宽速域来流中气体辅助预热横向射流掺混机理研究

Mixing Mechanism of Gas-Assisted Preheated Transverse Jet in Inlet Flow at Wide-Range Mach Numbers

关键词:  爆震发动机  冲压发动机  横向射流  两相流  掺混  雾化  数值模拟

Key words:  Detonation engine  Ramjet engine  Transverse jet  Two-phase flow  Mixing  Atomization  Numerical simulation

摘要:

为研究气体辅助条件下液体横向射流与超声速来流的掺混机理，对旋转爆震冲压发动机宽速域超声速空气流中预热煤油横向射流在气体辅助喷注条件下的喷雾流场结构和液滴破碎展开数值模拟，分析了来流马赫数、辅助气体位数及气体喷注压降等因素的影响。采用离散相模型研究气液相互作用，通过Rayleigh-Taylor和Kelvin-Helmholtz混合模型描述液膜的破碎，选取Discrete Randow Walk模型计算液滴的湍流耗散，通过无限热传导率模型描述液雾的蒸发过程。研究表明，有/无气体辅助工况中，在当量比、孔径及喷注压降等恒定的条件下，液体射流穿透能力与来流马赫数成反比。合理的单/双位气体辅助方案都可提升液体射流穿透深度，但后者更为显著。双位气体辅助下甲烷的加入扩大了可燃组分的分布。随着甲烷喷注压降的升高，其后位置的卷吸涡对充分发展，热煤油射流的穿透深度显著提高，但液雾的蒸发距离变长。

Abstract:

In order to study the mixing mechanism between the transverse liquid jet and supersonic airflow under gas-assisted conditions， the numerical simulation of the spray flow field structure and droplet breakup of the preheated kerosene cross jet in the wide-range Mach number supersonic flow of the rotating detonation ramjet with assisted gas is carried out. The effects of factors such as the incoming flow Mach number， assisted gas number， and gas injection pressure drop are analyzed. The discrete phase model is used to study the gas-liquid interaction. The Rayleigh-Taylor and Kelvin-Helmholtz mixed model is used to express the breaking of the liquid film. The discrete randow walk model is selected to calculate the turbulent dissipation of the droplet. The infinite heat conductivity model is adopted to describe the evaporation process of the spray. Studies have shown that the liquid jet’s penetration capability is inversely proportional to the incoming Mach number in the presence/absence of gas-assisted conditions under constant conditions such as equivalence ratio， aperture， and injection pressure drop. Reasonable single/dual-position gas-assisted schemes can increase the penetration depth of the liquid jet， but the latter is more significant. The addition of dual-position methane assisted-gas expands the distribution of combustible components. As the pressure drop of the methane injection increases， the reverse vortex pair in the subsequent position is fully developed， and the penetration depth of the preheated kerosene jet increases significantly. However， the evaporation distance of the liquid mist becomes longer.