硼基粉末燃料冲压发动机掺混燃烧特性研究

Co-combustion characteristics in boron-based powdered fuel ramjet

针对硼基粉末燃料冲压发动机超声速燃烧组织难题,建立气-固两相掺混燃烧方法,开展典型工况(26 km,Ma=6.0)的数值仿真研究,得到了发动机燃烧室内的流动燃烧特性,仿真分析了粉末燃料喷注速度、燃料颗粒粒径以及凹腔结构对燃烧室内气-固两相掺混燃烧情况的影响。结果表明:粉末燃料点火温度是影响燃料掺混燃烧效率的关键因素,当粉末喷注于气相燃烧高温区时,可显著提高燃烧效率;合理的喷注速度有利于增强颗粒与燃气和来流的掺混程度,使得颗粒燃烧更充分;当颗粒粒径从5μm提高至20μm时,射流穿透深度显著增加,粒径5μm时粉末燃烧效率最高,随着粒径增大颗粒点火的难度提高,不利于燃料充分燃烧释热;凹腔结构形成的回流区可以形成较好的点火区域,对于粉末燃料及富燃燃气和超声速来流的掺混起到较好的增益效果,有利于提高燃烧效率。

Aiming at the problem of combustion organization of boron-based powdered fuel ramjet,a gas-solid two-phase mixed combustion method was established.Numerical simulations were conducted under typical operating condition(26 km and Ma=6.0).The flow and combustion characteristics within the combustion chamber were obtained.And the effects of powder injection velocity,fuel particle size,and cavity structure on the gas-solid two-phase mixing combustion within the chamber was analyzed.The results reveals that the ignition temperature of powdered fuel is a key factor affecting the combustion efficiency of fuel blending.When powder is injected into the high-temperature zone of gas-phase combustion,the combustion efficiency can be significantly improved.A reasonable injection speed is beneficial for enhancing the mixing degree of particles,gas and incoming flow,making combustion more complete;When the particle size increases from 5 μm to 20 μm,the jet penetration depth significantly increases.The powder combustion efficiency is highest when the particle size is 5 μm.As the particle size increases,the difficulty of particle ignition increases,which is not conducive to sufficient combustion and heat release of the fuel;the recirculation zone formed by the concave cavity structure can create a better ignition area,which promotes the mixing of powdered fuel,rich combustion gas,and supersonic inflow,and improves combustion efficiency.