Abstract:

To investigate the influence of afterbody on the infrared radiation characteristics of S-shaped nozzles in airframe-propulsion integration designs， this study employed scaled models of an S-shaped nozzle and a flying-wing aircraft’s afterbody. Utilizing a partitioned measurement method， experiments were conducted to characterize infrared radiation properties across representative detection surfaces in the rear hemispherical space.Results indicate that under the experimental conditions， the zonal measurement method has solved the problem that the core area of the tail jet flow cannot be covered under large-angle detection. In the upper， horizontal and lower detection surfaces， the integral radiation intensities of the second shooting account for 21.4%， 8.7% and 29.2% of the total integral radiation intensities respectively. The rear fuselage significantly alters the original infrared radiation characteristics of the S-shaped nozzle： In the forward tail direction （ α = 0°）， the heated afterbody acts as a secondary radiation source， increasing the peak radiation intensity by 12.3% compared to the model without afterbody. At lateral angles （ α > 5°）， afterbody shields the high-temperature exhaust and wall surfaces， reducing the radiation intensity of the afterbody test specimen by an average of 10.52% and 40.51% on the horizontal and downward detection planes， respectively， compared to the S-shaped nozzle.

Key words: airframe-propulsion integration, S-shaped nozzle, afterbody, infrared radiation, infrared suppression