Experimental Study on Infrared Radiation Characteristics and Matching Performance of Low-Observable Nozzles

Abstract

Infrared stealth performance is one of the most crucial criteria for modern warplanes. The low-observable nozzle suppresses the infrared radiation by shielding the high-temperature engine components and enhancing the exhaust plume mixing with the atmosphere, thereby improving warplane survivability. Using a Fourier transform infrared spectrometer, the infrared radiation characteristics of two low-observable nozzles, including a two-dimensional nozzle and a serpentine nozzle, were measured in this paper. The nozzles were mounted on a micro-turbojet engine, and the variations of engine thrust, exhaust gas temperature, and fuel consumption rate were also measured to evaluate the matching performance of low-observable nozzles. The results show that the engine exhaust temperature rises after installing the low-observable nozzles. The two-dimensional nozzle has a maximum effect of 1.3% on the fuel consumption rate, and the serpentine nozzle has a maximum impact of 5%. The influence of low-observable nozzles on engine thrust is less than 1.9%. The infrared radiation intensity of the two-dimensional nozzle increases by 9% when the detection angle is 0° compared to the axisymmetric nozzle, while the serpentine nozzle decreases by 7%. When the detection angle is 90°, both low-observable nozzles achieve more than a 70% reduction in infrared radiation intensity.