A novel damage identification method for flue gas turbine blades based on tip timing

Area of Science:

• Mechanical Engineering
• Aerospace Engineering
• Condition Monitoring

Background:

• Traditional tip timing analysis is effective for high-speed blades but unsuitable for low-speed turbines.
• Online condition monitoring of low-speed turbine blades requires specialized analysis methods.

Purpose of the Study:

• To propose a novel blade tip timing signal analysis method for low-speed flue gas turbines.
• To investigate the dynamic response characteristics of low-speed blades for damage detection.
• To develop a method for monitoring local stiffness variations and identifying blade damage.

Main Methods:

• Utilized finite element modal theory to analyze blade damage characteristics.
• Developed an equivalent cantilever beam model for flue gas turbine blades under complex conditions.
• Proposed a damage identification method based on free end deflection variations of the equivalent beam.
• Established a rotating blade tip timing monitoring testing rig for experimental validation.

Main Results:

• Cracks at approximately 80% of blade height significantly impact blade stiffness, followed by blade root damage.
• Calculated blade damage parameters were 4.8464 mm and 3.7588 mm.
• Identified crack influencing factors as 4.7476 and 3.6822, consistent with known blade damage rules.

Conclusions:

• The proposed tip timing signal analysis method is feasible for low-speed turbine blades.
• The method effectively correlates stiffness variations with specific blade damage locations and severity.
• This approach enhances the online condition monitoring capabilities for low-speed turbine applications.