Semi Floating Ring Bearing Research Articles

Analysis of Thermo-Hydrodynamic Lubrication of Three-Lobe Semi-Floating Ring Bearing Considering Temperature–Viscosity Effect and Static Pressure Flow

Analysis of Thermo-Hydrodynamic Lubrication of Three-Lobe Semi-Floating Ring Bearing Considering Temperature–Viscosity Effect and Static Pressure Flow

Vibration characteristics of turbocharger rotor system considering internal thread texture parameters of semi-floating ring bearing

The internal thread texture causes changes in the dynamic characteristics of the oil film of the semi-floating ring bearing, which affects the amplitude of vibration and operating life of the turbocharger rotor system. Based on the fluid lubrication theory, the oil film governing equation of a semi-floating ring bearing with surface texture parameters is derived. The effects of the texture depth, position, and number of turns of the internal thread on the dynamic characteristics of the bearing oil film, such as the maximum pressure, load-carrying capacity and stiffness damping, are analyzed. Taking a type of turbocharger as an example, a hydrodynamic model is established to analyze the oil film lubrication in the semi-floating ring bearings, and the dynamic characteristic of the oil film is analyzed by computational fluid dynamics method. The results show that the maximum pressure, bearing capacity, and stiffness damping coefficient of oil film increase firstly and then decrease with the increase of texture depth and the number of thread turns in the range of journal rotation speed from 1000 to 20,0000 r/min. Compared with the non-texture bearings, the dynamic characteristics coefficients of the oil film such as bearing capacity and stiffness damping increase the most, when the depth of texture is 0.006 mm and the number of thread turns is 9. Secondly, the dynamic characteristic coefficient of oil film is improved when the texture is distributed in the middle than on both sides. The thread texture with appropriate parameters can suppress the rotor system vibration amplitude. The conclusion can provide a reference for the design of textual parameters of semi-floating ring bearings.

A Nonlinear Rotordynamics Model for Automotive Turbochargers Coupled to a Physical Model for a (SEMI) Floating Ring Bearing System

Abstract Automotive turbochargers (TCs) use an engine oil lubricated bearing system to produce acceptable performance (as per the engine volumetric efficiency) and proven reliability. However, the bearings also cause TC rotordynamic responses that are rich in subsynchronous whirl motions through reaching stable limit cycles. The paper describes the lubrication model for a finite length semi-floating ring bearing (SFRB) system and its coupling to the rotor and ring structure models for prediction of both linear and nonlinear system responses and their characterization in terms of motion amplitudes and whirl frequency content. The SFRB model includes a thermal energy transport network for the inner and outer films in both radial bearings and the thrust bearings located on the end sides of the ring. The large temperature difference between the hot shaft and a cold housing induces a three-dimensional thermal gradient in the fluid films and the floating ring, further exacerbated by the heat generated from drag power losses in the inner films adjacent to the rotor. The temperature gradients affect the lubricant viscosity and the bearing system operating clearances. The integration of the rotor and bearing system (RBS) equations of motion accounts for the SFRB nonlinear forces and starts from static equilibrium position, if existing. The model predictions of nonlinear behavior are accurate when benchmarked to a set of measurements procured in a gas stand test rig. The analysis also investigates the influence of the bearing inner clearance and rotor mass imbalance distribution on the onset, persistence and severity of SSV.

Wire Mesh Dampers for Semi-Floating Ring Bearings in Automotive Turbochargers: Measurements of Structural Stiffness and Damping Parameters

The current work introduces a new semi-floating ring bearing (SFRB) system developed for improving the rotordynamic and vibration performance of automotive turbochargers (TCs) at extreme operation conditions, such as high temperature, severe external force excitation, and large rotor imbalance. The new bearing design replaces outer oil films, i.e., squeeze film dampers (SFDs), in TC SFRBs with wire mesh dampers (WMDs). This SFRB configuration integrating WMDs aims to implement reliable mechanical components, as an inexpensive and simple alternative to SFDs, with consistent and superior damping capability, as well as predictable forced performance. Since WMDs are in series with the inner oil films of SFRBs, experimentally determined force coefficients of WMDs are of great importance in the design process of TC rotor-bearing systems (RBSs). Presently, the measurements of applied static load and ensuing deflection determine the structural stiffnesses of the WMDs. The WMD damping parameters, including dissipated energy, loss factor, and dry friction coefficient, are estimated from the area of the distinctive local hysteresis loop of the load versus WMD displacement data recorded during consecutive loading-unloading cycles as a function of applied preload with a constant amplitude of motion. The changes in WMD loss factor and dry friction coefficient due to increases in preload are more significant for the WMDs with lower density. The present work shows, to date, the most comprehensive measurements of static load characteristics on the WMDs for application into small automotive TCs. More importantly, the extensive test measurements of WMD deflection versus increasing static loads will aid to anchor predictions of future computation model.

