Full Infrared band shock layer radiation noise analysis of a high-speed vehicle at high altitude based on virtual detection array method

In this study, an algorithm was developed for analyzing the infrared radiation noise of aircraft shock layer flow fields based on virtual detection arrays. The spatial-spectral characteristics and influencing factors of infrared radiation noise in the 1–25 μm range in shock layer flow fields at high altitudes (40–80 km) was investigated. By comparing two flight trajectories, the contribution of different molecules (air chemical components NO, NO₂, OH, and atmospheric trace components CO₂, H₂O, CO) as sources to radiation noise, the spatial distribution patterns of radiation noise, and the relationship between radiation noise and trajectory characteristics were analyzed. The results show that: (1) In terms of the spectral characteristics of radiation noise, the atmospheric trace component CO₂ is identified as the strongest contributor to spectral radiation noise in both trajectories, with concentrations in 2.0–2.2 μm, 2.6–3.0 μm, 4.15–4.5 μm and 15 μm, while the shock layer chemical component NO is recognized as the second strongest radiation source, primarily concentrated in the 5–6 μm range. (2) In terms of spatial distribution patterns, the band irradiance in different positions of the blunt cone region decays exponentially along the streamline direction. (3) In terms of the magnitude of radiation noise, the band irradiance in the 3–5 μm band can be three orders of magnitude higher than that in the 8–12 μm band. (4) The band irradiance in the 40 km-50 km airspace of the low trajectory is determined to be one order of magnitude higher than that in the 50 km-80 km airspace of the high trajectory, with atmospheric pressure being identified as the main contributing factor.