Performance of Plain Journal Bearings Operating Under Vortex Flow Conditions

1974 ◽  
Vol 96 (1) ◽  
pp. 145-149 ◽  
Author(s):  
J. Freˆne ◽  
M. Godet
Keyword(s):  
Reynolds Number ◽  
Friction Torque ◽  
Point Of View ◽  
Taylor Vortex ◽  
Experimental Program ◽  
Frictional Torque ◽  
Taylor Vortices ◽  
Attitude Angle ◽  
Relative Eccentricity ◽  
High Reynolds

An experimental program conducted on an original device was undertaken to study the performance of plain bearings operating at sufficiently high Reynolds number to introduce Taylor vortices. Curves of relative eccentricity, attitude angle, and friction torque were obtained versus speed and load. Experimental results conducted for Reynolds number smaller than 1100 indicate that both laminar and Taylor vortex regimes are encountered. The occurrence of the vortices is identified by a break in the slope of the friction torque versus speed curves. The position of the break is in good agreement with the theoretical predictions of Di Prima and Ritchie. From the practical point of view, the data show that for constant viscosity the occurence of Taylor vortices does not alter the curves of eccentricity versus either speed or load but modifies the attitude angle and frictional torque. In turn, the increase in frictional torque, and subsequently of temperature may cause a decrease in viscosity and thus a drop in load carrying capacity for fluids such as oils whose variations of viscosity with temperature is large.

Fine Scale Structure of High Reynolds Number Taylor-Couette Flow

2007 ◽  
Author(s):  
W. He ◽  
M. Tanahashi ◽  
T. Miyauchi
Keyword(s):  
Reynolds Number ◽  
Couette Flow ◽  
High Reynolds Number ◽  
Flow Fields ◽  
Fine Scale ◽  
Azimuthal Direction ◽  
Taylor Vortices ◽  
Taylor Couette ◽  
High Reynolds ◽  
Taylor Couette Flow

Direct numerical simulation (DNS) has been conducted to investigate turbulence transition process and fine scale structures in Taylor-Couette flow. Fourier-Chebyshev spectral methods have been used for spatial discretization and DNS are conducted up to Re = 12000. With the increase of Reynolds number, fine scale eddies are formed in a stepwise fashion. In relatively weak turbulent Taylor-Couette flow, fine scale eddies elongated in the azimuthal direction appear near the outflow and inflow boundaries between Taylor vortices. These fine scale eddies in the outflow and inflow boundaries are inclined at about −45/135 degree with respect to the azimuthal direction. With the increase of Reynolds number, the number of fine scale eddies increases and fine scale eddies appear in whole flow fields. The Taylor vortices in high Reynolds number organize lots of fine scale eddies. In high Reynolds number Taylor-Couette flow, fine scale eddies parallel to the axial direction are formed in sweep regions between large scale Taylor vortices. The most expected diameter and maximum azimuthal velocity of coherent fine scale eddies are 8 times of Kolmogorov scale and 1.7 times of Kolmogorov velocity respectively for high Reynolds Taylor-Couette flow. This scaling law coincides with that in other turbulent flow fields.

Suspension Taylor–Couette flow: co-existence of stationary and travelling waves, and the characteristics of Taylor vortices and spirals

2019 ◽  
Vol 870 ◽  
pp. 901-940 ◽  
Author(s):  
Prashanth Ramesh ◽  
S. Bharadwaj ◽  
Meheboob Alam
Keyword(s):  
Reynolds Number ◽  
Velocity Field ◽  
Couette Flow ◽  
Vortex Flow ◽  
Travelling Waves ◽  
Taylor Vortex ◽  
Taylor Vortices ◽  
Spiral Vortex ◽  
Taylor Couette ◽  
Taylor Couette Flow

