Axial-centrifugal combined compressors are commonly used, and the stresses of their impeller are important and influenced by temperature and pressure. The effects of temperature and pressure on the stresses of the impeller with different inlet conditions are investigated. Conjugate heat transfer analysis and three-dimensional structural finite element analysis are used to get the stresses of the impeller. The effects of temperature and pressure are obtained by comparing the equivalent (Von-Mises) stresses between cases taking and not taking them into account. From the result, the temperature effect is surprisingly large for low inlet temperature, reaching 57% of the total equivalent stress, and should be carefully considered. The effect strongly relates with the inlet conditions and the disk thermal boundary conditions. Thus, the later can't be treated as adiabatic as usual. For certain inlet conditions, the stress of the impeller can be improved by adjusting the disk thermal boundary conditions. In addition, the temperature mainly affects the stress on the disk and the root of the blade. The pressure effect is small for low inlet temperature and can be sufficiently large for high inlet temperature. Furthermore, the pressure mainly influences the stress on the blade part and can reduce the stresses at the inducer of a negative-lean impeller.

Multistage axial compressors are widely used in the gas turbine engines. The strength of rotors is one of the key factors for the reliability of multistage axial compressors. The stresses of rotors at real working conditions can be caused by the centrifugal load, thermal load, and aerodynamic load. It is important to figure out the roles and the mechanism of the three kinds of loads in the stresses generating process. In this paper, the stresses of rotors in a typical five-stage axial compressor are calculated with different kinds of loads by solid-fluid coupling method. The results show that the proportion of the stress caused by centrifugal load is more than 80% of the total stress, which is dominant. The maximum proportion of the stress caused by thermal load is about 20% of the total stress at the front stages. However, the influence of thermal load is quite different from the first stage to the last stage. It is surprising that thermal load can decrease the stresses of the last stage rotor, which is mainly because of the variation of radial temperature gradient at disks for different stages. The proportion of the stress caused by aerodynamic load is usually less than 4%, and it tends to make the stresses at the suction side of the blades lower and enlarge it at the pressure side. According to the above results, centrifugal load is necessary of consideration at the conceptual design phase for the multistage axial compressor rotors. At preliminary three-dimensional design phase, centrifugal load and thermal load should be considered together. At optimized three-dimensional design phase, aerodynamic load cannot be neglected and all the three loads should be considered.