动和未扰动的情况下的临界初始压力。这可以归因于微扰对爆轰波整体曲率的影响很小。还测试了扰动的几何形状，同时通过改变障碍物的数量和位置来保持阻塞面积恒定。结果表明，爆轰波的传播与阻塞几何形状无关，而仅是阻塞面积的函数。因此，所需的最小压力的变化传输显示出相同的行为，在不稳定的混合物不同的扰动几何形状，而稳定的混合物的传输特性保持不受影响。
In this experimental study, the critical tube diameter phenomenon of gaseous detonations is investigated in both stable and unstable mixtures with focus on the failure mechanism. It was previously postulated that in unstable mixtures, where the cellular detonation front is highly irregular, the failure is caused by the suppression of local re-initiation centers linked to the dynamics of instabilities. In stable mixtures, typically with high argon dilution, the detonation structure is very regular and the failure mode is attributed to the excessive curvature of the global front. In order to differentiate between these two failure mechanisms, flow perturbations are introduced by placing an obstacle resulting in a minimal blockage ratio of approximately 8 %. The obstacle is placed at the tube exit, before the detonation diffraction. Results show that the perturbations caused by the obstacle only have an effect on undiluted (i.e., unstable) mixtures, causing a decrease in the minimum initial pressure required for successful detonation transmission. This thus demonstrates that local hydrodynamic instabilities play an important role for the critical tube diameter phenomenon in undiluted, unstable mixtures. In contrast, the results for the stable, argon-diluted mixture exhibit little variation in critical initial pressure between the perturbed and unperturbed cases. This can be attributed to the minimal effect of the perturbations on global curvature for the emergent detonation wave. The geometry of the perturbation is also tested, while holding the blockage area constant, by varying the number and position of the obstacle(s). The results demonstrate that the transmission of a detonation is independent of the blockage geometry and is only a function of its imposed blockage area. Consequently, the change in required minimum pressure for transmission shows an identical behavior in unstable mixtures for different perturbation geometries while the transmission characteristics of the stable mixture remain unaffected.