膛口初始流场对火药燃气流场影响的数值研究

Numerical Study on Effects of Precursor Flow on Muzzle Propellant Flow Field

枪炮发射时,身管内被弹丸压缩的空气柱喷出膛口后形成初始流场,它对后续火药燃气流场的发展及弹丸的运动产生很大影响,甚至会降低射击精度。因而,研究初始流场对火药燃气流场的影响机理对于武器设计具有重要的意义。基于ALE方程的有限体积方法,利用AUSM+格式和分区结构化贴体网格对含有复杂形状弹丸的膛口流场进行了数值模拟。根据数值结果绘制的计算阴影图与实验阴影照片符合较好。分别计算了有、无初始流场两种条件下的流场发展过程,详细比较讨论了它们的流场结构与参数特征。结果表明,初始流场的存在是火药燃气流场形成冠状冲击波的必要条件。同时,含有初始流场条件下的近膛口区域最大滞止压力相对于无初始流场条件增加了2倍以上。

During the gun firing, the in-bore air column compressed by the projectile is ejected from the muzzle to the external ambience to form the precursor flow field, and has a great effect on the develop- ment of the subsequent propellant flow and the movement of the projectile even reduces the shooting accu- racy. Thus, it is important to study this effect mechanism. The muzzle flow with a complicated projectile is simulated numerically by using second order AUSM ＋ scheme with MUSCL interpolation method. Multi-domain structured grids are employed to solve ALE governing equations. The real shooting condi- tions, for example, moving projectile, precursor and propellant flow, interior ballistics conditions are considered in the simulations. Two cases, with or without precursor flow field, are also predicted and the resulted shadowgraphs with precursor flow coincide with the experimental ones. And then flow patterns and development of the propellant flow field in these two cases are discussed in detail to reveal the effect of the precursor flow based on the numerical results. It is demonstrated that the precursor flow is the es- sential condition for the generation of the bow shock ahead of the projectile. And the maximal stagnation pressure in the area near the muzzle increases more than 2 times for the precursor flow relatively to the condition without it.