Variable Nozzle Flap Segmentation for Thrust Loss Reduction
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Solution Overview
Problem
Real flaps and seals in variable nozzles for aeronautic gas turbines, being flat, deviate from ideal shapes determined by numerical analysis, leading to shock wave structures and non-negligible thrust losses.
Innovation Solution
The design incorporates primary flaps with two sections of distinct angles to suppress shock waves between primary and secondary flaps, optimizing the flow path and reducing thrust loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If flat flaps and flat seals are used to construct the variable nozzle, then the manufacturing complexity is reduced and ease of manufacture is improved, but the flow path shape deviates from the ideal shape determined by numerical analysis, causing shock wave structures and thrust loss
Solution Approach 1:
The flaps are divided into multiple segments with different curvature radii (first curvature radius R1 for the convergent section, second curvature radius R2 for the divergent section). This segmentation allows each flap to approximate the ideal flow path shape more closely while remaining manufacturable using standard curved panel techniques, thereby reducing thrust loss without excessively complicating manufacturing
Solution Approach 2:
Different portions of the flap are given different geometric properties: the convergent section has curvature radius R1 and the divergent section has curvature radius R2. This local differentiation of geometric quality allows the flap to better match the ideal flow path shape in different regions, reducing shock wave formation and thrust loss while maintaining manufacturing feasibility
2Manufacturing precision
If the number of flat flaps and flat seals is increased to approximate the ideal flow path shape, then the flow path shape accuracy is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
Rather than using many small flat panels, the invention uses a smaller number of flaps that are each segmented into two curved sections. This reduces the total number of components and assembly operations while achieving comparable or superior flow path accuracy through the use of appropriate curvature radii R1 and R2
Solution Approach 2:
The invention transitions from flat panels to curved panels with specific curvature radii. By incorporating curvature into the flap geometry (first curvature radius R1 for convergence, second curvature radius R2 for divergence), the flow path shape accuracy is significantly improved without requiring an excessive number of components, thus avoiding excessive device complexity
3Device complexity
If conventional flat flap design is used, then the structural simplicity is maintained, but shock waves are generated at the interfaces between flaps, causing non-negligible thrust loss
Solution Approach 1:
By giving the flaps curved surfaces with specific radius of curvature instead of flat surfaces, the invention eliminates the sharp angular interfaces that generate shock waves. The curved transition between flaps creates a smoother flow path that reduces shock wave formation and preserves thrust, while the number of flaps remains manageable
Solution Approach 2:
The flap surfaces are given different local curvature properties (R1 in the convergent section, R2 in the divergent section) to optimize flow characteristics in different regions. This local differentiation reduces shock wave formation at critical interfaces while maintaining overall structural simplicity
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
This configuration results in a thrust coefficient increase to 0.991, comparable to ideal nozzle performance, with a 2% higher thrust ratio and 1.2% increased flow rate coefficient, effectively minimizing thrust loss.
Implementation Method 1
shock waves by angular flexures between the primary flaps and the secondary flaps are suppressed
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A variable nozzle that discharges the exhaust gas of an aeronautic gas turbine engine, along the axis thereof, from the fore end to the aft end of the aircraft, is comprised of an exhaust duct (3) guiding the exhaust gas toward the aft end, a plurality of primary flaps (5) arranged to define a primary flow path (15) converging toward the aft end, each axially supported, so as to be rotatable, by the exhaust duct that adjusts the opening of the primary flow path, and each comprising a first section (53) and a second section (55) that forms an angle outward in the radial direction relative to the first section; and a plurality of secondary flaps (7) arranged to define a secondary flow path (17) in communication with the first flow path and capable of forming a fan shape towards the aft end, the plurality of secondary flaps each axially supported to be rotatable, by the second section of the primary flaps that adjust the opening of the secondary flow path.