Operation flexibility and the high efficiency of thermal cycle are the two hot research topics for the steam turbine unit. For the operation flexibility, it requires the turbine unit be able to start up quickly and frequently, and good thermal fatigue properties of the components are a must. On the other hand, the trend to higher temperature with ultra supercritical (USC) steam is the key drive of ongoing development for the validation of a method to improve the thermal cycle efficiency, but the application of the higher steam temperature will intensify the component’s thermal fatigue.
In this paper, a high pressure inner casing for the new designed solar steam turbine was studied, and the Finite Element Method (FEM) combined with linear elastic material was applied to simulate the transient stress and temperature fields during the daily warm/hot startup process. On the basis of the stress spectrum in the critical zone, the standard DIN EN-12952-3 and the fatigue curve were used to evaluate the low cycle fatigue life consumption in the transient process.