Adaptive reverse Monte Carlo method and evaluation for infrared radiation characteristics of scramjet

Scramjet is the most promising propulsion system for Air-breathing Hypersonic Vehicle (AHV), and the Infrared (IR) radiation it emits is critical for early warning, detection, and identification of such weapons. This work proposes an Adaptive Reverse Monte Carlo (ARMC) method and develops an analytical model for the IR radiation of scramjet considering gaseous kerosene and hydrogen fueled conditions. The evaluation studies show that at a global equivalence ratio of 0.8, the IR radiation from hydrogen-fueled plume is predominantly from H₂O and spectral peak is 1.53 kW·Sr⁻¹·μm⁻¹ at the 2.7 μm band, while the kerosene-fueled plume exhibits a spectral intensity approaching 7.0 kW·Sr⁻¹·μm⁻¹ at the 4.3 μm band. At the backward detection angle, both types of scramjets exhibit spectral peaks within the 1.3–1.4 μm band, with intensities around 10 kW·Sr⁻¹·μm⁻¹. The integral radiation intensity of hydrogen-fueled scramjet is generally higher than kerosene-fueled scramjet, particularly in 1–3 μm band. Meanwhile, at wide detection angles, the solid walls become the predominant radiation source. The radiation intensity is highest in 1–3 μm and weakest in 8–14 μm band, with values of 21.5 kW·Sr⁻¹ and 0.57 kW·Sr⁻¹ at the backward detection angles, respectively. Significant variations in the radiation contributions from gases and solids are observed across different bands under the two fuel conditions, especially within 3–5 μm band. This research provides valuable insights into the IR radiation characteristics of scramjets, which can aid in the development of IR detection systems for AHV.