Gas Turbine Engine Pivotable Flaps for Reverse-Thrust Flow Alignment
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Solution Overview
Problem
Gas turbine engines experience significant aerofoil separation during reverse thrust operations due to large adverse negative incidence angles, leading to distorted flow conditions and deteriorated core engine performance, with existing solutions either ineffective or causing undue performance penalties during normal operation.
Innovation Solution
Incorporation of pivotable flaps that guide the reverse airflow circumferentially to align with the nominal inlet angle of stator vanes, mitigating aerofoil separation by rotating between positions to intercept and guide airflow during reverse thrust without obstructing forward flow in normal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gas turbine engine uses conventional generic aerofoil designs to tolerate large incidence angle variations, then the aerofoil separation problem is partially addressed, but the nominal cruise performance deteriorates
Solution Approach 1:
The invention employs movable flaps that can dynamically adjust their position based on operational mode. During reverse thrust, the flaps rotate to a first position to guide airflow and prevent aerofoil separation. During normal forward thrust, the flaps rotate to a second position (aligned with the casing) to minimize interference with the flow path, thereby maintaining nominal cruise performance while addressing aerofoil separation only when needed.
Solution Approach 2:
The invention changes the geometric configuration parameter of the flow path by introducing movable flaps with variable positions. The flaps can assume different angular positions (first position for reverse thrust, second position for forward thrust), effectively changing the flow guidance parameters adaptively. This allows the engine to optimize airflow characteristics for each operational mode without compromising the other.
2Reliability
If the gas turbine engine architecture is modified to address core engine operability during reverse thrust (e.g., moving OGVs forward), then the reverse thrust operation is improved, but the engine design is significantly altered and compromised, affecting normal operation performance
Solution Approach 1:
Instead of permanently altering the engine architecture by moving OGVs forward, the invention uses dynamically adjustable flaps that can be positioned as needed. The flaps rotate to a first position during reverse thrust to guide airflow properly, and rotate to a second position during normal operation to be substantially aligned with the casing, thus avoiding any negative impact on normal operation performance while improving reverse thrust operability.
Solution Approach 2:
The invention introduces flaps as an intermediary component between the bypass duct and the core engine duct. These flaps mediate the airflow transition during reverse thrust by guiding the flow at the required angle, without requiring permanent structural modifications to the OGV position or other critical engine components, thereby preserving normal operation characteristics.
3Reliability
If the flaps are positioned to guide reverse flow, then aerofoil separation is reduced, but the flaps may obstruct forward flow during normal operation
Solution Approach 1:
The flaps are designed to be movable between two distinct positions. During reverse thrust operation, the flaps are positioned at an angle to guide the reverse flow and prevent aerofoil separation. During normal forward thrust operation, the flaps rotate to be substantially aligned with the casing, minimizing their obstruction to the forward flow path. This dynamic repositioning ensures optimal performance in both operational modes without compromising either.
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
The flaps effectively reduce aerofoil separation and maintain engine performance during reverse thrust, minimizing design modifications' impact on nominal operation and ensuring efficient airflow alignment with minimal weight and power requirements.
Implementation Method 1
Aerofoil separation may increase a total pressure loss at the entry duct of the core engine during the reverse thrust operation
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A gas turbine engine (100) includes a core engine casing (114), a bypass duct (122) and a core engine duct (111). The gas turbine engine (100) further includes a plurality of flaps (130) pivotally coupled to the core engine casing (114) and arranged circumferentially around a principal rotational axis (102). Each flap (130) extends from a first casing end (116) and is configured to pivotally rotate relative to core engine casing (114) about a pivot axis (P) between a first position (X1) and a second position (X2). In the first position (X1), each flap (130) is disposed in a circumferential direction (C) and is radially disposed between a plurality of OGVs (140) and a plurality of stator vanes (142). In the second position (X2), each flap (130) is inclined to the first position (X1) and extends at least partially into the bypass duct (122) and the core engine duct (111).