| As one of the landmark of the development level of a country’s manufacturing equipment, centrifugal compressors are widely applied in energy, machinery, water conservancy, and many other areas. As the core component of the centrifugal compressor, impeller bears the main function of energy conversion, its reliability directly affects the safety and performance of the compressor unit. This paper uses the whole life-cycle analysis and shakedown analysis method for the safety assessment of a large centrifugal compressor impeller.Impeller in the whole life cycle experience lots of loads, including over-speed preload, start-stop, rotation speed fluctuation, flow induced vibration and so on. The main research content of this paper contains:(1) A method for impeller whole life-cycle fatigue assessment considering the effect of over-speed preloading. Results of impeller’s elasto-plastic analysis show that after speeding preloading treatment will produce residual stress in high stress area. This makes the subsequent fatigue analysis can’t simply use S-N curve. This paper puts forward a kind of general strain fatigue algorithm based on the ε-N curve of the material for whole life-cycle analysis.(2) Analysis of the fatigue life of the semi-open impeller in two different conditions of the starting and stopping and the speed rotating is accomplished through FE-SAFE. By comparing the results of processing with and without over-speed preloading, we can see that the treatment of over-speed preloading can improve the fatigue life of impeller in a great extent. Moreover, over-speed preloading can also avoid the occurrence of fatigue damage in some conditions of impeller’s speed rotating.(3) Meanwhile, a variety of complex load which impeller faced in engineering such as aerodynamic excitation and rotating stall are equivalent simplified. Based on this, fatigue analysis has been done for the closed impeller. The results show that the impeller treated with over-speed preloading can resist larger aerodynamic load without fatigue damage. Thus over-speed preloading is extremely important in the process of impeller manufacture.(4) To explore the method for impeller shakedown analysis, a mathematical programming model is established based on the lower bound shakedown theorems, considering impeller’s structure and load characteristics. With the application of MATLAB optimization algorithm, we get the shakedown rotating speed of the impeller. At the same time, we find the finite element result of impeller’s shakedown rotating speed by step loading in ANSYS. By contrast, the mathematical programming model has good applicability and it has great reference value for shakedown analysis of impeller. |
