Thermal effects on the tensile forces of rods in rod-fastened rotor of heavy-duty gas turbine

Abstract

Circumferential tie-rods fastened rotor is a common structure widely used in gas turbine. The preloads of rod groups are of great importance to ensure the strength, stiffness, and stability of the rotor in gas turbine. The tensile force of rods obtained through preload may change due to inconsistent axial thermal expansions between rods and discs during transient startup and shutdown processes, and the change should be within the safety margin. Based on the finite element method, thermal-structural analyses of a gas turbine are carried out to quantify the effect of temperature field on tensile force of rods under multiple operating conditions including steady state, shutdown process, turning gear operation, startup, and standstill. Results show that the maximum increase of the tensile force of rods reaches about 33% and 25% for the compressor and turbine shafts during startup. The tensile force of rod-groups presents nonuniform distribution with sine wave shapes during the standstill condition, and the unevenness is highly relative to the time on turning gear. The quantitative results provide a theoretical reference for the preload design of rods in gas turbine.