Variable-Geometry Convergent-Divergent Exhaust Nozzle
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Solution Overview
Problem
Variable-geometry convergent-divergent exhaust nozzles for gas turbine engines face issues with increased radar return and reduced aerodynamic efficiency due to discretized designs.
Innovation Solution
A variable-geometry convergent-divergent exhaust nozzle design featuring rotatable flap assemblies with converging and diverging surfaces, where the connection between flaps is decoupled from the throat, reducing radar return and maintaining high expansion ratios with a low radar signature, utilizing actuators for precise control of flap positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If discretized nozzle design with hinged flaps is used, then variable geometry control is achieved, but radar return increases
Solution Approach 1:
The patent applies dynamics by making the entire nozzle contour movable through a single hinge point, allowing continuous adjustment of the exhaust flow area and nozzle geometry. This dynamic design enables the nozzle to vary its shape smoothly without discrete segmented movements, reducing radar cross-section while maintaining variable geometry capability for different flight regimes.
Solution Approach 2:
The patent employs curved surfaces and smooth contours on the movable nozzle flaps rather than sharp edges or angular discontinuities. The curved geometry helps to deflect radar waves more effectively and maintains aerodynamic efficiency, thereby reducing radar return while preserving the variable geometry function.
2Adaptability or versatility
If discretized nozzle design with hinged flaps is used, then variable throat area control is achieved, but aerodynamic efficiency reduces
Solution Approach 1:
The dynamic hinge mechanism allows the nozzle to achieve smooth, continuous adjustment of the throat area and exit area simultaneously. This eliminates the stepped or discontinuous flow paths that would result from multiple discrete hinged flaps, thereby maintaining high aerodynamic efficiency while providing variable geometry control.
Solution Approach 2:
The patent merges the control of multiple nozzle parameters (throat area, exit area, contour shape) into a single hinge mechanism. This unified approach ensures that all geometric changes occur in coordination, maintaining optimal flow alignment and aerodynamic performance across the full range of motion, unlike discretized designs where independent flap movements can create flow disturbances.
Data Source
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AI summary
There is described a variable-geometry convergent-divergent exhaust nozzle (30) for a gas turbine engine (10). The variable-geometry convergent-divergent exhaust nozzle (30) comprises: an exhaust duct (32) configured to receive an exhaust flow of gas from a combustor (15) of the gas turbine engine (10); a first flap assembly (202) comprising a first proximal flap (206) and a first distal flap (208); and a second flap assembly (204) comprising a second proximal flap (210) and a second distal flap (212). The first proximal flap (206) is rotatably coupled to the exhaust duct (32) and comprises a first entry surface (214) that in part defines a nozzle passageway (38), the nozzle passageway (38) being configured to convey the exhaust flow of gas to an exterior (40) of the gas turbine engine (10). The second proximal flap (210) is rotatably coupled to the exhaust duct (32) and comprises a second entry surface (218) that in part defines the nozzle passageway (38). The first distal flap (208) is rotatably coupled to the first proximal flap (206). The second distal flap (212) is rotatably coupled to the second proximal flap (210). The first distal flap (208) comprises a first converging surface (250) and a first diverging surface (252) angled with respect to the first converging surface (250). The second distal flap (212) comprises a second converging surface (256) and a second diverging surface (258) angled with respect to the second converging surface (256). The first converging surface (250) and the second converging surface (256) define at least in part a convergent portion (262) of the nozzle passageway (38). The first diverging surface (252) and the second diverging surface (258) define at least in part a divergent portion (264) of the nozzle passageway (38).