Gas Turbine Rotor Blade Tip Dihedral Design
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Solution Overview
Problem
Gas turbine engines experience performance losses due to airflow escaping through gaps between rotor blades and the surrounding shroud assembly, which existing designs have not adequately addressed.
Innovation Solution
The rotor blade design incorporates a tip portion with a dihedral angle, varying taper configurations, and sweep angles, which extends between the root and tip, and is partially surrounded by a shroud assembly to minimize airflow escape and enhance aerodynamic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If rotor blade tips are designed with conventional configurations, then manufacturing is simpler, but airflow leakage through the gap between blade tips and shroud assembly causes performance losses
Solution Approach 1:
The blade tip is segmented into multiple functional zones including a tip portion with dihedral angle, a platform portion with varying thickness, and a root portion. This segmentation allows each zone to perform specific functions: the tip portion with dihedral angle reduces airflow leakage, the platform portion provides structural support, and the root portion connects to the blade body, thereby reducing energy loss without excessive complexity
Solution Approach 2:
The invention introduces a dihedral angle in the tip portion that extends in a direction substantially perpendicular to the spanwise direction. This adds a vertical dimension to the blade tip geometry, creating a three-dimensional structure that effectively reduces the gap between blade tips and shroud assembly, thereby minimizing airflow leakage while maintaining manufacturing feasibility
2Loss of energy
If the tip portion extends perpendicular to the spanwise direction, then airflow leakage is reduced, but the structural complexity and manufacturing difficulty increase
Solution Approach 1:
The dihedral angle is applied locally only to the tip portion of the blade, while the rest of the blade maintains conventional geometry. This localized application reduces airflow leakage at the critical tip region without requiring complex manufacturing throughout the entire blade, making fabrication more feasible
Solution Approach 2:
The platform portion has a thickness that varies along the spanwise direction, being greater near the tip and decreasing toward the root. This partial variation in thickness provides structural support where needed (near the tip with high stress and leakage risk) while reducing material usage and manufacturing complexity in lower-stress regions
3Productivity
If rotor blades operate with tip gaps to shroud assembly, then clearance for rotation is maintained, but aerodynamic performance is degraded due to escape of airflow
Solution Approach 1:
The invention converts the harmful effect of the tip gap into a beneficial feature by designing the tip portion with a dihedral angle that directs airflow constructively. The perpendicular extension creates a barrier that redirects leakage flow back into the productive airflow path, converting what was previously a performance-degrading gap into an aerodynamic feature that maintains clearance while improving performance
Data Source
Figure 1
Figure 2~4
Figure 5A~5C
AI summary
A rotor blade for a gas turbine engine according to an exemplary aspect of the present disclosure includes, among other things, an airfoil extending in span between a root region and a tip region and a tip portion extending at an angle from the tip region of the airfoil.