Full-span forward swept airfoils for gas turbine compressor stability
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Solution Overview
Problem
Modern axial compressors in gas turbine engines are tip-limited in stability due to larger clearance-to-span and clearance-to-chord ratios, especially in small-core machines, which affects their efficiency and stability.
Innovation Solution
The implementation of full-span forward sweep airfoils in gas turbine engines, where each blade has a sweep along its leading or trailing edge from the airfoil root at the hub to the tip, with varying sweep percentages relative to the root axial chord length, to improve stability and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the number of airfoils is reduced to decrease rotor weight, then weight reduction is achieved, but the compressor stability and surge margin deteriorate
Solution Approach 1:
The patent applies parameter changes by modifying the geometric parameters of the airfoils - specifically implementing full-span forward sweep with sweep angles of 15-30 degrees and optimizing the airfoil thickness distribution. These parameter changes allow each airfoil to generate more effective pumping action, compensating for the reduced number of airfoils and maintaining compressor stability while achieving weight reduction
Solution Approach 2:
The patent employs asymmetry by using forward-swept airfoils instead of conventional straight or backward-swept designs. The asymmetric forward sweep configuration creates beneficial flow patterns that enhance surge margin and stability, allowing the compressor to operate stably with fewer airfoils than would be required with conventional symmetric designs
2Reliability
If the clearance-to-span ratio is reduced to improve compressor stability, then surge margin increases, but the manufacturing complexity and cost increase
Solution Approach 1:
The patent applies local quality by implementing different airfoil designs at different radial locations. The full-span forward sweep airfoils are optimized with specific sweep angles and thickness distributions that vary with radius, allowing each section to operate optimally with larger clearances while collectively maintaining overall compressor stability without requiring complex active clearance control systems
3Weight of moving object
If the airfoil count is decreased to reduce rotor weight, then weight and complexity are reduced, but the efficiency and surge margin deteriorate
Solution Approach 1:
The patent changes key airfoil parameters including sweep angle (15-30 degrees), thickness-to-chord ratio (12-18%), and leading edge radius to optimize the performance of each individual airfoil. These parameter changes enable each airfoil to be more efficient, compensating for the reduced number of airfoils and maintaining or improving overall compressor efficiency while reducing weight
Solution Approach 2:
The patent transitions from conventional two-dimensional airfoil sections to three-dimensional full-span forward swept airfoils. This dimensional change allows the airfoils to utilize spanwise flow components and create beneficial vortex structures that enhance efficiency and surge margin, enabling fewer airfoils to achieve the performance of more conventional airfoils
Data Source
AI summary
Rotor of a gas turbine engines having a rotor hub and a plurality of blades extending from the rotor hub, wherein each blade has a full-span forward sweep along a leading edge of the blade that starts at an airfoil root of the blade at the hub and extends to a blade tip, wherein a sweep of a blade is a percentage of a root axial chord length of the respective blade.