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Imbalance response of a rotor supported on a floating ring fluid film bearing
Abstract
Turbochargers are commonly used to increase the power output and efficiency of internal combustion automotive engines. Conventional turbocharger rotors are usually supported on floating ring journal bearings (FRBs) running with engine oil as lubricant. FRBs are comprised of an inner and outer thin lubricated films in series, and offer lower power losses and also cooler operation conditions than a single-land hydrodynamic journal bearing (Wilcock, 1983). FRBs are also very attractive for turbomachinery because of the inherent high damping characteristics associated to the presence of two fluid films (Orcutt and Ng, 1968). However FRBs can lead to rotordynamic instability, exhibiting subsynchronous rotor whirl in most of their operating range. Nonetheless, FRBs often reach stable limit cycles, thus becoming cost-effective solutions to the rotor support design. The main objective of the research was to identify the fundamental physical parameters that affect the dynamic performance of a rotor supported on a floating ring bearing from measurements of the rotor response to calibrated imbalance masses. Experiments were performed on a test rig to measure the system threshold of instability, amplitude of limit cycle, and range of whirl frequencies as a function of bearing load, rotor imbalance and the rotor speed. Measurements of the rotor response demonstrate that the rotor-FRB system renders an unstable behavior for almost the entire journal speed range and achieves a limit cycle at the maximum running speed (10,000 rpm). The system non linearity is evidenced by two self-excited subsynchronous vibration components identified from the experiments. The first subsynchronous component is associated with the instability of the inner film and the second component is associated with the instability of the outer film. Localized absence of subsynchronous vibration components is evident for higher supply pressures at specific operating speeds. Full floating ring and semi floating ring conditions are examined in the study. The semi floating bearing ring is the most unfavorable condition for the rotor bearing system due to the high levels of vibration observed on the test rotor-FRB.
Description
Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to digital@library.tamu.edu, referencing the URI of the item.Includes bibliographical references (leaves 101-104).
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Citation
Naranjo, Julio Enrique (1999). Imbalance response of a rotor supported on a floating ring fluid film bearing. Master's thesis, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1999 -THESIS -N37.
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