Flow Diverter for Gas Turbine Bleed Duct Pressure Instability
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Solution Overview
Problem
Gas turbine engines experience dynamic pressure instability in bleed ducts due to high magnitude pressure oscillations when the flow control valve is closed, leading to structural damage and sonic fatigue, and existing methods to mitigate this involve valve leakage, which is not acceptable under recent operational requirements.
Innovation Solution
A flow diverter is positioned adjacent the inlet of the bleed duct to divert air from entering when the flow control valve is closed, and to allow air to enter when the valve is opened, thereby preventing dynamic pressure instability without allowing valve leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the flow control valve is closed to prevent air flow through the bleed duct, then air leakage is prevented, but dynamic pressure oscillations occur causing structural damage
Solution Approach 1:
A flow diverter is introduced as an intermediary component between the fan bypass duct and the bleed duct inlet. This flow diverter redirects the high-velocity air flow from the fan bypass duct away from the bleed duct inlet, preventing the formation of dynamic pressure oscillations while allowing the flow control valve to remain fully closed. The flow diverter acts as a mediator that eliminates the harmful interaction between the bypass flow and the closed bleed duct.
2Object-affected harmful factors
If the flow control valve is allowed to leak to reduce pressure oscillations, then dynamic pressure instability is suppressed, but valve leakage occurs which is not acceptable under operational requirements
Solution Approach 1:
The flow diverter serves as an intermediary that eliminates the need for valve leakage to suppress dynamic pressure oscillations. By redirecting the bypass air flow away from the bleed duct inlet, the flow diverter prevents the formation of pressure oscillations at their source, allowing the flow control valve to maintain a fully closed position without any leakage.
3Productivity
If high velocity air flow enters the bleed duct inlet directly, then cooling performance is maintained, but dynamic pressure instability occurs when the valve is closed
Solution Approach 1:
The flow management is segmented into two independent pathways: (1) The flow diverter handles the high-velocity bypass air flow from the fan bypass duct, redirecting it away from the bleed duct inlet to prevent instability. (2) The flow control valve independently controls the bleed air flow to the heat exchanger for cooling purposes. This segmentation allows each component to perform its function without causing dynamic pressure instability.
4Loss of substance
If the flow control valve is fully closed to meet operational requirements, then valve leakage is eliminated, but sonic fatigue damage occurs due to pressure oscillations
Solution Approach 1:
The flow diverter is positioned as an intermediary component that intercepts and redirects the bypass air flow before it can interact with the closed bleed duct inlet. This prevents the formation of dynamic pressure oscillations and subsequent sonic fatigue damage, while allowing the flow control valve to remain fully closed and eliminate leakage.
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 flow diverter effectively suppresses dynamic pressure oscillations, preventing structural damage and sonic fatigue in gas turbine engines by redirecting air flow away from the inlet when the valve is closed and allowing it to pass through when open, thus maintaining engine performance without valve leakage.
Implementation Method 1
a flow diverter positioned adjacent an inlet of the bleed duct. The flow diverter is configured to prevent a flow of air in the fan bypass duct of the gas turbine engine from entering the inlet of the bleed duct when a flow control valve disposed within the bleed duct is closed
Implementation Method 2
The bleed duct has a characteristic one-quarter wavelength organ pipe acoustic resonance, and the oscillating pressure fluctuations tend to couple in a non-linear, unstable fashion with the acoustic resonance
Implementation Method 3
The flow of air through the bleed duct is typically controlled by a flow control valve, for example a butterfly valve
Data Source
AI summary
An apparatus and method for suppressing dynamic instability in a bleed duct of a gas turbine engine includes a fan bypass duct configured to permit a flow of air through the gas turbine engine. The fan bypass duct defines a fan duct surface, and the bleed duct has an inlet in fluid communication with the fan bypass duct and a flow control valve having an opened position and a closed position. A flow diverter is positioned on the fan duct surface proximate the inlet of the bleed duct and diverts the flow of air from the inlet when the flow control valve is closed, while permitting a portion of the flow of air to enter the inlet when the flow control valve is opened.