Non-Symmetrical Bleed Slots for Gas Turbine Compressor Stability
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Solution Overview
Problem
The existing compressor bleed systems in gas turbine engines suffer from non-axis-symmetric bleed flows due to uneven pressure distribution, leading to lower compressor stall margins, which can be mitigated by reducing slot areas but results in increased pressure losses.
Innovation Solution
The compressor design includes a circumferential manifold with a distribution of smaller, transitional, and larger bleed slots of varying areas, strategically located around the central axis, with specific slots proximate to mid-turbine frame/low pressure turbine ports, a buffer port for bearings, and an environmental control system port, optimizing bleed air distribution to achieve axis-symmetric flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the area of bleed slots is decreased to reduce flow asymmetry, then compressor stall margins are improved, but pressure losses increase
Solution Approach 1:
The patent applies local quality by varying the bleed slot areas at different circumferential locations. Specifically, first bleed slots have a first area, second bleed slots have a second area that is 80-95% of the first area, and third bleed slots have a third area that is 50-70% of the first area. This non-uniform distribution compensates for uneven pressure distribution in the manifold, achieving axis-symmetric bleed flow without requiring a uniform reduction in all slot areas, thus avoiding excessive pressure losses while improving compressor stall margins.
2Quantity of substance
If discrete flow extractions are made at manifold locations, then bleed air is delivered to critical systems, but uneven pressure distribution and flow asymmetry are created
Solution Approach 1:
The patent implements local quality by strategically positioning and sizing bleed slots at different locations around the compressor casing. The first, second, and third bleed slots are distributed circumferentially with different areas to match the specific bleed air requirements of different manifold ports (e.g., N2 bearing, LP turbine, mid-turbine frame, ECS). This localized optimization ensures sufficient bleed air delivery to each critical system while maintaining overall pressure distribution uniformity and axis-symmetric flow.
Solution Approach 2:
The patent applies segmentation by dividing the bleed slot system into multiple groups (first, second, and third bleed slots) with different areas and locations. Each group serves specific manifold ports with different bleed air demands. This segmented approach allows independent optimization of bleed air delivery to each critical system while collectively achieving uniform pressure distribution and symmetric flow across the entire compressor.
Data Source
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AI summary
A compressor of a gas turbine engine includes a plurality of rotors rotatable about a central longitudinal axis, a plurality of stators, and a circumferential inner case wall located outwardly of the plurality of rotors and the plurality of stators. The inner case wall includes a plurality of first slots located in a first section of the circumferential inner case wall and a plurality of second slots located in at least one second section of the circumferential inner case wall. A first area of each of the first slots is greater than a second area of each of the second slots. A circumferential manifold is located outwardly of the inner case wall including a port. At least one of the plurality of second slots is located proximate to the port.