气态/超临界态RP-3航空煤油喷嘴内部流动可视化研究

Internal Flow Visualization of Gaseous/Supercritical RP-3 Aviation Kerosene in an Injector

为研究气态/超临界态RP-3航空煤油在喷嘴内部的流动特性,自主设计了模拟喷嘴内部收缩通道的透明试验件,通过阴影法对气态/超临界态RP-3在喷嘴内部的流动过程开展可视化研究,并采用一维流动分析方法对观测结果进行了分析。试验首次获得气态/超临界态RP-3航空煤油在喷嘴内部的流动结构可视化图像,图像透明区域的形状随着燃油在收缩通道中膨胀而引起的密度变化而改变。结果表明,喷射压力和喷射温度对燃油在喷嘴内部流动特性有显著影响,燃油密度在不同喷射压力和喷射温度工况下沿轴向及径向的变化趋势存在明显差异,因而在可视化图像上展现出不同大小或形状的透明区域。轴向上,燃油密度变化在喷口处最为剧烈,该变化趋势随着喷射温度的降低、喷射压力的升高而增大。径向上,受温度边界层的影响,燃油密度变化在喷嘴壁面处最为剧烈,该变化趋势随着喷射温度的降低而减小;近临界喷射温度下,亚临界喷射温度工况的透明区域沿轴向呈均匀状,超临界喷射温度工况的透明区域沿轴向呈收缩状。

In order to study the flow characteristics of gaseous/supercritical RP-3 aviation kerosene in an injector, a transparent test piece simulating the converging internal passage of the injector was independently designed, visualization of flow structure was performed by shadowgraph images, and the phenomenon was analyzed by using one-dimensional flow analysis method. The visualization images of gaseous/supercritical RP-3 aviation kerosene flow structure of injector internal passage were obtained, and the expansion in the converging channel caused the density gradient, resulted in the change of the shape of the transparent area in the passage. The results revealed that the changes of injection temperature and pressure have influence on the supercritical and gaseous fuel flow characteristics in the converging internal passage. The phenomenon can be attributed to differences in axial and radial variations of fuel density under different operation conditions, therefore the transparent areas in different sizes or shapes were shown in the injector. In the axial direction, the greatest density variation occurred at the nozzle outlet, and change increased with the decrease of injection temperature and the increase of injection pressure, respectively. In the radially direction, due to the temperature boundary layer, the density changed near the nozzle wall, and the variation decreased with the decrease of injection temperature. At the near critical injection temperature, the transparent region under the condition of subcritical injection temperature is uniform along the axis, while the transparent region under the condition of supercritical injection temperature is shrinking along the axis.