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Wedge-Induced Oblique Detonations with Small Heat Release
AIAA Journal ( IF 2.5 ) Pub Date : 2021-08-30 , DOI: 10.2514/1.j060653
Alba Domínguez-González , Daniel Martínez-Ruiz , Luca Scotzniovsky , Antonio L. Sánchez , Forman A. Williams

The present work exploits simplifications arising in weakly exothermic detonations when the postshock conditions are supersonic to investigate the structure of wedge-induced oblique detonations. These simplifications enable the linearized Euler equations (employed here in characteristic form) to be efficiently solved numerically, subject to the linearized Rankine–Hugoniot jump conditions across the leading oblique shock. A first set of computations employs one-step first-order Arrhenius chemistry appropriate for describing detonations when the postshock chemistry exhibits a thermal-explosion character. In that case, the relevant chemical-kinetic parameter of order unity β is the product of the heat release and the activation energy divided by the square of the postshock thermal enthalpy. The transition from the shock to the detonation wave is continuous at small β, begins to develop spatially decaying oscillations as β increases, and develops a singularity at the shock at a critical value of β; above which, the transition must become discontinuous and involve a triple point. Parametric results are presented in a plane of the wedge angle and the incident-flow Mach number: the two important controlling parameters. The triple point is found to develop when the incident-flow Mach number falls below a critical value that exhibits a U-shaped dependence on the wedge angle, becoming large at both high and low wedge angles and reflecting large differences between shock angles with and without heat release in those two extremes. Additional computations are performed for a three-step branched-chain scheme with the heat-release step having zero activation energy and for very fuel-lean hydrogen–air detonations with postshock temperatures above crossover. These cases, for which ignition develops as a chain-branching explosion, do not develop a singularity at the shock; although they display many of the features identified with the Arrhenius chemistry, including oscillations and appearance of a precursor point indicative of criticality. The results suggest a strong potential influence of the chemistry on the transition.



中文翻译:

小热释放楔形诱导斜爆轰

目前的工作利用当后震条件为超音速时弱放热爆炸中出现的简化来研究楔形引起的倾斜爆炸的结构。这些简化使得线性化的欧拉方程(这里以特征形式使用)能够有效地进行数值求解,受制于前斜激波的线性化 Rankine-Hugoniot 跳跃条件。第一组计算采用一步一阶阿伦尼乌斯化学,适用于描述当震后化学表现出热爆炸特征时的爆炸。在这种情况下,有序统一的相关化学动力学参数β是放热能和活化能的乘积除以震后热焓的平方。从冲击波到爆震波的过渡是连续的β, 开始发展空间衰减振荡 β 增加,并在临界值的冲击下发展出奇点 β; 在此之上,过渡必须变得不连续并涉及三点。参数结果显示在楔角和入射流马赫数的平面中:两个重要的控制参数。当入射流马赫数低于临界值时,发现三相点出现,该值对楔角呈 U 形依赖性,在高楔角和低楔角处变大,并反映有和没有冲击角之间的巨大差异在这两个极端中释放热量。对于具有零活化能的放热步骤的三步支链方案以及具有高于交叉后温度的非常贫燃料的氢-空气爆炸,进行了额外的计算。在这些情况下,点火发展为链分支爆炸,不要在冲击时形成奇点;尽管它们显示出许多与阿伦尼乌斯化学相同的特征,包括振荡和指示临界性的前体点的出现。结果表明化学对转变有很强的潜在影响。

更新日期:2021-08-31
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