Research on Radial Crack Evolution in Labyrinth Fins of Turbine Blade Crown under Thermal Cycling Load

doi:10.3901/JME.2025.24.139

Abstract

Abstract: The radial cracks generated by the friction of the turbine blade crown endanger the safe operation of the engine, and its evolution mechanism has not been verified. To clarify the evolution mechanism of radial cracks, the thermal cycle tests were conducted on the fins, and numerical analysis were conducted using the XFEM method based on Abaqus software. Under cyclic high-temperature loading at 700 ℃, the fins did not initiate cracks and the prefabricated cracks did not propagate. Under cyclic high-temperature loading at 900 ℃, no cracks appeared on the fins, and the prefabricated cracks opened but propagated along the circumference and eventually peeled off. The radial cracks were formed under cyclic high-temperature loading at 1 050 ℃, and the crack length increased with the increase of the number of cycles. The parallel test under the load of 1 050 ℃ also formed radial cracks, which propagated to the blade crown，and the fitting formula of crack length with the number of cycles was obtained. The results show that the radial crack is caused by the circumferential tensile stress in the cooling process. When the circumferential tensile stress is greater than the yield strength, the crack initiates at the junction of the top and side of the fin. The crack first propagates the top surface of the fin and then propagates along the radial direction. The increase of temperature will promote the crack initiation and propagation. Therefore, the experimental and numerical studies under thermal cyclic loading verify the evolution mechanism of radial cracks, and thermal load is the driving force for the initiation and propagation of radial cracks.

Key words: labyrinth seal fins, crack initiation, crack propagation, thermal cycle experiment, XFEM

CLC Number:

V231

YANG Yicheng, SONG Zhiheng, ZHANG Beixuan, DUAN Chaopeng, MI Zhaoguo, BI Yance, YANG Weihua. Research on Radial Crack Evolution in Labyrinth Fins of Turbine Blade Crown under Thermal Cycling Load[J]. Journal of Mechanical Engineering, 2025, 61(24): 139-147.

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