Turbomachine Blade Thickness Law for Flutter Margin
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Turbomachine blades face challenges in maintaining mechanical resistance, aerodynamic performance, and reducing flutter phenomena, which can lead to blade rupture and engine damage, with existing designs struggling to effectively manage flutter without compromising operational zones.
Innovation Solution
The design of turbomachine rotor blades with specific maximum thickness to chord ratios varying along the blade height, defined by piecewise affine functions, to maximize the flutter margin without degrading mechanical or aerodynamic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the blade thickness is increased to improve mechanical resistance, then the strength increases, but the aerodynamic performance degrades and flutter resistance worsens
Solution Approach 1:
The patent applies different thickness-to-chord ratios at different locations along the blade height. The root section has a higher ratio (20-40%) for mechanical strength, while intermediate and tip sections have lower ratios (10-30% and 5-20% respectively) to reduce flutter. This spatial variation of geometric properties resolves the contradiction between strength and flutter resistance.
Solution Approach 2:
The patent changes the geometric parameters (thickness and chord) along the blade height according to specific mathematical laws. By varying the thickness-to-chord ratio as a function of relative height, the blade achieves optimal mechanical properties at the root while minimizing flutter-prone characteristics at the tip, thus resolving the contradiction.
2Reliability
If the blade thickness is increased to reduce bending-torsion coupling, then the flutter margin improves, but the blade mass increases
Solution Approach 1:
The patent increases thickness locally at the blade root where bending moments are highest and flutter effects are most problematic, while maintaining thinner sections at the tip where mass reduction is more beneficial. This localized thickening reduces bending-torsion coupling without proportionally increasing overall blade mass.
Solution Approach 2:
The patent employs composite material structures that allow for optimized thickness distribution. The composite construction enables achieving high flutter margin through strategic thickness variation while controlling overall mass through material selection and structural efficiency.
3Reliability
If the blade geometry is modified to increase flutter margin, then the flutter resistance improves, but the aerodynamic performance may be degraded
Solution Approach 1:
The patent modifies geometry locally at the root section with higher thickness-to-chord ratios to improve flutter resistance, while keeping the aerodynamic sections (intermediate and tip) with lower ratios to maintain good aerodynamic performance. This localized modification isolates the flutter mitigation措施 from the aerodynamic critical zones.
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 increases the flutter margin by reducing bending-torsion coupling and enhancing the frequency of the first bending mode, thereby minimizing flutter effects while maintaining blade integrity and efficiency.
Implementation Method 1
Flutter is an aeromechanical coupling due to the relative movement of the air with respect to the structure of the blades and of the blading. Flutter is a self-maintaining phenomenon, the modification of the solid structure modifying the flow of the fluid and the modification of the flow of the fluid generating forces on the solid structure.
Data Source
AI summary
A turbomachine rotor blade is formed of plural blade sections stacked along an axis extending from a blade root to a blade tip. Each blade section located at various heights along the blade is designed to have a given ratio between a maximum thickness, which is measured between a suction side and pressure side of the blade, and a chord, which is defined by a line connecting a leading edge and a trailing edge of the blade. Each blade section is further designed to have a ratio of the maximum thickness to the chord at a given height of the blade relative to a ratio of the maximum thickness to the chord of another blade section located at a different height of the blade.