Analysis on the Electromagnetic Scattering Characteristics of Aeroengine Exhaust Systems Based on ISAR Imaging

To investigate the electromagnetic scattering mechanisms and stealth performance of aero-engine exhaust systems, five typical nozzle configurations(axisymmetric nozzle, super-elliptic exit straight nozzle, single S-bend nozzle, double S-bend nozzle, and multi-dimensional deflection S-bend nozzle) were devised using the super-elliptic method with consistent geometric constraints including nozzle length, inlet/outlet areas, and cross-sectional area variation laws along the flow path. Electromagnetic scattering simulations were performed via the shooting and bouncing ray (SBR) method, and integrated analyses of one-dimensional range profiles, two-dimensional ISAR imagery, and scattering center distributions were conducted under varying detection angles and polarization modes. Results indicate that the detection angle significantly modulates scattering characteristics: at 0°, the closed inlet interface dominates as the primary strong scattering source, with the single S-bend nozzle exhibiting the highest amplitude and the multi-dimensional deflection S-bend nozzle the lowest. At 30°, S-bend cavity structures effectively shield the inlet wall, inducing a posterior shift and amplitude reduction of the scattering center. Two-dimensional ISAR imaging reveals that strong scattering sources are predominantly concentrated on the inlet wall and central cone; increasing the number of S-bends reduces scattering source density while expanding their distribution range. The multi-dimensional deflection S-bend nozzle, benefiting from bidirectional offset shielding, avoids large-area scattering source aggregation and achieves the lowest average scattering amplitude, with reductions of 81.02% (vs. single S-bend), 73.86% (vs. axisymmetric) in the pitch detection plane, and 78.73% (vs. axisymmetric) in the yaw detection plane. These findings demonstrate that optimizing cavity geometry—particularly via multi-dimensional deflection S-bend designs-enhances stealth performance across diverse detection scenarios by extending electromagnetic wave propagation paths and amplifying shielding effects.