Objective With the rapid development of modern weaponry technologies such as missiles, and radars, aircraft with high stealth capability and high maneuverability have become a key focus for future development. Thus, to achieve "stealth" for combat aircraft, the primary task lies in implementing infrared suppression for the major infrared radiation sources on military aircraft. Among these, the engine exhaust system stands as the most significant infrared radiation source. Therefore, the most critical aspect of achieving infrared stealth for military aircraft involves suppressing the infrared radiation from the engine exhaust system. This study aimed to investigate the effect of injecting aerosols on suppressing the infrared radiation signature of an exhaust system. The research focused on examining the influence of aerosol concentration and solid particle size on the aerodynamic characteristics and infrared radiation features of an axisymmetric nozzle.

Methods This study investigates the effects of injecting aerosols on suppressing the infrared radiation characteristics of an exhaust system. A combined approach of numerical simulation and experimental testing was adopted. Specifically, an axisymmetric nozzle model was created using UG, with mesh generation performed in ICEM. Flow field simulations were conducted using Fluent, and the infrared radiation characteristics of the nozzle were obtained the RMC method. By comparing cases with and without aerosol injection, as well as varying aerosol concentration and solid particle size, the influence of aerosol injection on the aerodynamic performance and infrared radiation features of the axisymmetric model was analyzed. Additionally, experiments were carried out to measure the infrared radiation intensity distribution of the axisymmetric nozzle before and after aerosol injection. These experimental results not only validated the numerical method for infrared radiation calculation but also revealed the impact of aerosol injection on the infrared radiation characteristics of the axisymmetric model.

Results and Discussions The results from both simulations and experiments indicated that after aerosol injection, the solid particles formed a wrapping and shielding layer around the exhaust plume, but their effect on the flow field was minimal. Compared to the baseline condition without aerosol injection, within the 3-5 µm mid-wave infrared band, the target’s infrared radiation signature was significantly suppressed at observation angles smaller than 30°, while the suppression effect was poor at larger angles. Furthermore, a higher aerosol concentration resulted in a thicker shielding layer and stronger infrared radiation suppression. At a mass flow rate of 3 kg/min, the suppression effect was notable, with a maximum reduction of 75% in the integrated infrared radiation signature. Additionally, there existed an optimal particle size for extinction efficiency, at which the infrared radiation suppression was the strongest.

Conclusions The simulation and experimental results indicate that after aerosol injection, solid particles form a wrapping and shielding layer around the exhaust plume, yet their impact on the flow field remains minimal. Compared to the baseline condition without aerosol injection, within the 3-5 μm mid-wave infrared band, the target's infrared radiation signature is significantly suppressed at observation angles smaller than 30°, while the suppression effect is notably weaker at larger angles. Furthermore, higher aerosol concentrations result in a thicker shielding layer and stronger infrared radiation suppression. At a mass flow rate of 3 kg/min, the suppression effect is considerable, with a maximum reduction of 75% in the integrated infrared radiation signature. Additionally, there exists an optimal particle size for extinction efficiency, at which the infrared radiation suppression reaches its peak.