Research on random unbalanced phase vibration characteristics of marine turbocharger

Abstract

Despite undergoing factory balancing procedures, turbochargers still exhibit significant operational vibration variability under complex working conditions. Long-term service may induce critical failures including impeller wear and turbine carbon deposition. To investigate the vibration mechanisms and control strategies, this study establishes an experimentally validated finite element model of the rotor system. Systematic simulations are conducted by varying the compressor impeller unbalance phase and rotational speed, while maintaining a fixed turbine-end phase. Key findings reveal: Persistent 1X synchronous vibrations with amplitudes below 0.02 mm are observed across the entire speed range, showing negligible correlation with unbalance phase variations. Prominent 0.13X sub-synchronous vibrations displayed phase-dependent characteristics: A pronounced amplification of sub-synchronous vibrations is observed. As the unbalance phase increases from 0° to 180°, the bandwidth of these intensified vibrations within the 30,000–60,000 r/min range expands by approximately 11.7 times. Vibration suppression emerges above 60,000 r/min, reducing bandwidth by 25%. The speed bandwidth of this vibration is increased by 40% when phase varies from 90° to 135°. The variation in the relative phase between the dual ends has minimal impact on the shape of the shaft trajectory; however, it significantly influences the trajectory radius, prompting the analysis to concentrate on the 0° phase condition. At 30,000 r/min, the limit cycle oscillation is dominant. Chaotic motion intensification at elevated speeds (>50,000 r/min). Optimal phase control (0°–90°) narrows the strong sub-synchronous vibration bandwidth across 30,000–60,000 r/min. Rotor orbit analysis confirms safe clearance margins, with maximum vertical trajectory radius measuring 0.064 mm at 60,000 r/min (70% below friction threshold). The findings demonstrate that strategic unbalance phase modulation can effectively suppress sub-synchronous vibrations, providing actionable insights for marine turbocharger rotor dynamics optimization and vibration mitigation.