Compressor Shroud Swept Grooves Stall Margin
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Solution Overview
Problem
Existing compressor designs for aircraft engines face challenges in maximizing compressor stall margin and minimizing performance loss, particularly in the rotor tip clearance region.
Innovation Solution
The compressor design incorporates a rotor with blades surrounded by a shroud featuring a series of circumferentially extending grooves with circumferential interruptions defined by baffles. These grooves are radially extended from inlet openings to closed-end surfaces, with a swept angle that axially offsets the center of the inlet openings from the closed-end surfaces, spanning an axial distance corresponding to 30% or more of the blade chord length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rotor tip clearance is reduced to improve compressor stall margin, then the compressor performance is improved, but the rotor casing becomes more complex and harder to manufacture
Solution Approach 1:
The rotor casing is segmented into discrete sections with individual grooves and baffles rather than a continuous complex structure. The grooves are divided into multiple segments around the circumference, allowing independent manufacturing and assembly of each segment, thereby reducing overall casing complexity while maintaining the stall margin improvement.
Solution Approach 2:
Instead of making the entire rotor casing complex, the invention applies localized grooves and baffles only in specific regions where they are most effective for controlling tip leakage flow. This local modification approach improves stall margin without requiring complex changes to the entire casing structure.
2Reliability
If surface treatments and structural modifications are added to the shroud to enhance rotor stall margin, then compressor performance is improved, but the manufacturing complexity and cost increase
Solution Approach 1:
The shroud modifications are segmented into discrete grooves and baffles that can be manufactured separately and then assembled or integrated into the shroud. This segmentation allows for simpler manufacturing processes compared to complex surface treatments, while still achieving the desired stall margin enhancement.
Solution Approach 2:
The invention changes the geometric parameters of the shroud by adding grooves with specific dimensions, depths, and orientations. These parameter changes provide a straightforward manufacturing approach compared to complex surface treatments, as they involve standard machining operations rather than specialized coating or treatment processes.
3Reliability
If the grooves are made continuous around the shroud circumference, then the flow control is improved, but the internal volume and weight of the rotor casing increase
Solution Approach 1:
The grooves are segmented around the shroud circumference rather than forming continuous rings. This segmentation reduces the total volume of material required for the grooves and baffles, thereby reducing the internal volume displacement and overall weight of the rotor casing, while still providing effective flow control at the critical groove locations.
Data Source
AI summary
A compressor for an aircraft engine. A rotor includes blades rotatable about an axis. Blade tips extend between leading and trailing edges. A shroud surrounds the rotor, with an inner surface surrounding the tips. Grooves are defined in the shroud inner surface adjacent the tips. The grooves extend circumferentially about the shroud and radially from inlet openings to closed end surfaces. Groove sidewalls extend circumferentially about the axis. The grooves are axially spaced-apart, the most upstream inlet opening having an upstream end disposed upstream of the leading edges of the blades. The grooves have a swept angle from the inner surface, with a center of the inlet openings is axially offset of a center of the closed-end surfaces. The grooves span an overall axial distance corresponding to 30% or more of the blades' chord length. The grooves have circumferential interruptions defined by baffles, and extend non-continuously around a shroud circumference.