Aerodynamic Intercompressor Bleed Ports for Gas Turbine Engines
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Solution Overview
Problem
Gas turbine engines face engine surges due to excessive air flow into the combustion chamber during throttling or startup, which can be mitigated by an effective air bleed system that minimizes pressure loss and provides structural support while directing air out of the engine cavity.
Innovation Solution
An air bleed system featuring an annular bleed case with a manifold and ligaments that define bleed ports, allowing for circumferential flow and reducing pressure loss and disturbances, while being machined for lighter weight and greater strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an air bleed system is provided to mitigate engine surges, then engine stability is improved, but pressure loss across the system increases
Solution Approach 1:
The patent applies parameter changes by optimizing the geometric parameters of the bleed ports (size, shape, orientation, and distribution) to minimize pressure loss while maintaining the required bleed flow rate for surge mitigation. The bleed ports are specifically designed with aerodynamic contours and angled orientations that reduce flow separation and turbulence, thereby lowering the pressure penalty associated with bleeding air from the compressor chamber.
Solution Approach 2:
The patent implements local quality by creating non-uniform bleed port distribution around the compressor chamber, with varying sizes and orientations tailored to local flow conditions. This allows the bleed system to effectively manage surge conditions while minimizing pressure loss in specific high-flow regions, rather than using a uniform distribution that would either over-bleed some areas or under-bleed others.
2Strength
If a bleed case with structural ligaments is used, then structural strength is improved, but device complexity increases
Solution Approach 1:
The patent merges the structural support function and the aerodynamic bleed function into a single integrated component - the bleed case with ligaments. The ligaments serve dual purposes: providing structural strength to withstand engine loads and defining aerodynamic bleed ports through their geometry and arrangement. This consolidation eliminates the need for separate structural supports and bleed port structures, thereby reducing overall device complexity while maintaining both structural integrity and aerodynamic performance.
Solution Approach 2:
The bleed case structure embodies multi-functionality by simultaneously serving as a structural load-bearing component and an aerodynamic flow management component. The ligaments are designed to carry mechanical loads while their geometry defines the bleed port characteristics, making the structure universal in its functionality rather than requiring specialized separate components for each function.
3Weight of moving object
If the bleed case is machined rather than cast, then weight is reduced and strength is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the bleed case into modular sections or features that can be machined from smaller, more manageable stock pieces or as separate components that are subsequently assembled. This segmentation makes the machining process more feasible despite the complex aerodynamic contours and ligament structures, reducing both weight and improving strength-to-weight ratio compared to a monolithic cast structure.
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 air bleed system effectively reduces pressure loss and stabilizes the low-pressure compressor, enhancing engine stability by directing excess air flow away from the combustion chamber and withstanding engine loads.
Implementation Method 1
aerodynamically designed and oriented with respect to the air flow coming off the compressor rotor to maximize air flow through the bleed ports and reduce pressure loss across the system
Data Source
AI summary
An air bleed system for a gas turbine engine includes an annular bleed case with a manifold therein. The annular bleed case has a forward section and an aft section and ligaments connecting the two sections. The forward section, the aft section and the ligaments define bleed ports. The manifold is disposed radially outward of the ligaments and communicates with the series of bleed ports.