【摘要】 为揭示氢气浓度梯度和阻塞比分布对填充氢气/空气的含障碍管道内火焰加速特性及爆燃转爆轰(DDT)机理的影响规律，基于OpenFOAM采用大涡模拟(LES)方法开展了含障碍管道内氢气/空气爆燃转爆轰数值模拟。研究表明:在3种不同阻塞比分布的情况下，均匀混合物中发现2种热点形成机制，分别是障碍物诱导反射压缩波导致激波聚焦形成热点以及火焰前沿在管道中间达到反应梯度条件后形成热点;在非均匀混合物中还发现火焰前沿马赫杆扫过的低氢气浓度区域也能够产生热点。这些热点最终触发爆轰，非均匀混合物中爆轰波的稳定传播速度能达到2 230 m/s，比均匀混合物中快7.2%。研究还发现，障碍物按阻塞比先减后增的布置方式最有利于火焰加速以及DDT现象的触发，在均匀混合物中先减后增布置时火焰达到稳定爆轰速度所需的传播距离比递增布置减少16.3%，非均匀混合物中则减少16.9%。该文发现的氢气浓度梯度与阻塞比分布对火焰加速及DDT过程的影响规律可以为工业爆炸安全防控与爆轰推进系统优化提供理论依据。更多还原

【Abstract】 To investigate the influence of hydrogen concentration gradients and blockage ratio distributions on flame acceleration and deflagration-to-detonation transition( DDT) mechanisms in hydrogen/air-filled obstructed ducts,large-eddy simulation( LES) based on OpenFOAM was employed to conduct numerical simulations of DDT processes. The study shows that,under three different blockage ratio distributions,two hot spot formation mechanisms are observed in homogeneous mixtures: one caused by shock focusing due to reflected compression waves induced by obstacles,and the other occurring in the mid-section of the ducts when the flame front satisfies the reaction gradient criterion. In inhomogeneous mixtures,an additional mechanism is identified: hot spots can also form in low hydrogen concentration regions swept by the Mach stem ahead of the flame front. These hot spots ultimately lead to detonation initiation. The stable propagation speed of detonation wave in inhomogeneous mixtures can reach 2 230 m/s,which is 7.2% faster than that in homogeneous mixtures. Furthermore,obstacle arrangements with a “decreasing-then-increasing ”blockage ratio sequence are found to be most conducive to flame acceleration and DDT initiation.Specifically,compared to a monotonically increasing blockage ratio layout,the flame propagation distance required to achieve a stable detonation velocity is reduced by 16. 3% in homogeneous mixtures and by 16. 9% in inhomogeneous mixtures. The influence of hydrogen concentration gradients and blockage ratio distributions on flame acceleration and DDT processes discovered in this paper can provide a theoretical basis for industrial explosion safety prevention and control as well as the optimization of detonation propulsion systems.更多还原