The transmission of detonation waves, propagating in a homogeneous, gaseous, reactive medium, from a tube into an unconfined space is well known to succeed or fail based on the tube diameter. Below a certain diameter, the detonation fails to transition into the unconfined space, while for a large enough geometry, the transition succeeds. This critical diameter is well correlated to the incoming detonation cell size. For common undiluted hydrocarbon mixtures with a strong degree of transverse instability, the ratio of critical tube diameter to cell size has been measured at D_c = 13λ. In this paper, stoichiometric acetylene-oxygen mixture at different initial pressures is detonated in a circular tube that transitions into an effectively unconfined space. The transition is observed with simultaneous schlieren photography and soot foil records to look at the role of transverse cellular instability. Three regimes of transition are observed: supercritical, where the cellular pattern is continuously connected from the donor tube to the larger space; subcritical, where the wave fails and the cellular pattern disappears; and a critical regime, where the wave initially fails, asymptoting to a weakly decoupled shock-reaction front regime, and exhibits a subsequent re-initiation in a critical zone of pre-shocked gas through the onset of an explosion bubble. A substantial amount of transverse instability remains even after the expansion wave reaches the central axis, sustaining the diffracted wave at a critical thermodynamic state for the re-initiation. The location of this critical zone is identified at about 22λ and a small obstacle is used to promote the generation of transverse waves and a re-initiation kernel. The re-initiation is effected by placing an obstacle in the critical region. The role of the resulting instability is also illustrated through a simple numerical simulation using an obstacle in the sub-critical regime to perturb the flow and promote the re-initiation.

众所周知，基于管的直径，在管中以均匀的，气态的，反应性介质的形式传播的爆炸波的成功与否。在一定直径以下，爆炸无法过渡到无限制空间，而对于足够大的几何形状，过渡成功。该临界直径与进入的爆轰孔的尺寸很好地相关。对于具有较大横向不稳定性的常见未稀释烃混合物，已在D _c  = 13λ下测量了临界管直径与孔尺寸的比率。。在本文中，化学计量的乙炔-氧气混合物在不同的初始压力下在圆管中引爆，该圆管过渡到有效的无侧限空间中。通过同时进行schlieren摄影和烟灰箔记录观察到过渡现象，以观察横向细胞不稳定的作用。观察到了三种过渡状态：超临界状态，其中细胞模式从供体管连续连接到更大的空间；亚临界的，其中波失败并且细胞模式消失了；以及一个临界状态，在该状态下，波浪最初会失效，逐渐减弱为弱耦合的冲击反应前沿状态，并在随后发生爆炸气泡之前，在预震气的临界区域内重新初始化。即使在膨胀波到达中心轴之后，仍然存在相当大的横向不稳定性，从而使衍射波维持在临界热力学状态以重新初始化。确定该关键区域的位置约为22λ和一个小的障碍物用于促进产生横波和重新初始化内核。通过在关键区域放置障碍物来进行重新初始化。通过使用次临界状态中的障碍物扰动流动并促进重新初始化的简单数值模拟，也说明了所导致的不稳定性的作用。