Abstract: In recent years, frequent cracking has occurred in the water walls of DG-2070/17.5-II4 type boilers during operation in a thermal power plant. This study focuses on the typical tube burst positions at the junction between the boiler water wall and the enclosure wall superheater under deep peak shaving. The finite element analysis models are established to evaluate the effects of different heating rates and the final temperature inside the boiler on the thermal stress and deformation at these typical tube burst positions. The results indicate that obvious thermal transition zones and stress concentration points are the primary causes of tube damage. The higher final temperature inside the boiler is the main factor leading to damage at the T-junction, while the influence of the heating rate on structural damage is relatively limited. Based on the results of the above study, it is recommended that the discontinuities at the T-junction should be reduced and the connection method of fins and tubes should be optimized, thereby mitigating the impact of flow-induced vibration and preventing tube burst.

Key words: tube burst, failure analysis, fluid-solid-heat coupling, water wall, enclosure wall superheater, fin