爆轰波管中铝粉尘爆轰的数值模拟

Numerical simulation of dust detonation ofaluminum powder in explosive tubes

用两相流模型对爆轰波管中的铝粉尘的爆轰波进行了研究。模型考虑了气体和颗粒两相间速度和温度的不同及由于管壁引起的对流热传导和粘性引起的耗散,考虑了由于铝颗粒表面粗糙使得表面积增加的因素。铝颗粒的点火判据使用了新的判据,即铝颗粒在激波后的气流中温度达到铝的熔点且铝全部熔化即被点火。数值模拟了内径为15.2cm的爆轰波管中铝粉尘中爆轰波的传播和发展,得到了爆轰波速度及铝颗粒点火距离,还得到了爆轰流场中物理量的分布。从前导激波面到CJ面处,两相间的速度和温度有明显的差别。还考虑了粒子由于粗糙引起的表面积增加对爆轰波的影响,这个因素对铝颗粒的点火距离的影响较大,对这里计算的铝粉尘爆轰波的速度基本没有影响。结果表明,两相流模型可以较好地描述铝粉尘的爆轰过程,得到具有很粗糙表面、平均粒子直径为3.4μm的铝粉尘浓度为304g/m3时爆轰波的速度为1.63km/s,点火距离为3mm,与实验值符合较好。

The dust detonation of aluminum powder in explosion tubes has been numerically investigated with a two-phase flow model, in which the different velocities and temperatures for gas and particles, the dissipation due to convective heat transfer and flow viscosity on the tube wall, and the influence of aluminum particle coarseness resulting its surface area increasing have been taken into account. A criterion of particle ignition and its chemical reaction beginning in the detonation wave is employed and can be described as the particle temperature reaching the melting point of aluminum 931.7 K. The aluminum particle diameter is 3.4 μm and the inner diameter of the explosion tube is 15.2 cm in the simulation. The dust detonation development and propagation have been simulated, and the detonation velocity, the ignition distance of particles and distributions of flow variables behind the detonation wave are obtained. There are distinct different velocities and temperatures for gas (air) and aluminum particles in the area from the leading shock front to the CJ surface. When the concentration of very coarse aluminum particles is 304 g/m3, the calculated detonation velocity is 1.63 km/s and the ignition distance of particles is 3 mm, that agrees with the experimental data well.