Analysis of Stress and Fatigue Damage of Centrifugal Turbine in Air Brayton Cycle System Under Transient Conditions

The air Brayton cycle is distinguished by its high efficiency, flexible start-up and shutdown capabilities, and environmental friendliness—attributes that render it a suitable energy conversion system for mobile small-scale reactors. As a core component of this cycle, the air turbine plays a critical role in system performance. Given that mobile small-scale reactors operate under dynamically varying conditions, the fatigue damage of air turbines is crucial for safeguarding the safe operation of the entire cycle system. This study establishes a thermo-fluid-structure coupling and fatigue life analysis workflow based on the ANSYS platform, and investigates the effects of variable load rate and inlet temperature change rate on the fatigue damage of an air centrifugal turbine during its load transition from 75% to 100% of the design power. The results indicate that when the load rate is 12.5%Pe·min -1 , the fatigue damage from a single load-transient process reaches a maximum of 2.25×10 -6 . When the inlet temperature change rate is 12 K·min -1 , the fatigue damage from a single temperature-change process reaches a maximum of 2.119×10 -6 . Both the variable load rate and inlet temperature change rate exhibit a positive correlation with the fatigue damage of centrifugal air turbines.