Local Thermal Buckling Analysis Method of Combustor Liner

Abstract

Aero-engine combustor liners are always plagued by local thermal buckling failure problems because of complex thermal and mechanical loading conditions caused by the continuously increasing thrust-to-weight ratio and turbine gas temperature. Traditional theoretical methods focus on simple plate and shell structures, and the numerical methods are not applicable in local thermal buckling analysis of complex structures and loading conditions. As a result, it is necessary to establish a local thermal buckling analysis method in which the failure mechanism must be taken into account. Firstly, the discriminant of thin-wall structure thermal buckling instability boundary is derived from governing equations of plates in which the stress function and deflection function are two variables, and the two buckling factors which are local temperature and compressive stress are included in the equations. Secondly, the three dimensional temperature distribution of a combustor liner is captured by the numerical simulation of an annular return-flow combustion chamber with ANSYS/CFX based on the thermal-fluid-solid coupling finite element (FE) method. The calculation includes the effect of heat source and heat radiation, the influence of variable flow field on heat transfer and variation of properties with temperature of the gas, kerosene, and the solid. In addition, the resultant imposed thermal load and design pressure load are used to capture the critical locations in the combustor liner through static analysis considering thermal buckling instability factors. The critical temperature and critical compressive stress which are the defining parameters of local thermal buckling discriminant are calculated with FE and the sub-model method. Then a judgment of local thermal buckling is performed through the discriminant. Analysis results for an example combustion chamber calculated by the method in this paper are compared with the experimental data. It is concluded that the local thermal buckling analysis method is accurate and valid.