Unducted Fan Hub Boundary Layer Ingestion for Stall Margin
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Solution Overview
Problem
Unducted fan gas turbine engines face efficiency losses due to boundary layer formation along the large hub or spinner, leading to distorted airflow and reduced stall margin, which conventional designs fail to address effectively.
Innovation Solution
The engine incorporates boundary layer openings and an airflow injection assembly to remove or re-energize the boundary layer airflow, resulting in a more uniform and higher-speed flow to the compressor, reducing aerodynamic losses and improving design flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a large hub or spinner is used in unducted fan gas turbine engines, then the engine can achieve higher power output, but boundary layer formation along the hub causes distorted airflow and reduced stall margin
Solution Approach 1:
The patent extracts the harmful boundary layer airflow from the system by providing openings in the hub or spinner that allow the boundary layer to be removed separately from the main airflow path. This extraction eliminates the distorted airflow that would otherwise reduce stall margin while preserving the large hub configuration needed for high power output.
Solution Approach 2:
The patent converts the harmful boundary layer into a beneficial feature by routing it through separate openings to drive a boundary layer turbine or generate useful work. This transforms the previously harmful distorted airflow into a useful energy source, maintaining high power output while eliminating its negative effects on stall margin.
2Device complexity
If conventional designs are used, then the engine structure is simple, but efficiency losses occur due to boundary layer formation and distorted airflow
Solution Approach 1:
The patent segments the airflow path into two separate channels: the main airflow path for power generation and the boundary layer path for removal or utilization. By providing distinct openings and pathways for boundary layer airflow, the system separates the harmful effects from the useful functions, reducing efficiency losses while adding manageable structural complexity.
3Adaptability or versatility
If boundary layer airflow is not addressed, then the engine design is straightforward, but aerodynamic losses increase and design flexibility is constrained
Solution Approach 1:
The patent introduces dynamic control capabilities by making the boundary layer opening configuration adjustable or variable. This allows the system to adapt to different operating conditions and optimize performance across various flight regimes, increasing design flexibility while continuously managing aerodynamic losses through active boundary layer control.
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 enhances airflow uniformity, reduces aerodynamic losses, and eases design constraints related to distortion and stall margin, thereby increasing efficiency and flexibility in engine design.
Implementation Method 1
boundary layer formation along the large hub or spinner, leading to distorted airflow
Implementation Method 2
an airflow injection assembly to remove or re-energize the boundary layer airflow
Data Source
AI summary
A gas turbine engine is provided, comprising: a turbomachine having a compressor section, a combustion section, and a turbine section in serial flow order; and a fan section having a fan drivingly coupled to the turbomachine and an airflow surface rotatable with the fan and exposed to a fan airflow provided to and through the fan during operation of the gas turbine engine, the airflow surface defining a plurality of boundary layer openings configured to ingest a boundary layer of the fan airflow over the airflow surface during operation of the gas turbine engine.