Compressor Shroud Bumps for Stall Prevention
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Solution Overview
Problem
The efficiency of turbomachines is limited due to blade wedge separations causing vortices and reducing the maximum flow through inter-blade passages, leading to stability issues such as stall and surge phenomena.
Innovation Solution
An axial turbomachine compressor with an annular surface featuring an arcuate row of bumps or recesses offset from the inter-blade pitch, where the maximum heights or depths vary progressively around the circumference, forming bump/hollow pairs with different radial amplitudes, and optionally including a third annular row of asperities that overlap the first row, providing a non-axisymmetric profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional axisymmetric annular surface is used, then the structure is simple and easy to manufacture, but blade wedge separations cause vortices that reduce maximum flow and compressor stability
Solution Approach 1:
The patent applies asymmetry by introducing a non-axisymmetric profile on the annular surface with bumps and hollows that vary in radial amplitude around the circumference. This asymmetric configuration disrupts the formation of blade wedge separations and vortices, thereby improving compressor stability and maximum flow capacity while maintaining manufacturing feasibility through controlled geometric variations.
Solution Approach 2:
The patent implements local quality by creating specific localized features (bumps and hollows) at particular circumferential positions on the annular surface. These localized modifications are designed to specifically address flow separation issues in critical regions while leaving other areas unchanged, thus improving stability without unnecessarily complicating the entire structure.
2Productivity
If the annular surface is made non-axisymmetric with varying bump heights, then flow efficiency and maximum flow capacity improve, but manufacturing complexity and precision requirements increase
Solution Approach 1:
The patent applies parameter changes by systematically varying the radial amplitude of bumps and hollows around the circumference. By controlling parameters such as height, depth, and circumferential positioning, the design optimizes flow capacity and efficiency. The progressive variation in these parameters allows for improved maximum flow while maintaining manufacturability through standardized variation patterns.
3Loss of energy
If bumps and hollows are added to the annular surface, then flow separation and vortex generation are reduced, but the structural complexity and number of features increase
Solution Approach 1:
The patent applies segmentation by dividing the annular surface into distinct features (bumps and hollows) arranged in a pattern around the circumference. This segmentation allows the surface to be designed with multiple discrete elements that collectively reduce flow separation and energy loss, while each individual feature can be manufactured using standard techniques.
Data Source
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AI summary
The invention relates to a low-pressure compressor of an axial turbomachine such as a turbojet. The compressor comprises a row of blades (34) extending radially from an annular surface (42) in a non-axisymmetric form, known as 3D contouring. In the inter-blade passages (44), the annular surface (42) comprises an arched row of bumps (56) offset in relation to the inter-blade pitch, each one having a maximum height (H); and an arched row of cavities (62) offset in relation to the inter-blade pitch, each one having a maximum depth (P). The maximum heights (H) and the maximum depths (P) vary according to the circumference of the annular surface (42) such that the profiling changes around the compressor. The invention also relates to a casing or a casing segment and a turbomachine.