低发射率热阻材料涂敷区域对某喷管红外抑制效果影响OA

Infrared stealth is critical for modern military aircraft to evade detection and tracking by infrared search-and-track systems.While aerodynamic and structural designs of nozzles have been extensively studied,the role of surface emissivity control through coatings remains an area with significant optimization potential.The work aims to systematically evaluate the infrared stealth issue of a certain type of engine aircraft two-dimensional(2D)nozzle and explore the optimal application scheme for a novel thermal resistance coating(TRC)applied inside the nozzle flow path,for balancing stealth performance with practical engineering considerations such as cost,weight,and thermal protection.The coating is designed to simultaneously suppress infrared radiation(in particularly in the 3-5 μm band)and provide thermal insulation for protecting nozzle structures.A three-dimensional compressible turbulent flow field-infrared radiation coupled numerical framework was established for a 2D nozzle.The flow field was solved through ANSYS Fluent with the k-ε turbulence model,while the infrared radiation intensity was subsequently calculated with the in-house software NUAA-IR,which integrated surface radiation,gas radiation(CO2 and H2O),and scattering effects.The analysis focused on the infrared radiation intensity within the 3-5 μm atmospheric window,at a detection distance of 5 000 m,and across azimuth angles from 0°(rear direction)to 90°(side direction).Four distinct coating schemes were designed:model 0(baseline,no coating),model 1(TRC applied only on the divergent section of the flow path,emissivity ε=0.12),model 2(TRC applied only on the convergent section,ε=0.12),model 3(TRC applied on both convergent and divergent sections,ε=0.12).By comparing spectral radiation curves and spatial distribution of infrared intensity,the suppression effectiveness of each scheme was quantitatively evaluated.Analysis confirmed that solid wall radiation was the dominant contributor to the total infrared intensity in the 3-5 μm band at various azimuth angles.The low emissivity coating significantly reduced wall radiation,especially on surfaces directly visible to the detector.However,within the sub-band 4.15-4.5 μm,where CO2 emission and absorption were strong,differences among the schemes were minimal due to the prevailing gas radiation effects.Compared with model 0,the reduction in radiation intensity for model 1 and model 3 first increased and then decreased with the increasing azimuth angle,reaching its maximum at an azimuth angle of 30°.At an angle of 30°,the wide-side radiation intensity decreased by 19.1%and 19.4%for model 1 and model 3 relative to model 0,respectively,while the narrow-side radiation intensity decreased by 6.9%for both models.When the azimuth angle increased to 90°,the radiation intensities of all four schemes converged to similar values.Model 2 showed almost identical infrared intensity to the baseline model 0 because the convergent section had nearly zero projection area to a rear detector,offering negligible stealth benefit.Thus,for infrared stealth optimization in the rear hemisphere,applying a low emissivity coating solely on the divergent section of the nozzle flow path is sufficient.This scheme achieves most of the achievable radiation reduction without the additional material and weight costs of full internal coating.If both infrared stealth and enhanced thermal insulation are required,for example,to prolong nozzle life or allow higher operating temperatures,a combined strategy is recommended:applying a low emissivity TRC on the divergent section for stealth,and a standard(not necessarily low emissivity)TRC on the convergent section solely for thermal protection.This hybrid approach delivers equivalent infrared suppression to a fully coated nozzle while minimizing cost and complexity.