Gas Turbine Blade Tip Geometry for Wear Reduction
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Solution Overview
Problem
Gas turbine engines experience excessive blade wear and tip fractures due to rub events, leading to decreased performance and increased maintenance costs, characterized by a high rub ratio where more material is lost from the blade tip than the penetration depth into the casing.
Innovation Solution
The airfoil tip geometry is modified with planar and recessed sections, where the recessed sections are offset from the leading and trailing edges, reducing the contact area and loads during rub events, thereby decreasing the rub ratio and material loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the blade tip penetrates the casing during rub events, then contact between blade and casing occurs, but excessive material loss from the blade tip results in high rub ratio and decreased performance
Solution Approach 1:
The blade tip is designed with non-uniform thickness distribution, featuring a thinner planar section and a thicker recessed section. This local quality variation allows the thinner planar section to contact the casing first during rub events, controlling the contact geometry and reducing the rub ratio by limiting material loss from the thicker recessed section.
Solution Approach 2:
The invention changes the geometric parameters of the blade tip by introducing specific thickness variations along the chord length. The planar section has a reduced thickness compared to the recessed section, creating a controlled contact geometry that modifies the rub event characteristics and reduces material loss.
2Force
If the blade tip contacts the casing, then radial and tangential loads are induced into the rotor blade, but excessive loads cause increased vibration and deflection
Solution Approach 1:
The non-uniform thickness distribution at the blade tip creates a specific contact geometry during rub events. The thinner planar section contacts the casing first, distributing the contact loads more favorably and reducing the magnitude of radial and tangential loads induced into the blade, thereby decreasing vibration and deflection.
3Loss of substance
If the blade tip geometry is modified with recessed sections, then contact area during rub events is reduced, but manufacturing complexity increases
Solution Approach 1:
The invention modifies the blade tip geometry by changing the thickness parameter along the chord length, creating planar and recessed sections. This parameter change achieves reduced material loss during rub events while maintaining a manufacturable geometry that can be fabricated using conventional blade manufacturing processes.
Data Source
AI summary
An airfoil for use in a turbomachine includes a pressure sidewall and a suction sidewall coupled to the pressure sidewall. The suction sidewall and the pressure sidewall define a leading edge and a trailing edge, the leading edge and the trailing edge define a chord distance. The airfoil includes a tip portion extending between the pressure sidewall and the suction sidewall. The tip portion includes a planar section and a recessed section. The recessed section extends adjacent to the planar section such that a thickness of the planar section is less than a thickness of the airfoil. The recessed section is offset a predetermined distance from the leading edge and the trailing edge along the chord distance.