Two-dimensional simulations were carried out to investigate the flame acceleration and deflagration-to-detonation transition (DDT) in a combustion chamber filled with a subsonic or supersonic mixture by employing Navier-Stokes equations together with a detailed chemistry reaction mechanism of 11 species and 27 steps under adaptive mesh refinement. The effects of the initial mixture Mach number and mesh resolution on the flame acceleration and DDT were studied in detail, and the entire processes of the flame acceleration, DDT and detonation propagation were revealed. Two DDT mechanisms are obtained in a chamber having the same low blockage ratio but with different initial velocities of the mixture. Regime I: multiple shock wave collisions, shock focusing and shock reflection result in a rapid energy deposition in a small region; a direct detonation subsequently occurs in the boundary wall for the subsonic mixture. Regime II: the classic hot-spot mechanism due to the reactive gradient mechanism is responsible for the detonation transition in the supersonic mixture when the intense leading shock wave impacts and reflects on the solid surface. By increasing the initial mixture Mach number, the run-up time and distance to DDT are dramatically reduced. The flame front structure and propagation in the supersonic flow demonstrate that the detonation cell size rapidly increases when propagating into the smooth region due to detonation attenuation and resulting pressure decrease. Additionally, a much higher combustion temperature occurs in the upper and lower walls because of the Mach stem. In comparison, the results show that the detonation overdrive degree and pressure gain ratio in the subsonic mixture are higher than in the supersonic mixture. Moreover, flame propagation upstream also suggests that increased pressure and temperature occur in the inlet isolation section, even forming a localized explosion point.

通过采用纳维-斯托克斯方程以及 11 种物质的详细化学反应机理，进行了二维模拟，以研究充满亚音速或超音速混合物的燃烧室中的火焰加速和爆燃到爆轰转变 (DDT)自适应网格细化下的 27 个步骤。详细研究了初始混合马赫数和网格分辨率对火焰加速和DDT的影响，揭示了火焰加速、DDT和爆轰传播的全过程。在具有相同低阻塞率但具有不同混合物初始速度的腔室中获得两种 DDT 机制。方式一：多次激波碰撞、激波聚焦、激波反射，导致小范围能量快速沉积；随后在亚音速混合物的边界壁上发生直接爆炸。方案 II：由于反应梯度机制导致的经典热点机制负责当强烈的前导冲击波冲击并在固体表面上反射时超音速混合物中的爆轰转变。通过增加初始混合气马赫数，启动时间和到 DDT 的距离会显着减少。超音速流中的火焰前锋结构和传播表明，由于爆轰衰减和由此产生的压力降低，爆轰单元尺寸在传播到平滑区域时迅速增加。此外，由于马赫杆，上壁和下壁的燃烧温度要高得多。相比下，结果表明，亚音速混合物的爆轰超速程度和压力增益比均高于超音速混合物。此外，火焰向上游传播也表明入口隔离段压力和温度升高，甚至形成局部爆炸点。