涡扇发动机轴对称引射收敛喷管红外辐射特性

数值研究了涡扇发动机轴对称引射收敛喷管的红外辐射特性.排气系统的流场计算采用商用数值模拟软件,红外辐射特性计算采用自主开发的软件NUAA-IR,计算分析了轴对称收敛喷管和引射收敛喷管在3~5μm波段红外辐射特性以及喷管内不同固体壁面在探测方向上的红外辐射贡献.结果表明:引射收敛喷管的红外抑制作用主要在于引射加强了尾喷流与环境大气的掺混,减小了尾喷流的长度,降低了燃气流的红外辐射;引射收敛喷管对喷管内固体壁面的遮挡以及降温作用很小,只在方位角为20°方向上对内涵壁面、外涵内壁等中低温壁面有效;引射收敛喷管的总积分辐射强度在方位角为0°~15°范围内与收敛喷管几乎相等,在其他方位角范围内均小于收敛喷管,且在方位角为40°方向上降低幅度达到最大,约为34%. 

Infrared radiation characteristics of axisymmetrical ejector convergent nozzle in turbofan engine

The infrared radiation (IR) characteristics of axisymmetrical ejector convergent nozzle in turbofan engine were investigated with the method of numerical simulation. The flow fields of exhaust systems were calculated with commercial software, while the IR characteristics were calculated with self-developed software NUAA-IR. The IR characteristics of 3-5μm waveband of axisymmetrical convergent nozzle and ejector convergent nozzle and the IR contributions of different solid walls in the nozzles on different detection directions were calculated and analyzed. The results show that the infrared suppression of ejector convergent nozzle mainly lies in the mixing of plume and environment atmosphere, helping to minimize the length of the plume, and then reducing the IR of gas. The shielding and cooling effect of ejector convergent nozzle on the nozzle's solid walls is very small, and this effect is effective only to the medium and low temperature walls such as main duct wall and inner wall of bypass duct at the azimuth angles greater than 20 degree. The total integral IR intensity of ejector convergent nozzle is less than that of the convergent nozzle except in the azimuth angles of 0 to 15 degree where these two nozzles' total integral IR intensities are nearly equal. The maximum reduction amplitude is about 34% at the azimuth angles of 40 degree.