Flow visualization and particle image velocimetry (PIV) measurements are used to unravel the pattern transition and velocity field in the Taylor–Couette flow (TCF) of neutrally buoyant non-Brownian spheres immersed in a Newtonian fluid. With increasing Reynolds number ($Re$) or the rotation rate of the inner cylinder, the bifurcation sequence in suspension TCF remains same as in its Newtonian counterpart (i.e. from the circular Couette flow (CCF) to stationary Taylor vortex flow (TVF) and then to travelling wavy Taylor vortices (WTV) with increasing $Re$) for small particle volume fractions ($\unicode[STIX]{x1D719}<0.05$). However, at $\unicode[STIX]{x1D719}\geqslant 0.05$, non-axisymmetric patterns such as (i) the spiral vortex flow (SVF) and (ii) two mixed or co-existing states of stationary (TVF, axisymmetric) and travelling (WTV or SVF, non-axisymmetric) waves, namely (iia) the ‘TVF$+$WTV’ and (iib) the ‘TVF$+$SVF’ states, are found, with the former as a primary bifurcation from CCF. While the SVF state appears both in the ramp-up and ramp-down experiments as in the work of Majji et al. (J. Fluid Mech., vol. 835, 2018, pp. 936–969), new co-existing patterns are found only during the ramp-up protocol. The secondary bifurcation TVF $\leftrightarrow$ WTV is found to be hysteretic or sub-critical for $\unicode[STIX]{x1D719}\geqslant 0.1$. In general, there is a reduction in the value of the critical Reynolds number, i.e. $Re_{c}(\unicode[STIX]{x1D719}\neq 0)<Re_{c}(\unicode[STIX]{x1D719}=0)$, for both primary and secondary transitions. The wave speeds of both travelling waves (WTV and SVF) are approximately half of the rotational velocity of the inner cylinder, with negligible dependence on $\unicode[STIX]{x1D719}$. The analysis of the radial–axial velocity field reveals that the Taylor vortices in a suspension are asymmetric and become increasingly anharmonic, with enhanced radial transport, with increasing particle loading. Instantaneous streamline patterns on the axial–radial plane confirm that the stationary Taylor vortices can indeed co-exist either with axially propagating spiral vortices or azimuthally propagating wavy Taylor vortices – their long-time stability is demonstrated. It is shown that the azimuthal velocity is considerably altered for $\unicode[STIX]{x1D719}\geqslant 0.05$, resembling shear-band type profiles, even in the CCF regime (i.e. at sub-critical Reynolds numbers) of suspension TCF; its possible role on the genesis of observed patterns as well as on the torque scaling is discussed.

Turbulent Lubrication—Its Genesis and Role in Modern Design

1974 ◽  
Vol 96 (1) ◽  
pp. 2-6 ◽  
Author(s):  
D. F. Wilcock
Keyword(s):  
Reynolds Number ◽  
Point Of View ◽  
Thrust Bearings ◽  
Viscous Forces ◽  
Taylor Vortices ◽  
Low Viscosity ◽  
Starting Point ◽  
Process Fluid ◽  
Inertia Forces ◽  
Lubricant Viscosity

Turbulence, a phenomenon well known in fluid flow, was first reported in journal bearings and thrust bearings in 1949. The observations were of higher torques and greater temperature rises than were expected from lower speed data. The transition from laminar behavior occurred at a Reynolds’ number corresponding to the predicted occurrence of Taylor vortices. This was the starting point for efforts to understand the phenomenon and to establish rules of behavior useful for predicting turbulent bearing performance. From an engineering point-of-view, good results in design have been achieved by treating turbulence as an increase in lubricant viscosity, the percent of increase being a function of the ratio of inertia forces to viscous forces, the Reynolds’ number. The effective result is greater film thickness and larger power losses in turbulent lubrication than would be anticipated from laminar theory. Where will the designer of the future encounter turbulence, and how will he treat its effects? Large turbogenerators have already reached a size where turbulent operation is experienced. The gradually increasing use of process-fluid-lubricated machinery, often involving low viscosity fluids such as water, liquid metal, and liquified gases, offers the designer fresh opportunities to understand and take advantage of turbulence in both hydrodynamic and hydrostatic designs.

