Gas Turbine Blade Twist Profile for Radial Gap Stability
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Solution Overview
Problem
Existing gas turbine blades are sensitive to variations in the radial gap between the rotor and stator due to thermal, centrifugal force, and aging, leading to reduced efficiency and stability.
Innovation Solution
A blade design with varying pitch angles and S-shaped profile sections, particularly near the tip, to reduce sensitivity to radial gap variations and improve efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional blade designs with constant pitch angles are used, then the structure is simple and easy to manufacture, but the blade is highly sensitive to radial gap variations caused by thermal expansion, centrifugal force, and aging
Solution Approach 1:
The blade profile is designed with different pitch angles in different radial regions. The first profile section (near root) has a first pitch angle, while the second profile section (near tip) has a second pitch angle that differs from the first. This local variation in geometric properties allows each section to optimally handle the local conditions, particularly the radial gap variations that increase toward the blade tip, thereby reducing overall sensitivity to thermal and centrifugal effects.
Solution Approach 2:
The blade profile incorporates a pitch angle that varies continuously or in steps along the radial direction, creating a dynamic geometric adaptation rather than a static uniform design. This dynamic profile allows the blade to maintain optimal aerodynamic performance and structural characteristics across different radial positions, compensating for the dynamic changes in radial gap due to thermal expansion and centrifugal forces during operation.
2Productivity
If the blade pitch angle is varied to reduce sensitivity to radial gap variations, then efficiency improves, but the manufacturing precision requirements increase
Solution Approach 1:
The pitch angle variation is implemented in a controlled manner with specific discrete sections or continuous gradients that can be manufactured using standard aerospace manufacturing techniques. The first and second pitch angles are defined as distinct parameters that can be achieved through precision blade molding or machining, balancing the need for efficiency improvement with manufacturability constraints.
3Reliability
If the blade tip profile is modified with S-shaped sections, then sensitivity to radial gap variations decreases by up to 25%, but the blade design complexity increases
Solution Approach 1:
The blade tip profile incorporates S-shaped curved sections that provide smooth transitions and optimized flow characteristics. These curved profiles reduce turbulence and improve aerodynamic performance while accommodating radial gap variations. The S-shape geometry is a classic aerodynamic solution that balances complexity with performance benefits.
Solution Approach 2:
The S-shaped profile modification is applied specifically to the blade tip region (second profile section) where radial gap variations are most significant, rather than throughout the entire blade. This localized application of complex geometry minimizes overall design complexity while achieving the primary objective of reducing sensitivity to radial gap changes in the critical tip region.
Data Source
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Figure 3~4
AI summary
The present invention relates to a blade for a gas turbine, in particular of an aero engine, having a blade aerofoil (B; V) which has a blade-root-side first profile section (P1B; P1V) and a blade-tip-side second profile section (P2B; P2V), which is spaced apart from the first profile section in a radial direction (RB; RV), from the first profile section to the second profile section, by a blade aerofoil height (H), wherein a stagger angle (ß) of the blade aerofoil changes with a height (R) in the radial direction over the first profile section at least over certain portions, wherein in a first region between a first height (R1) and a second, greater height (R2), the change (dß/dR) in the stagger angle (ß) over the height (R) does not decrease with increasing height (R) at least over certain portions, and in an adjoining second region between the second height (R2) and a third, greater height (R3), the change (dß/dR) in the stagger angle (ß) decreases with increasing height (R) at least over certain portions, the first height (R1) representing at least 30% and at most 60% of the blade aerofoil height (H), the second height (R2) representing at least 50% and at most 80% of the blade aerofoil height (H) and the third height (R3) representing at least 80% and at most 100% of the blade aerofoil height (H).