气相爆轰波在分叉管中传播现象的数值研究

数值研究气相爆轰波在分叉管中的传播现象.用二阶附加半隐龙格-库塔法和5阶WENO格式求解二维欧拉方程,用基元反应描述爆轰化学反应过程,得到了密度、压力、温度、典型组元质量分数场及数值胞格结构和爆轰波平均速度.结果表明:气相爆轰波在分叉管中传播,分叉口左尖点的稀疏波导致诱导激波后压力、温度急剧下降,诱导激波和化学反应区分离,爆轰波衰减为爆燃波(即爆轰熄灭).分离后的诱导激波在垂直支管右壁面反射,并导致二次起爆.畸变的诱导激波在水平和垂直支管中均发生马赫反射.分叉口上游均匀胞格区和分叉口附近大胞格区的边界不是直线,其起点通常位于分叉口左尖点上游或恰在左尖点.水平支管中马赫反射三波点迹线始于右尖点下游.分叉口左尖点附近的流场中出现了复杂的旋涡结构、未反应区及激波与旋涡作用.旋涡加速了未反应区的化学反应速率.反射激波与旋涡作用并使旋涡破碎.反射激波与未反应区作用,加速其反应消耗,并形成一个内嵌的射流.数值计算得到的波系演变和胞格结构与实验定性一致.

Numerical Study of Gaseous Detonation Propagation Through a Bifurcated Tube

Gaseous detonation propagation through a bifurcated tube was numerically investigated.A 2~(nd) additive semi-implicit Runge-Kutta method and a 5~(th) order WENO scheme were used to solve two-dimensional reactive Euler equations.A detailed chemical reaction model was utilized to describe the heat release of detonation.The contours of density,pressure,temperature,species OH mass fraction,the computed cellular pattern and the traveling speed of detonation were obtained.The results show that,influenced by the rarefaction waves from the left sharp corner,the reaction zone is separated from the leading shock.Then,the detonation is degenerated into the deflagration.The winkled reaction front can be clearly identified in numerical schlieren and temperature contours.Re-initiation is induced by the leading shock reflection on the right wall in the vertical branch.Mach reflection of disturbed detonation occurs in both vertical and horizontal branches.The boundary between regions of uniform and larger cells is not a straight line;it doesn't exactly start at the left sharp corner and is usually upstream of the left sharp corner.The triple-point trajectory characterizing Mach reflection locates downstream of the right corner in the horizontal branch.Complex structures of vortices,the unreacted region,and shock-vortex interaction are observed in flow field around the left corner.Vortices accelerate reaction rates of the unreacted region.The reflected shock interacts with vortices and breaks them into pieces.Reflected shock also accelerates the consumption of the unreacted region and then an embedded jet is produced.The evolution of detonation wave and computed cellular pattern are qualitatively consistent with those from experiments.