Fluid-Film Journal Bearings Operating in a Hybrid Mode: Part II—Experimental Investigation

1981 ◽  
Vol 103 (4) ◽  
pp. 566-572 ◽  
Author(s):  
D. Koshal ◽  
W. B. Rowe
Keyword(s):  
Journal Bearings ◽  
Friction Torque ◽  
Experimental Program ◽  
Frictional Torque ◽  
Hybrid Mode ◽  
A Value ◽  
Theoretical Predictions ◽  
Oil Flow ◽  
Higher Temperature ◽  
Oil Film Pressure

An extensive experimental program was carried out to test the theoretical predictions discussed in Part I of this paper. The design of the bearing test rig is described. Line-source plain hybrid journal bearings have been investigated and results are presented for bearings at the optimum and higher speeds. Such parameters as load, eccentricity, oil-film pressure, speed, inlet and outlet temperatures, friction torque, oil flow-rate, and attitude angle have been measured. A description of the appropriate instrumentation is also included. Whereas close agreement was found between theory and experiment, there was a tendency for measured loads to be slightly higher than predicted, particularly as the eccentricity ratio approached a value of unity. It was also found that at high values of power ratio corresponding to higher temperature rise conditions, frictional torque was lower than predicted.

Prediction in Rotor-Stator Cavities at High Reynolds Numbers up to Re ≈ 2·108: Towards a New Parametric Model

2020 ◽  
Author(s):  
Tilman Raphael Schröder ◽  
Sebastian Schuster ◽  
Dieter Brillert
Keyword(s):  
Radial Pressure ◽  
Reynolds Numbers ◽  
Friction Torque ◽  
Frictional Torque ◽  
Lower Efficiency ◽  
Axial Thrust ◽  
Wrong Prediction ◽  
Turbulence Effects ◽  
High Reynolds ◽  
Cfd Analyses

Abstract Side chambers of centrifugal turbomachinery resemble rotor–stator cavities. The flow in these cavities develops complex patterns which substantially influence the axial thrust on the shaft and the frictional torque on the rotor. Axial thrust caused by the flow pattern in side chambers accumulates in multistage single shaft radial compressors where it is often balanced by a single axial bearing. Miscalculation of axial thrust may lead to axial loads significantly higher than predicted or even undefined load situations which may cause early bearing failure. Likewise, a wrong prediction of friction losses may lead to lower efficiency than originally intended. Current models for axial thrust and friction torque are limited to circumferential Reynolds numbers of Re ≤ 107. New models are needed for modern high-pressure centrifugal compressors which reach circumferential Reynolds numbers up to Re = 109. The rotor–stator cavity flow model by Kurokawa and Sakuma [16] for merged boundary layers is analysed. It is based on the assumptions of axisymmetric and time invariant flow. Functional forms of the mean tangential and radial velocity and the surface stress vectors on the rotor and stator are assumed. Reynolds averaging is applied to consider turbulence effects in the model. The modelling assumptions are compared with detailed RANS CFD analyses at Reynolds numbers of 4 · 106 ≤ Re ≤ 2 · 108 to investigate their accuracy. Based on these CFD results, a way towards a high Reynolds number model is presented, providing prediction of disc torque, radial pressure distribution and axial thrust in rotor–stator cavities.

Modeling and Simulation of High Reynolds' Number Flows During Reaction Injection Mold Filling

1994 ◽  
Vol 9 (3) ◽  
pp. 279-285 ◽  
Author(s):  
Rahima K. Mohammed ◽  
Tim A. Osswald ◽  
Timothy J. Spiegelhoff ◽  
Esther M. Sun
Keyword(s):  
Reynolds Number ◽  
Modeling And Simulation ◽  
High Reynolds Number ◽  
Mold Filling ◽  
Injection Mold ◽  
High Reynolds ◽  
Reynolds Number Flows
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