Compressor Shroud Bleed Holes for Stall Margin Improvement
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Solution Overview
Problem
Existing gas turbine compressor systems face performance losses due to low momentum air flow along the outer shroud, which can lead to premature rotor stall, and known recirculation systems that improve stall margin come at the expense of reduced performance.
Innovation Solution
The implementation of reverse-angled bleed holes in the compressor shroud to passively bleed low momentum air flow and recirculate it back into the compressor, effectively targeting and reducing tip leakage flow, thereby improving aerodynamic performance and operability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If recirculation systems are used to improve stall margin, then compressor stall margin is improved, but engine performance is reduced
Solution Approach 1:
The invention applies different treatment to different regions of the compressor flow. High momentum air at the shroud is bled off locally, while low momentum air near the blade tips is recirculated. This localized differentiation allows improvement of stall margin through tip flow recirculation while minimizing performance loss by selectively removing only the harmful high momentum shroud flow.
Solution Approach 2:
The invention changes the momentum parameter of the air flow by selectively bleeding high momentum air and recirculating low momentum air. By altering the momentum distribution in the compressor flow path, the system improves stall margin while maintaining acceptable performance levels.
2Productivity
If high momentum air flow is maintained at the shroud, then engine performance is improved, but premature rotor stall is triggered
Solution Approach 1:
The invention extracts or bleeds off the high momentum air flow from the shroud region through strategically placed bleed holes. This removal of high momentum air prevents the adverse interaction between shroud flow and rotor blades that would otherwise trigger premature stall, while the bled air is subsequently recirculated to maintain mass flow.
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
This approach enhances the compressor's stall margin while minimizing performance losses, leading to improved aerodynamic performance, reduced fuel consumption, increased thrust, and extended component life, along with potential structural and cost benefits.
Implementation Method 1
low momentum flow along the outer shroud of the compressor is known to be detrimental
Implementation Method 2
bleeding such low momentum air flow at the shroud is performed to improve engine performance
Data Source
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AI summary
A compressor (20) for a gas turbine engine having a bleed air recirculation system includes a plurality of bleed holes (36) extending through a shroud (32) at a first axial location thereon substantially adjacent the rotor blade tips (28). The bleed holes (36) have a closed outer perimeter along their complete length. An annular bleed cavity (38) surrounds the shroud (32) and is in communication with outlet openings (35) of the bleed holes (36). The bleed holes provide communication between said main gas flow passage and the bleed cavity (38). The bleed cavity (38) includes exit passages having outlets (39) disposed in said shroud (32) at a second axial location which is upstream of both the first axial location and the leading edge (46) of the blades (28) of the rotor (24). Bleed air is passively bled from the main gas flow passage via the bleed holes (36), recirculated through the bleed cavity (38) and re-injected back into the main gas flow passage at the second axial location.