Stiffness and Damping Properties of (Semi) Floating Ring Bearing Using Magnetorheological Fluids as Lubricant

Magnetorheological fluids (MRFs) are applicable for achieving semi-active control in smart bearings. For hydrodynamic bearings lubricated with MRF, changes of the viscosity induced by magnetic field lead to changes of the dynamic characteristics such as stiffness and damping properties, providing the controllability to the bearings in rotor applications. Two main defects of the MRF, however, may potentially limit the use of this kind of bearings. One is that the magnetic field-induced viscosity alteration capability decreases as the shear rate increases; the other is the extra friction introduced by iron particles in the MRF in external magnetic field. In this study, the floating ring bearing (FRB) and semi-floating ring bearing (sFRB) are introduced to replace common journal bearing for MRF-lubricated smart bearings. Performance enhancement is achieved using FRB and sFRB. The lubrication behavior of MRF is studied using the Herschel–Bulkley (HB) model that incorporates the yield stress and the shear-thinning effect, which are the two main features of the MRF under shearing. A kind of MRF is developed for lubrication application, and a test rig is setup to measure its shear rate–stress relationship and then to identify its HB model parameters. With the identified HB model, stiffness and damping characteristics of the MRF-lubricated FRB and sFRB are studied. Results show that, compared to MRF-lubricated common journal bearings, the MRF-lubricated FRB and sFRB both achieve better performances in damping enhancement, while limiting the journal friction to a relatively lower degree.

세미 플로팅 링 베어링으로 지지된 터보차저의 Subsynchronous 진동 특성

세미 플로팅 링 베어링으로 지지된 터보차저의 Subsynchronous 진동 특성

Effects of semi-floating ring bearing outer clearance on the subsynchronous oscillation of turbocharger rotor

Semi-floating ring bearing(SFRB) is developed to control the vibration of turbocharger rotor. The outer clearance of SFRB affects the magnitude and frequency of nonlinear whirl motion, which is significant for the design of turbocharger. In order to explore the effects of outer clearance, a transient finite element analysis program for rotor and oil film bearing is built and validated by a published experimental case. The nonlinear dynamic behaviors of rotor-SFRB system are simulated. According to the simulation results, two representative subsynchronous oscillations excited by the two bearings respectively are discovered. As the outer clearance of SFRB increases from 24 μm to 60 μm, the low-frequency subsynchronous oscillation experiences three steps, including a strong start, a gradual recession and a combination with the other one. At the same time, the high-frequency subsynchronous oscillation starts to appear gradually, then strengthens, and finally combines. If gravity and unbalance are neglected, the combination will start starts from high rotor speed and extents to low rotor speed, just like a “zipper”. It is found from the quantitative analysis that when the outer clearance increases, the vibration amplitude experiences large value firstly, then reduction, and suddenly increasing after combination. A useful design principle of SFRB outer clearance for minimum vibration amplitude is proposed: the outer clearance value should be chosen to keep the frequency of two subsynchronous oscillations clearly separated and their amplitudes close.

Nonlinear Rotordynamics of Automotive Turbochargers: Predictions and Comparisons to Test Data

Abstract Passenger vehicle turbochargers (TCs) offer increased engine power and efficiency in an ever-competitive marketplace. Turbochargers operate at high rotational speeds and use engine oil to lubricate fluid-film-bearing supports (radial and axial). However, TCs are prone to large amplitudes of subsynchronous shaft motion over wide ranges of their operating speed. Linear rotordynamic tools cannot predict the amplitudes and multiple frequency shaft motions. A comprehensive nonlinear rotordynamics model coupled to a complete fluid-film-bearing model solves in real time the dynamics of automotive turbochargers. The computational design tool predicts the limit cycle response for several inner and outer film clearances and operating conditions including rotor speed and lubricant feed pressure. Substantial savings in product development and prototype testing are the benefits of the present development. The paper presents predictions of the linear and nonlinear shaft motion of an automotive turbocharger supported on a semi-floating ring bearing. The shaft motion predictions are compared to measurements of shaft motion at the compressor nose for speeds up to 240krpm, and for lubricant inlet pressure of 4bar at 150°C. Linear and nonlinear rotordynamic models reproduce very well the test data for synchronous response to imbalance. The nonlinear results show two subsynchronous whirl frequencies whose large magnitudes agree well with the measurements. A large side load predicted for this turbocharger must be considered for accurate prediction of the rotordynamic response.