Transient Thermal Stress Analysis of Power Turbine Welded Rotor in a Heavy-Duty Gas Turbine during Rapid Load Changes

The fluctuation and intermittency in renewable energy sources present an immediate need for peaking power sources, typically gas turbine. During the process of load change, the rotor of the gas turbine undergoes significant transient thermal stresses, posing a great challenge to the structural strength and reliability design of the rotor. To achieve rapid load changes, a heavy-duty gas turbine draws on the lightweight design concepts of aero-engines, adopting a welded rotor connection and three separated shafts. Since the key to whether a gas turbine can achieve rapid load changes lies in the strength design of the power turbine, this paper takes the power turbine welded rotor as the research object and predicts the transient thermal stresses during rapid start-up process based on the transient multi-physics coupling method. Compared to steady-state method, transient method can predict differences of up to 13.4% in maximum thermal stress and 2.2% in maximum equivalent stress difference. The trends of the transient thermal stress sequence distribution are similar across different time steps, with a maximum calculation deviation of 1.38%. The results of this paper can not only support the strength design of the welded rotor but also provide methodological support for similar engineering designs.