This study developed the ESTRI numerical simulation software for infrared characteristics of hydrocarbon-fueled exhaust systems by integrating Embedded Large Eddy Simulation (ELES) and the Atmospheric Transmissivity Weighted Multi-Species Wide-Band (ATWMSWB) k-distribution gas radiation model. The reliability of the ELES and ATWMSWB models was verified by comparing with measurement data of flow field parameter distributions for both subsonic and supersonic nozzle exhaust plumes, as well as Line-By-Line (LBL) calculation results for transient flow field remote sensing infrared imaging. The computational accuracy of the ESTRI software for the time-averaged infrared signals of turbulent gas jets was further validated by comparing numerical results with measured integral radiation intensity data from a small aero-engine exhaust system plume. Based on this, a numerical study was conducted to investigate the impact of three often-neglected factors in exhaust system infrared characteristic calculations-Turbulence-Radiation Interaction (TRI), humidity of engine ingestion ambient air, and real-gas effects-on the infrared signals in the 3.7–4.8 μm wavelength band. The results show that TRI significantly influences the infrared characteristics of gas jets, with its effect slightly increasing with detection distance increase. The water vapor ingested from ambient air by the engine has little impact on the near-field infrared signals of the exhaust plume but can account for up to one-third of its far-field infrared signals. Real-gas effects also have a noticeable influence on the infrared signature of gas jets.

To address the issue of low prediction accuracy of gas jet Sub-Grid Scale Turbulence-Radiation Interaction (SGS-TRI) properties with the existing modeling methods, a correlation fluctuation term that accounts for the interaction between radiation-participating components and temperature into the sublattice Snegirev relationship is introduced. Simultaneously, a new and more user-friendly model for complex projects is established. The algorithm solving the dynamic sub-grid model coefficients facilitates the calculation of the dynamic Smagorinsky model and temperature variance model coefficients. The validity of this algorithm is confirmed through Direct Numerical Simulations (DNS) of isotropic turbulence and high-temperature air jet flow characteristic test data. Furthermore, considering the detection distance, the TRI properties and SGS-TRI properties of the 3-5 μm band infrared signal of the gas jet from an axisymmetric exhaust system are calculated and analyzed by utilizing the multi-scale multi-group wide-band k-distribution model. The properties of the multi-line group wide band model elucidate the formation mechanism of the observed phenomena.