Experimental Study on Damping Adjustment of Air Bearings with Integrated ISFD Driven by Piezoelectric Actuators for Bearing–Rotor System Stability

High-speed rotating machinery imposes increasingly stringent requirements on the vibration performance and operational stability of supporting systems. Integral squeeze film dampers (ISFDs) can effectively enhance bearing damping, and their damping characteristics are strongly influenced by the end-seal gap. Integrating an ISFD with an aerostatic tilting-pad journal bearing can compensate for the relatively limited damping and excessive vibration that may occur under complex operating conditions, while retaining the advantages of air bearings, such as low friction, high motion accuracy, and a wide applicable speed range. However, the end-seal gap of conventional ISFDs is generally fixed and cannot be readily adjusted according to variations in operating conditions such as rotational speed and load. To address this issue, this study investigates an aerostatic tilting-pad journal bearing integrated with an ISFD and examines the influence of an adjustable-damping ISFD on the vibration characteristics of the bearing–rotor system. A combined mechanical coarse-adjustment and piezoelectric fine-adjustment scheme is adopted, and a method is proposed to regulate the ISFD damping by dynamically adjusting the end-seal gap using a piezoelectric actuator. Dynamic excitation experiments reveal a nonlinear enhancement in the equivalent damping of the ISFD as the end-seal gap decreases. The effects of the adjustable-damping ISFD on the vibration characteristics of the aerostatic tilting-pad journal bearing–rotor system are further investigated. The results demonstrate that damping regulation through end-seal gap adjustment can effectively improve the vibration attenuation performance of the bearing and enhance the operational stability of the rotor system.