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.
Highlights
Axial-centrifugal combined compressors are commonly used in small aeroengines,[1] of which the stresses of the impeller are very important for the reliability
The temperature mainly affects the stress on the disk and the root of the blade
The effects of temperature and pressure on the stress of the impeller working at the same state in different inlet conditions of temperature and pressure were studied
Summary
Axial-centrifugal combined compressors are commonly used in small aeroengines,[1] of which the stresses of the impeller are very important for the reliability. The blade will suffer high-cycle fatigue because of the unstable aerodynamic load,[4] and easier to break up when the stress is high.[5] Besides, the weight of the machine tends to decrease for better economy and performance For those reasons, it is important to predict the stress of the impeller accurately. The stress level of the impeller is supposed to be affected by this varied inlet conditions, even when the operating point (e.g. total pressure ratio and mass flow rate) of the centrifugal compressor is kept the same. This effect is not quite clear yet. The influence of temperature and pressure is obtained by comparing the equivalent (Von-Mises) stress between cases taking and not taking the certain load into account
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