Infrared radiation characteristics of shock vectoring control serpentine nozzle

The Shock Vectoring Control Serpentine Nozzle (SVCSN) is an important configuration of exhaust system that supports next-generation fighters in achieving high maneuverability and strong stealth capabilities. In order to investigate the infrared radiation characteristic and generation mechanism of SCVSN, numerical simulation was employed to calculate the spatial distribution of backward infrared radiation intensity of SVCSN with auxiliary injection channels. The formation mechanism of the spatial distribution pattern was analyzed by combining flow field characteristic, and the infrared radiation characteristics of SVCSN without auxiliary injection/shock vectoring and under different Secondary flow Pressure Ratios (SPR) were compared. The results indicate that the average proportion of gas radiation in total radiation reaches as high as 83.08% and 76.95% on the horizontal plane and the vertical plane respectively. Additionally, the thrust vector angle reaches approximately 19.24° under the baseline condition, demonstrating that SVCSN can effectively suppress wall infrared radiation while achieving favorable thrust vectoring performance. Compared with the conventional serpentine nozzle, SVCSN exhibits the phenomena of separation shock and significant deflection of the plume. These two phenomena affect the infrared radiation characteristic of SVCSN by inducing the generation of wall hot spots and altering the gas path as well as the projected area of the plume, respectively. Moreover, both auxiliary injection and shock vectoring will degrade the infrared stealth performance. SPR influences the infrared radiation characteristic by altering the separation shock angle and the nozzle outlet pressure. As SPR increases from 1.0 to 1.4, the intersection area between the separation shock and the upper wall expands, and the outlet pressure difference increases, which exerts an adverse impact on the performance of SVCSN: the thrust coefficient decreases by 1.22%, the vector angle reduces by 12.99%, the gas radiation increases by an average of 23.49% on the vertical plane (excluding the 20° angle) and an average of 18.38% on the horizontal plane.