稀薄环境下发动机高空羽流流动与辐射特征

Flow and infrared radiation characteristics of high-altitude plume in thin atmosphere

  • 摘要: 高空羽流指发动机在稀薄环境工作时产生的燃气射流迅速膨胀扩散流动状态。急剧膨胀的羽流产生的红外信号被广泛应用于空间目标的探测、跟踪和识别。建立了直接模拟蒙特卡洛方法结合带滑移修正的计算流体力学方法,研究了从喷管内部到出口以至近场、远场的高空羽流场,在此基础上,采用佛奥特线型描述稀薄气体展宽,结合逐线积分法和视在光线法计算得到了超窄谱的高空羽流红外辐射特性,利用理论模型和实验数据,综合校验了高空羽流流动与辐射模型的有效性。研究结果表明:高空羽流辐射能量主要集中于喷口附近以及激波层内,沿着射流轴线方向及越过分离波线后,亮度呈指数下降,整体上高空羽流流场与亮度场具有相似性,羽流场分布类似羽毛状,光谱的发射和吸收集中在谱线中心区,表现为谱线较分立,亮度场呈现月牙状;发动机射流总压增大会显著扩大分离波线和羽流辐射亮度,而发动机射流总温增大对其分离波线不产生影响,但会极大提升其羽流辐射亮度;自由来流密度或速度增大,会显著压缩羽流膨胀边界,但对辐射强度影响较小;利用推力及其自由来流速度、密度无量纲化表征后,其分离流线具有非常好的一致性,发动机射流总压、总温对高空羽流辐射影响显著,而自由来流变化对其影响较小。

     

    Abstract:
    Objective  For relatively high-density areas inside and near the exit, axial symmetry can be used to compress the Navier-Stekes equation description, and the realizable turbulence model is closed to the model equation. Use a limited volume method to discrete, and the time is promoted to adopt hidden methods. Axially simulates the Monte Carlo method described by axisymmetric in the spray exit and far field. Combined with the HITEMP2010 database, the spectral absorption coefficient of the gas component of infrared radiation is calculated by line-by-line integral method. The radiation transmission equation that is regarded in the light method is used to solve the high-altitude feathers. Experimental data of high-altitude feather flow flow is used to verify the effectiveness of high-altitude feathers flow and radiation computing models in this article.
    Results and Discussions  Through the effects of analysis of the total pressure and total temperature conditions of different shots and the effects of the general temperature conditions on the flow of high-altitude feathers and their infrared radiation characteristics, the calculation conditions of different shots are used (Tab.1). The display of the non-balance effect mainly occurs in the shock area (Fig.3). The pressure at the ink at the entrance will have a more obvious impact on the contour, spectral level, and the brightness of the ranceling layer of the separation wave line (Fig.4). The brightness distribution of the same calculation in different bands is similar, and the differences are mainly magnitude (Fig.5). The difference between the brightness in the same calculation in different bands is mainly values (Fig.6). Calculation conditions of different freedom flow (Tab.2) show that the greater the density of freedom, the more powerful the impact on the compression of the shooting (Fig.7). Increased freedom flow density will slowly raise the spectral radiation intensity (Fig.8). Freedom flow has a small impact on the relatively high-voltage area near the engine exit (Fig.9-Fig.10). After different operating conditions, after using the formula for infinite outline, its boundary characteristics are no longer affected by the engine and freedom, and have good consistency (Fig.11). Different bands have a similar change trend (Fig.12). The characteristics of high-altitude feathers flow and radiation are mainly determined by the total pressure, total temperature, freedom to flow density, speed, etc., which will significantly affect the distribution of the brightness of the feather flow radiation.
    Conclusions  Under the same boundary conditions, high-altitude feathers have similar structures, that is, internal flow, turbulence, and outflow areas. The location of the separation wave line is basically the same. The launch and absorption are mainly concentrated in the center of the spectrum. It is manifested as a relatively separate spectrum line. Its radiation energy is mainly concentrated near the spray mouth and in the rim layer. After the direction of the shot axis and crossing the separation wave line, the brightness has decreased. It has similarity, the distribution of feathers is similar to feather-like, and the brightness field presents crescent-shaped; The total pressure of the engine has increased, and the shot and freedom flow form a relatively obvious wave layer. The effect, with the further increase of the density of the shot, the unbalanced effect of the shooting area itself weakened, the overall expansion of the separation wave line and the radiation of the feather flow will significantly, and the increase in the total temperature of the engine's shooting will not affect its separation wave line. However, the temperature of the high-altitude feathers inner flow area and the swarm area will increase, and the non-balance effect of the swarm area increases, which will greatly increase the radiation of the feather flow; The increase in density or speed of freedom will significantly compress The inflating of the feather is continuously shifted in the position of the separation wave line. Due to the changes in the flow field structure, the brightness distribution of different bands has a relatively significant difference. Under the conditions of different shots and freedom, the spectral radiation structure is similar. The difference is mainly reflected in the difference. In terms of numerical values; From the perspective of the characteristics of the flow boundary, after the total pressure, total temperature and freedom flow, density, and density of the shot flow, the separation streamline calculated under different conditions has very good consistency; From radiation in terms of strength characteristics, the increase in the total pressure and total temperature of the engine shot will significantly increase the radiation intensity of high-altitude feathers, and when the density and speed of freedom are changed, although the flow field and brightness distribution will have a great impact, it will have a great impact on the distribution of the flow field and the distribution of brightness, but it will be on its radiation intensity has less impact.

     

/

返回文章
返回