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.