超声速飞行状态下热喷流中离散颗粒的分布特性

Distribution Characteristics of Discrete Particles in Hot Jet in Supersonic Flight

关键词:  超声速飞行  红外隐身技术  气固剪切流  挡板构型  气溶胶分布  离散颗粒  数值模拟

Key words:  Supersonic flight  Infrared stealth technology  Gas-solid shear flow  Baffle configuration  Aerosol distributions  Discrete particles  Numerical simulation

摘要:

针对气溶胶红外隐身技术在飞行状态下隐身效果急速下降的现象，提出了一种在喷管尾部加装挡板结构以解决超声速飞行状态下离散颗粒难以扩散的方法，设计了曲线型和直线型两种挡板构型，通过对含气溶胶颗粒的飞行器排气喷管尾部气固两相剪切流的数值模拟研究，对比分析了挡板构型和气溶胶喷嘴数目对于离散颗粒空间分布特性的影响规律。研究表明，飞行马赫数为1.2时，挡板对提升该飞行状态下气溶胶颗粒在剪切流中的扩散能力具有显著作用，且直线型挡板结构优于曲线型；夹角α=30°，挡板高度与喷嘴内径比d/D_in=40时，离散颗粒对尾喷流的包裹效果最佳；当气溶胶喷嘴数目大于1时，颗粒分布的均匀性明显增加，且当喷嘴数目为5时，颗粒在流场中的扩散能力最强，浓度最均匀，颗粒整体温度较低，在热喷流周围形成“厚且冷”的气溶胶遮蔽层，有利于提高超声速飞行状态下飞行器排气热喷流的主动红外隐身效果。

Abstract:

The effect of the aerosol infrared （IR） stealth technology decreases obviously when in flight. A new method of installing the baffles around the jet nozzle is proposed to solve the difficulty of discrete particle distribution in supersonic flight conditions. Two types of baffle configurations， the curved and the straight， are designed in this study. The influences of the baffle configurations and aerosol nozzle numbers on the aerosol particle distribution characteristics are investigated by the numerical simulations. It is found that the baffle has a significant effect on enhancing the diffusion ability of aerosol particles in shear flow at a flight Mach number of 1.2， and the straight baffle configuration is better than the curved. The discrete particles could get the best distribution around the hot jet when α=30° and d/D_in=40. Besides， the uniformity of particle distribution increases significantly with the increasing aerosol nozzle number. The particles have more heavy dispersion characteristics and get a more even concentration and lower temperature distribution when the nozzle number is 5. The “thick and cold” aerosol particles layer around hot jet is conducive to improving the active IR stealth effect in supersonic flight conditions.