A numerical study on the influence of multiple nozzles on the infrared radiation signatures of liquid rocket exhaust plumes

Abstract

A numerical study was conducted to examine the relationship between the infrared radiation characteristics of liquid rocket engine exhaust plumes under the same thrust conditions and the number and expansion degree of nozzles. This study used the Reynolds-averaged computational fluid dynamics method to simulate the flow field of multiple nozzles. A single-line group combined with the G-C approximation was used to calculate the molecular spectral properties, and a three-dimensional radiation transfer calculation model was established based on the line-of-sight method. The infrared radiation characteristics of the exhaust plume were calculated for single, double, three, and four nozzles. The radiation intensity of two typical bands, 2.7 μm and 4.3 μm, was studied, including spectrum, intensity, and radiation intensity distribution. The results show that the integrated infrared radiation intensity of the double-nozzle plume is 51.36 % lower than the average of the other three nozzle configurations under the over-highly under-expansion state. The radiation difference of the double nozzle reaches up to 38.3 % at different detection angles, whereas the differences between the three and four nozzles are below 10.5 % and 6.1 %, respectively, indicating that the radiation difference at each detection angle gradually decreases with the increase in the number of nozzles.

Keywords

• multiple nozzle
• rocket exhaust plume
• infrared radiation
• under-expansion state