Velocity behavior downstream of perforated plates with large blockage ratio for unstable and stable detonations
Velocity behavior downstream of perforated plates with large blockage ratio for unstable and stable detonations
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DOI：
10.1016/j.ast.2019.01.010
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发表时间：
2019-03
影响因子：
5.6
通讯作者：
Bo Zhang;Hong Liu;Bingjian Yan
中科院分区：
文献类型：
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作者：
Bo Zhang;Hong Liu;Bingjian Yan
由于爆轰具有良好的热推进性能，它已被应用于航空航天推进装置，如脉冲爆震发动机(PDE)、旋转爆震发动机(RDES)和斜爆轰波发动机(ODWE)。然而，这些新概念推进装置的研制仍然具有挑战性，主要是因为在高超声速流动和可燃混合物中建立稳定的自持爆轰是一项艰巨的任务。最基本的问题之一是了解发动机内部绕射和爆轰波的相互作用。在本研究中，不同堵塞比的孔板被放置在爆轰传播的开始处，以探讨孔板产生的绕射对爆轰传播机理的影响。以C2H2+5N2O和C2H2+2.5O2+70%Ar两种炸药混合物为研究对象，研究了爆轰波在大范围绕射后传播速度行为的差异。结果表明，绕射对高度不稳定混合物的传播影响较小，当BR值增加到0.962时，这种影响变得明显，这是因为爆轰具有不规则的泡状结构，亚结构以高度不稳定爆轰为特征，其中爆震不稳定性被障碍物的大扰动放大，导致其前沿形成更多的爆轰细胞，掩盖了绕射的减弱效应。相反，绕射对稳定的混合物影响很大，表现为随着堵塞比的增大，障碍物下游的自持爆轰临界压力显著增加，这可归因于绕射沿着曲率分布在爆轰表面上，从而导致整个爆轰波阵面过大的曲率，从而加剧了爆轰失败。
Due to the excellent thermal propulsion performances of detonation, it has been applied for the purpose of aerospace propulsion devices, e.g., pulse detonation engines (PDEs), rotating detonation engines (RDEs), and oblique detonation wave engines (ODWEs). However, it remains challenging for developing those new-concept propulsion devices, mainly because it is a formidable task to establish a steady and self-sustained detonation in the hypersonic flow and combustible mixture. One of the fundamental problems is to understand the interaction of diffractions and the detonation waves within the engines. In this study, perforated plates with various blockage ratios are seated at the beginning of the detonation propagation to explore the diffractions that generated from the plates on the detonation propagation mechanism. Two explosive mixtures of C2H2+ 5N2O and C2H2+ 2.5O2+ 70% Ar are studied to illustrate the difference in propagation velocity behavior of detonation after it suffers from large-scale diffractions. The results show that diffractions have less effect on the propagation of highly unstable mixture, and the effect becomes obvious asBRincreases to 0.962; this phenomenon occurs because detonation has an irregular cellular pattern and sub-structures are characterized by highly unstable detonation, in which the detonation instabilities are amplified by the large perturbations of obstacles, leading to an augment in forming more cellular cells of detonation in its front that cover the weakening effects from diffractions. In contrast, the diffractions significantly affect the stable mixture, manifested by a remarkable increase of the critical pressure for a self-sustained detonation downstream of the obstacle with the augment of blockage ratio; this phenomenon can be attributed to the diffractions being distributed along the curvature over the detonation surface, thereby causing more excessive curvature of the entire detonation front, which in turn exacerbates the failure of detonation.