枪口压力对水下发射膛口流场特性的影响

为了研究机枪水下发射枪口燃气喷射压力对膛口流场分布特性的影响,基于流体计算软件FLUENT,采用结构化网格并结合动网格技术,建立了水下枪膛口流场二维轴对称仿真模型,针对14.5 mm水下枪,分别采用30 MPa、45 MPa和60 MPa燃气喷射压力对水下密封式发射膛口流场进行了数值模拟。计算结果表明:3种枪口喷射压力条件下,火药燃气喷出膛口后都迅速形成射流膨胀区,膛口轴向压力急剧衰减,燃气扩展过程中受到水和弹丸的较大阻力,在弹后空间聚集,使得压力有不同程度的升高; 燃气喷射压力在30～60 MPa范围内,膛口马赫盘初步形成的时间略有不同,约在145～152 μs之间,压力越小时,马赫盘形成越早且弹丸越早脱离火药燃气的包围; 3种压力条件下马赫盘距离膛口中心位置随时间的变化都呈指数分布规律。

Influence of Muzzle Pressure on Muzzle Flow Field Characteristics of Underwater Launching

In order to study the influence of muzzle gas injection pressure on the distribution characteristics of muzzle flow-field of underwater gun firing,based on computational fluid dynamics software Fluent,a two-dimensional axisymmetric simulation model of underwater muzzle flow-field was established by using structured mesh and dynamic mesh technology. For the 14.5 mm gun,the numerical simulation of the underwater sealed launching muzzle flow-field was carried out with the gas injection pressure of 30 MPa,45 MPa and 60 MPa respectively. The calculation results show that,under the three kinds of muzzle gas injection pressure conditions,a jet expansion zone forms rapidly after the gas is sprayed out of the muzzle,and the axial pressure of the muzzle decreases sharply. The gas expansion process is greatly hindered by water and projectile,resulting in gas accumulation in the space behind the projectile,and the pressure increases again. While the gas injection pressure is in the range of 30～60 MPa,the initial formation of the Mach disk is slightly different. For about 145～152 μs,the smaller the pressure is,the earlier the Mach disk forms,and the sooner the projectile breaks away from the gunpowder gas. Under the three kinds of pressure conditions,the position of the Mach disk at the center of the muzzle distributes exponentially with time.