Eccentric Grinding for Blade Outer Air Seal Surface Profile
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Solution Overview
Problem
Disparate thermal growth between rotor assemblies and outer cases in turbine engines leads to inconsistent contact between rotor blade tips and blade outer air seals, resulting in reduced engine efficiency due to gas leakage.
Innovation Solution
A blade outer air seal with a substrate and coating having varying thicknesses and an eccentric grinding method to create a desired surface profile, ensuring consistent contact between rotating blades and static hardware by offsetting the grinding rotation centerline from the engine rotation centerline.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gap between rotor blade tips and blade outer air seal is increased to avoid interference from thermal growth, then reliability is improved, but gas leakage increases and engine performance deteriorates
Solution Approach 1:
The blade outer air seal incorporates an abradable material coating with non-uniform thickness distribution. The coating is thinner at locations where blade tip contact is expected and thicker at other locations. This local variation in material property allows the seal to maintain adequate clearance under normal conditions while providing a controlled abradable interface where blade tips may contact, thus preventing interference damage while minimizing gas leakage paths.
Solution Approach 2:
The invention changes the physical state and dimensions of the blade outer air seal coating through controlled abradable material removal. The coating thickness parameter is deliberately varied across the seal surface, and during operation, the coating undergoes controlled abrasion from blade tip contact, dynamically adjusting the clearance parameters to maintain optimal sealing while accommodating thermal growth variations.
2Reliability
If abradable material is used in blade outer air seals with abrasive coating on blade tips, then sealing performance is improved through customized clearance, but device complexity increases
Solution Approach 1:
The abradable material coating is applied with spatially varying thickness characteristics - thinner in regions where blade tip contact occurs and thicker in regions where contact is less frequent. This local differentiation of material properties enables the seal to provide customized clearance at specific locations, improving sealing performance where needed while maintaining simplicity in other areas.
3Ease of manufacture
If uniform coating thickness is used on blade outer air seal, then manufacturing is simplified, but consistent contact with rotating blades cannot be achieved due to thermal growth disparities
Solution Approach 1:
Rather than applying uniform coating thickness, the invention deliberately varies the coating thickness locally across the blade outer air seal surface. The coating is thinner at locations corresponding to expected blade tip contact zones and thicker elsewhere. This local quality variation compensates for thermal growth disparities, ensuring that the seal maintains consistent contact with rotating blades despite temperature-induced dimensional changes.
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
The solution promotes consistent rub between rotating blades and static hardware, reducing gas leakage and enhancing turbine engine efficiency by maintaining optimal contact and sealing.
Implementation Method 1
applying the rotating grinding surface to the blade outer air seal while rotating the rotating grinding surface about the grinding rotation centerline to create the desired surface profile
Data Source
AI summary
A blade outer air seal for a gas turbine engine having a surface that is eccentric with respect to the engine rotation centerline, and a method for creating same, are disclosed. Also, a method for grinding a work piece having nominal curvature defined by a work piece curvature centerline is disclosed, comprising the steps of: a) determining a desired surface profile for the work piece; b) providing a rotating grinding surface having a grinding rotation centerline; c) offsetting the grinding rotation centerline from the work piece curvature centerline; and d) applying the rotating grinding surface to the work piece while rotating the rotating grinding surface about the grinding rotation centerline to create the desired surface profile.