The thrust characteristics and infrared radiation characteristics in the waveband of 3-5μm of 2-D ejector nozzle with long/short shrouds in the high-flying unmanned aerial vehicle(UAV) were studied.The thrust characteristics and infrared radiation characteristics of 2-D ejector nozzle under the conditions of high-altitude and ground state were compared.The system of the exhaust jet

UAV flow field and temperature field were calculated with commercial software Fluent

and the infrared radiation characteristics were calculated with an infrared analysis software(NUAA-IR) developed independently.The results show that the 2-D ejector nozzle can still improve thrust characteristic under the condition of high-altitude

but the thrust characteristic is a little weaker than that under ground condition.The effect of infrared radiation suppression of 2-D ejector nozzle used by UAV is obvious in most of the detection directions

with the largest decreasing amplitude of 90%.The trend of infrared radiation suppression of these two types of 2-D ejector nozzles in the direction of UAV's tail is different from that under ground condition;the infrared radiation of the 2-D ejector nozzle with short shroud is greater than that with long shroud

and the largest increasing amplitude is 7%.