Failure Analysis Of Centrifugal Compressor Impeller

Impeller is the most important part of centrifugal compressor, serious consequences could happen if the high rotating impeller breaks down (malfunction). This paper concentrates on researching the methods to analyze the fracture failure of centrifugal compressor impeller. Completely failure analysis process is done to reveal the mechanism and occurrence conditions of impeller fracture failure. The results can be taken as reference as to design optimization, supervise operation condition and diagnose malfunction of the impeller. The main research contents are as follows:1.The appearance of blade surface and fracture, locations of fracture and crack origin, crack propagation process are obtained through macroscopic and microcosmic test analysis of the blades and fractures. The analysis results indicate that:all fractures show high-cycle fatigue fracture characteristic; cracks initiate at flaws on the leading edge root of blades. Initial flaw sizes are measured for further analysis.2. Based on fatigue crack growth analysis technique, fatigue propagation occurrence conditions of flaws on blades are discovered. Blades that contains flaws is treated as a two-dimensional model and initial flaws are defined as corner cracks on plane. The impact of working load is analyzed through stress calculation while stress on the crack surface is extracted to apply on the simplified model. The behavior of the crack growth of the blade is simulated by utilizing crack growth analysis technique, also the influence of related parameters is discussed.3. The comparing between test and simulation results indicate that:1) the failure type of the blade is fracture failure under high-cycle fatigue and the simulation of the crack growth is basically consist with the actual failure situation of the blade; 2) thresholds of crack size and life prediction are highly influenced by the size, shape and dynamic stress level of initial flaws; 3) the failure mechanism of the blade is:the surface of the leading edge is rough, many small flaws exists on root part of the leading edge; great dynamic stress on the root of the leading edge is caused by aerodynamic load when operating in critical service condition, under which the crack size that already exceeds thresholds keep fatigue growth and eventually crack the blade then fall off.This paper provides a complete set of method to analyze the fracture failure of the impeller of centrifugal compressor, has reference value to engineering use in the future.