Influence Laws of Blade Gradient Angle on Natural Frequency of Compressor Impellers

The natural frequency analysis of the turbocharger impeller played a vital role in predicting the reliability life. In order to obtain the influences of the geometry of the compressor impellers on the natural frequency, the blade gradient angle related to the thickness and blade cantilever length was defined. Concepts NREC software was used to design serial impellers, then ANSYS finite element analysis software was used to simulate impeller natural frequency and strength. Moreover, 8 representative size milling impellers were selected for vibration test experiments by the impeller modal test system. The results show that blade thickness has a greater influence on the blade gradient angle than that of the blade cantilever length. The ratio of the blade gradient angle and the first-order natural frequency always show a monotonous increasing linear relationship, and the same with the ratio of the blade gradient angle and the first-order frequency multiplication ratio. The maximum stress at the blade roots of the compressor first decrease with the increase of the blade gradient angle, and then increase with the increase of the blade gradient angle. When the value range of blade gradient angle is as 3.258°, the maximum equivalent stress of the impellers is smallest. The errors between the experimental results and the simulation calculations are 2. 13%~4. 92%, indicating that the calculation results are reliable. When the compressor impeller rotates, the pre-stress of centrifugal force increases the stiffness of the impellers, thereby increasing the modal frequency of the impellers. © 2022, China Mechanical Engineering Magazine Office. All right reserved.