Non-axisymmetric Fan Flow Path for Gas Turbine Stability
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Solution Overview
Problem
Gas turbine engines face instability due to ingested boundary layer flow distortion, particularly during take-off, landing, and in lateral wind conditions, which affects inlet total pressure and swirl distortions.
Innovation Solution
The design incorporates a non-axisymmetric fan flow path with perturbations, spoilers, and wavy portions on the fan and core case surfaces to redistribute aerodynamic loading and mitigate distortions, including perturbations on the inner and outer surfaces of the fan and core cases, and the use of spoilers and rub strips to manage airflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional axisymmetric fan flow path is used, then the engine structure is simple and easy to manufacture, but the stability margin is reduced due to ingested boundary layer flow distortion
Solution Approach 1:
The patent applies asymmetry by introducing a non-axisymmetric geometry in the fan flow path, specifically through perturbations on the inner surface of the fan case and the outer surface of the core case. These asymmetric features redistribute aerodynamic loading and mitigate the effects of ingested boundary layer flow distortion, thereby increasing the stability margin without requiring complex active control systems
Solution Approach 2:
The patent implements local quality by placing specific perturbations at particular locations on the fan case and core case surfaces. The inner surface of the fan case has perturbations at specific angular positions, while the outer surface of the core case has corresponding perturbations, creating localized modifications that collectively improve overall flow stability without complicating the entire structure
2Reliability
If perturbations are added to the fan case and core case surfaces, then incoming pressure and radial distortion are reduced, but manufacturing complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the perturbations into distinct components: perturbations on the inner surface of the fan case, perturbations on the outer surface of the core case, and separate spoiler assemblies. These segmented features can be manufactured and positioned independently, simplifying the overall manufacturing process while achieving the desired flow redistribution effect
Solution Approach 2:
The patent implements preliminary action by incorporating the perturbations and spoilers into the engine structure during manufacturing, so that the flow distortion mitigation features are already in place before the engine operates. This eliminates the need for complex real-time adjustments or assemblies during operation, improving ease of manufacture
Data Source
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AI summary
A gas turbine engine propulsion system and method of assembling such is disclosed. The gas turbine engine propulsion system comprises a gas turbine engine that includes a fan flow path. The fan flow path may extend from the fan inlet to the rear exhaust outlet of the bypass flow path. A portion of the fan flow path, proximal to the fan, is non-axisymmetric. The non-axisymmetric portion may be upstream or downstream of the fan.