Gas Turbine Compressor Blade Squealer Tip Coating Fatigue
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Solution Overview
Problem
The repeating vibrations in gas turbine compressor rotors cause fatigue cracks in both the blade body and the hard coating, leading to a significant reduction in the rotor blade's lifetime due to the severe stretching and compressive stresses at the surface where the hard coating is applied.
Innovation Solution
A rotor blade design featuring a squealer tip with a mechanically neutral surface on its second face, which is coated with a hard material like tungsten carbide, titanium carbide, or silicon carbide, reduces stress concentrations and prevents crack formation by minimizing the impact of repeating stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hard coating is applied to the distal end of the blade to protect against frictional wear, then wear resistance is improved, but fatigue lifetime is reduced due to crack formation in the coating under repeating stresses
Solution Approach 1:
The patent applies local quality by differentiating the coating application based on stress levels. The hard coating is applied only to regions with low equivalent stress (below threshold σth), while leaving high-stress regions uncoated. This localized approach maintains wear protection where needed while preventing crack initiation in high-stress areas, thereby resolving the contradiction between wear resistance and fatigue lifetime.
Solution Approach 2:
The patent employs parameter changes by using equivalent stress distribution as the criterion for determining coating application. By calculating and mapping the equivalent stress parameters across the blade surface, the invention identifies specific regions where coating is beneficial versus where it would be harmful, enabling optimized coating placement that balances wear resistance and fatigue performance.
2Power
If the suction side is made convex and pressure side concave to increase compression effect, then compression performance is improved, but stress concentration increases leading to crack formation
Solution Approach 1:
The patent applies local quality by maintaining the aerofoil profile geometry (convex suction side, concave pressure side) for optimal compression performance, while locally modifying the coating application to avoid high-stress concentration regions. The equivalent stress analysis identifies specific areas where the aerofoil geometry creates stress concentrations, and the coating is strategically omitted or reduced in these zones to prevent crack formation while preserving overall compression effectiveness.
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 design significantly extends the fatigue lifetime of the rotor blade by reducing the likelihood of crack formation in both the blade and the hard coating, while maintaining abrasiveness to protect against frictional wear.
Implementation Method 1
The repeating load caused by the repeating vibration generates repeating stretching and compressive stresses on both the suction side and the pressure side of each blade. These repeating stresses may cause occurrence of fatigue cracks in the main body of the blade or the hard coating coated thereon.
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A blade (11) as a main body of a rotor blade has a suction side (11a) made convex and a pressure side (11b) made concave so as to have an aerofoil profile. A squealer tip (17) having a back face (17a) continuous to the suction side and a front face (17b) matching with a center plane of the blade (11) is formed as a distal end of the blade. The front face (17b) is coated with a hard coating.