An Experimental Study of the Stabilizing Effect of Floating-Bush Journal Bearings

Tatara, Atsusuke

doi:10.1299/jsme1958.13.858

Cited by 21 publications

(13 citation statements)

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“…Kettleborough [8] as early as in 1955 already noted significant discrepancies between test data and predictions. Later, Tatara [9] presented further experimental results showing the ring speed ratio reduction, and noting that, over certain speed ranges and for high feed pressures, FRBs operate in a stable Trippett and Li [10,11] also found experimentally that ring speed ratios decrease dramatically as shaft speed rises, and advanced a simple thermal model that predicts the measurements well. In essence, the temperature rise due to the conversion of mechanical energy into heat carried away by the lubricant and also conducted through the ring and bearing not only reduces the lubricant viscosity but also, most importantly, induces a notable variation in film clearances owing to thermal growth of the components.…”

mentioning

confidence: 94%

Thermal effects on the performance of floating ring bearings for turbochargers

Andrés

Kerth

2004

Proceedings of the Institution of Mechanical Engineers, Part J:

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Physical models and fast computational programs aim to improve the design and performance of turbocharger (TC) rotordynamics. Most commercial automotive TCs incorporate floating ring bearings (FRBs) owing to their low cost and reduced power losses. However, persistent subsynchronous motions afflict this type of rotor/bearing system, albeit reaching limit cycles that enable their continuous operation. FRBs comprise two fluid films in series and are prone to show one or two subsynchronous instabilities over extended speed ranges of operation. A flow model for prediction of FRB forced response is detailed here. The model incorporates a lumped-parameter thermal energy balance for estimation of the lubricant viscosity and thermal growth of the rotor, bearing and floating ring. The FRB model, fully integrated into a non-linear rotordynamics computational program, predicts the floating ring speed, journal and ring eccentricities, power loss and the rotordynamic force coefficients of the inner and outer films as a function of the load applied at a given rotor speed. Knowledge of the actual load conditions, static and dynamic, and the changes in operating clearance and effective lubricant viscosity are most important for accurate estimation of a TC dynamic forced response. Predictions for the exit lubricant temperature, power losses and floating ring speeds agree well with measurements obtained in an automotive turbocharger test rig. The rotordynamic stability characteristics of the test TC are also highlighted. NOTATIONa, b parameters in Vogel's equation A area for heat transfer (m 2 ) ¼ pDL c p lubricant specific heat (J/kg K) C bearing radial clearance (m) D bearing diameter (m) ¼ 2R e eccentricity vector ðe X , e Y Þ (m) FRB floating ring journal bearing F fluid film force ðF X , F Y Þ (N) h film thickness (m) H heat convection coefficient (W/m 2 K) I R ring mass moment of inertia (kg m 2 ) L bearing length (m) M mass (kg) } mechanical power (W) P hydrodynamic pressure (Pa) Pr Prandtl number ¼ c p m/k Q volumetric flowrate (m 3 /s) R radius (m) ¼ D/2 Re Reynolds number ¼ rORC/m TC turbocharger T temperature (8C) W external force ðW X , W Y Þ ( N) x, z circumferential and axial coordinate on the plane of the film, x ¼ Ry X, Y inertial coordinate system a thermal expansion coefficient (K À 1 ) g lubricant shear rate (m À 1 ) G torque (N m) DT temperature difference ðKÞ ¼ T À T S e dimensionless eccentricity ¼ e/C y angle (rad) ¼ x/R k lubricant thermal conductivity (W/m 2 K) m lubricant viscosity (N s/m 2 ) r lubricant density (kg/m 3 ) O rotational speed (rad/s) O ring speed ratio ¼ O R /O J The MS was

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confidence: 94%

Thermal effects on the performance of floating ring bearings for turbochargers

Andrés

Kerth

2004

Proceedings of the Institution of Mechanical Engineers, Part J:

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“…In addition, the bush rotation speed is determined by the balance of the viscous friction forces that act on the inside and outside of the floating bush, and tends to increase linearly with increasing shaft rotation speed [4][5][6][7]. However, it has been reported that rotors supported by floating bush bearings are stable at high speeds; furthermore, for rotation speeds at high, the increase in the bush rotation speed is suppressed and the speed remains constant [8][9][10][11]. Several studies have been conducted to explain this suppression phenomenon, but the cause has not yet been clarified.…”

Section: Introductionmentioning

confidence: 99%

Investigation of Bush Rotation Speed of Floating Bush Bearings by Oil Film Observation Using X-ray CT

Kotani

Ochiai

2019

Tribology Online

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A floating bush bearing has a double oil film, which is difficult to observe using traditional methods. In this study, the oil film of a floating bush bearing is observed using X-ray computer tomography. By appropriately processing the acquired CT images, double oil films can be observed efficiently. The CT images show that the oil film area decreases in the inner clearance and does not change in the outer clearance when the increase of the bush rotation speed is suppressed despite the increase in the shaft rotation speed. This phenomenon can be explained by the oil film area of the inner clearance decreasing under the influence of the centrifugal force acting on the oil film. When there is enough oil in the inner clearance, it is observed that the bush rotation speed increases linearly. These results indicate that the bush rotation speed is closely related to the oil film area of the inner clearance.

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“…Tartara [14] had conducted experiments and concluded, that remarkable effects of stabilizing system can be expected, when the bearings with floating rings are used. Namely, the ring starts rotating as soon as the whirl occurs, and the further stable operation is realized as the journal speed increases.…”

Section: Introductionmentioning

confidence: 99%