RP-3航空煤油/O_(2)预混火焰不稳定性研究

Study on the Instability of RP-3 Aviation Kerosene/O_(2)Pre-mixed Flame

为获得RP-3航空煤油不稳定燃烧特性,采用定容燃烧实验装置开展初始压力0.1 MPa、0.2 MPa、0.3 MPa,初始温度420 K、450 K、480 K,当量比1.0~1.7工况下RP 3航空煤油/O_(2)预混火焰层流燃烧特性的实验研究。结果表明:随着初始压力和当量比增加,火焰锋面明显由光滑变为褶皱,内部出现胞状结构,火焰趋于不稳定。通过分析过渡加速起始半径发现,随着初始温度、初始压力和当量比增加,过渡加速起始半径减小,预混火焰的不稳定现象提前。另外,计算扰动增长率并分析其对火焰稳定性的影响发现,质热扩散作用对火焰稳定性的影响占据主导地位,流体动力学作用其次。进一步研究发现,质热扩散作用主要取决于分子扩散项,随着当量比增加,其值由负向正变化,证明分子扩散作用对预混火焰不稳定影响逐渐增强。

In order to obtain the unstable combustion characteristics of RP-3 aviation kerosene,experiments are carried out in a constant volume chamber to study the unstable combustion process of RP-3/O_(2)premixed flame at initial pressures of 0.1 MPa,0.2 MPa and 0.3 MPa,initial temperatures of 420 K,450 K and 480 K and over a wide equivalence ratio range from 1.0 to 1.7.Results show that with the increase of initial pressure and equivalence ratio,the flame front obviously changes from smooth to folded,and cellular structure appears inside,which indicates that the flame tends to be unstable.The study on initial radius of transition acceleration indicates that with the increase of initial temperature,initial pressure and equivalence ratio decreases,which means that the instability of premixed flame is advanced.By calculating the disturbance growth rate and analyzing its influence on flame stability,it is found that the effect of mass and heat diffusion on flame stability is dominant,and the effect of hydrodynamics is secondary.The mass-thermal diffusion mainly depends on the molecular diffusion term.With the increase of the equivalence ratio,its value changes from negative to positive,which indicates that the molecular diffusion has an enhanced effect on the instability of premixed flame.