大功率汽轮机末级轮盘-叶片结构疲劳裂纹扩展分析

Finite Element Analysis of Fatigue Crack Growth Between Last Disc and Blade of a Large Capacity Steam Turbine

采用ABAQUS软件对国产某600MW汽轮机末级轮盘-叶片结构进行裂纹扩展分析,研究了该机组末级轮盘-叶片结构的应力分布以及轮缘应力最大处的裂纹扩展情况。考虑到波动汽流力载荷对轮缘疲劳裂纹的影响,分别模拟了额定转速3 000r/min和超速3 300r/min工况下轮缘最大应力处疲劳裂纹的扩展规律。通过模拟得到疲劳裂纹扩展循环次数与端面裂纹长度的关系曲线,比较了在循环1×10~6次后2种工况下的裂纹扩展长度。结果表明:超速工况下不仅容易造成轮缘裂纹扩展,而且裂纹扩展速率较额定工况下要快。

An analysis was conducted on the fatigue crack growth between last disc and blade of a domestic 600 MW steam turbine using software ABAQUS, so as to study the stress distribution in that area and the crack propagation in the rim with maximum stress. Considering the effect of fluctuating steam load on the rim fatigue crack, the growth law of fatigue crack in the rim with maximum stress was simulated respec- tively at the rated speed of 3 000 r/min and the overspeed of 3 300 r/min, thus to find the relationship between the number of crack growth cycles and the length of end surface cracks, and to compare the crack length under two working conditions after 1×10^6 cycles. Results show that the crack tends to grow more easily under overspeed condition, and the propagation rate is also higher than that under rated condition.