• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.6
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• pp.375-382
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• 2020

Owing to the rapid development of infrared guided weapon systems, the threat to aircraft survivability is constantly increasing, and research on infrared stealth technologies are being conducted to ensure aircraft survival. In this study, we analyze the minimum infrared signature of an aircraft according to its flight altitude by considering the characteristics of infrared guided missiles, which detect the contrast signature between the aircraft and background. We conducted computational fluid dynamics simulations for the convective coefficient, and heat transfer simulations were performed considering convection, conduction, and radiation for flight conditions. Thus, we obtained the surface temperature distribution of the aircraft and analyzed the aircraft infrared signature based on the flow characteristics around it. Furthermore, the optimum emissivity for the minimum infrared signature was derived, and the effect of the infrared signature was analyzed when this optimum emissivity was applied to the fuselage surface for each flight condition.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.4
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• pp.28-35
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• 2021

Infrared (IR) stealth technology to protect aircraft from heat-tracking missiles is a very important factor in the development of military aircraft. In this study, the intensities of signal generation were compared by observing the IR signals generated from the plumes of the engine and identifying them for each measurement angle. To simulate a jet engine applied to an actual aircraft, a small turbojet engine was constructed, the infrared signal characteristics for each wavelength were identified according to the measurement angle, and the total infrared radiance was derived by integrating the signal for each wavelength. Through this study, we intend to present basic data for improving the infrared stealth performance of aircraft.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.5
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• pp.34-42
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• 2020

In modern air combat, infrared signals play an important role in the detection of opponents and must be reduced to improve survivability and stealth. In particular, IR signals generated in the wake of aircraft engines have high intensity and short wavelengths, so most heat-tracking missiles detect these signals. Accordingly, the measurement and characteristic analysis of Gas radiation signals from the engine's wake were carried out in this study. Micro turbojet engine has been configured to simulate a real aircraft turbofan engine, and the characteristics of IR signal reduction by adjusting the bypass ratio were identified. Through this, the IR signal characteristics for each wavelength are analyzed and verification of signal reduction technologies is performed.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.5
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• pp.27-35
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• 2019

Stealth technology is a technique to avoid detection from detectors such as radar and infrared seekers. In particular, detection by infrared signature is more threatening because infrared missiles detect heat from the aircraft itself. Therefore, infrared stealth technology is essential for ensuring the survival of aircraft and unmanned combat aerial vehicles (UCAV). In this study, we analyzed aerodynamic and infrared stealth performance in relation to UCAV nozzle design. Based on simulation results, a double serpentine nozzle was effective in reducing the infrared signature because it could shield high-temperature components in the engine. In addition, we observed that the infrared signature was reduced at the turning position of the duct located at the rear part of the double serpentine nozzle.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.5
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• pp.455-461
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• 2016

Survivability of an aircraft has been greatly threatened by the development of a weapon system using infrared. Therefore, the infrared stealth technology is a very important technique to improve the survivability of an aircraft. In this study, the infrared signal of an aircraft was analyzed which corresponding to the aircraft surface temperature and environmental conditions with various surface conditions(especially emissivity changed). Based on the analyzed infrared signal, the optimized surface emissivity was suggested to reduce the average contrast radiance and contrast radiant intensity(CRI). In addition, we confirmed that the infrared contrast radiant intensity between the aircraft and the background can be minimized through an appropriately controlled surface emissivity of the aircraft at specific background.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.3
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• pp.185-193
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• 2013

The plume infrared signature effects at various flight conditions of aircraft were investigated for the purpose of reducing infrared signature level. The nozzle of a virtual subsonic unmanned combat aerial vehicle was designed through a performance analysis. Nozzle and associated plume flowfields were first analyzed using a density-based CFD code and plume IR signature was then calculated on the basis of the narrow-band model. Finally, qualitative information for the plume infrared signature characteristics was obtained through the analysis of the IR signature effects at various flight conditions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.8
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• pp.688-694
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• 2012

A study on the effect of engine nozzle configuration on the engine plume Infra-red (IR) signature characteristics is performed. Configuration design of an engine nozzle with high aspect ratio to reduce IR signature level and a cylindrical nozzle which is typically used for conventional aircraft which does not require IR signature reduction is performed. And CFD analysis for the two nozzles is performed to compare the flowfields characteristics of the two nozzles. Finally IR signature analysis for the two nozzles is accomplished to calculate the total intensity level at mid-wave infra-red and investigate the differences of IR signature characteristics between the two nozzles.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.3
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• pp.204-212
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• 2015

The infrared lock-on range of target aircraft plays a critical role in determining the aircraft survivability. In this investigation, the effects of various UAV engine nozzle configurations on the aircraft lock-on range were theoretically analyzed. A virtual subsonic aircraft was proposed first, based on the mission requirement and the engine performance analysis, and convergent-type nozzles were then designed. After determining thermal flow field and nozzle surface temperature distribution with the CFD code, an additional analysis was conducted to predict the IR signature. Also, atmospheric transmissivity for various latitude and seasons was calculated, using the LOWTRAN code. Finally, the lock-on and lethal envelopes were calculated for different nozzle configurations, assuming the sensor threshold of the given IR guided missile. It was shown that the maximum 55.3% reduction in lock-on range is possible for deformed nozzles with the high aspect ratio.

• Journal of the Korea Institute of Military Science and Technology
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• v.17 no.6
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• pp.764-772
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• 2014

The stealth performance of supersonic aircraft in recent air battlefield is one of the most significant feature for latest fighters. Especially, as the technology is advancing, the IR stealth capability becomes more important because of its passive characteristic. To design an aircraft with stealth capability, we must know how much the IR signature is generated from the aircraft. Also, predicting the IR signature of enemy's aircraft is tactically crucial. In this study, we calculated MWIR and LWIR infrared signature of $5^{th}$ generation supersonic aircraft against air-to-air and surface-to-air threat using IR simulation code and CFD coupled procedure.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.7
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• pp.652-659
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• 2011

A computational system to predict flowfield and infrared signature in aircraft exhaust system is developed. As the first step, a virtual mission profile is considered and an engine is selected through a performance analysis. Then a nozzle that meets the requirement of each mission is designed. The internal flow in the exhaustion nozzle at the maximum thrust is analyzed using a state-of-the-art CFD code. In addition, a system to combine information of the skin temperature distribution of the nozzle and after-body surface with an infrared prediction code is developed. Finally, qualitative results for the infrared signature reduction design are obtained by investigating the infrared signature level under various conditions.