Analysis on whirling vibration of waterjet propulsion shafting based on finite element method

Abstract

Objectives Based on the ANSYS simulation software platform, a complete calculation method for the whirling vibration of waterjet propulsion shafting is established.Methods First, a parameterized FE model of the shafting system is built using ANSYS command flow, then curves of the Eigen frequencies are drawn and a Campbell diagram is obtained. Next, the primary and blade whirling critical speeds are calculated, and the trajectory of each node of the shafting system around the axis at the critical speed is plotted. Finally, the influence of the arrangement of the thrust bearing and the stiffness of the bearing on critical speed are analyzed.Results The results show that the amplitude of the whirling vibration displacement of the impeller shaft is the largest. When the thrust bearing was moved from the front end of the tail seal to the inside of the propulsion pump, the critical speed of the first-order positive-whirling of the shafting decreased by 32.8%, and the critical speed of the first-order blades of positive-whirling decreased by 31.3%. Therefore, the arrangement of the thrust bearing has a greater impact on the critical speed of waterjet propulsion shafting. With the increase of bearing support stiffness, the change in the first-order resonance speed of the shafting and the critical speed of the first-order blades of positive-whirling are both less than 8%, and the change in the critical speed of the first order positive whirling is less than 9%. Therefore, whirling critical speed is not sensitive to bearing support stiffness, which is conducive to the stable operation of the shafting.Conclusions The results of this study can provide references for the safety evaluation of the whirling vibration of waterjet propulsion shafting.

Keywords

• waterjet propulsion shafting
• whirling vibration
• vibration analysis
• ansys command flow
• campell diagram
• vortex trajectory