During operation of transport and maneuverable gas-turbine units, there are crack formation in turbine disc rims what exerted by thermomechanical cycling loads. For in-depth study of these problems we have to use theories of plasticity and creep which form the basis for determining the complex stress-strain state in the stress concentration zone for disc rims, and a modern failure criterion which can predict lifetime under conditions of simultaneous plastic and creep strain accumulation. There is a finite-element method (FEM) that allows us to evaluate the stress-strain state in a stress concentration zone for a non-elastic material behavior. With plasticity and creep theories, it is possible to determine local strain quiet reliable by FEM.

Thermal-Fatigue Analysis of Turbine Discs under Complex Thermo-Mechanical Loading with Account of Plasticity and Creep Effects

Model of cyclic stress-strain curve and corresponded damage model are developed for simulation of nonisothermal cyclic loading and for estimating life time of turbomachinery components. Material cyclic model describes change of Bauschinger's effect, Young's module and parameters of hardening as functions of accumulative plastic strain. Model of damage is based on reaching value of accumulative plastic strain ultimate state at cyclic loading. Simulation of nonisothermal plasticity of turbomachinery components based on FE code which uses for calculation theory of strain plasticity, that was generalized to cyclic noniosthermal loading. Results of calculation of turbine engine details under cyclic loadings (discs, high-loaded concentrators of blade locks and turbine blades) are presented.

Numerical simulation of nonisothermal plasticity and thermomechanical fatigue of turbomachinery components

The methodology to solve the interrelated problems of secondary gas flows in turbomachines, thermal and stressed states of their parts, and clearance change over a flight cycle is described using an example of high pressure compressors (HPC) of aviation engines. An iterative calculating scheme is proposed to take into account mutual interferences between these solution modules. An additional optimization module is used to minimize weight and to achieve the prescribed displacements and safety margins. Mathematical 1D and 2D models for accurate calculation of secondary flows are described in detail. The results of the application of this iterative calculation scheme for the HPC with one of the possible secondary flows design are shown. The methodology is used to estimate the efficiency of alternative secondary flows schemes with hot gas redirection to a compressor's disks hubs in order to minimize disks temperature gradients and to stabilize clearances aimed to achieve higher efficiency and gas-dynamic stability.

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G.Yurchenko

Papers

HPC design based on multidisciplinary numerical simulation