Turbomachine Blade Sweep Law for High Flutter Margin
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Solution Overview
Problem
Turbomachine rotor blades face challenges in maintaining a sufficient flutter margin without increasing mass, as existing designs struggle to effectively manage the flutter phenomenon, which can lead to blade rupture and engine damage.
Innovation Solution
The design incorporates a specific maximum camber law where the ratio of maximum camber to chord at various blade heights is optimized between 25% and 40% of the ratio at the blade root, with a gradual decrease in camber ratio from the root to the mid-height and a quasi-constant ratio from mid-height to the tip, reducing flutter risk without increasing mass.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the blade structure is reinforced to increase flutter margin, then the resistance to flutter is improved, but the mass of the blade increases
Solution Approach 1:
The invention changes the geometric parameters of the blade by implementing a specific camber law that defines the camber ratio (maximum camber divided by chord) as a function of the relative height along the blade. This parameter optimization allows achieving better flutter margins through shape optimization rather than mass increase
Solution Approach 2:
The camber law applies different camber ratios at different locations along the blade height. The ratio varies from 10-20% at the root to 25-40% at the tip, creating local variations in structural properties that optimize flutter resistance without uniformly increasing mass throughout the blade
2Strength
If the camber ratio is increased at the blade root, then the structural strength is improved, but the flutter margin decreases
Solution Approach 1:
The invention optimizes the distribution of camber ratio along the blade height, establishing that the ratio at any given height should be between 25-40% of the root camber ratio. This parameter relationship ensures that while the root maintains sufficient strength, the tapering camber toward the tip enhances flutter margin
Solution Approach 2:
Different sections of the blade are assigned different camber ratios appropriate to their functional requirements. The root section (0-20% height) has higher camber ratio for strength, while mid and tip sections (20-100% height) have lower ratios (25-40% of root) optimized for flutter resistance
Data Source
AI summary
A turbomachine rotor blade includes plural blade sections stacked along an axis between a blade root and a blade head defining between the blade root and the blade head the height of the blade, each blade section including a chord and a maximum sweep defined by the maximum length of a segment perpendicular to the chord line and connecting a point of the chord line and a point of a camber line formed of all points located equidistant from the extrados and the intrados in the section, and verifying that the ratio between the maximum sweep and the chord at mid-height of the blade and the same blade head ratio is between 25% and 40% of the ratio between a maximum sweep and a blade root chord.