The effect of instability of detonation on the propagation modes near the limits in typical combustible mixtures
The effect of instability of detonation on the propagation modes near the limits in typical combustible mixtures
复制标题
典型可燃混合物中爆炸不稳定性对接近极限的传播模式的影响
DOI：
10.1016/j.fuel.2019.05.006
复制
发表时间：
2019
期刊：
影响因子：
7.4
通讯作者：
Li Yuanchang
中科院分区：
文献类型：
--
作者：
Zhang Bo;Liu Hong;Li Yuanchang
在近极限条件下，爆轰传播行为表现为不稳定模式，这些模式分为三种类型，即，稳态模式、波动模式和快速失效模式。这项工作旨在阐明这些不稳定传播模式与爆轰不稳定性之间的本质物理关系。五种混合物中燃烧波的速度（即，实验测量了C_2H_4 - 6N_2O、CH_4 - 2O_2、2H_2-O_2、70%和85%Ar稀释的C_2H_2 - 2.5O_2）在极限附近的速度行为。根据CHEMKIN软件包和化学动力学计算稳定性参数χ。根据爆轰胞格图和χ的计算，C2 H4 - 6 N2 O和CH 4 - 2 O2被认为是不稳定的混合物（胞格高度不规则），2 H2-O2被认为是稳定的混合物（胞格高度规则），70%和85%Ar稀释的C2 H2 - 2.5O2被认为是高度稳定的混合物（胞格高度规则）。在上述不稳定/稳定/高稳定混合物中，爆轰波在近极限条件下的传播行为呈现慢衰减/波动/快速失效模式。有证据证实，不稳定性（或细胞规则性）占主导地位的传播模式，爆轰接近极限。爆轰不稳定性与边界效应之间的竞争机制导致爆轰波传播速度在边界条件外衰减缓慢。然而，对于稳定混合物，由于不稳定性对爆轰传播的影响非常有限，这种竞争机制缺乏，导致爆轰迅速衰减为快速火焰。此外，中性稳定性曲线（Ng等人，CombustTheorModel 2005;9：385-401）是快速失效/涨落模式的合适分界线，本文提出了一条新的第二稳定性曲线，它是涨落/慢衰减模式的分界线。
At the near-limit conditions, the behavior of detonation propagation manifests unstable modes; those modes are classified into three types, i.e., steady mode, fluctuation mode and fast failure mode. This work aims to elucidate essential physical relation between those unstable propagation modes and the instability of detonation. The velocity of the combustion wave in five mixtures (i.e., C2H4-6N2O, CH4-2O2, 2H2-O2, 70% and 85% Ar diluted C2H2-2.5O2) are experimentally measured to analyze velocity behavior near the limits. The stability parameter χ is computed from CHEMKIN package and chemical kinetics. According the detonation cellular pattern and the calculation of χ, C2H4-6N2O and CH4-2O2are considered as unstable mixtures (with highly irregular cells), 2H2-O2is characterized as stable mixture (with regular structure), 70% and 85% Ar diluted C2H2-2.5O2are determined to be highly stable mixtures (with highly regular pattern). In the above unstable/stable/highly stable mixtures, the detonation propagation behavior at the near-limit condition presents Slow Decay/ Fluctuation/ Fast Failure modes. Evidences confirm that instability (or cell regularity) dominates the propagation modes as detonation approaches the limits. The competition mechanism between detonation instability and boundary effect resulting in the slow decay of propagation velocity as the condition is outside the limits. However, for stable mixtures, due to the instability has very limited effect on the propagation of detonation, this competition mechanism is lacking, and resulting in detonation rapidly attenuates to a fast flame. In addition, the neutral stability curve (Ng et al., Combust Theor Model 2005;9:385-401) is an appropriate separatrix between Fast Failure/Fluctuation modes, a new second stability curve is proposed in this work, which is the boundary of Fluctuation/Slow Decay modes.