Dynamic Analysis of a Rotor System Supported on Squeeze Film Damper with Air Entrainment
Squeeze film dampers (SFDs) are widely used in compressors and turbines to suppress the vibration while traversing critical speeds. In practical applications, air ingestion from the outside environment and cavitation may lead to a foamy lubricant that weakens oil film damping and dynamic performance of rotor system. In this paper, a rigid rotor model is established considering both lateral and pitching vibration under different imbalance excitations to evaluate the effect of air entrainment on rotor system. Tests with three different imbalances are carried out on a rotor-SFD apparatus. Volume controlled air in mixture ranging from pure oil to all air are supplied to the SFD. The transient response of rotor is measured in the experiments. The results show that two-phase flow produces significant influence on the system stability and dynamical response. The damping properties are weakened by entrained air, such as the damping on high frequency components of rolling ball bearing. Super-harmonic resonance and bifurcation are observed, as well as the low frequency components due to air entrainment.
Study on Mechanism of Shaft Fault Suppression Based on Squeeze Film Damper
Considering the action of the squeeze film damper (SFD), the dynamic characteristics of a rotor-rolling bearing system are studied under rub-impact faults. Based on Lagrange equation, the dynamic model of the rotor-rolling bearing system with rub-impact faults and the SFD was established by using the finite element method, and the Newmark method was used to solve equations of the model. The results show characteristics following. Within a certain range of the SFD oil film clearance can effectively inhibit resonance amplitude of the rotor system, and with the decrease clearance of the oil film, the inhibition effect is more obvious. The rotational speed has an important effect on the rotor-rolling bearing system under rub-impact faults. When the rotational speed enters in the vicinity of the major critical speed, the system will occur complex phenomena with the increase of the rotational speed, such as synchronous full annular rub, period-doubling local rub-impact, single period local rub-impact and quasi-period local rub-impact successively. The clearance of the oil film is an important factor affecting the stability of the rotor system, and the appropriate clearance of the oil film has a higher inhibition effect on the rub-impact. In addition, less clearances of the oil film will aggravate the rub-impact, or even nonlinear phenomena.
The squeeze Film Damper over four decades of investigations. Part I: Characteristics and operating features
The present review aims to summarize the main research findings, in the last four decades, on the Squeeze Film Damper (SFD) and its application. In this first part, a survey of the construction characteristics and operating features of the SFD, as a separate component, is reported, as inferred from the technical literature consulted, through a number of theoretical approaches and experimental results. Part II of the paper will review research work on the dynamic behavior of rotors on supports equipped with SFDs.