U-Shaped Blocking Fin Infrared Suppression Gas Turbine Nozzle
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Solution Overview
Problem
Gas turbine engines in military aircraft emit significant infrared radiation due to hot exhaust gases, making them susceptible to detection by enemy anti-aircraft systems, including heat-seeking missiles, and existing infrared suppression systems can increase their own temperature, exacerbating the issue.
Innovation Solution
A method and apparatus for reducing infrared signatures from gas turbine engines, involving an exhaust assembly with a U-shaped blocking fin and cooling passages that channel ambient air to dissipate heat and reduce infrared emissions, including a primary nozzle with cooling fins and an insulated cowl to manage temperature and emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If ambient air is channeled past exposed metal surfaces to dilute exhaust gases, then infrared emission is reduced, but the cooling air flowpath becomes visible to infrared-guided weapons
Solution Approach 1:
A blocking fin is introduced as an intermediary element between the cooling air flowpath and the external environment. The blocking fin intercepts infrared radiation from the cooling air flowpath before it can be detected by external sensors, while still allowing the cooling air to flow through the exhaust system to reduce exhaust gas temperature and infrared emission.
Solution Approach 2:
The harmful infrared radiation from the cooling air flowpath is extracted and blocked by the blocking fin. The blocking fin captures and absorbs the infrared energy that would otherwise be emitted from the cooling air flowpath, separating this harmful radiation from the useful cooling function.
2Object-generated harmful factors
If infrared suppression systems absorb heat from exhaust gases, then infrared signature is reduced, but the suppression system temperature increases
Solution Approach 1:
The exhaust system is segmented into multiple functional zones: the exhaust gases flow through one path while ambient cooling air flows through a separate cooling air flowpath. The blocking fin is positioned to intercept infrared radiation from the cooling air flowpath without requiring the suppression system to directly contact or absorb heat from the hot exhaust gases, thus reducing the suppression system temperature.
Solution Approach 2:
The blocking fin serves as a thermal intermediary that blocks infrared radiation from the cooling air flowpath without requiring direct thermal contact with the hot exhaust gases. This allows the suppression system to reduce infrared signature while maintaining lower operating temperatures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively suppresses the infrared signature of gas turbine engines by reducing the temperature of exposed surfaces and extending the heat conduction path, thereby minimizing detectability by infrared-guided weapons, enhancing aircraft survivability.
Implementation Method 1
channel ambient air past at least some of the exposed visible surfaces to facilitate diluting exhaust gases discharged from the engine
Implementation Method 2
extending the heat conduction path
Implementation Method 3
exposed metal surfaces within the exhaust pipe emit infrared electromagnetic radiation at all wavelengths after being exposed to the high temperature exhaust gases
Data Source
AI summary
A method for assembling a gas turbine engine includes mounting a core engine to a vehicle, coupling a fuselage radially outward and around the core engine, coupling an exhaust nozzle to the core engine to channel exhaust gases discharged from the core engine, wherein the exhaust nozzle includes a cowl and a primary nozzle coupled radially inward from the cowl, and coupling an infrared suppression system in flow communication with the engine exhaust nozzle to facilitate suppressing an exhaust infrared signature of the core engine, wherein the infrared suppression system includes a blocking fin having a substantially U-shaped cross-sectional profile and such that a cooling air flowpath is defined between the cowl and the blocking fin.