Review of Infrared signature suppression systems using optical blocking method

Baranwal, Nidhi; Mahulikar, Shripad P.

doi:10.1016/j.dt.2018.12.002

Cited by 51 publications

(12 citation statements)

References 20 publications

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“…EGT goes as high as 2000 K or beyond in afterburner mode based on the engine configuration 2 . Infrared (IR) suppression systems in the latest stealth aircraft also require EGT measurement to know the wavelength of emitted IR radiation from the aircraft engine 3 .…”

Section: Introductionmentioning

confidence: 99%

Error Estimation of Measured Exhaust Gas Temperature in Afterburner Mode in an Aero Gas Turbine Engine

George

Muthuveerappan

2022

Def. Sc. J.

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In a turbofan engine, thrust is a key parameter which is measured or estimated from various parameters acquired during engine testing in an engine testbed. Exhaust Gas Temperature (EGT) is the most critical parameter used for thrust calculation. This work presents a novel way to measure and correct the errors in EGT measurement. A temperature probe is designed to measure EGT in the engine jet pipe using thermocouples. The temperature probe is designed to withstand the mechanical and temperature loads during the operation. Structural analysis at the design stage provided a strength margin of 90% and eigenfrequency margin of more than 20%. Thermal analysis is carried out to evaluate maximum metal temperature. Errors are quite high in high-temperature measurements which are corrected using the available methodologies. The velocity error, conduction error, and radiation error are estimated for the measured temperature. The difference of 97 K between the measured gas temperature and calculated gas temperature from measured thrust is explained. The estimated velocity error is 1 K, conduction error is 3 K, and radiation error is 69 K. Based on the error estimation, the measurement error is brought down to 24 K. After applying the above corrections, the further difference of 24 K between measured and estimated value can be attributed to thermocouple error of +/-0.4% of the reading for class 1 accuracy thermocouple, other parameter measurement errors, and analysis uncertainties. The present work enables the designer to calculate the errors in high-temperature measurement in a turbofan engine.

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Section: Introductionmentioning

confidence: 99%

Error Estimation of Measured Exhaust Gas Temperature in Afterburner Mode in an Aero Gas Turbine Engine

George

Muthuveerappan

2022

Def. Sc. J.

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“…4 Details and performance of several infrared signature suppression systems based on this working principle can be found in literature. 1,[5][6][7] Although not present in the reviews, 4,8 there are also some attempts to cool down exhaust gases by directly injecting coolants such as liquid water. 9,10 Despite the limited literature, it is observed that required coolant mass flow rate is excessive for the resulting IR signature reduction, and there is no practical application of these systems.…”

Section: Introductionmentioning

confidence: 99%

Obstruction of infrared signature with cold gases

Bas

2022

Proceedings of the Institution of Mechanical Engineers, Part G:

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The idea of infrared signature reduction by injecting cold gas between the source and observer has been investigated. Statistical narrow band coefficients of ethylene have been generated from HITRAN spectroscopic database and proposed to attenuate radiation on the 8–14 μm spectral region whereas CO2 is employed for 3–5 μm wavelength band suppression. Dilution of ethylene with CO2 also suppresses the flammability and guarantees safe operation. Several 1-D test cases are solved to validate the developed solver, and the proposed method is tested on 1-D and 3-D problems. The results satisfactorily show that a significant and safe radiance reduction can be achieved with cold CO2 diluted ethylene injection between the exhaust and observer on the whole spectrum.

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“…The main elements that generate infrared signals in aircraft are high-temperature engines and nozzles, exhaust gas, heating parts by exhaust gases, surface heating by aerodynamic heating, surface radiation and sun reflection. In particular, the technology to reduce infrared signal is important for improving aircraft survivability, as the high-temperature, high-pressure exhaust gas emitted from the aircraft engine (1,2) .…”

Section: Introductionmentioning

confidence: 99%

Infrared signal of the lobed mixer with external air mixing

2021

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In order to know the characteristics of reducing the exhaust gas infrared signal of the lobed mixer according to the external air mixing ratio, an infrared signal and temperature distribution measurement using a micro-turbojet engine is performed. A certain amount of compressed air is supplied through an external duct mounted on the micro-turbojet engine exhaust to simulate bypass flow, which is mixed with high-temperature core air and ejected to the atmosphere. The exhaust nozzle used in the experiment is a lobed mixer with a lobe of sinusoidal shape and is designed to have a penetration of 0.2. Exhaust gas temperature and infrared signal are measured according to distance from nozzle outlet under conditions of bypass ratio of 0.5, 1.0 and 1.4. Infrared reduction rates are compared to data without compressed air supply. As a result of the experiment, as the bypass ratio increased, the infrared signal of the exhaust gas and the temperature decrease with bypass ratio increase, and in the case of a bypass ratio of 1.4, the effect of reducing the temperature is observed even at a long distance. In addition, we compared the results of previous studies of a simple cone shape without mixer with infrared reduction effect. The results show that the lobed mixer has a greater effect on reducing the temperature of the exhaust gas and reducing the infrared signal than the cone nozzle. The structure of the mixed jet flow is also studied through Schlieren visualisation and 3D temperature distribution.

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Review of Infrared signature suppression systems using optical blocking method

Cited by 51 publications

References 20 publications

Error Estimation of Measured Exhaust Gas Temperature in Afterburner Mode in an Aero Gas Turbine Engine

Error Estimation of Measured Exhaust Gas Temperature in Afterburner Mode in an Aero Gas Turbine Engine

Obstruction of infrared signature with cold gases

Infrared signal of the lobed mixer with external air mixing

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