Thermostressed State of a Nozzle Vane from Max Phase Ceramics

Abstract

Numerical simulation results for the unsteady thermal and stressed states of a nozzle vane under unsteady operation conditions of the gas turbine are presented. The vane and nozzle block duct 3D computer model was constructed. The finite element mesh form, its sizes, and calculation time steps were optimized. The vane and duct contained 1.7 and 3.6 mln elements and 2.3 and 0.8 mln nodes, respectively. The mesh smoothing with corresponding nodal displacement near the transition zones and in the vicinity of curvilinear surfaces was used. The simulation consisted in successive numerical solutions of nonstationary flow problems for a moving medium and heat, transfer, thermal conductivity, and thermoelasticity problems for the vane. The parameters of unsteady thermal loading conditions were defined. The thermal properties of the moving medium and vane material were assumed to be time-dependent. For turbine power improvement conditions, time variations of duct flow parameters, temperatures, thermal stresses in different vane zones, their gradients and rates were analyzed. The essential nonuniformity of the thermostressed vane state and zones of thermal stresses, almost reaching the ultimate strength of the material, were noted. The effect of general heat flow components on the disturbance of thermal stresses was shown. Emphasis was placed upon the appearance of tensile stresses on a heated trailing edge of the vane (most critical zone). The conclusion was drawn regarding a potential application of a MAX phase Ti2ALC us a structural material for the vanes of short-life gas turbines.