水下机枪密封式发射膛口流场特性分析

Analysis of Flow Field Characteristics of Sealed Launching Muzzle of Underwater Machine Gun

基于有限体积法,采用动网格技术,建立了膛口流场二维轴对称仿真模型,对12.7 mm水下枪在无初始流场,弹丸发射初速不同工况下的膛口流场进行了数值模拟。计算结果表明:弹丸出膛后,燃气迅速喷出,形成一个射流膨胀区,压力迅速衰减,由于燃气喷射过程中受到水和弹丸的较大阻碍,导致燃气在弹后空间聚集,压力又升高。膛口射流场压力随时间的衰减呈指数规律衰减。在475~650 m/s初速范围内,膛口马赫盘的形成时间基本一致,约在150μs后马赫盘生成;火药燃气经过马赫盘时压力会有不同程度的增加,475 m/s初速时,燃气压力最早增加且幅度较大。

A 2-Daxisymmetric simulation model of muzzle flow field was established based on finite volume method and dynamic grid technique,numerical simulation for 12.7 mm gun without the precursor flow field and the initial velocity of projectile under different conditions were carried out.The calculation results show that after the projectile exits,the gas ejects rapidly,forming a jet expansion zone,and the pressure attenuates rapidly.As the gas continues to eject,the gas accumulates behind the projectile,and the pressure rises,due to the bigger obstruction of water and the projectile.The attenuation of the gas jet pressure at the muzzle follows the exponential attenuation law.The formation time of Mach disk is basically the same in the initial velocity range of 475~650 m/s about 150μs after it is formed.The pressure of gunpowder gas increases in varying degrees when it passes through Mach disk,at the initial velocity of 475 m/s,the gas pressure increases firstly and larger.