二次进气对Mg/CO2粉末火箭发动机性能影响的数值研究

Numerical Investigation on Effects of Secondary Intake on Performance of Mg/CO2 Powder Rocket Engine

关键词:  推进系统  粉末火箭发动机  Mg/CO₂  二次进气  燃烧效率  数值研究

Key words:  Propulsion system  Powder rocket engine  Mg/CO₂  Secondary intake  Combustion efficiency  Numerical investigation

摘要:

为了提高Mg/CO₂粉末火箭发动机的燃烧效率，在一次进气结构发动机基础上增设CO₂的二次进气，增强Mg粉与CO₂的掺混率，采用数值模拟的方法对比了一次进气和二次进气结构的发动机燃烧特性，以及二次进气喷注速度及预燃段长径比对燃烧室燃烧流动特性的影响。结果表明：二次进气结构相对于一次进气发动机结构延长了Mg颗粒在燃烧室内滞留时间，增强了燃烧室内湍流强度，使得气固掺混程度增加，从而提高粉末火箭发动机的燃烧效率；当二次进气喷注速度在6.5 ~39.9m/s内时，喷注速度越快，燃烧效率越高，喷注速度为39.9m/s时的燃烧效率最高，为82.8%；当预燃段长径比L/D<0.8时，发动机燃烧火焰失稳；当预燃段L/D>0.8时，L/D越小，燃烧效率越高，L/D取0.8时的燃烧效率最高，为84.1%。

Abstract:

In order to improve the combustion efficiency of Mg/CO₂ powder rocket engine， the mixing rate of Mg powder and CO₂ was enhanced by adding CO₂ secondary intake on the basis of primary intake structure engine. The combustion characteristics of primary and secondary intake engines were compared by numerical simulation. The effects of injection velocity of secondary intake and ratio of length to diameter of precombustion region on combustion and flow characteristics of combustion chamber were studied. The results show that the secondary intake structure prolongs the residence time of Mg particles in the combustion chamber compared with the primary intake structure. The secondary intake structure enhances the turbulence intensity in the combustion chamber and increases the degree of gas-solid mixing， so as to improve the combustion efficiency of powder rocket engine. When the secondary intake injection velocity is in the range of 6.5~39.9m/s， the combustion efficiency increases with the increases of secondary intake injection velocity. The highest combustion efficiency is 82.8% when the secondary intake injection velocity is 39.9m/s. The combustion flame becomes unstable when the ratio of length to diameter（L/D） of precombustion region is less than 0.8.When the L/D is more than 0.8， the combustion efficiency increases with the decrease of L/D.The highest combustion efficiency is 84.1% when the L/D of precombustion region is 0.8.