The Impeller’s Modal Analysis And It’s Rotor System’s Critical Speed Calculation

By taking a type of turbocharger rotor system as the research object, this paperstudies the finite element modeling and experimental modal analysis of impeller as wellas calculation of the critical speed of the rotor system respectively.Based on the structure features of the turbocharger impeller, the problem ofuncorresponding match between freedom degree of nodes and nodes is solved bysimulating impeller blades with shell units, discretizing core substrate with hexahedralunits and using MPC method.The modal identification of the impeller has been taken by using vibration testequipment. According to the experimental principle, a test bench is set to determine thesupport way of the impeller, the location of the excitation points and response points. Inorder to reduce the noise interference, the window function is applied to excitationsignal and response signal when collecting signals. The way of multi-hammering andthen master average is taken to reduce random error and the inherent frequency andmodal damping ratio of the impeller is obtained by component analysis.In stable operation the rotor system can rotate tens of thousands times per minute,or even higher. In order to achieve safe and steady operation, it is necessary to study thedynamic characteristics of rotor system and calculate its critical speed to make sure thatrotor’s rotating speed is far away from various critical speeds. In the process, twodifferent calculation of natural frequency, that is one only considers prestress and theother considers prestress and gyroscopic effect at the same time, are used to analyze thedynamic characteristics and calculate the critical speed of the rotor system in differentconditions.