Effect of temperature and pressure on stress of impeller in axial-centrifugal combined compressor

Abstract

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.