Bypass Turbomachine Flap Control for Reverse Thrust Flow Separation
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Solution Overview
Problem
In bypass turbomachines for aircraft, the reverse operating mode leads to areas of separation in the air flow at the flow-splitting nose, degrading the efficiency of the gas generator and potentially jeopardizing its operation.
Innovation Solution
A bypass turbomachine with a ducted fan and a gas generator, featuring variable pitch vanes and a stator vane assembly connected by flaps that are pivotally movable, allowing for optimized air flow from the secondary duct to the primary duct, particularly in reverse mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If variable pitch vanes are used to enable reverse thrust mode, then the turbomachine can generate counter-thrust for landing, but areas of separation appear in the air flow at the flow-splitting nose which degrade the efficiency of the gas generator
Solution Approach 1:
The patent introduces movable flaps that can dynamically adjust their position based on the operating mode (forward or reverse). These flaps are pivotally mounted and can rotate between closed and open positions to control the opening of the first openings in the outer casing, thereby optimizing air flow paths according to the current operational requirements and preventing flow separation areas.
Solution Approach 2:
The patent changes the topological parameter of the air flow paths by introducing controllable openings in the outer casing that are not present in conventional designs. By opening or closing these openings via the movable flaps, the system can alter the air flow distribution between the primary and secondary ducts, thereby eliminating harmful flow separation areas while maintaining reverse thrust capability.
2Reliability
If flaps are added to control air flow openings, then air flow separation is reduced and gas generator efficiency is improved, but the device complexity increases
Solution Approach 1:
The movable flaps serve multiple functions: they control the opening of the first openings in the outer casing, optimize air flow paths during both forward and reverse operations, and prevent flow separation. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity while achieving the desired efficiency improvement.
Solution Approach 2:
The flaps act as intermediary elements between the air flow and the casing structure. By positioning these flaps strategically at the first openings, they mediate the air flow interaction with the primary and secondary ducts, enabling efficient flow control without requiring complex active control systems or multiple moving parts.
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 solution enhances the efficiency and service life of the turbomachine by optimizing air flow during reverse operations, reducing the negative impact of air flow separation and ensuring proper feeding of the primary duct.
Implementation Method 1
the appearance of areas of separation of the air flow at the level of the nose. In reverse operating mode, these separation areas strongly degrade the efficiency of the gas generator
Data Source
AI summary
The invention relates to a bypass turbomachine (2) for an aircraft, comprising a gas generator (5) and a ducted fan (4) comprising variable pitch blades (18) configured to take a reverse thrust position driving a reverse flow (24) of air within a secondary duct (16), the gas generator (5) being connected to a fan casing (3) by a stator blade assembly (40) that passes through the secondary duct, first openings (28) for letting in air from the reverse flow being located on an outer casing (17) at least partially internally delimiting the outer duct, and second openings (29) for letting said air out being located on an inner casing (14) at least partially externally delimiting an inner duct (12). The first openings are located within a plane that is perpendicular to a longitudinal axis (C) of the turbomachine and passes substantially through the middle of the blade assembly.