Correlation analysis between the infrared radiation intensity of exhaust plume and the scale of rocket engine in continuous-flow regime

The exhaust plume of rocket engines is a key target of interest for strategic defense systems in various countries. The experimental study of rocket plume employs typically small-scale models. It is of great importance to establish the similarity relationships between the results of different scale models, as this is a crucial step in applying these findings to thermal analysis of actual rocket engines. This study compares the flow field characteristics and infrared radiation features of the rocket engine exhaust plume with and without afterburning effect based on non-aluminized HTPB propellant under a series of engine scale ratios ranging from 0.1 to 10. The exhaust plume uses reactive flows. When the incoming condition is air, the exhaust plume exhibits the afterburning effect, while there is no afterburning effect when the incoming condition is pure nitrogen. The exhaust plume flow field is obtained through computational fluid dynamics (CFD), and the radiation signal is calculated by solving the radiation transport equation using the line of sight (LOS) method. The simulation results indicate that the flow field parameter distribution and infrared image shapes of the exhaust plumes from rocket engines of different scales are similar; Compared to the non-afterburning exhaust plume, the radiance peak of exhaust plume with the afterburning reaction is increased by 4.62 % to 10.21 %. The gain in infrared radiation intensity caused by the afterburning effect increases with increasing scale in the 2.7–3.0 μm and 3.3–4.0 μm bands. In the 4.2–4.5 μm of waveband, the gain stabilizes as the scale increases. The relationship between the engine scale and radiation intensity is exponential, with the exponent being influenced by both the waveband and the nozzle pressure ratio (NPR). The exponent value falls within the range of 1.5 to 3.4. The results of this study contribute to the understanding of rocket motor exhaust plume flow and radiation characteristics, which can aid in their engineering assessment.